Carbohydrates PDF

Carbohydrates AP Biology  CH2OH H O H H OH H HO OH H OH Ca...

Carbohydrates AP Biology  CH2OH H O H H OH H HO OH H OH Carbohydrates energy molecules AP Biology 2010-2011  Carbohydrates ▪ Carbohydrates are composed of C, H, O carbo - hydr - ate CH2O (CH2O)x C6H12O6 ▪ Function: (CH2O)x C6H12O6 ◆ fast energy ◆energy storage ◆ raw materials ◆ structural materials ▪ Monomer: sugars ▪ ex: sugars, starches, cellulose sugar sugar sugar sugar sugar sugar sugar sugar AP Biology  Sugars ▪ Most names for sugars end in -ose ▪ Classified by number of carbons ◆ 6C = hexose (glucose) ◆ 5C = pentose (ribose) ◆ 3C = triose (glyceraldehyde) H O CH2OH CH2OH C H O O H H C OH H H OH 6H H 5 HO 3OH HO OH HO H H C H OH OH H H AP Biology Glucose Ribose Glyceraldehyde  Functional groups determine function carbonyl aldehyde carbonyl ketone AP Biology  Sugar structure 5C & 6C sugars form rings in solution Where do you find solutions in biology? In cells! AP Biology Carbons are numbered  Numbered carbons These will become important! C 6' 5' C O 4' C C1' energy stored in C-C bonds harvested in cellular respiration C3' C2' AP Biology  CH2OH Simple & complex sugars H O H H ▪ Monosaccharides HO OH H OH ◆ simple 1 monomer sugars H OH ◆ glucose Glucose ▪ Disaccharides ◆ 2 monomers ◆ sucrose ▪ Polysaccharides ◆ large polymers ◆ starch AP Biology  Building sugars ▪ Dehydration synthesis monosaccharides disaccharide H2O | | | glucose glucose maltose glycosidic linkage AP Biology  Building sugars ▪ Dehydration synthesis monosaccharides disaccharide H2O | | | glucose fructose sucrose (table sugar) AP Biology  Polysaccharides ▪ Polymers of sugars ◆ costs little energy to build ◆ easily reversible = release energy ▪ Function: ◆ energy storage ▪ starch (plants) ▪ glycogen (animals)  in liver & muscles ◆ structure ▪ cellulose (plants) ▪ chitin (arthropods & fungi) AP Biology  Linear vs. branched polysaccharides slow release starch (plant) What does energy branching do? storage glycogen (animal) Faster digestion! fast AP Biology release  Polysaccharide diversity ▪ Molecular structure determines function in starch in cellulose ◆ isomers of glucose ◆ structure determines function… AP Biology  Digesting starch vs. cellulose starch easy to digest enzyme cellulose hard to digest enzyme AP Biology only bacteria can digest  Cellulose ▪ Most abundant organic compound on Earth ◆ herbivores have evolved a mechanism to digest cellulose ◆ most carnivores have not ▪ that’s why they eat meat to get their energy & nutrients ▪ cellulose = undigestible roughage But it tastes like hay! Who can live AP Biology on this stuff?!  Cow can digest cellulose well; no need to eat other sugars Gorilla can’t digest cellulose well; must add another sugar source, like fruit to diet Regents Biology  Helpful bacteria ▪ How can herbivores digest cellulose so well? ◆ BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals Caprophage Tell Ime about eat the rabbits, Ruminants Regents Biology WHAT! again, George!  EAT Let’s build X some Carbohydrates! Regents Biology 2010-2011  Nutrients and Carbohydrates A nutrient is any substance that has a useful function when consumed and absorbed into cells.  The 3 macronutrients are: 1. Carbohydrates 2. Lipids 3. Proteins The 3 micronutrients 1. vitamins 2. minerals 3. water  Carbohydrates Function: Carbohydrate molecules are the main energy source for an organism. Food Sources: pasta, rice, sugars, potatoes Chemical Structure of glucose is C6H12O6 - hydrogen: carbon: oxygen in the ratio 1:2:1 There are two main types of carbohydrates, sugars and starches. At least 40% of a healthy diet should be complex carbohydrates or starches and simple carbohydrates like sugar should be avoided. Carbohydrates - Monosaccharides Sugars or simple carbohydrates taste sweet. The most important is the monosaccharide glucose as well as fructose and galactose. Sugar names end in “ose” The basic chemical structure is a ring of 6 carbons shown as: LE 5-4 Glucose dissolved in water is found almost always in a ring form, but dry glucose can have a linear structure. a Glucose Linear and b Glucose Abbreviated ring ring forms structure a and b glucose ring structures  Carbohydrates - Disaccharides Joining two monosaccharides forms a disaccharide. Still taste sweet like sucrose and maltose. The basic chemical structure is two 6 carbon rings joined together in a condensation reaction. The bond between 2 monosaccharides is a glycosidic bond.  LE 5-5 Dehydration reaction in the 1–4 synthesis of maltose glycosidic linkage Glucose Glucose Maltose Dehydration reaction in the 1–2 synthesis of sucrose glycosidic linkage Glucose Fructose Sucrose Remember: A glycosidic linkage is a specific type of ether linkage. LE 5-8 Cellulose microfibrils in a plant cell wall Cell walls Microfibril 0.5 µm Plant cells Cellulose molecules b Glucose monomer  Carbohydrates - Polysaccharides Two important polysaccharides are starch and cellulose. Starches taste dry not sweet. Starches are formed by joining many monosaccharides together to form a polysaccharide. LE 5-7b There are two types of glycosidic bonds, alpha or beta bonds. In an alpha glycosidic bond the –OH group on the second carbon is on the opposite side of the ring than the carbon 6 –CH2OH group. This is starch. Starch: 1–4 linkage of a glucose monomers. LE 5-7c In cellulose or plant fibre, every second glucose is flipped over and a beta glycosidic bond is formed. Cellulose: 1–4 linkage of b glucose monomers. Lipids  Lipids have three main functions: 1. Long term energy storage, each gram of fat sources twice as much energy as a gram of carbohydrates 2. Protects and cushions organs 3. Dissolves fat soluble substances Foods that contain lipids are fats and oils. There are three main types of lipids: 1. Triglycerides 2. Phospholipids 3. Steroids  1. Triglycerides or Fats These molecules are formed by dehydration synthesis between the monomers, a glycerol and 3 long chain fatty acids. The hydroxyl group of the glycerol reacts with the carboxyl group of the fatty acid. An ester link is formed by this dehydration synthesis and a water is released.  Saturation of Triglycerides Saturated fats have only single bonds. Saturated fats come from animal sources and are solid at room temperature. Unsaturated fats have some double or triple bonds. Unsaturated fats come from plant sources and are liquid at room temperatures. We call them oils and they are healthier. Unsaturated fats take more space because the fatty acids do not pack together.  2. Phospholipids Formed by the bonding of the monomers; a glycerol, two fatty acids and a phosphate functional group. The long chain fatty acids are hydrophobic and reject water. The phosphate is hydrophilic and aligns with water. Phospholipids are the major structural component of cell membranes. Cell Membranes are made of two layers of phospholipid molecules. The phosphate group, faces outward from the cell membrane. The two fatty acids, which repel water, face inwards towards the other fatty acids.  3. Steroids They are all formed from 4 fused rings. Different functional groups attached to the rings change the molecules from cholesterol, testosterone, estrogen and progesterone.  Cholesterol Testosterone Cholesterol Nucleic Acids SBI 4U1  Nucleic Acids Nucleic acids are molecules that store information for cellular growth and reproduction There are two types of nucleic acids: - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) These are polymers consisting of long chains of monomers called nucleotides A nucleotide consists of a nitrogen base, a pentose sugar and a phosphate group:  Nitrogen Bases The nitrogen bases in nucleotides consist of two general types: - Purines: adenine (A) and guanine (G) - Pyrimidines: cytosine (C), thymine (T) and Uracil (U)  Pentose Sugars There are two related pentose sugars: - ribose (found in RNA) - deoxyribose (found in DNA) Names of Nucleotides  AMP, ADP and ATP adenosine 5’-triphosphate, ATP, is the major energy source for cellular activity  Primary Structure of Nucleic Acids The nucleotides in nucleic acids are joined by phosphodiester bonds A polymer of nucleotides is called a “strand” The 3’-OH group of the sugar in one nucleotide forms an ester bond to the phosphate group on the 5’-carbon of the sugar of the next nucleotide  Example of DNA Primary Structure In DNA, A, C, G, and T are linked by 3’-5’ ester bonds between deoxyribose and phosphate  Example of RNA Primary Structure In RNA, A, C, G, and U are linked by 3’-5’ ester bonds between ribose and phosphate  Secondary Structure: DNA Double Helix In DNA there are two strands of nucleotides that wind together in a double helix - the strands run in opposite directions - the bases are arranged in step-like pairs - the base pairs are held together by hydrogen bonding The pairing of the bases from the two strands is very specific The complimentary base pairs are A-T and G-C - two hydrogen bonds form between A and T - three hydrogen bonds form between G and C Each pair consists of a purine and a pyrimidine, so they are the same width, keeping the two strands at equal distances from each other Base Pairing in the DNA Double Helix  Ribonucleic Acid (RNA) RNA is much more abundant than DNA There are several important differences between RNA and DNA: - the pentose sugar in RNA is ribose, in DNA it’s deoxyribose - in RNA, uracil replaces the base thymine (U pairs with A) - RNA is single stranded while DNA is double stranded - RNA molecules are much smaller than DNA molecules Proteins  Functions of Proteins Most structurally & functionally diverse group of biological macromolecules Function: – Involved in almost everything – Enzymes – structure (keratin, collagen) – carriers & transport (membrane channels) – receptors & binding (defense) – contraction (actin & myosin) – signaling (hormones) – storage (bean seed proteins)  Amino Acids The Building Blocks of Proteins Amino Acids = Monomer Also used as single molecules in biochemical pathways 20 standard amino acids (amino acids) – 8 essential and 12 non-essential Two functional groups: – Carboxyl group – Amino group Have different side groups (R) – Dictates properties of amino acids When dissolved in water the carboxyl group donates a H+ ion to the amino group.  Classification of Amino Acids They are classified by structure of R group they posses – Nonpolar (hydrophobic) – Polar (hydrophilic) – Acidic – Basic Nonpolar Hydrophobic Amino Acids Polar Hydrophilic Amino Acids  Acidic and Basic Amino Acids Acidic Basic – R group = carboxylic acid – R group = amine – Donates H+ – Accepts H+ – Negatively charged – Positively charged  Building Proteins Polymer of AAs called a polypeptide Peptide bonds: dehydration synthesis – Linkage between the amino group and the carboxyl group.  Chemistry of Protein Structure Primary Assembly STRUCTURE PROCESS Secondary Folding Tertiary Packing Quaternary Interaction  Primary (1°) Structure Unique sequence of amino acids in a polypeptide chain Each amino acid referred to as a “residue” Determined by DNA A change in amino acid sequence can affect the protein’s structure and it’s function  Secondary (2°) Structure Coiling & Folding at various locations on the polypeptide Result of H bonds Interactions between adjacent amino acids – α-helix – β-pleated sheet  Tertiary (3°) Structure Hydrophobic & Hydrophilic interactions Van der Waals interactions H bonds Ionic bonds Disulfide bridges  Quaternary (4°) Structure Two or more polypeptide chains forming a functional protein Protein Structure Review  Denaturing Proteins Disrupt 3° structure: – Addition of salt, Change of pH or temperature Results in disruption of H bonds, ionic bonds and disulfide bridges Some proteins can return to their functional shape after denaturation, many cannot  Chaperone Proteins Guide protein folding Provides shelter for folding polypeptides Protects new protein from cytoplasmic influences  The Chemistry of Life AP Biology 2009-2010  Why are we studying chemistry? Chemistry is the foundation of Biology AP Biology  The World of Elements H C N O Na Mg P S K Ca AP Biology  Elements & their valence shells Elements in the same column have the same valence & similar chemical properties Remember some food chains are built on reducing O to H2O & some on reducing S to H2S AP Biology  Chemical reactivity ▪ Atoms tend to ◆ complete a partially filled valence shell or ◆ empty a partially filled valence shell This tendency drives chemical reactions… and creates bonds – – – AP Biology  Hydrogen bond Bonds in Biology H2O ▪ Weak bonds ◆ hydrogen bonds ▪ attraction between + and – H2O ◆ hydrophobic & hydrophilic interactions ▪ interactions with H2O Covalent bond ◆ van derWaals forces – ◆ ionic ▪ Strong bonds – ◆ covalent bonds AP Biology ▪ sharing electrons H2 (hydrogen gas)  Nonpolar covalent bond ▪ Pair of electrons shared equally by 2 atoms ◆ example: hydrocarbons = CxHx ▪ methane (CH4 ) Lots of energy stored… & released balanced, stable, AP Biology good building block  Polar covalent bonds ▪ Pair of electrons shared unequally by 2 atoms ◆ example: water = H2O ▪ oxygen has stronger “attraction” for the + – electrons than hydrogen H – ▪ oxygen has higher electronegativity ▪ water is a polar molecule Oxygen  + vs – poles  leads to many interesting – properties of water… H + – AP Biology  Hydrogen bonding ▪ Polar water creates H bonds molecular attractions ◆ attraction between positive H in one H2O molecule to negative O in another H2O H ◆ also can occur wherever H O an -OH exists in a larger molecule ▪ Weak bond ◆ but common in biology AP Biology  Chemistry of Life Properties of Water AP Biology 2010-2011  More about Water Why are we studying water? All life occurs in water ◆ inside & outside the cell AP Biology  Chemistry of water ▪ H2O molecules form H-bonds with each other ◆ +H attracted to –O ◆ creates a sticky molecule AP Biology  Elixir of Life ▪ Special properties of water 1. cohesion & adhesion ▪ surface tension, capillary action 2. good solvent ▪ many molecules dissolve in H2O ▪ hydrophilic vs. hydrophobic Ice! 3. lower density as a solid I could use ▪ ice floats! more ice! 4. high specific heat ▪ water stores heat 5. high heat of vaporization AP Biology ▪ heats & cools slowly  1. Cohesion & Adhesion ▪ Cohesion ◆ H bonding between H2O molecules ◆ water is “sticky” ▪ surface tension ▪ drinking straw Try that with flour… ▪ Adhesion or sugar… ◆ H bonding between H2O & other substances ▪ capillary action ▪ meniscus ▪ water climbs up paper towel or cloth AP Biology  How does H2O get to top of trees? Transpiration is built on cohesion & adhesion AP Biology  2. Water is the solvent of life ▪ Polarity makes H2O a good solvent ◆ polar H2O molecules surround + & – ions ◆ solvents dissolve solutes creating solutions AP Biology  What dissolves in water? ▪ Hydrophilic ◆ substances have attraction to H2O ◆ polar or non-polar? AP Biology  What doesn’t dissolve in water? ▪ Hydrophobic ◆ substances that don’t have an attraction to H2O Oh, look hydrocarbons! ◆ polar or non-polar? AP Biology fat (triglycerol)  3. The special case of ice ▪ Most (all?) substances are more dense when they are solid, but not water… ▪ Ice floats! ◆ H bonds form a crystal Ice! I could use more ice! And this has made all the difference! AP Biology  Why is “ice floats” important? ▪ Oceans & lakes don’t freeze solid ◆ surface ice insulates water below ▪ allowing life to survive the winter ◆ if ice sank… ▪ ponds, lakes & even oceans would freeze solid ▪ in summer, only upper few inches would thaw ◆ seasonal turnover of lakes ▪ sinking cold H2O cycles nutrients in autumn AP Biology  4. Specific heat ▪ H2O resists changes in temperature ◆ high specific heat ◆ takes a lot to heat it up ◆ takes a lot to cool it down ▪ H2O moderates temperatures on Earth Specific heat AP & Biology climate  Evaporative cooling 5. Heat of vaporization Organisms rely on heat of vaporization to remove body heat AP Biology  Ionization of water & pH ▪ Water ionizes ◆ H+ splits off from H2O, leaving OH– ▪ if [H+] = [-OH], water is neutral ▪ if [H+] > [-OH], water is acidic ▪ if [H+] < [-OH], water is basic ▪ pH scale ◆ how acid or basic solution is ◆ 1 → 7 → 14 AP Biology H2O → H+ + OH–  H+ Ion Examples of Solutions Concentration pH 100 pH Scale 10–1 0 1 Hydrochloric acid 10–2 2 Stomach acid, Lemon juice tenfold change 10–3 3 Vinegar, cola, beer in H+ ions 10–4 4 Tomatoes pH1 → pH2 10–5 5 Black coffee, Rainwater 10-1 → 10-2 10–6 6 Urine, Saliva 10 times less H+ 10–7 7 Pure water, Blood Seawater pH8 → pH7 10–8 8 10-8 → 10-7 10–9 9 Baking soda 10 times more H+ 10–10 10 Great Salt Lake 10–11 11 Household ammonia pH10 → pH8 10–12 12 10-10 → 10-8 Household bleach 100 times more H+ 10–13 13 Oven cleaner 10–14 14 Sodium hydroxide AP Biology  Buffers & cellular regulation ▪ pH of cells must be kept ~7 ◆ pH affects shape of molecules ◆ shape of molecules affect function ◆ therefore pH affects cellular function ▪ Control pH by buffers 9 8 ◆ reservoir of H+ 7 ▪ donate H+ when [H+] falls 6 Buffering 5 pH range ▪ absorb H+ when [H+] rises 4 3 2 1 0 AP Biology 0 1 2 3 4 5 Amount of base added  He’s gonna earn a Darwin Award! Any Questions? Do one brave thing today…then run like hell! AP Biology 2009-2010  Ice Fishing in Barrow, Alaska Regents Biology  Enzymes and biochemical Reactions Metabolism is all the chemical reactions that occur in a cell to keep an organism alive. Cells are challenged to make chemical reactions go quickly. The best way to speed up a reaction is to increase the temperature. But cells will die if they get heated. Instead, cells use enzymes to lower the energy required for a reaction to occur.  Laws of Thermodynamics First Law of Thermodynamics Energy can not be created or destroyed but can only be changed from one form to another. Cells for example, change chemical bond energy to kinetic or motion energy like in a muscle cell. Second Law of Thermodynamics When energy is changed from one form to another, some useful energy is always “lost” as heat. This is also a challenge for cells as they cannot be overheated. Biochemical reactions in cells must be as efficient as possible so the least amount of heat is lost.  Energy and Chemical Reactions The two main types of reactions are: 1. Exothermic or exergonic reactions release energy from bonds the product molecules are smaller than the reactant molecules For example, cellular respiration: Glucose + oxygen → carbon dioxide + water + energy (useful and heat energy) LE 8-6a Reactants Amount of energy Free energy released (G < 0) Energy Products Progress of the reaction Exergonic reaction: energy released  2. Endothermic or endergonic reactions - energy is stored in the bonds of molecules - the product molecules are larger than the reactant molecules For example, photosynthesis: carbon dioxide + water + sunlight →glucose + oxygen LE 8-6b Products Amount of energy Free energy required (G > 0) Energy Reactants Progress of the reaction Endergonic reaction: energy required  Free Energy The energy available for chemical reactions is called free energy. The symbol is G. The hydrolysis of table sugar (sucrose) to glucose and fructose is exergonic so the free energy is negative. G = −29 kJ/mol Forming sucrose is endergonic with G = +29 kJ/mol Enzymes Enzymes are special proteins that speed up or catalyse a reaction. Enzymes are biological catalysts. Enzymes are not permanently changed by the reaction. All enzyme names end in “ase”. Enzymes can be reused and reused. Enzymes have specific shapes and work only for one exact reaction or step in a biochemical pathway of many steps. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 8-13 Sucrose Glucose Fructose C12H22O11 C6H12O6 C6H12O6 How Do Enzymes Work? Enzymes work by lowering the energy of activation. Every chemical reaction between molecules involves bond breaking and bond forming. The initial energy needed to start a chemical reaction is called the free energy of activation, or activation energy (EA). Activation energy is often supplied in the form of heat from the surroundings. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 8-14 A B C D Transition state A B EA Free energy C D Reactants A B G < O C D Products Progress of the reaction LE 8-15 Course of reaction without EA enzyme without enzyme EA with enzyme is lower Free energy Reactants Course of G is unaffected reaction by enzyme with enzyme Products Progress of the reaction Induced Fit Model of Enzyme Action The reactant that an enzyme acts on is called the enzyme’s substrate. The enzyme binds to its substrate, forming an enzyme-substrate complex. The active site is the region on the enzyme where the substrate binds. Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How do active sites work? The active site involves a small number of key functional groups that actually bind the substrates. The rest of the protein structure is needed to maintain these functional groups in position. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 8-16 Substrate Active site Enzyme Enzyme-substrate complex How does an enzyme lower activation energy? In an enzymatic reaction, the substrate binds to the active site. The active site can lower an EA barrier by: 1. Orienting substrates correctly 2. Straining substrate bonds 3. Providing a favorable microenvironment 4. Covalently bonding to the substrate Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Substrates enter active site; enzyme changes shape so its active site Substrates held in Holds the substrates (induced fit). active site by weak interactions, such as hydrogen bonds and ionic bonds. Quick Active site acts on substrates Substrates Review of Enzyme-substrate complex Induced Fit Model Active site is available of for two new substrate molecules. Enzyme Enzyme Action Products are Substrates are released. converted into products. Products Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  HOMEWORK Read p 36 – 44 Do p 40 # 2-5, 7,8 Do p 54 # 1-7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Factors Influencing Enzyme Action Substrate Substrate Active site Active site Enzyme Enzyme-substrate Enzyme Enzyme-substrate complex complex  Enzyme reactions enzyme + enzyme- enzyme + substrate substrate products complex  Factors that affect enzyme rates of reaction An enzyme’s rate of reaction is measured by the amount of substrate converted to a product per minute. An enzyme’s activity can be affected by: 1. General environmental factors, such as temperature and pH. 2. Cofactors and coenzymes. 3. Enzyme and substrate concentration which affects the saturation of the active site. 4. Inhibitors.  Optimal temperature for Optimal temperature for typical human enzyme enzyme of thermophilic What is the (heat-tolerant bacteria) effect of temperature on enzyme 0 20 40 60 80 100 Temperature (°C) function? Optimal temperature for two enzymes Optimal pH for pepsin Optimal pH What is the (stomach enzyme) for trypsin (intestinal enzyme) effect of pH on enzyme function? 0 1 2 3 4 5 6 7 8 9 10 pH Optimal pH for two enzymes  1. Environmental Factors Each enzyme has an optimal temperature in which it can function. Each enzyme has an optimal pH in which it can function. The wrong temperature of pH can denature an enzyme, which means the enzyme proteins shape is destroyed.  2. Cofactors and Coenzymes Cofactors are nonprotein inorganic enzyme helpers. – For example, metal ions like iron in hemoglobin hold oxygen. Coenzymes are organic cofactors. – For example, vitamins like niacin which serves as an electron acceptor.  Example of Cofactor Enzyme Activation: Binding of one oxygen to hemoglobin activates other sites to enhance oxygen binding at the three other sites.  3a. Enzyme Concentration What does the graph tell us Rate of Reaction about the effect of increasing [enzyme]? Increasing the [enzyme] means the rate of Enzyme Concentration reaction keeps increasing.  3b. Substrate Concentration What does the graph show us about [substrate]? Increasing [substrate] only increases the reaction rate until all the enzyme active sites are in use.  4. Enzyme Inhibitors Competitive inhibitors bind to the active site of an enzyme, competing with the substrate. Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective. Noncompetitive inhibition is also called allosteric regulation.  LE 8-19 Substrate A substrate can normally bind to the Active site active site of an enzyme. Enzyme Normal binding A competitive Inhibitor mimics the substrate, Competitive inhibitor competing for the active site. Competitive inhibition A noncompetitive inhibitor binds to the enzyme away from the active site, altering the shape of the enzyme so that its active site no longer functions. Noncompetitive inhibitor Noncompetitive inhibition  AZT and AIDS AZT is the first retroviral drug approved to fight the HIV virus. It is a competitive inhibitor for the enzyme reverse transcriptase.  Allosteric Regulation of Enzymes Allosteric regulation is the term used to describe cases where an enzyme’s function is affected by the binding of a regulatory molecule at a different site than the active site. Allosteric regulation may either inhibit or stimulate an enzyme’s activity. Usually the end product of a long series of reactions that make a metabolic pathway inhibits an enzyme near the beginning of the pathway. This way when the [product] is high the chemical reactions leading to the product are slowed down. Allosteric Regulation  Homework Read MHR p 41 – 50 Do p 54 # 1 – 11, 13 Adapt and redraw the diagram on p43 to illustrate an anabolic reaction instead of a catabolic reaction. Note: anabolic = synthesis catabolic = hydrolysis or breakdown Feedback Inhibition Initial substrate (threonine) Active site available Threonine in active site Enzyme 1 (threonine Isoleucine deaminase) used up by cell Intermediate A Feedback inhibition Enzyme 2 Active site of enzyme 1 can’t bind Intermediate B theonine pathway off Enzyme 3 Intermediate C Isoleucine binds to Enzyme 4 allosteric site Intermediate D Enzyme 5 End product (isoleucine)  Substrates enter active site; enzyme changes shape so its active site Substrates held in Holds the substrates (induced fit). active site by weak Quick interactions, such as hydrogen bonds and ionic bonds. Review of Active site acts on Induced Fit Substrates Enzyme-substrate substrates complex Model of Enzyme Active Action site is available for two new substrate molecules. Enzyme Products are Substrates are released. converted into products. Products