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What are Enzymes?
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Protein Catalysts that can slow the rate of a reaction
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Protein Catalysts that can accelerate the rate of a reaction
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Tightly bound coenzymes
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A reaction such as the addition of a molecule of water to carbon dioxide requires an enzyme, carbonic anhydrase, in red blood cells. What are some functions of this enzyme?
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Operates in animal cells, plants cells, and in the environment to stabilize carbon dioxide concentrations
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The conversion from carbon dioxide to bicarbonate, would be extremely fast without this enzyme
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The conversion from carbon dioxide to bicarbonate, would be extremely slow, without this enzyme
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Carbonic anhydrase adjusts the acidity of the chemical environment to prevent damage to the body
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Reactants in enzyme-catalyzed reactions are called [blank_start]substrates[blank_end]
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substrates
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apoenzyme
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coenzyme
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What enzyme catalyzes the hydrolysis of peptide bonds and ester bonds?
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Proteolytic Enzymes
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Lytic Enzymes
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Carbonic anhydrase
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Enzymes can display a high degree of specificity
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- True
- False
Frage 6
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Specificity of enzymes is due to the precise interaction of the enzyme and its cofactor
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- True
- False
Frage 7
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What are functions of Trypsin ?
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Protein digesting enzyme
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Present in pancreatic juices secreted into your small intestine during a meal
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Pancreas secretes trypsin as an inactive proenzyme called trypsinogen
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Helps break down food protiens
Frage 8
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Proteolytic enzymes trypsin and papain have different degrees of specificity
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- True
- False
Frage 9
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Enzymes do not require cofactors for activity
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- True
- False
Frage 10
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Cofactors are
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Large molecules that some enzymes require for activity
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Small molecules that some enzymes require for activity
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The two main classes of cofactors are
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Coenzymes and metals
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Coenzymes and acids
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Metals and acids
Frage 12
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Tightly bound coenzymes are called
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Apoenzyme
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bioenzyme
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prosthetic groups
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Substrates
Frage 13
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An enzyme with its cofactor is an apoenzyme, without the cofactor, the enzyme is called an holoenzyme
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- True
- False
Frage 14
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Specific Enzymes play key roles in the conversion of light energy and carbon oxidation energy into ATP
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- True
- False
Frage 15
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Using ATP, enzymes can generate
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Red blood cells
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Chemical gradients
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Electrical gradients
Frage 16
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The free- energy change provides information about the spontaneity but not the rate of reaction
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- True
- False
Frage 17
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Exogeneric reactions are
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A reaction that will occur without the input of energy, or spontaneously, lf delta G is negative
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A reaction that will occur without the input of energy, or spontaneously, if delta G is positive
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A reaction that will occur with the input of energy, or nonspontaneous, if delta G is positive
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A reaction that will occur without the input of energy, or nonspontaneous, if delta G is positive
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Exergonic reactions refers to
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a reaction where energy is taken up
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a reaction where energy is released
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Delta G is negative
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Delta G is positive
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Do require energy to proceed occur nonspontaneously
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Do not require energy to proceed, occur spontaneously
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Endergonic reaction refers to
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Energy being absorbed
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Energy being released
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Delta G is positive
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Delta G is negative
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Nonspontaneous reaction
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Spontaneous reaction
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The delta G reaction depends only on the free energy difference between reactants and products and is independent of how the reaction occurs
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- True
- False
Frage 21
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The delta G, of a reaction provides information about the rate of the reaction
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- True
- False
Frage 22
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Enzymes alter only the reaction rate and not the reaction equilibrium
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- True
- False
Frage 23
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The energy required to form the transition state from the substrate is called the
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Activation energy
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Catalyst
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Endergonic
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Exergonic
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A chemical reaction proceeds through a [blank_start]transition state[blank_end], a molecular form that is no longer substrate but not yet product
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transition state
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What is the first step in the enzymatic catalysis process?
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The formation of an enzyme substrate complex
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The formation of an enzyme product complex
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The formation of an enzyme reactant complex
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Enzymes bring substrates together to form an [blank_start]enzyme-substrate[blank_end] complex on a particular region of the enzyme called the [blank_start]active site[blank_end]
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enzyme-substrate
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enzyme-product
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active site
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transition site
Frage 27
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Enzymes function by lowering the activation site
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- True
- False
Frage 28
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The interaction between enzyme and substrate was established by
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The observation that a fixed amount of enzyme displays a maximal velocity
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The observation that a fixed amount of enzyme displays a minimal velocity
Frage 29
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The maximal rate of catalysis, Vmax occurs when all of the enzyme is bound to substrate
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- True
- False
Frage 30
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Active sites of enzymes have common features such as
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Active site is a 3 dimensional cleft or crevice created by amino acids from different parts of the primary structure
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Active sites constitutes a small portion of the enzyme volume
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The interaction of the enzyme and substrate at the active sites involves multiple strong interactions
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Enzyme specificity depends on molecular architecture at the active site
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Active sites create unique microenvironments
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The enzyme changes shape upon substrate binding, a phenomenon called [blank_start]induced fit[blank_end]
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induced fit
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Binding energy is
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Free energy released upon interaction of enzyme and substrate
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greatest when the enzyme interacts with the transition state
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Free energy released upon interaction of enzyme and product
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greatest when the enzyme interacts with the active state
Frage 33
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Enzymes do not interact with their substrates like a lock and key
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- True
- False
Frage 34
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The Michaelis constant equal to the substrate concentration at which reaction rate is half its maximal value
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- True
- False
Frage 35
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[blank_start]Alcohol[blank_end] dehydrogenase converts [blank_start]ethanol[blank_end] into [blank_start]acetaldehyde[blank_end]
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Alcohol
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Aldehyde
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ethanol
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acetaldehyde
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acetaldehyde
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acetate
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[blank_start]Aldehyde[blank_end] dehydrogenase converts [blank_start]acetaldehyde[blank_end] to [blank_start]acetate[blank_end]
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Aldehyde
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Alcohol
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acetaldehyde
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ethanol
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acetate
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acetaldehyde
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What two enzymes play a key role in the metabolism of alcohol
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Alcohol dehydrogenase and Aldehyde dehydrogenase
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Alcohol dehydrogenase and Acetaldehyde dehydrogenase
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Aldehyde dehydrogenase and Acetaldehyde dehydrogenase
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What are the two different acetaldehyde dehydrogenase in most people ?
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Low km in mitochondria
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High km in cytoplasm
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Low km in cytoplasm
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High km in mitochondria
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Kcat, is the turnover number of the enzyme,
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which is the number of substrate molecules converted into product per second
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which is the number of reactant molecules converted into product per second
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Irreversible enzyme inhibitors bind
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covalently or noncovalently to the enzyme, but with a negligible dissociation constant
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covalently to the enzyme, but with a negligible dissociation constant
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noncovalently to the enzyme, but with a negligible dissociation constant
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Reversible inhibition is characterized
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by slow dissociation of the enzyme inhibitor complex
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by rapid dissociation of the enzyme inhibitor complex
Frage 42
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Name three common types of reversible inhibition
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Competitive inhibition
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Uncompetitive inhibition
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Noncompetitive inhibition
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None of the above
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Competitive inhibition
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The inhibitor is structurally similar to the substrate and can bind to the active site, preventing the actual substrate from binding
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The inhibitor binds only to the enzyme substrate complex in what is essentially substrate dependent inhibition
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The inhibitor binds either the enzyme or enzyme substrate complex
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Uncompetitive inhibition is essentially substrate dependent inhibition
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- True
- False
Frage 45
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Noncompetitive inhibition
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Binds either the enzyme or enzyme substrate complex
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Substrate dependent inhibition
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Prevents the actual substrate from binding
Frage 46
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Penicillin
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is an antibiotic that consist of a thiazolidine ring fused to a reactive β-lactam ring
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inhibits the formation of cell walls in certain bacteria such as S. aureus.
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binds to the transpeptidase because it resembles the substrate.
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participates in its own inhibition, penicillin is a suicide inhibitor
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The cell wall of S. aureus is constructed from the molecule peptidoglycan, which is a linear polysaccharide chain cross-linked by short peptides.
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- True
- False
Frage 48
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What catalyzes the peptide cross links
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peptidoglycan
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Glycopeptide transpeptidase
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Penicillin
Frage 49
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The transpeptidase reaction proceeds through an acyl-enzyme terminator.
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- True
- False
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When penicillin binds to the transpeptidase,
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a serine residue at the active site attacks the carbonyl carbon of the lactam ring as if penicillin were a substrate.
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a serine residue at the active site attacks the carbonyl carbon of the lactam ring as if penicillin were a product
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Penicilloyl-serine derivative is inactive and very unstable
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- True
- False
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