AP Biology Enzymes and Proteins

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AP Biology Enzymes and Proteins
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2013-12-05 23:22:25
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Study cards for an Enzymes and Proteins test in AP Biology
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  1. Dehydration synthesis and synthesis are known as ______ because they form bonds between molecules.
    Anabolic reactions
  2. Hydrolysis and digestion are known as ____ reactions because they break bonds between molecules.
    catabolic reactions
  3. Reactions that release energy are called _____. They digest polymers. This is known as hydrolysis = catabolism
    Exergonic
  4. Reactions that require input of energy are called ____ reactions. These build polymers. Example is dehydration synthesis = anabolism
    Endergonic
  5. In this reaction, energy is released like in digestion, resulting in a lower energy level from reactant to product.
    Exergonic
  6. In this reaction, energy is invested like in synthesis, resulting in a higher energy level from reactant to product.
    Endergonic
  7. Organisms require energy to live. Where does the energy required for life come from?
    This energy is a result of coupling exergonic reactions (releasing energy) with endergonic reactions (needing energy).
  8. What prevents reactions, which are downhill, from happening spontaneously?
    Covalent bonds that keep everything stable.
  9. What initially is required to break down large, stable molecules?
    Activation Energy
  10. What is activation energy?
    The amount of energy needed to destabilize the bonds of a molecule that moves the reaction over an "energy hill"
  11. What are used to reduce the amount of energy to start a reaction?
    Catalysts
  12. What are catalysts?
    A tool that is used to reduce the amount of energy needed to start a reaction.
  13. What does a cell need to reduce activation energy?
    Enzymes
  14. What are the biological catalysts?
    Proteins and RNA
  15. How are proteins and RNA utilized in the cell?
    They facilitate chemical reactions, are required for most biological reactions, are highly specific, and control the reactions of life.
  16. How do Proteins and RNA facilitate chemical reactions?
    They increase rate of reaction without being consumed, reduce activation energy, and don't change free energy released or required.
  17. What is a reactant which binds to enzymes?
    Substrate. The enzyme-substrate complex is a temporary association.
  18. What is the end result of a reaction?
    Product
  19. What is an enzyme's catalytic site?
    Active site. The substrate fits into this.
  20. What are the properties of enzymes?
    Reaction specific, not consumed in a reaction, affected by cellular conditions.
  21. How are enzymes reaction specific?
    Each enzyme works with a specific substrate. There is a chemical fit of H bonds and ionic bonds between the active site and substrate.
  22. Explain how enzymes are not consumed in reactions?
    A single enzyme molecule can catalyze thousands or more reactions per second. The enzymes are unaffected by the reaction.
  23. How are enzymes affected by cellular conditions?
    Conditions like temperature, pH, and salinity can affect the structure of a protein.
  24. What is the lock and key model?
    It is a simplistic model of enzyme action. The substrate fits into 3-D structure of an enzyme active site. H bonds form between the substrate and enzyme. It fits like a key in a lock.
  25. What is the induced fit model?
    It is a more accurate model of enzyme action. 3D structure of enzyme fits a substrate. The substrate binding causes the enzyme to change shape, which leads to a conformational change. This brings chemical groups in position to catalyze.
  26. How does this work in synthesis and digestion?
    A variety of mechanisms lower activation energy and speed up the reaction. In synthesis, the active site orients substrates in correct position for the reaction. The enzyme brings the substrate closer together. In digestion, the active site binds substrate and puts stress on bonds that must be broken, making it easier to separate the molecules.
  27. What are the factors that affect enzyme function?
    Remember pISTASE. pH, Inhibitor, Salinity, Temperature, Activator, Substrate Concentration, Enzyme Concentration.
  28. How does enzyme concentration affect enzyme function?
    As the amount of enzymes goes up, so does the reaction rate. The more enzymes, the more frequently they collide with substrate. Eventually, the reaction rate levels off. The substrate becomes the limiting factor and not all enzyme molecules can find a substrate.
  29. How does substrate concentration affect enzyme function?
    As the substrate concentration goes up, so does the reaction rate. The more substrate, the more frequently they collide with an enzyme. Eventually the reaction rate levels off because all enzymes will have an active site engaged; the enzyme is saturated. It reaches the maximum rate of reaction.
  30. How does temperature affect enzyme function?
    There is an optimum temperature for enzymes to operate at. This is where there are the greatest number of molecular collisions. Heat increases energy level of molecules, which disrupts bonds in enzymes and between enzymes and substrate, since H and ionic bonds are weak. This results in denaturation (loss of 3D shape). Cold causes the molecules to move slower. This decreases collisions btw enzymes and substrates.
  31. How does pH affect enzyme function?
    Changes in pH adds or removes H+. This disrupts bonds, disrupts 3D shape (denatures protein). This disrupts attractions between charged amino acids. The optimal pH in human enzymes is 6-8. Depends on localized conditions. Pepsin requires a pH of 2-3. Trypsin requires a pH of 8.
  32. How does salinity affect enzyme function?
    Changes in salinity adds or removes cations (+) & anions (-). It disrupts bonds, disrupting 3D shape. It disrupts attractions btw charged amino acids. Denatures protein. Enzymes are intolerant of extreme salinity.
  33. How do activators help enzymes?
    Cofactors are nonprotein, small inorganic compounds and ions. Bound within enzyme molecule. ex. Fe in hemoglobin. Coenzymes are nonprotein, organic molecules. They temporarily or permanently bind to enzymes near the activate site. These are many vitamins. ex. Mg in chlorophyll.
  34. How do inhibitors regulate enzymes?
    They are molecules that reduce enzyme activity. 4 types: competitive inhibition, noncompetitive inhibition, irreversible inhibition, and feedback inhibition.
  35. In this, the inhibitor and substrate compete for the active site. Penicillin blocks enzyme bacteria use to build cell walls. Disulfiram (Antabuse) treats chronic alcoholism. This is overcome by increasing substrate concentration. This causes the substrate to outcompete the inhibitor for active site on enzyme.
    Competitive Inhibitor
  36. What is a noncompetitive inhibitor?
    The inhibitor binds to a site other than the active site. This causes the enzyme to change shape. causes a conformational change. The active site is no longer a functional binding site.
  37. What is irreversible inhibition?
    The inhibitor permanently binds to an enzyme. Can be a competitor. This permanently binds to the active site. Can also be allosteric. This permanently binds to allosteric site. This permanently changes the shape of an enzyme. ex. nerve gas.
  38. Whats allosteric regulation?
    conformational changes by regulator molecules. ex. inhibitors keep enzyme in an inactive form. Activators keep an enzyme in an active form.
  39. Explain metabolic pathways.
    Chemical reactions of life are organized in pathways. They divide chemical reactions into many small steps. It is the artifact of evolution. Increases efficiency and control/regulation.
  40. Explain the efficiency of enzymes.
    There are organized groups of enzymes. They link endergonic and exergonic reactions.
  41. What is feedback inhibition?
    the regulation and coordination of production. The product is used by the next step in a pathway. The final product is the inhibitor of the earlier step. The allosteric inhibitor of the earlier enzyme. this is feedback inhibition. This results in an unnecessary accumulation of a product.
  42. What is an example of feedback inhibition?
    The synthesis of isoleucine from theonine. Isoleucine becomes the allosteric inhibitor of the first step in the pathway. As the product accumulates it collides with enzyme more often than the substrate.
  43. What are proteins?
    The most structurally and functionally diverse group of biomolecules. It is used in almost everything.
  44. What are proteins used in?
    enzymes, structure (keratin, collagen), carriers & transport (membrane channels), receptors & binding (defense), contration (actin & myosin), signaling (hormones), and storage (bean seed proteins)
  45. What structures can proteins exist in?
    1. monomer = amino acids. 20 different amino acids. 2. polymer = polypeptide. A protein can be 1 or more polypeptide chains folded and bonded together. They are large and complex molecules. (3D shape)
  46. What makes up an amino acid?
    A central carbon, an amino group, a carboxyl group (acid), and an R group (side chain). The R group is different in each amino acid and has unique chemical properties.
  47. How do you build a protein?
    with peptide bonds formed by dehydration synthesis. This is the linking of NH2 of 1 amino acid to COOH of another. Forms a C-N bond.
  48. How are polypeptide chains formed?
    The N-terminal(NHend) combines with the C-terminal (COOH end) of another. The repeated sequence (N-C-C) is the polypeptide backbone. chains grow in 1 direction.
  49. Explain how function relates to structure in proteins?
    Function depends on structure. The 3D structure. Proteins twist, fold, and coil into a unique shape.
  50. What is the Primary (1o) Structure?
    The order of amino acids in chain. the amino acid sequence is determined by DNA. a slight change in amino acid sequence can affect a protein's structure & it's function. Even 1 amino acid can make the difference.
  51. What is the Secondary (2o) Structure?
    contains "local folding". This is folding along short sections of polypeptide. There is an interaction btw adjacent amino acids. H bonds form btw R groups. form alpha helixes and beta pleated sheet.
  52. What is the Teriary (3o) structure?
    "Whole molecule folding". This is determined by interactions btw R groups. These are hydrophobic interactions. They are anchored by disulfide bridges (H & ionic bonds)
  53. What is the Quaternary (4o) structure?
    This joins together more than 1 polypeptide chain. Then it becomes a functional protein. The collagen is similar to skin and tendons.
  54. Review the protein structure
    • 1- aa sequence peptide bonds. determined by DNA
    • 2o - R groups & H bonds
    • 3o - hydrophobic interactions, disulfide bridges.
    • 4o - multiple polypeptides, hydrophobic interactions.
  55. What are chaperonin proteins?
    They guide protein folding. They provide shelter for folding polypeptides. They keep the new protein segregated from cytoplasmic influences.
  56. How are protein models viewed?
    X-ray crystallography, extrapolating from amino acid sequence, computer modelling
  57. What is denaturing a protein?
    This disruptions the 3o structure. Caused by pH, salt, temperature. This unravels or denatures a protein. Disrupts h bonds, ionic bonds, and disulfide bridges. Some proteins can return to their functional shape after denaturation, most cannot.

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