Deck 20: Enzymes and Vitamins

Question 1

In the induced-fit model of enzyme action, the enzyme active site

A)stays the same shape during substrate binding.
B)adjusts shape to adapt to the shape of the substrate.
C)stays the same shape while causing a change in the shape of the substrate.
D)uses an inhibitor to adjust its shape for the substrate.
E)uses a cofactor to change the shape of a substrate.

Answer 1

adjusts shape to adapt to the shape of the substrate.

Question 2

To what main class of enzymes does the enzyme that catalyzes the conversion of lactose to galactose and glucose belong?

A)oxidoreductase
B)transferase
C)hydrolase
D)lyase
E)isomerase

Answer 2

hydrolase

Question 3

The presence of enzymes to catalyze bioreactions in our bodies allows

A)us to eat non-nutritious substances without consequence.
B)the activation energy of a reaction to be raised.
C)the rate of a desired chemical reaction to slow down.
D)bioreactions to occur under extreme conditions of temperature and pH.
E)bioreactions to take place under mild conditions.

Answer 3

bioreactions to take place under mild conditions.

Question 4

When a substance bonds to an enzyme for reaction, its place of binding is the

A)allosteric site.
B)primary pocket.
C)end pocket.
D)primary site.
E)active site.

Question 5

In any reaction catalyzed by an enzyme, the reacting molecule is called the

A)substrate.
B)cofactor.
C)coenzyme.
D)isozyme.
E)allostere.

Question 6

To what main class of enzymes does the enzyme that catalyzes the following reaction belong? O OH | CH₃ C COO- → CH₃ C HCOO-

A)oxidoreductase
B)transferase
C)hydrolase
D)lyase
E)isomerase

Question 7

Compared to an uncatalyzed reaction, an enzyme-catalyzed reaction

A)uses less substrate.
B)produces different products.
C)occurs at a faster rate.
D)requires more energy.
E)requires a higher temperature.

Question 8

Most enzymes are

A)fluid-mosaic proteins.
B)induced proteins.
C)substrate proteins.
D)fibrous proteins.
E)globular proteins.

Question 9

Which of the following is NOT a step in the enzyme-catalyzed conversion of a substrate to product?

A)The substrate binds to the enzyme away from the active site.
B)The substrate binds in the active site to form the E-S complex.
C)The enzyme assists in the conversion of the substrate to product.
D)The product is released from the active site.
E)A new substrate molecule binds to the enzyme for a new cycle.

Question 10

An increase in concentration of the enzyme LDH in the blood can be used to detect

A)heart attack.
B)kidney damage.
C)anemia.
D)uremia.
E)bulimia.

Question 11

The active site of an enzyme

A)is remote from the site of substrate attachment.
B)is converted to a product.
C)catalyzes the reaction.
D)increases the energy of reaction.
E)includes the entire enzyme.

Question 12

The function of the enzyme-substrate complex is to provide an alternative reaction pathway that

A)lowers the energy of the products.
B)lowers the energy of the substrate.
C)changes the concentration of the substrate.
D) decreases the activation energy for the reaction.
E)changes the possible product formed.

Question 13

The general function of an enzyme in the body is to

A)catalyze chemical reactions.
B)maintain a neutral pH.
C)act as a reactant in carbohydrate storage.
D)maintain homeostasis.
E)eliminate waste products from the blood.

Question 14

Substances that react under the influence of an enzyme are usually held to the enzyme by

A)peptide bonds.
B)side chains of amino acids in the enzyme protein.
C)ester bonds.
D)pH changes.
E)competitive inhibition.

Question 15

The formation of an enzyme-substrate complex is the ________ step in enzyme action.

A)first
B)second
C)third
D)fourth
E)last

Question 16

Creatine kinase can be used in the diagnosis of

A)hepatitis.
B)rickets.
C)heart attack.
D)prostatitis.
E)cancer.

Question 17

Urease catalyzes only the hydrolysis of urea, and no other substrates. This limited activity is called

A)absolute specificity.
B)extreme specificity.
C)rigid specificity.
D)noncompetitive specificity.
E)hyperspecificity.

Question 18

Hexokinase catalyzes only the addition of phosphate to any hexose sugar. This type of activity is called

A)regional specificity.
B)collateral specificity.
C)group specificity.
D)noncompetitive specificity.
E)general specificity.

Question 19

How many generalized steps are there in the reaction of an enzyme (E) with a substrate (S) to form and release the product (P)?

A)one
B)two
C)three
D)four
E)five

Question 20

In the lock-and-key model of enzyme action, the enzyme active site is thought of as

A)a rigid, nonflexible shape that fits the substrate exactly.
B)an area of the enzyme that can adjust to fit the substrate shape.
C)a key-like shape that fits into a pocket of the substrate surface.
D)a hydrophilic area on the enzyme surface.
E)a lock that bars a noncompetitive inhibitor from reacting.

Question 21

In an enzyme-substrate reaction, when excess substrate is present, increasing the concentration of the enzyme will

A)increase the number of substrate molecules available.
B)inhibit the formation of products.
C)increase the decomposition rate of the enzyme-substrate complex.
D)decrease the turnover rate for the substrate.
E)increase the amount of reaction occurring.

Question 22

Urea is converted to ammonia and carbon dioxide by the action of urease. What will be the effect on the rate if the temperature of the reaction is lowered from 37 °C (the optimum temperature) to 27 °C? O NH2 - C - NH2 + H2O 2NH₃ + CO2

A)There will be no effect.
B)The rate will slow down.
C)The rate will double.
D)The rate will triple.
E)The rate will slow down, then speed up again.

Question 23

Allosteric enzymes can control their output of product by

A)binding the substrate at a site away from the active site.
B)binding an irreversible inhibitor at the active site.
C)binding a positive or negative regulator at a noncompetitive site.
D)changing the pH in the active site.
E)reversible inhibition using the product as the inhibitor.

Question 24

The hydrolysis of ester bonds in triglycerides is catalyzed by a(n)

A)lipase.
B)lyase.
C)isomerase.
D)hydrolase.
E)oxidoreductase.

Question 25

Some insecticides kill insects by inhibiting the enzyme

A)alcohol dehydrogenase.
B)acetylcholinesterase.
C)creatine kinase.
D)lipase.
E)penicillinase.

Question 26

"Physiological conditions" for reactions within the body are approximately

A)pH 3 and 37 °C.
B)pH 7 and 37 °C.
C)pH 7 and 37 °F.
D)pH 8 and 273 °C.
E)pH 7 and 273 K.

Question 27

The optimum temperature for sucrase activity is 37 °C. The hydrolysis of sucrose is slowest at which temperature in the choices below?

A)0 °C
B)10 °C
C)20 °C
D)25 °C
E)45 °C

Question 28

An irreversible inhibitor is one that

A)forms hydrogen bonds with the substrate.
B)binds to the enzyme with hydrophobic interactions.
C)reacts covalently with the substrate.
D)binds covalently to the enzyme active site.
E)reacts covalently with a cofactor.

Question 29

The surface of a freshly cut apple turns brown because of

A)inhibition of the surface enzymes by nitrogen.
B)interaction of the surface enzymes with oxygen.
C)a change in pH at the surface.
D)an increase in substrate concentration at the cut surface.
E)the presence of vitamin C in the apple.

Question 30

Most enzymes are deactivated permanently above a temperature of about

A)25 °C.
B)37 °F.
C)40 °C.
D)45 °F.
E)50 °C.

Question 31

Consider an enzymatic reaction in which the initial concentration of substrate is low. If the amount of enzyme is held constant, but the amount of substrate is increased, the rate of an enzyme catalyzed reaction will

A)increase in an exponential fashion.
B)decrease at first, then increase in a linear fashion.
C)increase at first in a linear fashion, then remain at a constant high rate.
D)stay the same.
E)be inhibited by the higher concentrations of substrate.

Question 32

A noncompetitive inhibitor has a structure that

A)does not resemble the substrate structure.
B)resembles the active site of the enzyme.
C)can bind to the active site of the enzyme.
D)does not interfere with the enzyme-substrate complex formation.
E)causes a change in the shape of the substrate.

Question 33

"Physiological pH", the pH for optimum activity for most enzymes, is a pH equal to

A)3.0.
B)5.4.
C)7.4.
D)8.6.
E)9.0.

Question 34

To what main class of enzymes does the enzyme that catalyzes the following reaction belong? Ser - Ala → Ser + Ala

A)oxidoreductase
B)transferase
C)hydrolase
D)lyase
E)isomerase

Question 35

A compound that binds to the surface of an enzyme, and changes its shape so that a substrate cannot enter the active site, is called a(n)

A)irreversible inhibitor.
B)proenzyme.
C)cofactor.
D)noncompetitive inhibitor.
E)competitive inhibitor.

Question 36

Pepsinogen is an example of a(n)

A)coenzyme.
B)cofactor.
C)isoenzyme.
D)allosteric enzyme.
E)zymogen.

Question 37

Penicillin functions as an antibiotic by

A)poisoning bacteria with toxins.
B)raising the temperature of a bacterium.
C)bonding to metal ions in bacterial electron transport systems.
D)inhibiting the enzymes for cell wall formation in bacteria.
E)acting as an acetylcholinesterase inhibitor.

Question 38

Penicillin-resistant bacteria can survive treatment with penicillin because they produce the enzyme

A)sucrase.
B)penicillin kinase.
C)penicillinase.
D)bacteriase.
E)phosphate lyase.

Question 39

A competitive inhibitor is one that

A)binds to the enzyme at a site far from the active site.
B)binds to the active site in place of the substrate.
C)destroys the substrate.
D)binds to the allosteric site on an enzyme.
E)forms a complex with the substrate.

Question 40

When an end product from an enzyme-mediated sequence is also an inhibitor for an earlier step in the reaction sequence, the process is referred to as

A)feedback control.
B)competitive inhibition.
C)irreversible inhibition.
D)negative catalysis.
E)concentration control.

Question 41

The names of many enzymes can be recognized by the suffix ________.

A)-ate
B)-ite
C)-ose
D)-ine
E)-ase

Question 42

The B vitamins are examples of

A)water-soluble vitamins.
B)essential amino acids.
C)essential minerals.
D)oil soluble vitamins.
E)vitamins that are stored in the liver.

Question 43

Enzymes that catalyze the same reactions but have slightly different structures are called ________.

A)coenzymes
B)cofactors
C)isoenzymes
D)competitive
E)noncompetitive

Question 44

A biological catalyst is called a(n) ________.

A)lipid
B)enzyme
C)cofactor
D)coenzyme
E)substrate

Question 45

The optimum pH for the activity of trypsin is about ________.

A)2.0
B)4.0
C)6.5
D)7.4
E)8.0

Question 46

When a cofactor is a small organic molecule, it is known as a(n)

A)isoenzyme.
B)vitamin.
C)zymogen.
D)coenzyme.
E)regulator.

Question 47

Allosteric enzymes can control their output of product by

A)binding the substrate at a site away from the active site.
B)binding an irreversible inhibitor at the active site.
C)binding a positive or negative regulator at a noncompetitive site.
D)changing the pH in the active site.
E)reversible inhibition using the product as the inhibitor.

Question 48

The optimum pH for the activity of pepsin is about ________.

A)2.0
B)4.0
C)6.5
D)7.4
E)7.6

Question 49

When an end product from an enzyme-mediated sequence is also an inhibitor for an earlier step in the reaction sequence, the process is referred to as

A)feedback control.
B)competitive inhibition.
C)irreversible inhibition.
D)negative catalysis.
E)concentration control.

Question 50

Iron(II) and iron(III) ions are used in the functioning of

A)urease.
B)alcohol dehydrogenase.
C)creatine kinase.
D)the cytochrome oxidase system.
E)pepsin.

Question 51

A noncompetitive inhibitor

A)binds at the active site of the enzyme.
B)alters the three-dimensional structure of the enzyme.
C)increases the rate of the enzyme-catalyzed reaction.
D)has a structure similar to the substrate.
E)has its effect reversed by adding more substrate.

Question 52

The water-soluble B and C vitamins supply

A)essential amino acids.
B)substrates necessary for most of the reactions in the body.
C)essential fatty acids.
D)coenzymes required by some enzymes.
E)competitive inhibitors needed to regulate enzyme activity.

Question 53

Metal ions such as Zn2+ and Fe3+ are often needed by enzymes as

A)isozymes.
B)allosteres.
C)inhibitors.
D)cofactors.
E)substrates.

Question 54

Pepsinogen is an example of a(n)

A)coenzyme.
B)cofactor.
C)isoenzyme.
D)allosteric enzyme.
E)zymogen.

Question 55

The full name of the enzyme LDH is ________.

A)lactate dehydrogenase
B)liver decompensation hexase
C)lactate dehydrase
D)liver dihydrogen kinase
E)lipase dehydrogenase

Question 56

Which of the following is NOT true for a competitive inhibitor?

A)It occupies the active site.
B)It cannot be converted to products.
C)It has a structure similar to the substrate.
D)Increasing the substrate concentration can reverse competitive inhibition.
E)It binds to the enzyme at a site remote from the active site.

Question 57

Another name for a zymogen is a(n) ________.

A)cofactor
B)coenzyme
C)prosthetic group
D)isozyme
E)proenzyme

Question 58

An enzyme that removes H from a substrate is classified as a(n) ________.

A)oxidoreductase
B)transferase
C)hydrolase
D)lyase
E)isomerase

Question 59

Coenzymes such as water-soluble vitamins are needed in only small amounts because

A)only small amounts of enzymes are present in each cell.
B)only small amounts of substrates are available at any one time.
C)they can be eliminated in the urine.
D)each vitamin molecule can be reused many times as a cofactor.
E)they can be stored in the liver for future use.

Question 60

An enzyme that converts a cis double bond to a trans double bond is classified as a(n) ________.

A)oxidoreductase
B)transferase
C)hydrolase
D)lyase
E)isomerase

Question 61

Indicate whether each of the following is fat soluble or water soluble.
pantothenic acid

Question 62

Indicate whether each of the following is fat soluble or water soluble.
vitamin D

Question 63

Indicate whether each of the following is fat soluble or water soluble.
vitamin E

Question 64

Alanine transaminase is an example of a transferase enzyme.

Question 65

Indicate whether each of the following is fat soluble or water soluble.
vitamin B6

Question 66

Indicate whether each of the following is fat soluble or water soluble.
vitamin K

Question 67

Indicate whether each of the following is fat soluble or water soluble.
ascorbic acid

Question 68

Indicate whether each of the following is fat soluble or water soluble.
vitamin A

Question 69

Pyruvate carboxylase is an example of a ligase enzyme.

Question 70

The optimum pH of most cellular enzymes is about 7.4.

Question 71

Phosphorylation is a common form of covalent modification.

Question 72

Indicate whether each of the following is fat soluble or water soluble.
riboflavin

Question 73

A diet very low in vitamin C can lead over time to the condition ________.

A)rickets
B)scurvy
C)cancer
D)carpal tunnel syndrome
E)anorexia nervosa

Question 74

Indicate whether each of the following is fat soluble or water soluble.
folic acid

Question 75

The active site is a large part of an enzyme.

Question 76

One deficiency disease that can be traced to insufficient intake of vitamin D is ________.

A)scurvy
B)rickets
C)beriberi
D)pellagra
E)pernicious anemia

Question 77

Indicate whether each of the following is fat soluble or water soluble.
niacin

Question 78

Insulin and digestive enzymes are produced as inactive forms called zymogens.

Question 79

Urease is an example of an oxidoreductase enzyme.

Question 80

In the induced fit model of enzyme activity, both the enzyme and the substrate change shape.