LS2 Midterm 2 Study Guide!!!
LS2 Midterm 2 Study Guide!!! Life Sciences 2
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Life Sciences 2
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This 12 page Study Guide was uploaded by Jenna Kovsky on Sunday November 8, 2015. The Study Guide belongs to Life Sciences 2 at University of California - Los Angeles taught by Dr. Cooper/Dr. Esdin in Fall 2015. Since its upload, it has received 300 views. For similar materials see Cells, Tissues, and Organs in Biology at University of California - Los Angeles.
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Date Created: 11/08/15
LS 2 Study Guide for Midterm 2 (11/10) CELL COMMUNICATION ● Endocrine System: composed of various glands throughout the body, generally regulates activities that require duration, not speed ● Hormone: longrange chemical messenger; synthesized in a gland and released into the bloodstream; works on target cells with the right receptors to bring about a physiological response ○ Local Mediators: ■ e.g.istamine:rea of injury gets red because Histamines are releaseast cellsin response to injury ● makes small blood vessels’ capillaries extra permeable ● larger capillaries let white blood cells (WBCs) infiltrate area to get rid of invading pathogens like bacteria ■ e.g.Growth Factors: proteins that promote growth via cell division ○ Types of Hormones ■ peptides/proteins:most hormones) a few amino acids linked together; water soluble secreted by hypothalamus, anterior and posterior pituitary, pancreas, and parathyroid; ■ amines: derived from tyrosine; water soluble; include secreted by thyroid gland and adrenal medulla ● catecholamines: adrenomedullary hormones (epinephrine, norepinephrine) ● e.g.Epinephrine: adrenal medullary catecholamine; causes: ○ contraction of vascular smooth muscle, ○ relaxation of respiratory airway smooth muscle ○ breakdown of liver glycogen ○ increased rate and force of contraction of heart ■ steroid:neutral lipids derived from cholesterol; lipophilic (lipid soluble) includes from adrenal cortex, ovaries, and testes ○ Mechanisms of Hormones ■ alter intracellular protein activity ■ bind w/speciftarget cell recepto starting a chain of events inside target cell ● plasma membrane receptors ● intracellular receptors ■ physiological response of target cell can be different between different types of target cells, even when responding to the same hormone ■ most hydrophilic hormones bind to a surface cell receptor and pecond messenger within the target cell ■ some open or close ion channels to alter cell permeability (no need for second messenger) ■ lipophilic hormones bind to intracellular receptors (b/c nonpolar and can pass through plasma membrane), activate genes, lead to formation of proteins ● Cell Surface Receptors ○ ligandgated ion channelshen a ligand (small molecule) binds, the channel opens to allow ions through, or closes to prevent them from entering or leaving the cell ■ e.g. Acetylcholine receptor: when 2 Acetylcholine (ACh) bind on a skeletal muscle fiber, the receptor opens to allow Na+ into the cell, causing muscle contraction ○ Gprotein coupled receptors (GPCRs):uanyl nucleotide binding proteins (G proteins) act as molecular switches: “on” when GTP is bound and “off” when GDP is bound ■ GTPase: enzyme that acts as “builtin timer”, and splits GTP into GDP ■ G proteins arheterotrimeri: have 3 different subunits (alpha, beta, and gamma) ■ alpha subunit can bind to GTP ■ hormone binds to receptor, turning G protein “on” (replaces GDP with GTP) ■ G protein dissociates from the Receptor, and the alpha subunit breaks off from others ■ alpha subunit binds to Effector Protein, then reassociates with other subunits ■ adenylyl cyclase:enzyme activated by a Gprotein ■ cyclic AMP (cAMP): a second messenger formed from ATP by adenylyl cyclase; ultimately leads to phosphorylation of a protein ● kinase: enzyme that splits ATP to ADP and transfers the resulting Phosphate group onto proteins ■ e.g.glycogenolytic cascade (kinase cascade that releases glucose from glycogen) ● happens in the liver to breakdown glycogen ● epinephrine binds to receptor on cell membrane ■ cascades = amplification of the signalso a small amount of hormone can lead to a big response in the target cell ■ e.g.Inositol Lipid Signaling pathway ● Phosphatidylinositol 4,5 bisphosphate is cleaved by phospholipase C after the Gprotein gets activated, forming two intracellular messengers: ○ diacylglycerol activates protein Kinase C ○ inositol trisphosphate (I3releases calcium from endoplasmic reticulum ○ enzymelinked receptors: made of two subunits (alpha and beta); alpha binds to hormone, beta spans cell membrane; when the hormone binds, 2 receptors form a dimer together ■ the protein kinase domain (the part in the cytoplasm) is activated when the two receptors come together, and a response substrate within the cell gets phosphorylated from the phosphate groups on the protein kinase domain ■ Tyrosine, serine, and threonine can accept phosphate groups (which are large and negatively charged, and change the shape of the protein when they bind) ■ e.g. insulin receptors ● Calcium as an intracellular messenger ○ concentration of Ca is actively transported out of the cell and into the ER to keep gradient ○ once channels open, Ca+ rises up to 100x resting concentration 2+ ○ Ca bind tcalmodulin, a protein that activFura 2, a fluorescent calcium indicator ● Signal Transduction pathways ○ e.g.nitric oxide gas (NO) causes vascular smooth muscle relaxation and vasodilation of blood vessels ■ reduces blood pressure, and linked to the effects of Acetylcholine ■ leads to influx of calcium in the endothelial cell that lines the blood vessel ■ nicotinicACh receptor opened by nicotine ■ guanylyl cyclase:converts GTP to cGMP ○ Ras mutations in cancer ■ Ras: monomeric Gprotein, acts like alpha subunit of the normal heterotrimeric Gprotein ■ involved in the signaling cascade of growth factors to the nucleus ■ Normal Ras: “protooncogene” Ras inactive when bound to GDP, stimulates cell division when bound to GTP, and then an intrinsic GTPase inactivates Ras ■ Mutated Ras: “oncogene”; GTPase activity inhibited, cell is overstimulated to divide, creates tumor ○ sense of smell ■ odorant molecules activate Gprotein and cause cAMP to bind directly to and open an ion channel, activating an action potential along the olfactory nerve to the brain ○ Apoptosis: programmed cell death; a normal part of development and aging; homeostatic mechanism to maintain cell populations in tissues ■ cysteine proteases (‘“caspases”) are activated, trigroteolysi a cascade of events, leading ultimately to the cell’s death ■ Fas:important cell surface death receptor ■ Tumor necrosis factor (TNF):one of the ligands that can trigger apoptosis ○ most known diseases have disrupted signaling pathways, signal transduction is important for the development of drugs 2+ ○ Viagra:inhibits cyclic GMP phosphodiesterase (which would normally lowe and lead to smooth muscle relaxation ■ uses muscarinic, not nicotinic ACh receptors ■ Normally, phosphodiesterase turns cAMP into 5’ AMP , and phosphodiesterase turns cGMP into 5’ GMP, but Viagra inhibits this phosphodiesterase ■ this inhibition causes the corpus cavernosum to fill with blood, keeping the penis erect PHOTOSYNTHESIS ● 6CO2 6H2 + light 6 12 66O2 ● used to fix carbon from the environment and make organic molecules like glucose ● CO2 ters and leaves through pores castomata, water is provided from the soil,2comes from H2 ● Experiment to determine where the Oxygen came from: ○ scientists put plant in two jarsz ○ in one jar, they put normal water and isotopically labelled carbon dioxide ○ in the other jar, they put isotopically labelled water and normal carbon dioxide ○ after photosynthesis, they found that the second one had isotopically labelled oxygen, so they concluded that the oxygen comes from water and not carbon dioxide ● 2 Pathways ○ light reactionsconvert light energy into chemical energy in the form of ATP and NADPH (a coenzyme) ○ CalvinBenson Cycle: (dark reactions) C and ATP with NADPH produced in the light reactions are used 2 to make sugars and other organic molecules in the stroma ● Light Reactions ○ lighta form of electromagnetic radiation that exists as photons with wavelike properties ■ c=speed of light=frequency x wavelength ■ energy of a photon is inversely proportional to the wavelength of the light ■ energy of photon=c/wavelength ■ when light strikes a molecule, there are three possibilities ● light gets reflected ● light gets transmitted ● light gets absorbed: if the molecular structure of the molecule is appropriate, an electron gets boosted into a higher energy, “excited” state ○ then the electron will drop back down to the ground state and release energy ○ Chlorophyll:a photosynthetic pigment that is in the thylakoid membrane ■ chlorophyll’s electrons can be excited by photons, leading to the uptake of that electron by an electron receptor ■ excited chlorophyll (Chl*) is a good reducing agent ● excited electron goes through an electron transport chain in the photosynthetic membrane, pumping out protons, which leads to the production of ATP ■ resonance energy transfer: vibrational energy transfer from one chlorophyll to another, increases efficiency ■ action spectrum: measures rate of photosynthesis as a function of wavelength ■ Noncyclic Electron Transport:uses two photosystems to produce NADPH and ATP, and Oxygen as a byproduct ● in the thylakoid membrane ● as electrons go through an electron transport chain, protons get pumped into the thylakoid ● Photosystem I: reaction center has chlorophyll a, which absorbs blue and red light ○ electrons go through Ferredoxin (Fd) ○ electrons end up in NADPH, and get replaced by the electrons from Photosystem II ● Photosystem II:comes before photosystem I; more energetic ○ water splitting occurs to replenish the electrons it passes on to Photosystem I ○ watersplitting complex: has manganese, oxygen, and calcium atoms ■ Cyclic Electron Transport:traps light energy and produces ATP but not NADPH ● just has photosystem I ● electron gets transferred back to the beginning, and water is not split ● just used to make additional ATP for use in the dark reactions ● Dark Reactions (CalvinBenson Cycle) ○ 3 parts ■ Carbon Fixation ● Rubisco adds CO2to Ribulose 1,5 Bisphosphate (RuBP) ■ Reduction and Sugar Production ● Phosphoglycerate Kinase (enzyme) converts 3phosphoglycerate (3PG) into 1,3bisphosphoglycerate using a phosphate group from an ATP molecule ● glyceraldehyde3phosphate dehydrogenase converts 1,3bisphosphoglycerate into glyceraldehyde3phosphate (G3P) using an electron from the reducing agent NADPH ■ Regeneration of RuBP ● 12 steps, using ATP (need cyclin phosphorylation to increase ATP levels) ○ Where does G3P go? ■ some of it is used to regenerate RuBP, but some of it exits the chloroplast and is converted into glucose or fructose in the cytoplasm ■ 3PG can be converted into pyruvate ● Photorespiration:light driven uptake of oxygen instead of carbon dioxide by rubisco; reduces the efficiency of photosynthesis; RuBP + O forms glycolate (a 2 carbon molecule) which enters peroxisomes, is oxidized, then 2 enters mitochondria and is broken down, releasing2CO ○ Rubisco can add either 2or CO2to RuBP because it evolved before oxygen was present ○ so Rubisco works best at a slower catalytic rate, so it can be better about sel cting CO 2 ○ Rubisco makes up 50% of a leaf PHYSIOLOGY, HOMEOSTASIS, TEMPERATURE REGULATION ● 75 trillion cells in the body ● 200 types of cells ● physiologists classify cells by how they interact with each other ● tissue:cluster of multiple cells with the same function; 4 types: ○ epithelial/surface, connective, muscle, and nervous/brain ● organ: group of tissues working together ● organ system: a group of organs with a common function (we have 11 systems in our body) ○ work in common functionality to maintain homeostasis, so cells are satisfied ● organism: ll the organ systems put together ● What do cells need to survive? ○ nutrients + oxygen =nergy ○ blood vessels are relied upon to transport these things ○ everything is delivered through three organ systems: ■ cardiovascular system: ■ digestive system:ensures the food we consume is properly broken down ● then the food needs to be moved from the digestive system to circulation to get to cells ● pepsin: enzymes that functions in digestion ■ respiratory systemoxygen in your lungs doesn’t do anything until it diffuses into the blood ● carbon dioxide travels through circulation back into the lungs to be exhaled ○ carbs and lipids are used to make ATP (and sometimes proteins)\ ● Other organ systems ○ renal system:metabolizes nitrogenous waste into urea/urine to be excreted ■ nitrogenous wastes: nucleic acids and amino acids ○ nervous system:brain is regulating organs ○ endocrine system:regulatory system, but different level of control than nervous system ○ reproductive system:ensures life continues ○ immune system: ensures we can fight off pathogens ● Homeostasis: maintenance of constant internal environment (sodium, glucose, pH, temperature, etc.) ○ components of homeostatic system ■ receptor:provides information about specific conditions; measures ■ control centerdecisionmaker; evaluates info from receptors then decides what to do (if anything) to return to the norm (set point); most control centers are in the brain ■ effectorworks to restore the deviation to the set points of the internal environment ○ e.gTemperature Control: ■ temperature decrease ● receptors=thermal receptors: sense temperature drop ● control center=hypothalamus: gets information from receptors ● effectors=skeletal muscles and skin blood vessels: get info from control center ○ shivering: skeletal muscles contract uncontrollably, generating heat ○ blood vessels vasoconstrict: because decreasing flow of water at the surface minimizes its interaction with the cold air and therefore minimizes the loss of heat ○ the effects stop when we’re back at the set point ■ This is negative feedback mechanism (stability) ● as opposed topositive feedback mechanism (instabilitye have very few of these (e.g lactation and menstrual cycles) ■ Classification of Animals ● endotherms: all mammals and birds regulate their body temperature by generating metabolic heat and/or preventing heat loss ● ectotherms: reptiles, etc. cannot regulate their body temperature, it mimics the external temperature NERVOUS SYSTEM ● function: everything ○ input: constantly receiving information ○ processing: processing the information ○ output: sending information out ● neurons: billions of them make up the nervous system; able to communicate with each other and with other cells in the body through electrochemical signals ○ “excitable cells”: exhibit electrical activities ○ components of a neuron ■ soma: cell body; main component of the cell (aka perikaryon); 5140 micrometer diameter; abundant protein synthesis organelles ■ dendritesspecial branches where electrical signals are received, one neuron has many, because each neuron receives many signals from many neurons ■ axon:where the electrical activity is created and sent out; most neurons only have one; lots of microtubules for transport (aka nerve fiber) ■ axon terminalsilled wieurotransmittermolecules that initiate activities in other neurons) ■ myelin:insulates the axon to speed up electrical activities ● schwann cellsproduce myelin sheaths ● nodes of ranvieraps in myelin sheaths along the axon; important in the propagation of electrical activities ■ synapse:the junction formed between two neurons, allowing communication to continue between neurons ● presynaptic neuron:ends signal ● postsynaptic neuron:eceives signal ● axosomatic:axon synapses on cell body ● axodendriticaxon synapses on dendrites ○ classification of neurons ■ based on function ● afferentsend info the the CNS, receive information ● interneurons:rocessing neurons (e.g. making sense of what prof is saying) ● efferentsend information out from the CNS (e.g. moving your hand) ■ based on structure (refers to extensions of the cell body ● multipolar:ots of dendrites, one axon, most common type of neuron; mostly motor neurons and interneurons; in brain ● bipolaronly two extensions from the cell body; ears, nose and eyes; sensory neurons; receive hearing, olfactory, and visual info ● unipolarone branch; short single process; branch later divides into two; sensory neurons; e.g touch ● Electricity: movement of electrons along a wire ● electrophysiology:electricity within our bodies ○ we never have free, lonely electrons, because they would wreak havoc in the cell ○ wire=plasma membrane ○ electrons=ions (charged atoms that have lost or gained electrons) ○ electricity caused by movement of ions across the membrane through channels ● diffusionthe movement of ions from an area of high concentration to an area of low concentration without the expenditure of energy ○ need driving force (always there) ○ need permeability (not always there because channels allowing movement to occur are not always open) ● action potenti: “ability to move” a change in voltage over a change in time (225 mph) ○ voltage is a way to quantify the ions ○ threshold:50 to 55 mV; critical point at which slow change in voltage becomes a rapid change ○ resting membrane potentialabout 70 mV ○ peak potentialabout +30 mV ○ slight fluctuation in electrical raded potentiain cell body and dendrites ○ large change in electrical actaction potenti in axon hillock and axon ● Membrane potential ○ Extracellular Fluid (EC Na+ provides positive charge; Cl provides negative ○ Intracellular Fluid ( K+ provides positive charge; Anions (large proteins) provide negative ○ charges across the cell are the same (no difference between inside and out)=no charge (this is how most cells in our body, non excitable cells are) ○ membrane has a potential when the charge is different inside (e.g. 5) than outside (e.g. +5) ○ we only care about net charges on each side of the membrane ○ membrane function w/respect to electricity: charge separator, that leads to potential for positives to run to the negatives ○ inside the cell is predominantly negative compared to the outside ○ sodium and potassium are slightly permeable through the membrane at rest (driving force is huge) ■ Na+: ECF: 150mM, ICF: 15mM (sodium always wants to move into the cell) ■ K+: ECF: 5mM, ICF: 140mM ○ equilibriumequal concentration on both sides. should NEVER happen in neurons (because we would lose the driving force), we just want mechanisms for diffusion to occur ● What happens at Rest ○ passiveSodium Leak Channels” always open, letting sodium enter the cell ○ passive“otassium Leak Channels always open, letting potassium leave the cell; wider than Na+ leak channels ○ at rest there is more K+ permeability than Na+ permeability ○ Na+/K+ Pump: requires ATP, maintains the ion gradients (to prevent equilibrium) ■ for every 1 ATP: 3 Na+ ions leave cell, 2 K+ ions enter cell ● Giant Squid Axon ○ everything we know about action potentials came from squid ○ Hodgkin and Huxley in the 60s studied the squid’s neurons (because they’re very large) ● depolarization:cell becoming more positive from K+ coming in ● hyperpolarization:cell becomes less positive when K+ leaves ● repolarizationcoming back to rest (from either depolarization or hyperpolarization) My Diagram of A Neuron (labelled) The Relative Concentrations of Important Ions at Rest Channels that are ALWAYS working (at rest and during action potentials) Note: these channels and pumps are located all over the neuron. The Na+/K+ Pumps require energy in the form of ATP, because they go against the concentration gradients of each ion. The leak channels, however, do not require energy, they just allow the ions to go down their concentration gradients. Also note that the potassium leak channel is wider than the sodium leak channel, so at rest the plasma membrane is more permeable to potassium than it is to calcium. Also note the amoung of potassium and sodium that the pumps move at a time, for every one ATP molecule, the pump moves 3 Na+ ions out and 2 K+ ions into the cell. Steps of the Action Potential Step 1: Triggering Event (voltage 70mV to 50mV/55mV) Notes for the above picture: in reality there will be lots of IPSP and EPSPs happening at the same time. Different neurons will be sending different types of NTs, I made a generic NT symbol for simplicity. The IPSPs and EPSPs will be summed by the postsynaptic neuron, and if the summation of all of those adds up to at least a 20 mV positive increase in voltage (taking us from the resting potential of 70mV to the threshold of 50mV, then we will get an action potential). Step 2: Action Potential Part 1: Rising Phase (voltage 50mV to +30mV) Notes: this is occurring at the axon hillock. The Voltagegated Sodium Channels (VGSC) open at 50mV/55mV (threshold), and Sodium floods into the cell, causing a rapid rise in voltage up to +30 mV (peak potential). VoltageGated Potassium Channels (VGKC) are triggered to open as well, but are very slow to open. Part 2: Falling Phase (voltage +30mV to 80mV) Notes: The VGKC finally open, allowing Potassium to exit the cell. The VGSC don’t just close at this point, but they inactivate, so that even if threshold is reached, they won’t open (this is trefractory period) . Once the VGKC close, only the leak channels and the Na+/K+ Pump will be active, and they will bring the membrane back to resting potential (70mV) Step 3: Propagation Notes: the Na+ that gather in the axon hillock repulse each other, & some of them go down the axon, depolarizing that part of the membrane, which opens the VGSCs and later the VGKCs, so step 2 will occur at that part of the membrane.This only happens at the Nodes of Ranvier, because the spots on the axon coated in myelin don’t have channels.Saltatory conducti: from the Latin word “saltare” (to jump), because the action potential “jumps” from node to node. Step 4: Neurotransmitter Release Notes: ere the action potential has reached the axon terminal. At this point,alciuChannels (VGCC) open, allowing Calcium ions to flow into the cell at the axon terminal. These calcium ions will bind to vesicles containing Neurotransmitters (NTs). As the next image shows, the binding of a Calcium ion to one of these vesicles causes the vesicle to move to the cell membrane, where exocytosis will occur, releasing the neurotransmitters into the synaptic cleft. The neurotransmitters will then bind to receptors on the membrane of the next neuron. This will lead to ion channels opening, allowing Na+ ions or Cl ions to enter the next neuron, creating either EPSPs or IPSPs, and the whole process starts over in that postsynaptic neuron (see step 1)!
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