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BIO 355- CELL BIO > Ch. 4 > Flashcards

Ch. 4 Flashcards

1
Q

How many different amino acids are used in making proteins?

A

20

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2
Q

Which parts of amino acids are involved in peptide bonds?

A

The amino group on one amino acid and the carboxyl group on the other

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3
Q

Which part of an amino acid gives it its unique properties?

A

The side chain

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4
Q

In a folded protein, the nonpolar (hydrophobic) amino acids tend to be:

A

tucked away inside the protein.

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5
Q

What provides the information necessary to specify the three-dimensional shape of a protein?

A

The protein’s amino acid sequence

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6
Q

The biological activity of a protein is determined by its:

A

Amino Acid Sequence

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7
Q

A protein can be unfolded by a process called:

A

denaturation

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8
Q

What hydrogen bonds have been found to stabilize a polypeptide’s folded shape?

A
  • Hydrogen bonds between side chain atoms
  • Hydrogen bonds between backbone atoms and side chain atoms
  • Hydrogen bonds between backbone atoms
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9
Q

What is the best type of model for visualizing the surface of a protein?

A

The space-filling model

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10
Q

Why are /alpha helices and /beta sheets common folding patterns in polypeptides?

A

Amino acid side chains are not involved in forming the hydrogen bonds, allowing many different sequences to adopt these folding patterns.

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11
Q

Those portions of a transmembrane protein that cross the lipid bilayer usually consist of which structures?

A

An /alpha helix with mostly nonpolar side chains

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12
Q

The two types of /beta sheets are:

A

parallel /beta sheets and antiparallel /beta sheets.

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13
Q

What does the primary structure of a protein refer to?

A

The amino acid sequence of the protein

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14
Q

What is the name for a modular unit from which many larger proteins are made?

A

Protein domain

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15
Q

.In a protein, intrinsically disordered sequences:

A

A. have a variety of important functions.
B. can wrap and bend around target proteins.
C. are ideal substrates for the addition of chemical groups that can modify protein behavior.

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16
Q

Theoretically, a vast number of different proteins can be assembled from 20 different amino acids. How many polypeptide chains are possible that are 10 amino acids long?

A

20^10

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17
Q

What are protein families?

A

Evolutionarily related proteins that are similar in amino acid sequence and three-dimensional conformation.

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18
Q

What is the definition of a binding site on a protein?

A

Any region that interacts with another molecule through sets of noncovalent bonds.

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19
Q

Actin filaments, microtubules, and the spherical shells of some virus particles are all:

A

structures built from sets of identical proteins.

20
Q

T or F: Enzymes are examples of fibrous proteins.

A

False

21
Q 
Which of the following is NOT formed by fibrous proteins? 
A. Actin filaments
B. Extracellular matrix
C. Collagen
D. Elastin
A

Actin filaments

22
Q 
Which of the following is formed by fibrous proteins? 
A. Actin filaments
B. Extracellular matrix
C. Collagen
D. Elastin
A

Extracellular Matrix
Collagen
Elastin

23
Q

The most common covalent cross-links in proteins are sulfur-sulfur bonds that form between two amino acids with -SH (thiol) groups as side chains. Which amino acid has this side chain?

A

Cysteine

24
Q

The ability of a protein to bind selectively and with high affinity to specific molecules is due to which types of bonds?
A. Weak, noncovalent bonds
B. Strong, covalent bonds

A

Weak, noncovalent bonds

25
Q

How many identical binding sites exist on an antibody?

A

2

26
Q

What determines the specificity of an antibody for its antigen?

A

The amino acid loops in its variable domain

27
Q

T or F: Enzymes that catalyze two or more chemical reactions link metabolic pathways in cells.

A

False

28
Q

Which of the following is NOT true about enzymes:
A. They can bring reactants together in the proper orientation for chemistry to occur.
B. They can change the shape of substrates to increase the rate of a particular reaction.
C. They require an input of energy from ATP for activation.
D. They can form covalent bonds with their substrates.

A

They require an input of energy from ATP for activation.

29
Q

All enzymes:
A. boost the activation energy of a reaction.
B. eliminate the activation energy of a reaction.
C. decrease the activation energy of a reaction.
D. do not alter the activation energy of a reaction.

A

do not alter the activation energy of a reaction.

30
Q

T or F: Most drugs work by inhibiting the functions of enzymes.

A

True

31
Q

Rhodopsin requires which small nonprotein molecule to detect light?

A

Retinal

32
Q

Which statement is false?
A. Feedback inhibition is a negative feedback system for controlling enzyme activity.
B. In feedback inhibition, an enzyme acting early in a reaction pathway is inhibited by a late product of that pathway.
C. Feedback inhibition regulates the flow through biosynthetic pathways.
D. Feedback inhibition is difficult to reverse and requires synthesis of new enzymes.

A

D. Feedback inhibition is difficult to reverse and requires synthesis of new enzymes.

33
Q

How does an allosteric inhibitor affect the active site of an enzyme?

A

It binds to a second site, causing a conformational change in the enzyme that makes the active site less accommodating to the substrate.

34
Q

T or F: Many protein molecules (not just enzymes) are allosteric.

A

True

35
Q

How does phosphorylation control protein activity?

A

The addition of a phosphate group can induce major conformational changes in a protein

36
Q

Phosphorylation of a protein:

A

either increases or decreases a protein’s activity.

37
Q

What kind of enzyme adds a phosphate group to another protein?

A

Kinase

38
Q

What kind of enzyme removes a phosphate group from a protein?

A

phosphatase

39
Q

T or F: Phosphorylation is the only form of covalent modification that can affect a protein’s activity or location.

A

False

40
Q

Many proteins are regulated by the binding of GTP or GDP. Which form is the active state of the protein?

A

GTP-bound form

41
Q

How does the GTP-bound form of a GTP-binding protein switch to a GDP-bound form?

A

It hydrolyzes GTP, releasing a phosphate.

42
Q

How do most motor proteins make their movements unidirectional (i.e., irreversible)?

A

They couple a conformational change to the hydrolysis of an ATP molecule.

43
Q

How do protein machines, such as those involved in DNA replication and protein synthesis, often coordinate their actions?

A

By the hydrolysis of bound nucleoside triphosphates (ATP or GTP)

44
Q

Which of the following are methods for isolating a protein of interest?
A. Electrophoresis and PCR
B. Electrophoresis and transfection
C. Chromatography and amino acid analysis
D. Chromatography and electrophoresis

A

Chromatography and electrophoresis

45
Q

T or F: At present, it is possible to predict the precise folding pattern of any protein.

A

False

46
Q

T or F: The large-scale production or proteins requires processing vast amounts of tissue and other biological materials.

A

False

47
Q

The majority of proteins belong to “protein families” that share:

A

sequence patterns and therefore structural domains.

BIO 355- CELL BIO (11 decks)

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