Deck 20: Enzymes and Vitamins

Question 1

When a substrate binds to an enzyme for reaction, it binds to the

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

Answer 1

active site.

Question 2

The general function of an enzyme in the body is to

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

Answer 2

catalyze chemical reactions.

Question 3

Most enzymes are

A)not proteins.
B)much larger than the substrate.
C)substrate proteins.
D)fluid-mosaic proteins.
E)induced proteins.

Answer 3

much larger than the substrate.

Question 4

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

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

Question 5

To what main class of enzymes does the enzyme that catalyzes the following reaction belong?

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

Question 6

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

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

Question 7

To what main class of enzymes does the enzyme that catalyzes the following reaction belong?

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

Question 8

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

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

Question 9

Substrates are usually bond to the active site of an enzyme by

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

Question 10

The active site of an enzyme

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

Question 11

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

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

Question 12

The presence of enzymes to catalyze bioreactions in our bodies allows

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

Question 13

Compared to an uncatalyzed reaction, an enzyme-catalyzed reaction

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

Question 14

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

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

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

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

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

Question 17

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

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

Question 18

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

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

Question 19

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

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

Question 20

How many 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 21

An irreversible inhibitor is one that

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

Question 22

An increase in concentration of the enzyme LDH1 in the blood can be used to detect

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

Question 23

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

A)It occupies the active site.
B)It binds to the enzyme at a site remote from the active site.
C)It has a structure similar to the substrate.
D)It cannot be converted to products.

Question 24

Pepsinogen is an example of a(n)

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

Question 25

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

A)
B)
C)
D)
E)

Question 26

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 (the optimum temperature) to

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

Question 27

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

Question 28

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

Question 29

"Physiological conditions" for reactions within the body are approximately

A)
B)
C) pH 7 and 273 K.
D)
E)

Question 30

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

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

Question 31

The creatine kinase can be used in the diagnosis of

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

Question 32

A competitive inhibitor is one that

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

Question 33

Most enzymes are deactivated permanently above a temperature of about

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

Question 34

Some insecticides kill insects by inhibiting the enzyme

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

Question 35

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

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

Question 36

Penicillin functions as an antibiotic by

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

Question 37

A noncompetitive inhibitor has a structure that

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

Question 38

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

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

Question 39

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

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

Question 40

Allosteric enzymes can control the output of product by

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

Question 41

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

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

Question 42

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

Question 43

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

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

Question 44

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

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

Question 45

ions are used in the functioning of

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

Question 46

The full name of the enzyme LDH is ________.

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

Question 47

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

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

Question 48

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

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

Question 49

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

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

Question 50

A noncompetitive inhibitor

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

Question 51

The water-soluble B and C vitamins supply

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

Question 52

Vitamin D is an example of a(n)

A)must be obtained from the diet daily.
B)fat soluble vitamin.
C)water-soluble vitamin.
D)essential mineral.
E)essential amino acid.

Question 53

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

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

Question 54

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

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

Question 55

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

Question 56

A biological catalyst is called a(n)________.

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

Question 57

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

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

Question 58

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

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

Question 59

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

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

Question 60

The B vitamins are examples of

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

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.
ascorbic acid

Question 63

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

Question 64

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

Question 65

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

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.
niacin

Question 68

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