Physiology Unit 1 Notes (chapters 1,2, and 3)
Physiology Unit 1 Notes (chapters 1,2, and 3) BMD 315
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Date Created: 08/29/15
Physiology and Pharmacology Unit 1 Chapters 1 2 and 3 Emily Nicholson Physiology the study of the functions of organisms Organ system collection of anatomical structures that work together to carry out a speci c function Cells smallest living unit 0 Neurons nerve cells four groups that are classi ed by their morphologies specialized to transmit information in the form of electrical signals from one body location to another typically possess branches that function to receive transmit signals Relay signals to muscles glands and other organs Pyramidal cell Basket cell Purkinje cell Stellate cell 0 Muscle cells muscle bers specialized to contract generate mechanical force and movement Voluntary control skeletal muscle Involuntary control smooth cardiac o Epithelial cells found in tissues called epithelia sheetlike layer of cells in combination with a thin underlying layer of noncellular material called the basement membrane Classi ed based on shape layers 0 One cell thick simple Several cells thick strati ed Short and attened squamous Square shaped cuboidal Tall and oblong columnar Epithelia are found wherever body uids must be kept separate from the external environment skin lining or lungs lining hollow organs stomach intestines blood vessels Lumen interior cavity of a hollow organ or vessel Some epithelial cells form glands organs specialized in synthesis secretion of a product Exocrine secrete a product into a duct leading to the external environment 0 Sweat glands salivary glands Endocrine secrete hormones into the bloodstream o Connective cells MOST DIVERSE refers to any structure whose primary function is to provide physical support for other structures or link them together or to anchor them in place Blood cells Bone cells bone Fat cells Tendons muscles to bone o Ligaments bone to bone 0 Elastic tissue gives skin exibility toughness Consists of scattered cells embedded in a mass of noncellular material called the extracellular matrix 0 Components of extracellular matrix long brous proteins elastin gives elasticity and collagen gives tensile strength Connective tissue also consists of lymph and blood they serve to connect the various parts of the body together 0 Organ two or more types of tissues make up structures to perform particular functions 0 Organ systems collections of organs that work together to perform certain functions 0 Pancreas part of both the digestive and endocrine systems 0 Epithelial tissue separates the external environment from the interior of the body skin linings of lungs gastrointestinal system and kidney tubules System Seine inrgamel eeuee within eyeltem lFumlihn Elllillll lin Hml lelemue gene Pnemee ememmieeiim mm eeile mime eeeiyreimeen the releeee lhyrmi gland meme 1113mm of rummnee infenme Illleeueliieem Hermm Breim eeir l emu twinned nerves mmmm m We mime ebelrieel eigr eniill lem ef e mum riengaeeleetween eeriemtelle Muemletel eeeleieii meme temlene Iigemene eueeuirt me emu eiteweeeniere muementeflliie wee elem feeiei Hill Heert mmeeineemrwgnmmtne HIM eerie Heeeiretnryr Lungs enemyne neenee emcee Being me time and eiimieeie eemem eieeiee time the tune llririmy llitlneyeuiuefemhle l tm lhm H eemetli imregi eiemmlemllmhmne im H lrl l mm mr gu Et lill 39l smell i it large EITHER IIEIWIlI filled em it il39ltlJ HIE Emil Ii39il39 lll39 ml mleir Hermie repredm ime heels glen e Immune Wll1ite leleed eelle immune liymeh quotnew spleen Helene me lately e r39 l and eelle telltale e lemiije heellyr39iimm the minent External environment ultimate source of oxygen nutrients and ultimate repository for discarded waste products 0 Most cells are not in direct contact with blood but are surrounded by a separate uid that exchanges materials with the blood internal environment Blood is contained within epitheliumlined blood vessels no connection with the external environment Epithelium that lines the blood vessels is called the endothelium endo within Inspiration oxygen enters the bloodstream from the air that is breathed Expiration air is breathed out Absorption ater inorganic salts and nutrients are transported from the lumen to the bloodstream Excretion eliminated from the body Filtration uid from the bloodstream enters the tubules Reabsorption needed materials are selectively transported back into the bloodstream 0 Water is the most abundant substance in the body a 4 r 1 r a 39Hc l quot j l s 39ELJLa l l I J1 l il39ta lb lntreeellulair uid IE F a Extracellular Iliuit l EC F Era y lulu anlurne le new are 1 IEF e r 1 EEF ta 39 Plla am a e w i 39 tel 11 a i la a u eiaama e imaratiiial Iliuiel new r1 Dietaautian at Tew Filure 11 Bandy uid eempartmente The uarieuefluidl temparhuente are indicated try blue in several Simpli ed hedge plane aimilar bu that Shawn in Figure 14 tal ll39utal 3r water In Intracellular uitl it Extracellular uid Edi Plasma e1luterstitial l luiij f Diatributiun ruttutal butly39water 0 Water is a solvent for many solutes inorganic ions sugars amino acids and proteins Total Body Water TBW total volume of uid enclosed within the outer epithelial layer 60 of total body weight PAGE 8 0 Includes uid inside ces intracellular uid or ICF 0 23 TBW 0 Many proteins rich in potassium 0 And uid outside the cells extracellular uid or ECF 0 13 TBW 0 Rich in sodium has few proteins 0 Synonymous with the internal environment 0 20 is found in the blood plasma rich in proteins 0 Interstitial uid ISF doesn t have many proteins 0 BOTH have many capillaries o ICF AND ECF are separated by cell membranes Homeostasis maintenance of relatively constant conditions in the internal environment 0 Nine of the ten organ systems function to maintain homeostasis exception reproductive 0 Composition temperature and volume of extracellular uid do not change signi cantly under normal conditions Normal temperature 986F Concentrations of solutes are kelp relatively steady Failure of any system to maintain homeostasis ultimately gives rise to signs symptoms of disease Body temperature is regulated to stay within relatively narrow limits it is a regulated variable Potassium sodium and calcium are also regulated variables 0 Negative feedback regulated variable increases system responds by making it decrease if it decreases the system responds by making it increase Only adjust when they detect a difference between the actual value and the normal desiredquot value called the SET POINT Sensors neurons Chemoreceptors sensitive to concentrations of oxygen and carbon dioxide in the blood Thermoreceptors are sensitive to temperature 0 These sensors relay signals called input to an integrating center often a particular set of neural circuts o The integrated center relays signals called output 0 Final response effectors 0 Blood glucose levels are detected by beta cells in the pancreas When blood glucose levels increase beta cells act as the integration center and release the hormone insulin into the blood insulin causes glucose to move from the plasma into cells throughout the body therefore decreasing blood glucose levels This is detected by beta cells that secrete insulin therefore feeding back into the system s input FEEDBACK LOOP 0 Positive Feeback the response of the system goes in the same direction as the change that sets it in motion Example pituitary gland secretes luteinizing hormone that stimulates the ovaries to secrete hormones called estrogens which regulate reproductive function Different from negative feedback positive feedback is useful in certain physiological systems because it allows a variable to change rapidly Diabetes Epidemic 0 Metabolic disease that affects blood glucose levels and plasma vmume OOOOOOO AFFECTS every system in the human body lt1 of younger people younger than 20 years old have diabetes gt10 older that 20 have diabetes gt27 older than 65 have diabetes Obesity is the number 1 cause of diabetes Obesity is having 3039 BMI body weight height 35 of adults are overweight 35 are obese Type 1 Juvenile onset insulin dependentquot Damage to the beta cells of the pancreas keeps them from secreting enough insulin in the blood to regulate blood glucose Have to administer insulin to control their blood glucose levels for 23 months Type 2 Characterized by failure to respond to insulin when its levels are normal Have normal beta cells in their pancreas that secrete insulin at appropriate levels to regulate blood glucose Target cells are incapable of responding to insulin Gestational o Subclass of type 2 during pregnancy 0 hormones produced in high amounts induce insulin resistance 0 4 of pregnant women 0 510 develop type 2 DM Diabetes lnsipidus Problem lies in regulating plasma volume Sulfonylureas and meglinides are drugs that stimulate beta cells to increase insulin secretion Thiazolindinediones enhance the action of insulin on muscle and fat cells decrease the amount of glucose produced by the liver Biguanides decrease the amount of glucose produced by the liver Cells must work together in a coordinated fashion to maintain homeostasis Biomolecules are molecules that are synthesized by living organisms and contain carbon atoms 0 Carbohydrates Monosaccharaides Simple sugars Glucose fructose galactose Ribose deoxyribose components of nucleotides Disaccharides 0 Two monosaccharaides o Sucrose lactose o Monosaccharaides disaccharides all end is ose Polysaccharides Glycogen Starch found in plants Cellulose found in plants consumed by humans 0 Unable to digest 0 Known as dietary ber 0 Important components of call membranes Condensation reaction that links monosaccharides together 0 Water is produced Hydrolysis reaction that splits larger molecule into smaller components 0 Lipids Contain carbon and hydrogen linked together by nonpolar covalent bonds DO NOT DISSOLVE IN WATER Main classes of lipids Triglycerides o quotfatsquot 0 non polar o composed of one glycerol 3 carbon alcoho 3 fatty acids Saturated carbon linked to maximum number of hydrogen atoms 0 Single bonds Unsaturated contain one or more pairs of carbons DOUBLE bonds 0 Monounsaturated one doublebond pair 0 Polyunsaturated more than one double bond 0 Cis fatty acids produced by natural processes 0 Trans fatty acids produced arti cially Ketone Phospholipids o Lipids that contain a phosphate group 0 Two fatty acids tail region nonpolar Face each other 0 Two fatty acids head region polar Face the water o Micelle spherical structure composed of phospholipids functions in the transport of nonpolar molecules in aqueous environment 0 Amphipathic molecule that contains both polar and nonpolar regions phospholipids decrease the attraction between water molecules 0 Surfactants are a type of phospholipid found in the airways of the lungs and decrease the attraction between water molecules Eicosanoids o Modi ed fatty acids that function in intercellular communication Steroids 0 Most common is cholesterol 0 Slightly amphipathic 0 Proteins Made of amino acids There are 20 different R groups Polymers of amino acids are formed by peptide bonds between the amino group od one amino acid and the carboxyl group of another amino acid CENTRAL CARBON is bonded to an amino group carboxyl group a hydrogen and an R group Peptides are short chains of amino acids Conformation 3D protein structure Fibrous o Elongated strands that function in structure or contractions Collagen tropomyosin Chemical messengers Globular o Irregular and bulky o Receptors carrier proteins 0 Enzymes EXAMPLES myoglobin insulin NAK pump Types of chemical interactions in proteins 0 Hydrogen bonds lonic bonds 0 Van der waals forces Covalent bonds 0 Nucleotides Function in the transfer of energy within cells and they form the genetic material of the cells Contain a nitrogenous base a 5carbon sugar and one or more phosphate groups Nitrogenous bases contain 0 Pyrimidines cytosine thymine and uracil o Purines adenine and guanine Phosphates energy contained in the phosphate bonds of ATP can drive cell processes when ATP is hydrolyzed to ADP NAD and FAD transfer energy in the form of electrons Cyclic nucleotides form a ring 0 Include chemical messengers 0 Cyclic cAMP 0 Cyclic cGMP Nucleotides make nucleic acids that function in the storage and expression of genetic information 0 DNA 0 Found in the nucleus 0 Nucleic acids are held together by hydrogen bonds 0 C and G form thee bonds hydrogen bonds 0 A and T form two hydrogen bonds 0 Found in the nucleus and the cytoplasm Cell structure 0 Each cell is bound by a plasma membrane Separates the cell from the extracellular uid Fluid mosaic uid because the phospholipids and other structures are not linked by bonds and can move around 0 mosaic because the presence of proteins in the bHayer Contains phospholipids cholesterol proteins and carbohydrates 0 Cytoplasm includes everything in the cell except nucleus Consists of two parts Cytosol gellike intracellular uid Organelles structures with speci c functions in the cell 0 Membranous separated from the cytosol by a membrane 0 Nonmembranous have no boundaries 0 Phospholipid bilayer Phospholipid hydrophilic heads face the aqueous environments inside the cell cytosol and the hydrophobic tails face each other Serves as a barrier to the movement of large polar molecules Water can permeate through the bilayer through aquaporins Two classes of membrane proteins Integral membrane proteins 0 Embedded and cannot be dissociated from the membrane 0 Transmembrane proteins surfaces span the whole bilayer Can be used as channels the allow ions to permeate the membrane Also can be used as carrier proteins Some function as enzymes that catalyze Or as G Proteins Peripheral membrane proteins 0 Loosely bound to the membrane and can be dissociated from the membrane 0 Most function as part of the cytoskeleton o Membrane Carbohydrates Form the glycocalyx a protective layer that also functions in holding cells together 0 Also functions in cell recognition 0 Nucleus DNA exists in thin threads called chromatin Functions in the transmission and expression of genetic information Surrounding the nucleus is the nuclear envelope 2 membrane Include gaps called nuclear pores Allow selective movement of molecules 0 Cytosol Enzymes in the cytosol catalyze reactions Inclusions masses that have stored energy as glycogen and triglycerides o Endoplasmic Reticulum Consists of network of membranes enclosing an interior compartment the lumen Smooth ER Rough ER 0 Have ribosomes on it Ribosomes assist in protein synthesis Membrane in continuous with one side of the nuclear envelope and the other side is continuous with the smooth ER 0 Golgi Apparatus Have membrane bound sacs called cisternae Cis face associated with the ER Trans face associated with the plasma membrane The Golgi contains molecules synthesized in the ER Packages and prepares them for transport to their nal location 0 Mitochondria Bound by two membranes Has two compartments ATP is produced here lntermembrane space area between two membranes Mitochondrial matrix innermost compartment houses the electron transport chain Cristae inner membrane folded into tubules o Lysosomes Contain enzymes that degrade intracellular debris that has been taken into the cell Endocytosis cells engulf extracellular particles particles are enclosed in a vesicle brought into the cell and lysosome degrades it o Peroxisomes Function in oxidation and degradation of amino acids fatty acids and toxic foreign matter Contains catalase which helps break down hydrogen peroxide to form water and oxygen Needed in liver and kidney cells 0 Ribosomes Composed of rRNA and proteins Function in protein synthesis Has two subunits 305 and SOS Two subunits come together in the cytosol during protein synthesis 0 Some proteins become attached to the rough ER 0 These proteins will be packaged into vesicles by the golgi and directed to their destination 0 Others remain free in the cytosol o Vaults May hold promise for cancer treatment Contain vRNA and proteins Studies suggest they assist in intracellular transport and may act as chemical signals for cell survival 0 Centrioles Each cell has TWO centrioles o Cytoskeleton Flexible lattice of brous proteins laments that give cell structure support Can disassemble and reassemble as necessary Filaments include Micro laments o SMALLEST in diameter 0 Actin Functions in muscle contraction Provide structural support for special cell projections called microvilli used to exchange molecules 0 Intermediate laments Stronger more stable Keratin Found in skin and hair cells Myosin Works with actin to produce muscle contractions Microtubules o Largest in diameter 0 Provide strength to the cytoskeleton 0 Form spindle bers which aid in distribution of chromosomes during mitosis and assist with directional movement of vesicles and large biomolecules within the cytosol 0 Components of two motile structures Cilia and agella Cilia is in the airways and moves mucus up toward the mouth 0 Cellto cell adhesions Cells can be held together by membrane proteins cell adhesion molecules 3 types 0 Tight junctions o Commonly found in epithelial tissue that is specialized for molecular transport 0 Integral membrane proteins called occludins fuse adjacent cells together for almost a impermeable membrane 0 Transephithelial transport Molecules move from one side of the epithelium to the other 0 Paracellular movement Going around the cell Desmosomes 0 Found in tissues subject to mechanical stress 0 Junction between two adjacent cells that provide strength so that cells do not tear apart when tissue is subjected to stress 0 Example heart Gap junctions 0 Present is smooth muscles and in cardiac muscle where they allow muscle to contract as a unit 0 Two cells are connected by membrane proteins called connexons composed of connexins Gap junctions in the heart allows contraction in unison Gap junctions in the bone allows nutrients to travel from cells close to bloodstream to cells deep within the Ussue Gap junctions also allow passage of some chemical messengers such as cAMP so a signal initiated in one cell can be transmitted to adjacent cells Metabolism refers to all chemical reactions that occur in the body 0 Anabolism synthesis of large molecules from smaller molecules Requires energy 0 Catabolism breakdown of large molecules into smaller ones Releases energy 0 Cellular Transport Transported by permeation carrier proteins channels or vesicles Lipid bilayer acts as a barrier to hydrophilic molecules Water and ions can move through channels Nonpolar molecules can permeate the plasma membrane and will move by diffusion Polar larger molecules cannot permeate the bilayer They are transported by carrier proteins Biggest molecules must be packaged into vesicles 0 lntercellular communication Communicating cells can be adjacent to each other or can be in different areas of the body Messenger molecules are released from one cell to reach other cells target cells 0 These contain proteins that function as receptors 0 Binding of a messenger molecule to speci c receptor triggers a response in the target cell 0 Protein synthesis 0 Takes place in the cytoplasm 0 Genetic code universal nding among all species 0 Gene portion of DNA that codes for a particular protein 0 Genome collection of genes in a given species 1 mFlHIA Figure 229 TI39IE garlic m Ira Agate Mich is a partim Eff M hai miles fin a pirtiular Jami15 I39r39qail sh Elle HIEhaw earnErica that cumin ll39l amima d seq 11m EjTlamt hEd rr m calcium with 3 m El39l39lE l39l39 iff l39lEil39l DMtriJIEIE 0 Steps of protein synthesis DNA is transcribed according to the genetic code to form a complementary mRNA in the nucleus mRNA moves from the nucleus to the cytoplasm mRNA is translated by ribosomes to form the amino acid sequence of the protein 0 Template strand contains the actual code Transcription Occurs in the nucleus 8 Process where RNA is synthesized using information contained in the DNA Code is passed on to mRNA mRNA base sequence is complementary to the template strand 64 possible codons 20 possible amino acids Can be turned on induced or turned off repressed Initiator codon AUG starts the transcription there are three terminator condons Three types of RNA can be transcribed from DNA all involved in protein synthesis 0 mRNA 0 rRNA o tRNA DNA uncoils and separates into two strands template strand contains gene and functions as template for synthesis of mRNA RNA polymerase binds to the promoter sequence this initiates separation of DNA into two strands REGULATION happens here RNA polymerase also catalyzes formation of free ribonucleotides and the DNA template using the law of complementary base pairing AU CG this makes a poynuceotide called premRNA preRNA undergoes posttranslational processing in the nucleus Introns that do not code for amino acid sequence are removed before mRNA leaves the nucleus and exons are joined together A chemical group CAP to the 5 end is necessary for initiating translation Addition of several adenine nucleotides called a poly A talk to the 3 end protects the mRNA from degradation in the cytoplasm After processing mRNA enters the cytoplasm i Translation Occurs in the cytoplasm in association with ribosomes Process in which polypeptides are synthesized using mRNA codons as a template for assembly of correct amino acids tRNA carries the appropriate amino acid to the ribosome based on interactions with the mRNA codon the 3 end of tRNA contains a binding site for speci c amino acids the other end contains an anticodon complementary to mRNA codon FE mm 10 11 Ribosomes align the mRNA with the tRNA carrying the amino acids and the enzymes that catalyze the formation of peptide bonds between the amino acids Ribosomes can hold 2 tRNA molecules in the P site and A site Initiation occurs initiation factors bind the CAP Other initiation factors form a complex with the 305 subunit of the ribosome and a tRNA that is bound to a complementary AUG amino acid 305 ribosomal subunit and mRNA bind SOS ribosomal subunit binds tRNA aligns in the P site of the ribosome the next tRNA molecule enters the A site and translation begins An enzyme in the ribosome peptidyl transferase catalyzes the formation of a peptide bond between the two amino acids The rst amino acid always methionine is released from tRNA and the free tRNA leaves the P site Ribosome moves down the mRNA one codon down and places the second tRNA into the P site The next tRNA brings the amino acid into the A site Process continues until termination codon is reached polypeptide is released and ribosome and mRNA dissociates malih nah ilk Elli i H Fania233 Mn mmhmtfmGahm mn n mg39uinsnfim l muleula mummy2 hmainle M mmmmm l mh md um binih 1E 15 hxinih IE Fa aim 0 Destination of proteins 0 0 Proteins can be secreted from the cell into the extracellular uid Proteins synthesized in a cell can also be destined for the nucleus cytosol plasma membrane or one of the organelles A leader sequence synthesized during translation determines the destination of the protein Leader sequence binds to signal recognition proteins on the ER protein synthesis continues Polypeptide chain travels from the rough ER to the smooth ER and then to the Golgi PostTranslational processing packaging of proteins 0 O 0 Post translational processing is changes in the initial polypeptide chain This includes cleavage of some amino acids excess amino acids and the leader sequence Other processes posttranslational processes are Addition of chemical groups such as lipids and carbohydrates to form lipoproteins and glycoproteins Carbohydrates are added to the polypeptide by glycoscylation Smooth ER packages the polypeptide into a vesicle and it fuses with membrane of the Golgi Polypeptide then travels to the trans face of the Golgi The Golgi then packagessorts proteins into vesicles that are targeted for certain locations premaing HEi39lnm E til irrlmne EElljliE 39l Inf Gail and pull A mil 539 1 3 r Humus 7 V gt e 7 Wham i IIl Figure 231 Festtranscriptional prncessinga Fulbwing Mns ip nni pre mFlll must mmtilergn further processing in the nucleus Transcribed in mns must be removed nd El39leremainirhgierzns spliced tgetherm themi Eil structure called a DEEPquot is added to ihe 5r end and a Final 5 tail Emmi nucleotides withthe adenine Inge is r lulli mthei39 end terpreacesaing is tnmplete l ran iL melatule can wave from the TELEIE39LE n the cytplasrn Cell Division 0 O O Mitosis division of cells Every cell except for mature red blood cells contain a copy of genes Replication copying DNA Chromosome one molecule of DNA and associated proteins 23 pairs within each pair 1 from mom one from father Chromosomes are coiled around proteins called histones scattered in the form of chromatin DNA serves as a template from synthesis of a new strand of DNA Semiconservative because each new strand consists of a new strand plus an old strand conserved strand Helicase causes DNA to unwind and separate forming replication fork DNA polymerase catalyzes a reaction that adds the next nucleotide to the chain In this process two phosphates are cleaved from the nucleotide providing energy DNA polymerase only replicates 5 to 3 LEADING strand DNA polymerase catalyzes portions of the new DNA from 5 to 3 forming a series of segments called Okazaki fragments DNA ligase links the fragments together to form the lagging strand 0 End result is two identical copies of the DNA one to pass onto each daughter cell The Cell Cycle o Interphase and cell division Interphase cell carries out its normal physiological funcUons Series in between cell divisions 61 S 62 o Skeletal muscle cells don t divide o S phase DNA replicates chromosomes exist in pairs 0 Centrioles are duplicated so they exist in pairs 0 62 rapid protein synthesis continues Cell division cell stops performing many of its normal funcUons Prophase Chromatin pairs condense individual chromosome pair is a chromatid sister chromatids are linked together at the centromere o Microtubules are used to form the mitotic spindle o Centriole pairs start moving to opposite poles of the cell and the mitotic spindle develops between them Prometaphase nuclear envelope breaks down centrioles are at opposite poles of the cell 0 Chromosomes become linked at their centromeres to the spindle bers Metaphase Chromosomes are aligned in a plane in the middle of the cell Anaphase chromatid pairs separate chromosomes move along the mitotic spindle toward opposite ends of the cell Telophase nuclear envelopes develop on the two sides of the cell chromosomes begin to decondense back to chromatin Cytokinesis division of the cytoplasm divides by cleavage Metabolic Reactions 3 general types 0 Hydrolysis Condensation reactions Hydrolysis breaking bonds using water Condensation making bonds water is generated as a product 0 Phosphorylation dephosphorylation Phosphorylation addition of a phosphate group EX synthesizing ATP Dephosphorylation removal of a phosphate group EX removal of phosphate ATP gt ADP o Oxidationreduction reactions Oxidation describes reactions that remove electrons from a molecule they must be accepted by another molecule called reduction EX oxidative phosphorylation the primary mechanism for synthesizing ATP in our cells Metabolic Reactions and energy 0 O O 0 Metabolic reactions provide us with energy Kinetic energy molecules possess kinetic energy because they move or vibrate randomly at any temperature above 0C Potential energy stored energy that can be converted to kinetic energy 1St law of thermodynamics Energy is constant cannot be created nor destroyed 2nOI law of thermodynamics Natural processes tend to go in a direction that spreads out energy like catabolism Energyreleasing reaction exergonic Can proceed spontaneously Energy requiring reaction endergonic Cannot proceed spontaneously go forward only with energy Equilibrium energy levels of reactant and product are equal Law of Mass action An increase in the concentration of reactants relative to products tends to push a reaction forward and an increase in the concentration of products relative to reaction tends to push a reaction in reverse Activation energy Difference between the energy of the transition state and the energy of either the reactants or products Activation energy can limit how fast a reaction can actually go The more quickly two molecules about to collide are moving the more potential energy they gain in the collision Reaction Rates Rate is how fast the reaction can produce products Catalyzed by enzymes Net rate difference between the rate of the forward reaction and the rate of the reverse reaction Rate is determined by a variety of factors Reactant product concentrations 0 Increase in concentration of reactants will increase net rate of reaction in the forward reaction 0 Increase in concentration of products will decrease net rate of reaction in the forward direction 0 Temperature 0 Rate of reaction increases with increasing temperature 0 Rate of reaction decreases with decreasing temperature 0 Height of reaction activation energy barrier 0 When height of the activation energy barrier decreases bother forward and reverse reactions increase because activation energy is lower 0 Enzymes Enzyme must bind to a substrate binding step Binding step is reversible the enzyme is not destroyed or altered It is then converted to product in the catalytic step Enzymes are able to recognize and bind to only one type of substrate 0 Lock and key a substrate matches the active site as a key matches a lock this is wrong because if that were the case it wouldn t be able to explain the reverse reaction Induced t model the substrate ts the active site more like a foot ts a sock than like a lock ts a key 0 Enzymes possess nonprotein components COFACTORS Contain metal ions which function as cofactors These cofactors hold the enzymes in their normal conformation o Enzymes possess vitamin derived cofactors COENZYMES They don t have catalytic activity Can be used by more than one enzyme Three examples are important in energy metabolism FAD electron carriers 0 NAD electron carriers CoA Factors affecting rates of enzymes also temperature and IOH 0 Catalytic Rate Measure of how many product molecules it can generate per unit time Rate of enzymatic reaction increases as the enzyme s catalytic rate increases 0 Substrate Concentration Based on the law of mass action Increase in the number of substrate increases the likelihood that the enzyme will bind to the substrate Higher substrate concentration means increased reaction rate 0 Enzyme Concentration An increase in the number of enzymes increases the likelihood that a substrate will bind At higher concentration of enzyme there is a faster reaction rate 0 Af nity Af nity of an enzyme is a measure of how tightly a substrate binds to its active site attraction Enzyme with higher af nity is able to catalyze the reaction at a faster rate Regulation of Enzyme Activity 0 Allosteric regulation Some enzymes possess a regulatory site A modulator induces a change in an enzyme s active site It is reversible Binding can cause and increase or decrease in the enzyme s activity Can be and activator increases activity or inhibitor decreases activity 0 Covalent regulation Changes in an enzyme s activity occur as a result of the covalent bonding of a chemical group to a site on the enzyme A common example is the addition or removal of a phosphate group to the enzyme 0 Protein kinase catalyzes phosphorylation of an enzyme Phosphatase catalyzes dephosphorylation of an enzyme 0 Feedbacklnhibition An intermediate product of a metabolic pathway allosterically inhibits and enzyme that catalyzes an earlier reaction in the same pathway The enzyme that is allosterically inhibited is called the ratelimitingenzyme O O Usually used to hold the reaction rate steady can also speed up or slow down based on body needs Endproduct inhibition the allosteric inhibitor is the end product of the reaction Feedforward activation gt Involves activation of an enzyme by an intermediate appearing upstream ATP synthesis occurs through 2 processes Substrate level phosphorylation phosphate group is transferred from a metabolic intermediate Oxidative phosphorylation ADP binds with free inorganic phosphate to form ATP o It requires electron transport system Coupling Glucose Oxidation O O O Glucose can be used to produce and store energy to maintain all bodily processes Cells are able to synthesize ATP using energy derived from glucose oxidation because it occurs spontaneously Cells use the energy released in glucose oxidation to synthesize ATP Reactions must occur together 7 kcal is required to synthesize one mole of ATP oxidation of one mole of glucose releases enough to make 98 moles of ATP but only 38 moles of ATP are produced When an energyreleasing reaction is used to drive an energy requiring process the released energy cannot be used 100 ef ciently
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