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Why are enzymes needed in biological reactions?
Uncatalyzied reactions want take place fast enough for survival
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Why does an enzyme catalyze a reaction of only certain substrates?
This combination of an enzyme and a substrate provides an alternative pathway for the reaction witha lower activation energy
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Why does the enzyme catalyzed hydrolysis of sucrose go faster than the hydrolysis of sucrose in the chemistry lab?
When a molecule of sucrose binds to the active site of sucrase, its glycosidic bond is in a position favorable for reaction
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How does the induced-fit model differ from the lock-and-key model?
In the lock-and-key model, a substrate fits the shape of the active site and forms and enzyme-substate complex. In the induced-fit model, a flexible active site and substrate adjust shape to provide the best fit for the reaction.
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Why is 37oC the optimum temperature for many enzymes?
This is body temp
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Why does the digestive enzyme pepsin have an optimum pH of 2?
Its most active when stomach acid is most active; i.e. after eating/ during digestion
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What happens to the rate of reaction when substrate saturates that enzyme?
Increasing the substrate concentration increases the rate of reaction until the enzyme molecules are saturated with substrate
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Does an increase in substrate concentration reverse the inhibition by a competitive inhibitor?
Yes, adding more substrate displaces the competitive inhibitor, which increases the rate of the reaction.
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Does an increase in the substrate concentration reverse the inhibition by a noncompetitive inhibitor?
Because a noncompetitive inhibitor isn't competing for the active site, the addtion of more substrate doesn't reverse this type of inhibition.
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Do the intermediate enzymes in a reaction sequence have regulatory sites?
no
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When would the Zn2+ be utilized as a cofactor by other enzymes?
With the substrate in the active site, the Zn2+ helps to stablize the negative charge on the oxygen atom of the carbonyl group and promotes the hydrolysis of the peptide bond
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What is the function of water-soluble vitamins in enzymes?
they are required by many enzymes as cofactors to carry out certain aspects of catalytic action
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What happens to any excess vitamin C that is consumed over the course of a day?
its eliminated in the urine each day
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Why is vitamin A called a fat-soluble vitamin?
it can be stored in the body
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Define: Active site
A pocket in a part of the teritary enzyme structure that binds substrate and catalyzes a reaction
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What is the rate at which an enzyme catalyzes the reaction that converts substrate to product called?
activity
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Define: Allosteric enzyme
an enzyme that regulates the rate of a reaction when a regulator molecule attaches to a site other than the active site
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What are substances that are usually produced by bacteria, mold, or yeast that inhibit the growth of bacteria?
Antibiotics
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Define: Coenzyme
An organic molecule, usually a vitamin, required as a cofactor in enzyme action
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What is a metal ino or an organic molecule that is necessary for a biologically fuctional enzyme?
cofactor
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Define: Competitive inhibitor
a molecule with a structure similiar to the substrate that inhibits enzyme action by competing for the active site
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Define: Enzymes
Globular proteins, sometimes with cofactors, that catalyze biological reactions
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What is an intermediate consisting of an enzyme that binds to a substrate in an enzyme-catalyzed reaction?
Enzyme-substrate (ES) complex
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Define: Fat-soluble vitamins
vitamins that are not soluble in water and can be stored in the liver and body
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What is a type of inhibition in which an end product inhibits the first enzyme in a sequence of enzyme-catalyzed reaction?
Feedback control
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Define: Induced-Fit Model
A model of enzyme action in which the shape of a substrate and the active site of the enzyme adjust to give an optimal fit
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What are substances that make an enzyme inactive by interfering with its ability to react with a substrate?
Inhibitors
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Define: Irreversible inhibition
The loss of enzymatic activity that can't be reversed
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What is a model of enzyme action in which the substrate is like a key that fits the specific shape of the active site (the lock)?
Lock-and-key model
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Define: Noncompetitive inhibitor
A type of inhibitor that alters the shape of an enzyme as well as the active site so that the substrate can't bind properly
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What is the pH at which an enzyme is most active called?
Optimum pH
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Define: Optimum Temperature
the temp at which an enzyme is most active
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What is the loss of enzymatic activity by an inhibitor whose effect can be reversed called?
Reversible inhibition
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Define: Simple Enzyme
An enzyme that is active as a polypeptide only
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What is the molecule that reacts in the active site in an enzyme-catalyzed reaction called?
substrate
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Define: Vitamins
Organic molecules that are essential for normal health and growth and are obtained in small amounts from the diet
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What are vitamins thar are soluble in water; they can't be stored in the body, are easily destroyed by heat, ultraviolet light, and oxyge, and function as conenzymes?
Water-soluble vitamins
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Define: Zymogen
An inactive form of an enzyme that is activated by the removal of a peptide portion from one end of the protein.
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