BIO 212 REVIEW SHEET #1
BIO 212 REVIEW SHEET #1 BIOL 212
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Biology 212 Principles of Human Physiology Fall 2013 REVIEW SHEET FOR WEEKS 13 material for inclass Exam 1 Disclaimer You will be tested on your understanding of all material covered in lecture on the textbook s information with resvect to the topics covered in leCtl and on the following specific textbook pages pp 111 introductory material and response loops DONE pp 4657 cell structures and organelles pp 7475 law of mass action DONE pp 5785 82 and 598600 insulin glucagon diabetes DONE and pp 592597 regulation of body temperature DONE pp 110113 endocytosis exocytosisDONE Some Stuff To Know Just in Case Feed forward regulation anticipates changes in regulated variables such as internal body temperature or energy availability improves the speed of the body s homeostatic responses and minimizes uctuations in the level of the variable being regulated that is it reduces the amount of deviation from the set point Ex Senses cold temp and shivers and contracts muscles in order to reduce temp lost before cold Temp from environment 1 From lecture and text Know levels of organization in body atoms molecules cells etc Atoms molecules cells tissues organs organ system organism 2 From text Know the 4 tissue types especially focusing on examples and properties of epithelial tissue and connective tissue Define lumen Define apical luminal membrane and basolateral membrane With which tissue type are these terms used With which tissue type is collagen associated The four tissue types are epithelial connective muscle and nervous tissue Epithelial tissue They are specialized for the selective secretion and absorption of ions and organic molecules and for protection They are characterized to their shape which are cuboidal squamous and columnar types and can form simple layers or stratified layers This is typically located in the exterior and interior lining of organs and inner structures and outer structures like the skin Apical membrane the membrane facing toward the lumenthe inside hollow space of something and the basolateral membrane the side of the cell facing anchored to the basement membrane is typically associated with this type of tissue Connective tissue As its name implies it connects anchors and support the structures of the body Examples include bones ligaments tendons cartilage bone extracellular matrix Collagen is usually associated with connective tissue 3 Define homeostasis extracellular uid intracellular uid What is the internal environment which is maintained in homeostasis What are the two main compartments of the ECF What is the third smaller compartment of the ECF In which compartment ECF vs ICF is sodium concentration high In which compartment is potassium concentration high In which compartment are anionic proteins in highest concentration Homeostasis is the internal processes made by the body to keep ranges of our bodily functions and the internal environment relatively stable within a normal range note bodily processes and internal environment are always changing but not much so they re dynamic that s why homeostasis is concerned with keeping things with a relatively constant set of ranges The internal environment maintained by homeostasis is plasma the liquid portion contained and owing through the blood vessels housing proteins and red blood cells and interstitial uid uid that surrounds cells which both contributes to the term extracellular uid ECF Another component of the ECF is the trans cellular uid which are small pockets of ECF in small places like in the eyes or in the joint cavities of synovial joints Comparative to the ECF is the intracellular uid ICF that is as its implies the uid inside cells Sodium concentration is higher in the ECF than in the ICF lSOmM V 15 mM Conversely potassium concentration is higher in the ICF than in the ECF lSOmM V 5mM Anionic proteins negatively charged proteins are concentrated in the ICF 4 From lecture and text Understand and be able to identify negative feedback positive feedback Which of these is more common Also know feedforward regulation Know the terms set point effector receptor integrating center afferent pathway efferent pathway stimulus Negative feedback is a selfregulating process where an increase or decrease in a variable being regulated brings about responses that tend to move the variable in the direction opposite the direction of the original change so that the original value can be reached once more For example consider the production of ATP As you produce more ATP the amount of ATP in the cell increases and processes then occur to slow down the production of ATP and cease it altogether since the objective of ATP have reached and you don t want to make more ATP when you don t need it thus conserving energy Most of the homeostatic processes about 90 are regulated by negative feedback On the other hand there is positive feedback which constitutes about 10 of all homeostatic processes and is thus less naturally occurring This type of feedback is selfpropagating and accelerates a certain type of process outside the range of homeostasis thus leading to an explosive system Feedforward regulation anticipates changes in regulated variables such as internal body temperature or energy availability improves the speed of the body s homeostatic responses and minimizes uctuations in the level of the variable being regulated that is it reduces the amount of deviation from the set point the target value of a controlled variable that is maintained physiologically Stimulus is a detectable change in an environment and the receptor is what senses it and sends information to the integrating center via the afferent pathway which then processes the information and sends out information to be regulated via the efferent pathway to the effector to cause an action 5 From lecture and text Know thermoregulation in the body Where is the body s primary thermoregulation integrating center thermostat Where are thermoreceptors and what does each type specifically monitor What are the effectors Explain the body s response to cold exposure and a drop in core body temperature Explain the body s response to heat exposure and an increase in core body temperature In the context of the thermoregulation system explain how a fever occurs What are endogenous pyrogens What is hyperthermia heat exhaustion heatstroke Thermoregulation is a homeostatic process of the body by maintaining normal temperatures of the body via mechanisms I ll describe now For example if your body is hotter than usual your body will undergo thermoregulation via the action of sweat to release heat from the body and vasodilation Conversely if your body is colder than usual you ll begin to shiver to produce energy in the form of heat from the contraction of skeletal muscle and vasoconstrict to keep heat in the body The body s main thermostat is the hypothalamus Thermo receptors are receptors that detect a change in temp from the set point and sends the info to the integrating center the hypothalamus so that it can process the information and make the body act accordingly to return the body temp back to normal ranges There are two types of thermoreceptors peripheral thermoreceptors on the skin and central thermoreceptors in deep body structures Effectors to initiate thermoregulation include skeletal muscle blood vessels and sweat glands among others A fever occurs typically during a bacterially infection where bacteria or the white blood cell itself release endogenous pyrogens which are small chemicals whose main function is to travel to the hypothalamus and reset the set point to a higher temperature thus raising your temp so that it d allow the death of some bacteria and allow white blood cells to act faster and kill off the bacteria causing the infection Hyperthermia is the increase of body temp not due to a higher set pt of internal temp which can be due to exercise Heat exhaustion is a state of collapse due to the overtaxing of heat loss thermoregulatory mechanisms which is caused by deletion of the plasma thus less cardiac output and hypotension It acts as a safety valve to cease activity causing heat gain preventing higher increases in body temperature which can potentially cause heat stroke Heat stroke is when all thermoregulatory mechanisms fail to work causing higher and higher increases of temperature which thus increase cell temp which thus drive metabolism to produce heat that increases temp even more and comes in the endstage of prolonged heat exhaustion and for some reason there isn t any sweatingfail to sweat prior to heat stroke 6 Know the basics of blood sugar regulation in the body from lecture and text Which molecule is blood sugar In humans which complex carbohydrate is the storage form for this blood sugar How does the body maintain blood sugar levels within a normal range and what type of feedback control is involved Big picture What is the role of insulin Details From which cells and from which organ does insulin come and what stimulates its release Which body cells respond to insulin and how do these cells know that insulin is there What do the responding cells do when insulin arrives Know response in liver cells know response in skeletal muscle and adipose tissue Thinking question why would it evolve that brain cells do not rely on insulin signals for glucose transport See text p 580 Big picture What is the role of glucagon Details From which cells and from which organ does glucagon come and what stimulates its release What do the responding cells do when glucagon arrives Blood sugar Glucose that is how much glucose is in your blood The storage form for this type of blood sugar is named glycogen The body responds to increase of blood sugar or decrease of blood sugar via hormones produced from pockets of cells in the pancreas termed islets of Langerhans which include insulin which are produced from the beta cells and glucagon which are produced by alpha cells cells that comprise the islets of Langerhans Through this homeostatic response blood sugar will return to normal if it was deviated beyond its normal range and thus is labeled as a negative type of feedback Now going to insulin it is a hormone that is secreted from the beta cell as mentioned earlier Insulin is secreted when plasma glucose concentration level is high and its function is to lower plasma glucose levels within normal acceptable ranges It goes to skeletal muscle cells hepatocytes liver cells and adipocytes since they have the receptors necessary to respond to insulin and to take in glucose Skeletal muscle and liver cells respond to insulin by storing glucose for later use asglycogen whereas adipocytes store excess glucose as fat Of great significance is that the cells of the brain express a different type of GLUT one that has very high affinity for glucose and whose activity is not insulindependent thus ensuring that even if the plasma concentration is very low as in prolonged fasting cells of the brain can continue to take up glucose from the blood and maintain their function Consequently you can imagine that if the brain hadn t evolved and were reliant on insulin to absorb glucose then every time our blood sugar levels are extremely low like in periods of fasting then we d probably die since in this situation our blood sugar levels would be very low and insulin wouldn t be produced thus absorption of glucose would not be present unless we brought our blood sugar high The role of glucagon is to increase blood sugar levels when blood sugar levels are low It is secreted by alpha cells from the islets of Langerhans from the pancreas It typically goes to liver cells so that it can either undergo glycogenolysis which is the production of glucose from glycogen and sends it out to the blood stream and it can undergo gluconeogenesis that is the production of glucose from scratch like from lipids or lactate a byproduct of anaerobic metabolism 7 From lecture and text Know diabetes mellitus know the different types Type 1 Type 2 which type of diabetes is more common for each type know typical age of onset what the defect is in each case how each is treated Refer to p 599 why is exercise an important treatment for Type 2 diabetes Type 1 diabetes is when you don t produce insulin and is usually diagnosed in childhood and is the least common compared to type 2 diabetes In order to treat this you would need to inject insulin youself so that cells can take up excess glucose in the blood and store it as glycogen as energy stores for later Type 2 diabetes is comes later in life and occurs due to lifestyles Originally this was typically diagnosed from the SOs60s but now it is diagnosed in the 2030s In this type of diabetes production of insulin may be okay but cells become insensitive to it so there may be something wrong with its receptors or not enough GLUT transporters available In this case it would be treated by diet and exercise and mediations to increase GLUT transporters in liver fat and skeletal cells Exercise is an important treatment for type 2 diabetes bc exercise sensitivity to insulin can be increased by frequent endurance type exercises independent of changes in body weight bc exercise causes an increase in the total number of plasma membrane GLUT in skeletal muscle cells so thus uptake of glucose from ECF is increased as the cell responds to the insulin 8 From text Review functions of the following organelles and cell structures cell membrane nucleus mitochondria cytoplasm cytoskeleton ribosomes rough ER smooth ER Golgi apparatus lysosomes peroxisomes Cell membrane selectively permeable membrane that allows certain things to come in and certain things to come out Separates the contents of the things inside the cell from outside the cell Nucleus houses DNA and nucleolus which produces subunits of ribosomes and RNA Mitochondria ATP production Cytoplasm space inside the cell the liquid in the cytoplasm is termed the cytosol Cytoskeleton the skeleton of the cell helps anchor the organelles down helps form the highway for the movement of substances of the cell Ribosomes protein synthesis Rough ER Protein synthesis from ribosomes on its structure into its lumen Smooth ER detoxification and lipids biosynthesis Golgi complex modifies proteins and sends out the protein out to within the cell or out of the cell Lysosomes has digestive enzymes to break down substancespathogens Peroxisomes breaks down hydrogen peroxide 9 Know adenosine triphosphate ATP How does ATP provide energy to the cell How and where does the cell make ATP What is the relationship between ATP and ADP Adenosine triphosphate provides energy to the cell by containing energy in its bonds between the 3phosphate groups in ATP It can be used to contract muscles move molecules into and out of the cell drive chem reactions in the cell etc The cell makes ATP via cellular respiration and it s and in a complicated process of glycolysis krebs cycle and the Electron transport chain in the cytoplasm of the cell and in the mitochondria of the cell ATP holds the energy of the cell and when of its bonds is broken to release energy you get inorganic phosphate and ADP which can then be converted to ATP again by substrate level phosphorylation the addition of a phosphate group to ADP via catabolism of nutrients 10 See online handout Know glycolysis pyruvate metabolism especially comparing the results during times of when oxygen is available aerobic and times when oxygen is limited anaerobic pyruvic acid s conversion to acetyl CoA Krebs cycle electron transport chain oxidative phosphorylation where speci cally does each process occur what are starting substances and endproducts of each process how many net ATP are produced in each process how many FADH2 and NADH molecules are produced in each process what is the purpose of FADHZ and NADH which processes stop if there is no oxygen Thinking questions a When a cell doesn t have many mitochondria what would be the primary purpose for this cell to convert pyruvate to lactic acid b Later if the cell can make more mitochondria some of the lactic acid is converted back to pyruvate Explain this in terms of the Law of Mass Action If necessary review the Law of Mass Action on pp 7475 Glycolysis occurs in the cytoplasm is an enzymatic 10 step process of the cell of making ATP without the necessary use of oxygen in the cytoplasm of the cell thus creating a net gain of 2 ATP the process of glycolysis itself consumes 2 ATP while the end product of the reaction creates 4 ATP thus causing a net gain of 2 ATP from a 6 carbon molecule of glucose SIDE NOTE READ AFTER READING EVERYTHING ELSE When oxygen is not present oxidative phosphorylation AKA electron transport chain ETC cannot occur because it needs oxygen to work Furthermore because you don t have the ETC working to make the coenzymes necessary to pick up the high energy electrons and hydrogen the krebs cycle would not work because it needs those coenzymes to pick up the high energy electrons and hydrogen it produces thus leaving glycolysis to make ATP for the cell You may ask however that glycolysis needs 2 NAD itself which is also a coenzyme but this process creates its own coenzymes separate from the mitochondria compartment Now if oxygen is not present the pyruvate that is created as a result of glycolysis would not turn to acetyl coA since that would then go to the krebs cycle and then proceed forward to the ETC but since those processes doesn t work it would not make sense to convert pyruvate to acetyl coA So what happens is that pyruvate is converted to lactate from 2 NADH and its hydrogen thus converting 2 NADH H back to 2 NAD to be recycled again for glycolysis to occur This lactate that is produced is mostly associated with muscle fatigue and can be sent to the liver to be processed to glucose via gluconeogenesis When oxygen is present again pyruvate is converted back to acetyl coA instead of lactate And because of the law of mass action since there s less reactants than products the process of converting pyruvate to acetyl coA would reverse itself thus making pyruvate which can then be converted to acetyl coA to enter the normal process of cellular respiration Process between glvcolvsis and krebs cvcle After 2 molecules of pyruvate 3 carbon molecule is made from glycolysis it is then converted to 2 molecules of acetyl coA in the mitochondrial matrix a 2 carbon molecule the extra carbon is given off as 2 molecules of CO2 Now begins the KREBS CYCLE occurs in the mitochondrial matrix Once acetyl coA enters the krebs cycle 6 NAD and 2 FAD 6 H20 and 2 ADP plus 2 inorganic phosphates enters the reaction to form 6 NADH H and 2 FADH2 and 4 CO2 and 2 net gain of ATP The outcome of these processes is a result of 2 molecules of acetyl coA entering this cycle Oxidative phosphorylation All the coenzymes of NADH H and FADH2 produced as a result from glycolysis and the krebs cycle enters the inner mitochondrial membrane folds cristae along with 6 molecules of O2 and 34 ADP 34 inorganic phoshates to produce 10 NAD and 2 FAD to be recycled and enter the krebs cycle so that it can function and 12 H20 as a result of the electrons being pulled from the coenzymes into the membrane and as it passes from the proteins embedded in the membrane releases energy for ADP inorganic phosphate to be converted to ATP so the electron goes somewhere else in the end and that it goes to an oxygen molecule to form water and about 3234 ATP 11 Describe the uid mosaic model of the cell membrane and the locations and roles of each molecule type phospholipids proteins cholesterol carbohydrates Understand the concepts of polar vs nonpolar molecules hydrophilic vs hydrophobic Hydrophilic water loving dissolves in water and is typically polar V hydrophobic water hating tends to be separated from water like oil on water if you try to mix that nonpolar Polar charged molecules tends to have electronegativity diff where it s attracted to an electron V nonpolar noncharged molecules that has no electronegativity difference Fluid Mosaic model refers to the overall shape and design of the plasma membrane and its components of phospholipids proteins cholesterol and carbohydrates Called Fluid because it has a uid consistency of olive oil but it still has some structural component to it Has the word mosaic to it because of the random pattern of proteins in the cell membrane compared to the typically expected design of the orientation of phospholipids Phospholipid main component of plasma membrane has a polar head and nonpolar tail Makes the plasma membrane mostly nonpolar as a result Proteins multiple functions like transport of material into and out of the cell and structural component of junctions discussed later Cholesterol controls the uidity of the cell membrane Very important and mostly hydrophobic so it binds to the nonpolar tails If cells didn t have this the cell membrane would literally collapse as said in class about the example of a lab test where scientists took out cholesterol of a cell membrane and it literally collapsed and stuff Every animal cell has this Carbohydrate Sticks out on the ECF side of the cell and acts as anteenas to distinguish between your cells and non you cells so that WBCs will kill the right cells that aren t yours Cell recognition Ex Blood type as a result of configuration of carbohydrate 12 Define distinguish and know purpose of desmosomes tight junctions and gap junctions Know examples of where each type of cell junction might be found Which cell junction consists of connexins cadherins What types of junctions are communicating junctions Connexins gap junctions cadherins desmosomes Gap junctions are communicating junctions Gap junctions where two cells with proteins of connexins that looks like hollow tubes connect to one another to connect their cytoplasm and transport very small things like ions EX Find in heart for electrical synchronizing motion Desmosomes dense plaques attached on cytoplasmic side of cell membrane with proteins on the dense plaques that stick out of the cell and connects with the same protein on the other cell called cadherins allows for stretching and exibility like in heart and skin Tight junctions proteins in cell membrane that fuses with protein on adjacent cell to form tight barrier that allows nothing to get in between the cell except water and ions Usually associated with epithelial tissue Good example in the digestive tract where you d want tight junctions like in the stomach You wouldn t want food particles to leak in between the cells and into the blood stream you d want the food particles to get right through the lumen and throughout the rest of the digestive tract 13 Understand the concept of membrane permeability What is meant by selectively permeable or semipermeable Semipermeable membrane describes a membrane that allows some particles to pass through whereas the selectively permeable membrane quotchoosesquot what passes through like the use of channel proteins and carrier proteins to transport certain things in and out of the cell 14 Understand the different types of membrane transport channel proteins vs carrier proteins simple diffusion across the phospholipid bilayer facilitated diffusion primary active transport mediated transport osmosis Which of these types of transport are passive and what does passive mean Which types require a carrier protein Channel proteins Mostly specific for ions Examples include leak channel proteins open all the times gated channel proteins open or closed with ligand voltage gated will open or close due to electrical property of membrane at time mechanically gated will open or close with pressure like stretching added to the channel protein So it s like open or closed continuously and will allow millions of molecules to go through in a second so it s very fast Whereas Carrier proteins concerned with all mediated transport Are opened one side at a time and acts as a shuttle bus by picking up only a few molecules then closing at that close and opens at another side to release those molecules and close back again to its original modification Very specific similar to channel proteins but very limited too Simple diffusion is just the passive means no ATP required of solute from high concentration to low concentration until equilibrium is reached that is until net movement of particles is zero Facilitated diffusion uses carrier protein and moves high concentration of solute to low concentration Passive process Example is GLUT transporterer Osmosis is the diffusion of water from low solute to high solute Primary active transport is the transport of molecules of low concentration to high concentration using ATPOsmosis is passive and primary active transport uses ATP so therefore it obviously isn t passive and also requires a carrier protein 15 Define concentration chemical gradient Define net movement Define equilibrium in terms of movement of molecules Concentration gradient refers to the diff of concentration of solute Net movement is the overall movement of all molecules For example if 2 solute goes from A to B and 4 solutes goes from B to A the net movement is 2 from B to A Equilibrium is when there is no longer movement any net movement and does not necessarily mean that both sides of a gradient is equal in concentration But that does not mean that solute won t move from left to right and from right to left Solutes will still move equally from left to right and right to left leading up to no net movement or molecules no net gain or anything like that 16 What are the primary factors which control the rate of diffusion across the cell membrane Know Fick s Law hydration shells membrane permeability and partition coefficient The primary factors that controls the rate of diffusion across the cell membrane are concentration gradient if high then high rate of diffusion surface area if high then high rate of diffusion partition coefficient for solute equal to lipid solubility divided by water solubility if it s most likely to be lipid soluble then it will diffuse across the membrane more readily molecular weight if low MW then high rate of diffusion and thickness of membrane if membrane small then high rate of diffusion Hydration shells Because ions are charged either positively or negatively it will either be attracted to water s oxygen that is negatively charged if the ion is positive or the water s hydrogen that is positively charged if the ion is negative Since ions are constantly exposed to water since the body is mostly water within the cell and outside the cell ions will always be surrounded by water because of this charge of ions That is it will always be attracted to water one way or the other making a shell of water surrounding the ion called a hydration shell and that diameter will be its true size So what diameter an ion is won t be like that in the body It will most likely be larger and it will affect the rate of diffusion See example of Na and K s hydration shell and ask the question which one has the higher rate of diffusion and the answer is K because it has a smaller hydration shell than Na when exposed to the body and thus exposed to water 17 Know properties of channel proteins Are channel proteins specific Do channel proteins typically get saturated What substances are transported through channels Distinguish between leak open channels and gated channels Channel proteins are specific to its molecules it ll let though Channel proteins do not get saturated Ions are mainly transported Leak channels are always open all the time and gated channels are only open when a ligand is bound and can be opened or closed Gated ligand gated meaning when the ligand a signal molecule is bound to the channel it will open 18 Know properties of carrier proteins How are they different from channel proteins Are carrier proteins specific Do they get saturated For a particular cell how can the rate of transport via a specific carrier protein be increased HINT think of the effects of insulin and of the effects of exercise as therapy for Type 2 diabetes Carrier proteins as expressed earlier is like a shuttle bus They are opened one side at a time compared to channel proteins and move very small amounts of solute compared to channel proteins And channel proteins are mostly continuous when it is opened Carrier proteins like channel proteins are specific and they do get saturated meaning the amount of amount that can be moved can move only so much as the number of carrier proteins present The rate of transport can possibly be increased by increasing the amount of transporters on the cell membrane 19 From lecture and text Know GLUT what is its function For what type of membrane transport is it used primary active transport facilitated diffusion or what Also understand online figures about facilitated diffusion of glucose showing the roles of GLUT2 and GLUT4 in the fasted no insulin vs fed insulin states in skeletal muscle and in liver hepatocytes GLUT s function is to transport glucose into a cell and it is transported via facilitated diffusion GLUT 4 is insulin dependent found on fat and muscle cells When insulin is secreted after eating to absorb glucose from the blood plasma into the cell GLUT 4 is typically used When you fast and there s no insulin and GLUT 2 begins to work since it s not insulin dependent to work 20 Understand NaK ATPase pump Which ions are moved How many In which compartment ECF vs ICF is sodium concentration high In which compartment is potassium concentration high Given these answers which direction does the NaK pump move each of these ions What is the relationship between ATP and the phosphorylationdephosphorylation of the pump and how do phosphorylation and dephosphorylation relate to the function of the pump Is this primary or secondary active transport Which cells have the sodiumpotassium pump Sodium concentration is high outside the cell in the ECF and in this pump 3 molecules of Na move out of the cell and 2 molecules of K is moved inside the cell Potassium is high inside the cell The relationship between ATP and phosphorylation is that the breaking of the bonds of ATP releases energy on the pump so that it can be phosphorylated thus initiating a conformational change in the pump to release Na out to the ECF and when the energy is gone it dephosphorylated and moves back to its starting position to restart the process once more with the necessary use of ATP This is primary active transport Because in ALL cells of the human body it is established that Na levels are low within the cell and high in K inside the cell it is necessary then for this pump to be established within all cells of the body since this difference in amount of ions can only be established due to this pump 21 Understand the different types of membrane transport channel proteins vs carrier proteins simple diffusion across the phospholipid bilayer facilitated diffusion primary active transport aquaporins secondary active transport simple diffusion through ion channels osmosis Which of these types of transport are passive and what does passive mean Which types are in the category of mediated transport What is cotransport and what is countertransport With which type of transport are these terms used Aquaporins are channel proteins embedded in the cell membrane of cells to allow for the osmosis of water that is the diffusion of water from low solute concentration to high solute concentration Channel proteins are proteins that usually allow for charged small things like ions to get into the cell to which the channel is highly specific Furthermore unlike carrier proteins when it s open it allows for the rapid in ux of solutes Carrier proteins on the other hand is slower and can only pass solute across from one side to the other depending on the space available for it so thus like the channel proteins can be saturated Simple diffusion across the phospholipid barrier just basically means that solutes that are mostly nonpolar will either diffuse through or out of the phospholipid barrier depending on the concentration gradient Primary active transport is basically the active transport of solutes against its concentration gradient by using a carrier protein and by using ATP while secondary active transport is when the use of a concentration gradient is used to move solute against its concentration gradient Passive just means that no ATP is used so osmosis using 21aquaporins is passive and so like simple diffusion facilitated diffusion The types in the category of mediated transport are facilitated diffusion and the primary and secondary form of active transport Cotransport is when the solute transported 22 Describe the glucose transport system using SGLT transporters in the intestinal cell membrane How does the body transport glucose from the lumen into the blood What transport proteins are in the luminal membrane What transport proteins are in the basolateral membrane What role do tight junctions play in how the apical luminal membrane is different from the basolateral membrane in transporting epithelia Where is energy ATP directly used What aspect of the system requires an alternate form of energy in the form of an ion concentration gradient Displayed mainly in the diagram regarding the facilialted diffusion from broken down molecules to glucose from the intestines into the blood stream Glucose and Na using concentration gradient established from the NaK pump on the basolateral membrane of the intestinal cells undergo secondary active transport via a carrier protein called sodium glucose transporter located on the apical luminal membrane which does not require ATP unlike the sodium potassium pump 23 From text Understand transport by endocytosis Compare and contrast pinocytosis receptormediated endocytosis and phagocytosis Why are these transport processes needed In other words why not just use a carrier protein What are coated pits and what is the role of clathrin Once an endocytotic or phagocytic vesicle is created where does it go Also understand transport by exocytosis What are the two main functions for exocytosis The function of pinocytosis cell drinking is just to nonspecifically take in substances from the ECF like solutes and water into the cell by using a vesicle Though a consequence of all endocytosis is the manipulation of the cell membrane to take in particles thus decreasing the size of the plasma membrane The function of phagocytosis is to take in pathogens using a phagosome and then combine it with a lysosome so that the digestive enzymes contained within the lysosome can kill the pathogen enclosed within the phagolysosome the fusion of a phagosome and a lysosome In receptor mediated endocytosis a ligand binds to a receptor and then clathrins proteins makes its way to the plasma membrane so that the ligand and receptor complex can link to the clathrin using an adaptive protein The entire complex as a whole will eventually creat a coated pit and then eventually invaginate and form an endocytotic vesicle This is for the specific taking in of certain types of molecules you want to get in not just ions as shown in channel proteins or carrier proteins Afterwards the receptor and the clathrin proteins are released from the vesicle and recycled while the vesicle and just the ligand itself will combine with an organelle like the ER to modify something like a protein or with a lysosome to break something down The two functions of exocytosis is to 1 provide a way to replace portions of the plasma membrane that endocytosis has removed and in the process a way to add new membrane compoenents to the plasma membrane too and 2 provide a way for solutes impermeable to the cell membrane like proteins to get out of the cell and into the ECF 24 See online worksheet Know osmosis osmotic pressure hydrostatic pressure relationship between osmotic pressure and solute concentration Distinguish between the following scenarios osmosis when membrane is permeable to solute osmosis when membrane is not permeable to solute osmosis when membrane separates pure water from nonpenetrating solute Osmosis is the diffusion of water from low solute concentration to high solute concentration Within a cell water is diffused using a channel protein called an aquaporin because since water is polar and thus hydrophilic it is unable to cross a cell membrane which is nonpolar Osmotic pressure is the pressure of water hitting the membrane The general rule is this the higher the solute concentration or the higher the concentration gradient the greater the osmotic pressure Hydrostatic pressure on the other hand is pressured developed as water ows from one side of a membrane to the other to try to establish equilibrium As the water rise from one side the hydrostatic pressure increases and eventually is strong even to stop the water from the other side of the membrane from going to the other side thus creating an equalized environment Osmosis when membrane is permeable to solute Water will move from low solute to high solute and solute will move from high concentration to low concentration Osmosis when membrane is not permeable to solute Water will continue to move from low solute to high solute to try to maintain an equilibrium state until a developing hydrostatic pressure stops the water from coming in from the side opposite of the hydrostatic pressure coming in Osmosis when membrane separates pure water from nonpenetrating solute Water will move to nonpenetrating solute a condition where it s lower in water concentration on the nonpenetrating solute side 25 What is the difference between molarity and osmolarity What is the normal osmolarity of a human cell You should have this number memorized Define and distinguish between the following terms hypoosmotic iso osmotic hyperosmotic hypotonic hypertonic isotonic What would happen to a red blood cell put into one of these solutions Why do IV solutions have to be isotonic What is lysis What is crenation Molarity is the concentration of a solute measured in moles per liter while osmolarity is the term used to refer to the concentration of all the dissolved solute particles and expressed the total number of solute particles per liter The normal osmolarity of a human cell is 03 osM Hypoosmotic is when the osmolarity of an environment is lower than the osmolarity of a cell hyperosmotic is when the osmolarity of an environment is greater than the osmolarity of human cell isosmotic is when the osmolarity of an environment is equal to the osmolarity of a human cell These osomotic terms refer to the entire concentration of solute regardless if it s penetrable or not Hypotonic is a solution that causes a cell to swell and when the solute concentration of nonpenetrable solute is lower than that of a cell s osmolarity Hypertonic is a solution that causes a cell to shrink in size by water diffusing out of it because an environment whose solute osmolarity of nonpenetrable solutes is greater than that of the cell Isontonic is a solution that causes no change in the cell where the solute osmolarity of nonpenetrable solutes is equal to that of the cell IV solutions must be isotonic so that it won t cause our cells to shrink or burst if placed in our body if it were hypertonic or hypotonic respectively Lysis or hemolysis is when a cell bursts because of water going to the cell and crenation means just that RBCs shrink and die If RBC put in hypertonic solution then it will crenate if placed in hypotonic solution then it would hemolysis GIVEN The following are the atomic masses of particular elements used in Questions 2628 C12 H1 O16 Na23 Cl35 Mg24 26 Calculate the osmolarity of a 2 glucose solution C6leO6 Answer 011 OsM Would this solution be isoosmotic hypoosmotic or hyperosmotic to the cell Hypoosmotic 27 What solution is a 0022 OsM glucose solution Answer 04 CHECK 28 Assuming the membrane is relatively impermeable to the following substances what will happen to RBCs placed in these solutions HINT need to think in terms of osmolarity a 02 M MgClz Answer it shrinks or crenates CRENATION b 02 NaCl Answer it swells and perhaps lyses SWELLS 29 Define and understand hematocrit serum plasma buffy coat anemia hematopoiesis pluripotent stem cell erythrocyte RBC WBC erythropoiesis platelet Hematocrit percentage of red blood cells of whole blood Serum is blood plasma without its clotting factors Plasma is the liquid part of the RBC and is considered part of the ECF which has solutes dissolved in it and proteins and other things except oxygen to be transported throughout the circulatory system Buffy coat is the fussy like liquid between red blood cells and its plasma after a cuvette have been centrifuged Anemia is a condition where you have low oxygen carrying red blood cells circulating in the body which can be as a result of lack of iron and thus lack of hemoglobin production which is essential to carry oxygen low RBC count or a combination of both Hematopoiesis is the creation of formed elements Pluripotent stem cell is a stem cell that can differenaite to any of the formed elements of the blood And erythrocyte is a RBC whose function is to carry oxygen and rid of carbon dioxide produced by cells to the lungs to be exhaled out WBCs are cells that plays a role in defense and the immune system Erythripoeissi is the name referred to the production of RBC Platelets is a cytoplasmic secretion of a formed element whose function is to kick start clotting 30 What is the composition of plasma What is the role of albumins globulins fibrinogen transferrin Where are most plasma proteins made Plasma consists of formed elements living in it wastes hormones amino acids glucose plasma proteins etc Albumins function is to maintain the osmolarity of plasma and maintain osmotic pressurebalance and blood volume Fibrinogen s function is to help with clotting and transferrin s function is to carry iron in the blood stream Globulins specifically that of alpha and beta globulins function as transporters like LDL or HDL which carries cholesterol in the blood stream The gamma globulins are antibodies which help in immune function Plasma proteins are mostly made in the liver 31 Describe the structure function and location of hemoglobin What is the role of iron Function of hemoglobin is to carry oxygen in the RBC Located in the RBC Structure consists of protein as suggested by its name globin specifically 4 poly peptides with a4 heme groups one on each polypeptide that has an iron molecule in the middle of each heme group and is red which is why RBCs are red since they are packed with hemoglobin which has heme groups which makes it red The role of iron is to reversibly bind to oxygen to carry oxygen diffused into the blood stream from the lungs and to exhale carbon dioxide produced from the cells and out the body 32 Where and when are RBCs destroyed What happens to hemoglobin when the RBC is destroyed Know the connection to bilirubin and bile What happens to the iron from hemoglobin Know the protein ferritin and the plasma protein transferrin RBCs are destroyed in both the spleen and the liver but its mostly the spleen s job to break down RBCs When RBCs are destroyed so is their hemoglobin When hemoglobin is destroyed it is broken down to globin and its heme groups The globin are broken down to amino acids in the body and then reabsorbed and recycled The heme group breaks down to bilirubin and iron The bilirubin goes into the blood stream and goes to the liver to become part of the liquid that liver produces bile which acts as an detergent and helps dissolves fats so that enzymes can then break it down and absorb lipids into the blood stream when its broken down enough Bilirubin becomes the main bile pigment One a side note like said earlier bile is produced by the liver and then stored into the gallbladder where it is stored and concentrated for later use when fats are eaten When eating fats the gallbladder will then secrete its concentrated bile readily into the small intestine to break down the lipids However some special cases can occur If the cholesterol in bile crystallizes it can cause a gall stone which can be very painful so thus the gall bladder can be removed and then you lose the ability to concentrate bile but live in itself can produce bile by itself and send it to the small intestines but not as readily if there were a gallbladder If bile was to get into the blood stream by say liver in ammation or an abrupt ow in the bile duct thus bursting it into the blood stream a symptom NOT A DISEASE called jaundice can occur which just causes your skin to be yellow and causes the white part of your eye to be yellow too Onto the next part what happens to iron Well it cannot be dissolved in the plasma and so plasma proteins called transferrin will take the iron to the liver and in the liver the protein ferritin will carry it and store it for later use to produce hemoglobin for whenever RBC production is to occur 33 Describe the production of RBCs First the kidney will detect low oxygen in the blood hypoxia and then the cells of the kidneys will release a hormone called Erythropoietin Epo which will stimulate the production of red blood cells in the bone marrow of the sternum the skull the breastbone and the ends of long bones which is called erythropoiesis The protein ferritin which is carrying iron in the liver will transport its iron to transferrin in the blood stream so that it can carry iron to the bone marrow as so to produce hemoglobin a vital component of blood And then pluripotent hematopoietic stem cells will then differentiate itself to a red blood cell and after before it will enter the blood stream it will give up its nucleus since human RBCs do not naturally have a nucleus Some RBCs however will enter the blood stream with a nucleus which is termed a reticulocyte and constitutes about less than 5 of all blood in the body Biology 212 Principles of Human Physiology Fall 2013 REVIEW SHEET FOR WEEK 5 material for inclass Exam 1 Disclaimer You will be tested on your understanding of all material covered in lecture on the textbook s information with resoect to the topics covered in leCtl and on the following specific textbook pages p 43 sicklecell trait p 430 folic acid vitamin B12 and anemia p 431 anemia and polycythemia 34 As discussed in class describe the regulation of RBC production Define and understand erythropoietin EPO and hypoxia In this context explain why Olympic athletes train at high altitude Explain the logic of why athletes inject synthetic erythropoietin How do officials test for EPO use How would they know that the EPO they detect is not naturally produced The regulation of the production of RBCs is stimulated by the kidneys via the production of the hormone erythropoietin Epo which drives the synthesis of RBCs in the blood marrow called erythropoiesis The release of Epo from the kidneys is highly regulated by oxygen levels in the blood so in cases such as hypoxia where there is low oxygen the kidneys would detect this and try to increase the production of oxygen carrying cells RBCs to offset and compensate for the low amount of oxygen in the blood In high altitude there is low oxygen so if an athlete was train there they would be exposed to a unusally low amount of oxygen than they are accustomed to so then their body would detect this and stimulated the production of Epo to create new RBCs to carry more oxygen in the body so that when they return back to sea level to compete they ll have a naturally higher RBC count than someone that trains in sea level where the oxygen levels in the environment is normal Athletes would inject synthetic Epo so that they can have more RBCs in the body carrying oxygen to the diff parts of the body more efficiently Officials detect this by sensing a one sugar difference between the real Epo and the fake one If it has a sugar difference between the real one it assumed that the person have injected fake Epo 35 From lecture and text What is anemia Know the following major causes of anemia dietary iron folic acid or vitamin B12 deficiencies and sicklecell disease For example what is pernicious anemia What is sicklecell disease vs sicklecell trait What causes the RBCs to sickle and what happens to sickled cells in the circulation On the other hand what is polycythemia How does polycythemia relate to blood doping Anemia is a condition defined as a decrease in the ability of the blood to carry oxygen which can be due to a low RBC count low hemoglobin or a combination of both Sickle cell disease is when someone is homozygous for a particular gene and produces a sickle like shape of RBC and an abnormal sized RBC These abnormal RBCs are thus transferred to the spleen to destroy it thus reducing the oxygen carrier cells in our body thus making us susceptible with symptoms typically associated with ones who have low RBCs since the sickle RBCs produced are destroyed before they can perform their functions and transfer oxygen to the diff parts of our bodies Folic acid a vitamin found in large amounts in leafy plants yeast and liver is required for the synthesis of the nucleotide base thymine It is therefore important for the formation of DNA and thus for normal cell division since cell division requires replication of DNA before division Thus when this is not in adequate amounts impairment of cell division occurs throughout the body especially in rapidly proliferating cells like RBC formation Therefore fewer RBCs are produced when folic acid is deficient Furthermore the production of RBCs also need a cobalt containing molecule called vitamin B 12 AKA cobalamin since this is required for the action of folic acid This vitamin is found strictly in animal products so therefore vegetarians are usually deficient in this Moreover the absorption of this vitamin in the gastrointestinal tract requires a protein called intrinsic factor which is secreted by the cells of the stomach Lack of this protein therefore causes vitamin B 12 deficiency and the resulting RBC deficiency is thus termed pernicious anemia In sickle cell trait the carrier is heterozygous for the deficient trait having one for the undesired trait and one normal gene This results in the production of both normal hemoglobin and poor hemoglobin but in stable conditions this is usually enough to keep a normal person going but when exposed to higher altitude or strenuous exercise the effect of this trait will start to become apparent On the other hand sickle cell disease is when you have the full blown disease and is homozygous for the undesired gene which results in you creating deformed RBCs as a result from the deformity of hemoglobin structure The abnormal production of hemoglobin causes the cell to sickle and when it sickles it goes out of the circulation into the spleen to be taken out and destroyed Polycythemia is when you have an abnormal high amount of RBCs and a high hematocrit level which can be caused by athletes training in higher altitude or by injection of synthetic Epo which is basically blood doping but can be dangerous and can kill you which is why blood doping is illegal 36 What are the different ways that chemical messengers are classified Know autocrine paracrine neurotransmitter endocrine Distinguish between lipophilic and hydrophilic messengers Where are the receptors for each of these chemical messengers located Synthetic chemical messengers can be classified as an agonist where it acts completely like the original signaling molecule and binds to the receptor and performs the same action as the messenger whereas another classification the antagonist is when the chemical messenger binds to the site of the original chemical messenger and blocks it from entering and does not perform the action similar to competitive inhibition as seen in enzymes Autocrine is when the ligand acts on the same cell that secreted the ligand whereas paracrine refers to the action of the ligand performing action on the neighboring cell as when it was secreted and an example of a paracrine situation would be the action of neurons and its release of neurotransmitters acting on nearby neurons Lipophilic messengers is when it is lipid liking meaning it is soluble in lipids and can readily diffuse through a cell membrane so this means that the receptor for this type of messenger is inside the cell On the other hand hydrophilic messengers are messengers that are soluble in water and will thus not diffuse through the cell membrane so therefore its receptors are typically on the cell membrane rather than inside the cell as seen with lipophilic messengers 37 Define ligand agonist antagonist signal transduction Ligands are signaling molecules which binds to a cell s receptors and stimulate a response due to its binding to a receptor Synthetic chemical messengers can be classified as an agonist where it acts completely like the original signaling molecule and binds to the receptor and performs the same action as the messenger whereas another classification the antagonist is when the chemical messenger binds to the site of the original chemical messenger and blocks it from entering and does not perform the action similar to competitive inhibition as seen in enzymes Signal transduction is basically the broad term of a ligand binding to a receptor thus causing a cell reaction which depends on the receptor and type of ligand for the type of signal transduction and many other factors too 38 Distinguish first messenger from second messenger Identify an example of a second messenger How do second messengers provide for signal amplification The first messenger is the ligand that first binds to the receptor in the very first step whereas a second messenger like cAMP is later created as a result from the action of the first messenger and amplifies the first messengers response by acting on other proteinssubstances within the cell and then that acting on other cells thus causing a cascade effect 39 Describe the signal transduction pathway that lipidsoluble messengers use Thinking questions As compared to hydrophilic messengers does the cellular response occur quicker or slower with lipidsoluble messengers Also as compared to the response with lipophobic ligands how long does the response to the lipidsoluble messenger last First lipid soluble messengers would diffuse through the cell membrane and bind to a receptor in the cell The ligand receptor complex will then bind to the cell s DNA to stimulate the activation of some specific genes which will then drive the production of mRNA and then proteins corresponding to the activation of that specific gene Because of a series of these steps it is typically slower than the action of hydrophilic messengers However its response would last longer since in order to stop this reaction you d have to destroy the protein whereas in hydrophilic messengers you d just had to take out the ligand or use some enzymes to stop the activation of some proteins or some second messenger 40 What are two mechanisms by which a first messenger can lead to the opening of an ion channel Distinguish fast ligandgated ion channels and slow ligandgated ion channels The first mechanism by which a first messenger can lead to the opening of an ion channel is when a hydrophilic ligand binds to an ion channel and either causes it to open or close depending on the ion channel This is called fast gated since it openscloses immediately after attachment of the ligand The second mechanism is slow gated because the steps required to perform the action to open or close an ion channel is many compared to the fast one and this is an example of Gprotein coupling receptor action Here the hydrophilic molecule would bind to the G protein thus causing the alpha subunit of the G protein to dissociate from the beta and gamma G protein subunit with GTP unstead of GDP attached It would then attach to an effector protein like an ion channel to stimulate a response 41 Describe the action of receptors with intrinsic or associated enzyme activity such as receptor tyrosinekinases e g the insulin receptor Know protein kinase cascade In tyrosine kinase a ligand binds to the receptor that has this specific enzyme What this does is that once the ligand binds on the cell membrane the enzymes activates itself by phosphorylating itself with its tyrosine amino acids Once it does that it phosphorylates other proteins and once it phosphorylates other protiens those proteins that were phosphorylated in itself phosphorylates other proteins and the cycle continues This is termed as an cascade effect In G protein coupling receptors the ligand binds to the receptor located on the cell membrane extracellularly Once it does this the alpha subunit with an GDP attached kicks off the GDP in place for GTP and dissociates from the beta and gamma G protein subunits Once it does this it activates adenylyl cyclase which converts ATP to cAMP a second messenger which in turn activates protein kinase A Once it activates that protein it in itself activates other proteins and that in itself activates other proteins and allows for the amplification of the 1st messenger s action leading to an cascade effect like the tyrosine kinase action 42 Describe G proteincoupled receptors Know the structure of the receptor and the structure of the G protein Know the individual steps of alpha subunit activation Then what is an example of an effector protein regulated by G proteins The G protein consists of three subunits alpha beta and gamma When inactivated the alpha subunit is bound to the beta and the gamma subunit But when a ligand binds to the G protein receptor the alpha dissociates from the beta and gamma subunits constraining it and it released GDP in place for GTP Once this occurs it is activated and it can either go to a protein like adenylyl cyclase to produce cAMP from ATP in order to amplify the original ligand s response or go to an effector protein and activate it and an example of this can be an ion channel but it would act slower as compared to the fast gated ion channel which is activated when the ligand binds directly to the ion channel which is also an receptor in that specific case separate from this one 43 Describe how the adenylatecAMP system participates in signal transduction pathways What is the role of adenylyl cyclase cyclic AMP protein kinase A cAMP phosphodiesterase phosphatase Adenylate cyclase is the enzyme activated from an activated alpha subunit with a GTP molecule that s activated from ligand binding to G protein coupling receptor and by doing so converts ATP to cAMP which activates protein kinase A which activates other proteins and so on to amplify the response of the cell to the 1st messenger and creates a cascade effect similar to the on e found in the tyrosince kinase receptor But how would you stop this action once the cell achieved its purpose and activated enough proteins Well this is first done by the ligand detaching thus deactivating the alpha subunit with GTP it has an GTPhase enzyme which slices GTP to GDP to GDP and rebinds to the beta and gamma subunit and stops the activation of the adenylyl cylase which produces the cAMP the second messenger Now that the first messenger is inactive what about the second messenger that s still working and apparently working even though the production of it have ceased In order to cease the activation of cAMP which is activating other proteins like protein kinase A still it will be deactivated by cAMP phosphodiesterase by breaking down cAMP to AMP and ceases it function This protein is actually continually working however the speed at which it is working is not nearly as fast as the production of cAMP originally when adenylyl cyclase was working but now that the enzyme is not working this enzyme can now catch up and cease its function Now that the second messenger is taken care of how are we going to stop the proteins from activating one another Well this is stopped by the enzyme phosphatase which deactivates phosphorylated proteins by chopping off a phosphate attached to the protein and adding ADP to produce ATP and the inactivated form of the protein Mind you this enzyme is always working in the cell and will react with any phosphorylated protein 44 Thinking questions Explain why different types of cells may respond differently to the same chemical messenger Also explain why the same second messenger can lead to different cellular responses in different cell types P 121 Well cells that are different may have different receptors so that a cell with a receptor for the ligand will react whereas another totally different cell will not respond since it may not have the receptor for the ligand Similarly second messengers can lead to different cellular responses because of the differentiation of the cell Because not all cells are alike some cells have some certain types of genes activated whereas others do not and have some other specific types of genes activated thus you can infer that different cells have different types of proteins or protein kinases inside So therefore because of the possibility of a diff in protein kinases the action of the second messenger can then lead to different responses according to the cell type 45 Understand the concept of membrane potential and how it is generated and maintained Which is a bigger potential 90mV or 30 mV What is the distinction between 70 mV and 70 mV Explain the roles of chemical driving force concentration gradient and the electrical driving force electrical gradient Be able to determine the direction of the electrochemical driving force on an ion Membrane potential basically means a separation of charge on the membrane extracellularly and intracellularly It is generated and maintained by the movement of ions in and out of the cell via proteins and by concentration gradient and by chemical gradients in order to establish an equilibrium potential which ll be described in the next question Anyway 90mV would have the large membrane potential simply due to the presence of more ions 70 just means the charge in the cell is positive while 70 means that the charge of the cell is negative 70 is the resting membrane potential of the cell The chemical driving force is the force of an ion moving across a membrane due to its concentration gradient and going from high concentration to low concentration while the electrical driving force is the electrical gradient where ions would tend to go to the side opposite to its charge For example an ion that is positively charged would be repelled by an other positively charged ion but would be attracted to its opposite charge of negative and vice versa Electrochemical driving force is basically the net chemical driving force and the electrical driving force added together and see what direction is the overall side to which the ion is moving 46 What is meant by the term equilibrium potential for an ion Memorize the Nernst equation and be able to calculate equilibrium potential if given ion concentrations Bring a calculator to the exam Understand how knowing the equilibrium potential for an ion helps you predict the ion s movement across the membrane Equilibrium potential is the charge within a cell when there is no more net movement of an ion Nernst equation61Z logcon of ion outsidecon Of ion inside If you know the equilibrium you should be able to know the ion s movement if it were to change For example because the eq for Na is 60 and if it were to be lowered to 40 Na would rush inside to try to increase the positive charge back to the eq at 60 Similarly at another situation for K if the eq is 94 and it s at 70 K would want to rush out to establish a more negative charge 47 From text p 188 3 and 4 are good questions to assess your understanding of equilibrium potential and of electrochemical driving force Explanation for the questions respectively 3 Use the nerst equation 4 Think using the equilibrium membrane potential and say it was increased to 42 and think of the diagram it would want to leak Na out in order to reestablish the lower equilibrium membrane potential Biology 212 Principles of Human Physiology Fall 2013 REVIEW SHEET FOR 1st HALF of WEEK 6 material for inclass Exam 1 Disclaimer You will be tested on your understanding of all material covered in lecture on the textbook s information with resoect to the topics covered in leCtl and on the following specific textbook pages p 149 electrogenic Na K pump and p 155156 Novocaine and tetrodotoxin 48 In a real cell does an ion ever reach equilibrium across the membrane Why or why not In terms of concentration of ions equilibrium will never be achieved because of the formation of an electrical driving force that opposes the chemical driving force which wants to achieve equilibrium via concentration balance but it s inhibited by the electrical driving force 49 What is resting membrane potential Which ion is the primary determinant of resting membrane potential Why and how would one know Thinking question from text What are two different roles that the sodiumpotassium pump has in establishing and maintaining resting membrane potential What does it mean to refer to the NaK pump as an electrogenic pump The resting membrane potential is 70mV The ion which is the primary determinant of resting membrane potential is potassium since the rest membrane potential is closer to the equilibrium potential of K which is 90mV instead of Na s which is 60mV The two diff roles of the sodium potassium pump is l establishment of concentration gradient high K inside low Na inside and 2 helps establish the resting membrane potential by directing 3 ions of Na outside and 2 ions of K inside thus making the inside of the cell overall negative and closer to 70mV the resting membrane potential of the cell When it is referred to as an electrogenic pump it is defined as when a pump that moves net charge across the membrane and contributes directly to the membrane potential 50 Know the following terms resting membrane potential threshold depolarization hyperpolarization repolarization absolute refractory period relative refractory period firing an action potential Resting membrane potential is 70mV meaning the separation of charge along the membrane is negative due to potassium diffusing out of the cell faster than sodium diffusing into the cell by leak channel proteins Threshold potential is basically the threshold or the minimum amount of stimuli needed to create an action potential Depolarization is the start of an action potential and is defined as when the resting membrane potential gets more negative Repolarization is when after depolarization peaks due to inactivation of gated voltage ion channels voltage gated K channels allows in ux of potassium inside the cell allowing for the cell to get to the resting membrane potential Hyperpolarization if when too much K diffuses into the cell following repolarization to get to the resting membrane potential due to the sluggish closing of the voltage K ion gate thus causing the membrane voltagepotential to get lower than the resting membrane potential of 70mVs Absolute refractory period is during the depolarization step of an action potential is when another action potential cannot be produced the same time an action potential is occurring no matter the strength of the stimulus This occurs when the voltage gated Na channels are open or are closed and unopenable unless reverted back to its original reset conformation point so that another action potential can follow suit In the relative refractory period since it occurs during the hyperpolarization step it is when an action potential can occur it s just that you would need an higher stimulus than usual to create an action potential since in this period you re farther away from the threshold potential and therefore would need more stimulus than usual to get to that point whereas when you re in resting membrane potential you d need a certain amount of stimulus rather than more in the relative refractory period This is how a firing of an action potential occurs 51 Know the mechanism of an action potential How are the voltage gated Na and K channels involved What aspect of the action potential exemplifies positive feedback Know the two types of gates in the voltage gated sodium channel and know the various conformations of this channel Mechanism of action potentiallook at previous question Voltage gated Na directly related to depolarizing the membrane and K channels directly related to repolarizing and perhaps hyperpolarizing a membrane in action potential The aspect of positive feedback is the opening of the voltage gated Na channels As it opens and allows Na to come into the cell and depolarizes the membrane more and increase the membrane potential to one that is more positive it causes the opening of even more voltage gated Na channels to let in more Na and so on and so forth until the inactivation gate closes thus closing the activation gate and the entire voltage gated Na channel The two types of gates in voltage gated sodium channel are the activation gate and the inactivation gate Before the action potential this gate is closed that is the activation gate is closed and the inactivation gate is open so therefore at this stage it is closed but openable During the depolarization of an action potential the activation gate is open to allow the in ux of sodium into the cell in order to depolarize it and the inactivation open is open too since the activation gate is open and allowing the in ux of sodium into the cell so overall at this stage both gates are open However at the peak of an action potential at 30mVs of the inside of the cell the inactivation gate closes and blocks the activation gate even though it s still open Because the inactivation gate is closed and closing the activation gate this ceases readily and immediately ceases the in ux of sodium into the cell and therefore stops the cell s membrane potential from increasing any further from 30mV At this stage the entire voltage gated sodium channel is closed but unopenable In order to get another action potential rolling you d need to reset the entire channel protein to its original conformational starting point of closed and openable 52 Explain the mechanism and ramifications for how the membrane can be absolutely refractory Explain the mechanism and ramifications for how the membrane can be relatively refractory Absolutely refractory basically just means that during the polarization step of an action potential another action potiential cannot occur in place of one already occurring so basically what this means is that action potentials cannot overlap on top of one another and this is due to the two gates present in the voltage gated sodium channels which was discussed on the previous question The ramification of this is that this limits the amount of action potentials that can be fired at given time since if action potentials can t overlap on top of another action potentials can therefore only occur after another action potential in place has finished In relative refactory the period following absolute refractory is when during hyperpolarization although an action potential can be produced it is harder to do so since the stimulus required to do so would have to be greater than normal as if one is in resting membrane potential since you re further away from the threshold potential The general ramification of refractory period is the all or nothing motto of action potentials an action potential eithers fires or it doesn t fire and that all action potentials are the same magnitude and same size 53 With respect to the nervous system what does all or none refer to Refers to the magnitude of the action potential All action potentials are always equal in magnitude 54 If action potentials are all or none how does the neuron transmit information about the strength of the stimulus Neuron transmits information about the strength of the stimulus by the frequency of the action potential If the action potential is frequent the strength of the stimulus is stronger 55 Know hyperkalemia and hypokalemia how would each affect membrane potential In each case what would be the ramifications with respect to neural and cardiac excitability 56 From lecture and text Explain the physiology of how Novocaine works as an anesthetic when you are at the dentist Also be able to explain the sources and mechanisms of action of saxitoxin and tetrodotoxin Novocaine like savitoxin created by dino aggesates found in dino aggates and fish that eats these single cell creatures and tetrodotoxin found in pufferfishsalamandersnewts acts by inhiting the voltage Na gate channel proteins Because of this action potentials cannot depolarize and thus an action potential cannot occur Since action potentials can no longer occur because of these drugstoxins then a action potential that s supposedly be sent to the brain by receptors in the body detecting changes in the environment like a dentist drilling your teeth or pulling a teeth the action potential would not thus be sent to the pain and then you wouldn t feel the pain Remember Bring a Zeus form a No 2 pencil and a calculator to the exam on Monday 107 The exam will begin at 800 am to maximize the available time
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