Deck 16: Amino Acids, Proteins, and Enzymes

Question 1

The R group for serine is -CH₂-OH. In the ionized form,serine has the structural formula ________.

A)
B)
C)
D)
E)

Answer 1

Question 2

Methionine is an amino acid that contains ________.

A)a sulfur atom
B)a chlorine atom
C)a sodium atom
D)a phenyl ring
E)a heterocyclic ring

Answer 2

a sulfur atom

Question 3

A completely vegetarian diet will contain all the essential amino acids if it includes ________.

A)wheat and rice
B)rice and beans
C)almonds and walnuts
D)corn and beans
E)wheat and corn

Answer 3

rice and beans

Question 4

Glycine is the only naturally occurring amino acid that is ________.

A)negatively charged
B)positively charged
C)neutral
D)in the L- form
E)achiral

Question 5

A basic amino acid has a side chain that contains ________.

A)an ammonium group
B)a carboxyl ate group
C)a methyl group
D)an alcohol group
E)a thiol group

Question 6

Which of the following functional groups of an amino acid would be in the ionized state at high pH?

A)
B)
C) -CH₃
D)
E)

Question 7

The peptide bonds that link amino acids in a protein are ________.

A)ester bonds
B)ether bonds
C)amide bonds
D)glycosidic bonds
E)sulfide bonds

Question 8

The structural formulas of amino acids are the same except for the ________.

A)carboxylate group
B)alpha carbon
C)ammonium group
D)R group
E)hydrogen bonding

Question 9

Collagen,a protein found in tendons and cartilage,would be classified as a ________ protein.

A)catalytic
B)structural
C)transport
D)storage
E)hormone

Question 10

Sucrase,the protein that facilitates the hydrolysis of sucrose,would be classified as a ________ protein.

A)transport
B)hormonal
C)catalytic
D)structural
E)contractile

Question 11

At a pH > 9,the ionized form of glycine will have ________.

A)a net positive charge
B)a net negative charge
C)an overall charge of zero
D)low solubility in water
E)a negative charge on the nitrogen

Question 12

The side chain for histidine is classified as a ________ side chain.

A)basic
B)neutral
C)acidic
D)nonpolar
E)polar

Question 13

Which of the following would be most likely to be deficient in at least one essential amino acid?

A)eggs
B)milk
C)beans
D)steak
E)ham

Question 14

At a pH < 5,the ionized form for alanine (pI = 6)will have ________.

A)a net positive charge
B)a net negative charge
C)an overall charge of zero
D)low solubility in water
E)a negative charge on the carboxyl group

Question 15

What is the structural formula of glutamic acid (pI = 3.2)at pH = 1?

A)
B)
C)
D)
E)

Question 16

The following amino acid side chain is ________.

A)polar
B)hydrophobic
C)hydrophilic
D)acidic
E)basic

Question 17

Which of the following is not a function of proteins?

A)provide structural components
B)stores the genetic information of a living organism
C)movement of muscles
D)catalyze reactions in the cells
E)transport substances through the bloodstream

Question 18

Amino acids that are not synthesized in the body and must be obtained from the diet are called ________.

A)essential
B)polar
C)nonpolar
D)complete
E)incomplete

Question 19

In the ionized form of an amino acid,the carboxylic acid end is ________.

A)positively charged
B)negatively charged
C)neutral
D)soluble in a nonpolar solvent
E)attached to an amine

Question 20

Wool is primarily made up of ________.

A)protein
B)carbohydrate
C)globin
D)triacylglycerols
E)enkephalin

Question 21

In insulin,two peptide chains are held together in a single unit by ________.

A)disulfide bridges
B)hydrogen bonds
C)salt bridges
D)a prosthetic group
E)a β-pleated sheet

Question 22

In the peptide Ser-Cys-Ala-Gly,the C-terminal end is ________.

A)serine
B)serotonin
C)glycine
D)glycerine
E)alanine

Question 23

In the peptide GLVIW,the C-terminal end is ________.

A)tryptophan
B)serotonin
C)glycine
D)glycerine
E)alanine

Question 24

The fibrous protein responsible for the structure of hair and wool is ________.

A)keratin
B)collagen
C)endorphin
D)myosin
E)casein

Question 25

In the peptide Ala-Try-Gly-Phe,the N-terminal amino acid is ________.

A)alanine
B)phenylalanine
C)tryptophan
D)aspartic acid
E)glycine

Question 26

Which of the following is a secondary protein structure?

A)α-helix
B)Ser-Met-Ala-Gly-Ile
C)disulfide bond
D)salt bridges
E)hydrophobic interactions

Question 27

What type of interaction would you expect between the following R groups in the tertiary structure of a protein?
and

A)disulfide bonds
B)salt bridges
C)hydrogen bonds
D)hydrophobic interactions
E)peptide bonds

Question 28

The α helix of the secondary structure of a protein is held together by ________ between two widely separated parts of a protein chain.

A)hydrogen bonds
B)disulfide bridges
C)salt bridges
D)hydrophilic interactions
E)hydrophobic interactions

Question 29

A chain made of more than 50 amino acids that has biological activity is referred to as a(n)________.

A)peptide
B)protein
C)enzyme
D)globulin
E)hormone

Question 30

Hemoglobin is an example of a protein with ________.

A)primary structure only
B)a single polypeptide chain
C)a globular structure
D)primarily a β-pleated sheet structure
E)primarily an α helix structure

Question 31

What kinds of interactions are not part of tertiary protein structure?

A)peptide bonds
B)disulfide bonds
C)hydrophilic interactions
D)salt bridges
E)hydrophobic interactions

Question 32

Which R group would most likely be found in a hydrophobic area of the tertiary structure of a globular protein?

A)
B)
C)
D)
E)

Question 33

Acids and bases denature a protein by disrupting ________.

A)peptide bonds and salt bridges
B)amide bonds and alkene bonds
C)hydrophobic interactions and peptide bonds
D)salt bridges and hydrophobic interactions
E)salt bridges and hydrogen bonds

Question 34

The secondary structure of collagen consists of ________.

A)single α-helix strands
B)double α-helix strands
C)many α-helixes wound into fibrils
D)a braided triple helix
E)many glycoside links

Question 35

In the peptide STFNA,the N-terminal amino acid is ________.

A)alanine
B)phenylalanine
C)tryptophan
D)aspartic acid
E)serine

Question 36

In the β-pleated sheet secondary structure of a protein,two or more amino acid sequences in separate parts of the protein are held together ________.

A)in a coil,by hydrogen bonding
B)in random order,due to hydrophobic interactions
C)in a triple helix
D)in a double helix
E)by hydrogen bonding between different sections of the polypeptide chain

Question 37

Heat denatures a protein by disrupting ________.

A)salt bridges and peptide bonds
B)hydrophobic interactions and hydrogen bonds
C)peptide bonds and hydrophobic interactions
D)disulfide bonds and peptide bonds
E)hydrogen bonds and disulfide bonds

Question 38

What type of interaction would you expect between the following R groups in the tertiary structure of a protein?

A)disulfide bonds
B)salt bridges
C)hydrogen bonds
D)hydrophobic interactions
E)peptide bonds

Question 39

Enkephalins are polypeptides that have ________.

A)a sweet taste
B)a bitter taste
C)extra caloric value
D)pain-killing properties
E)hormone activity

Question 40

The attractive forces that are important in the secondary structure of a protein are ________.

A)hydrogen bonds
B)hydrophobic interactions
C)disulfide bonds
D)salt bridges
E)peptide bonds

Question 41

Disulfide bonds in a protein chain connect ________.

A)an amine and a carboxylic acid group
B)an alcohol and a carboxylic acid group
C)tryptophan and alanine residues
D)two cysteine residues
E)two asparagine residues

Question 42

In sickle-cell anemia,the hemoglobin molecules ________.

A)come apart into separate chains
B)enlarge to twice normal size
C)clump together into insoluble fibers
D)dissolve in the plasma
E)undergo crenation

Question 43

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

Question 44

Heavy metals denature proteins by ________.

A)releasing amino acids
B)disrupting hydrophobic interactions
C)changing the pH of the protein solution
D)changing the temperature of the protein solution
E)disrupting disulfide bonds

Question 45

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

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

Question 46

The function of myoglobin is to ________.

A)carry vitamins in the blood
B)carry oxygen in the blood
C)support the skeletal muscles
D)carry oxygen in the muscle
E)provide strength in cartilage

Question 47

One heavy metal that can cause denaturation of a protein is ________.

A)silver
B)sodium
C)barium
D)iron
E)calcium

Question 48

Hemoglobin has a total of ________ protein chains in its quaternary structure.

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

Question 49

Enkephalins,naturally produced opiates in the body,are found in ________.

A)muscles and bone tissue
B)brain and kidney tissue
C)thalamus and spinal cord tissue
D)heart and lung tissue
E)pancreas and liver tissue

Question 50

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 51

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 52

Denaturation of a protein ________.

A)changes the primary structure of a protein
B)disrupts the secondary,tertiary,or quaternary structure of a protein
C)is always irreversible
D)hydrolyzes peptide bonds
E)can only occur in a protein with quaternary structure

Question 53

The heme in hemoglobin is a(n)________.

A)protein chain
B)small molecule within a protein
C)helix area in the hemoglobin molecule
D)pleated sheet area in the hemoglobin molecule
E)oxygen molecule within the hemoglobin molecule

Question 54

An acid can denature a protein by ________.

A)agitating the protein chains
B)disrupting hydrogen bonds between side chains
C)disrupting hydrophobic interactions within a protein chain
D)removing helping molecules such as heme
E)breaking disulfide bridges

Question 55

A biological catalyst is called a(n)________.

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

Question 56

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 57

The purpose of the many chemical reactions in our bodies is to ________.

A)store chemical energy in the body for future use
B)produce the amino acids
C)produce the lipids
D)release chemical energy for the production of macromolecules
E)all of the above

Question 58

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

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

Question 59

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 60

Within hemoglobin,the heme functions as ________.

A)a disulfide bridge
B)an oxygen carrier
C)a reducing agent
D)an α subunit
E)one of the four protein subunits

Question 61

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

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

Question 62

Most enzymes are ________.

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

Question 63

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?

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 64

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 65

The active site of an enzyme ________.

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

Question 66

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

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

Question 67

The hydrolysis of ester bonds in triacylglycerols is catalyzed by a ________.

A)lipase
B)lyase
C)isomerase
D)peptidase
E)oxidoreductase

Question 68

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

Question 69

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 70

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

Question 71

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

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

Question 72

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 73

"Physiologic 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 74

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)lowers the activation energy for the reaction
E)changes the possible product formed

Question 75

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

A)coenzyme
B)proenzyme
C)steroid
D)noncompetitive inhibitor
E)competitive inhibitor

Question 76

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 77

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 78

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 79

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 80

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