Proteins

Question 1

Function of protein where collagen and keratin are the chief constituents of skin, bone, hair, and nails.

Answer 1

Structure

Question 2

Function of protein where virtually all reactions in living systems are catalyzed by proteins called enzymes.

Answer 2

Catalysis

Question 3

Functions of proteins where muscles are made up of proteins called myosin and actin.

Question 4

Functions of proteins where hemoglobin transports oxygen from the lungs to cells, other proteins transport molecules across cell membranes.

Answer 4

Transport

Question 5

Functions of protein where __________ are proteins, among them insulin, oxytocin, and human growth hormone.

Answer 5

Hormones

Question 6

Are the chief constituents of skin, bone, hair, and nails.

Answer 6

Collagen and Keratin

Question 7

Virtually all reactions in living systems are catalyzed by proteins called __________

Answer 7

enzymes

Question 8

Muscles are made up of proteins called __________ and __________

Answer 8

myosin; actin

Question 9

Transports oxygen from the lungs to cells, other proteins transport molecules across cell membranes.

Answer 9

Hemoglobin

Question 10

Function of protein where blood clotting involves the protein fibrinogen; the body used proteins called antibodies to fi ght disease.

Answer 10

Protection

Question 11

Functions of protein where casein in milk and ovalbumin in eggs store nutrients for newborn infants and birds. Ferritin, a protein in the liver, stores iron.

Answer 11

Storage

Question 12

Functions of proteins where certain proteins not only control the expression of genes, but also control when gene expression takes place.

Answer 12

Regulation

Question 13

Proteins are divided into two types:

(1) __________
(2) __________

Answer 13

(1) Fibrous proteins
(2) Globular proteins

Question 14

Blood clotting involves the protein __________; the body used proteins called antibodies to fight disease

Answer 14

fibrinogen

Question 15

(1) __________ in milk and (2) __________ in eggs store nutrients for newborn infants and birds.

Answer 15

(1) Casein
(2) ovalbumin

Question 16

__________, a protein in the liver, stores iron.

Answer 16

Ferritin

Question 17

Certain proteins not only control the expression of (1) ______, but also control when (2) __________ takes place.

Answer 17

(1) genes
(2) gene expression

Question 18

A compound that contains both an amino group and
a carboxyl group.

Answer 18

Amino Acid

Question 19

An amino acid in which the amino group is on the carbon adjacent to the carboxyl group.

Answer 19

a-Amino Acid

Question 20

Although a-amino acids are commonly written in the (1) __________ form, they are more properly written in the (2) __________ form.

Answer 20

(1) un-ionized
(2) zwitterion (internal salt)

Question 21

With the exception of (1) __________, all protein-derived amino acids have at least (2) __________ and are (3) __________.

Answer 21

(1) glycine
(2) one stereocenter (the a-carbon)
(3) chiral

Question 22

The vast majority of a-amino acids have the __________ at the a- carbon

Answer 22

L-configuration

Question 23

Each ionizable group is shown in the form present in highest concentration at pH 7.0).

Answer 23

Nonpolar side chains

Question 24

In nonpolar side chains, each ionizable group is shown in the form present in highest concentration at __________ .

Answer 24

pH 7.0

Question 25

For 19 of the 20, the a-amino group is (1) __________; for proline, it is (2) __________

Answer 25

(1) primary (2) secondary

Question 26

Isoleucine and threonine contain a __________.

Answer 26

second stereocenter

Question 27

The (1) __________ on an amino acid depends on the pH of the solution in which it is dissolved.

Answer 27

net charge

Question 28

If we dissolve an amino acid in water, it is present in the aqueous solution as its __________.

Answer 28

zwitterion

Question 29

If we add a strong acid such as HCl to bring the pH of the solution to pH 0, the strong acid donates a (1) ______ to the _______ of the zwitterion turning it into a (2) __________.

Answer 29

(1) proton; –COO– (2) positive ion

Question 30

If we add a strong base such as NaOH to the solution and bring its pH to 14, a (1) __________ is transferred from the __________ to the base turning the zwitterion into a (2) __________.

Answer 30

(1) proton; NH3+ group (2) negative ion

Question 31

A pH at which a sample of amino acids or protein has an equal number of positive and negative charges.

Answer 31

Isoelectric point (pI)

Question 32

Proteins are long chains of (1) ______ joined by (2) ______.

Answer 32

(1) amino acids (2) amide bonds

Question 33

The special name given to the amide bond between the a-carboxyl group of one amino acid and the a-amino group of another.

Answer 33

Peptide bond (peptide linkage)

Question 34

A short polymer of amino acids joined by peptide bonds; they are classified by the number of amino acids in the chain.

Answer 34

Peptide

Question 35

A molecule containing two amino acids joined by a peptide bond.

Answer 35

Dipeptide

Question 36

A molecule containing three amino acids joined by peptide bonds.

Answer 36

Tripeptide

Question 37

A macromolecule containing many amino acids joined by peptide bonds.

Answer 37

Polypeptide

Question 38

A biological macromolecule containing at least 30 to 50 amino acids joined by peptide bonds.

Answer 38

Protein

Question 39

The individual amino acid units are often referred to as “__________.”

Answer 39

residues

Question 40

By convention, peptides are written from (1) ______, beginning with the free (2) __________ and ending with the free (3) __________.

Answer 40

(1) left to right (2) –NH3+ group (3) –COO– group

Question 41

The amino acid at the end of the chain having the free –COO– group.

Answer 41

C-terminal amino acid (C-terminus)

Question 42

The amino acid at the end of the chain having the free –NH3+ group.

Answer 42

N-terminal amino acid (N- terminus)

Question 43

The amino acids phenylalanine, tryptophan, and tyrosine have __________ on their side chains.

Answer 43

aromatic rings

Question 44

The precursor to the neurotransmitter serotonin.

Answer 44

Tryptophan

Question 45

Are precursors to norepinephrine and epinephrine, both of which are stimulatory neurotransmitters.

Answer 45

Phenylalanine and Tyrosine

Question 46

A peptide bond is typically written as a (1) __________ bonded to an (2) _________.

Answer 46

(1) carbonyl group (2) N–H group

Question 47

Discovered that there is about 40% double bond character to the C–N bond and that a peptide bond between two amino acids is planar

Answer 47

Linus Pauling

Question 48

Linus Pauling discoveries: • There is about (1) __________ character to the C–N bond. • a peptide bond between two amino acids is (2) __________.

Answer 48

(1) 40% double bond (2) planar

Question 49

Pauling explained her discoveries using this concept.

Answer 49

Resonance

Question 50

Proteins behave as __________.

Answer 50

zwitterions

Question 51

At its isoelectric point, the protein has __________.

Answer 51

no net charge

Question 52

At any pH above (more basic than) its pI, proteins have a __________

Answer 52

net negative charge.

Question 53

At any pH below (more acidic than) its pI, proteins have a __________.

Answer 53

net positive charge

Question 54

Has an almost equal number of acidic and basic side chains; its pI is 6.8.

Answer 54

Hemoglobin

Question 55

Has more acidic side chains; its pI is 4.9.

Answer 55

Serum Albumin

Question 56

Proteins are least soluble in (1) __________ at their isoelectric points and can be precipitated from solution when (2) __________.

Answer 56

(1) water (2) pH = pI

Question 57

The sequence of amino acidsina polypeptide chain. Read from the N-terminal amino acid to the C-terminal amino acid.

Answer 57

Primary Structure

Question 58

Conformations of amino acids in localized regions of a polypeptide chain. Examples are a-helix, b-pleated sheet, and random coil.

Answer 58

Secondary Structure

Question 59

The complete three-dimensional arrangement of atoms of a polypeptide chain.

Answer 59

Tertiary Structure

Question 60

The spatial relationship and interactions between subunits in a protein that has more than one polypeptide chain.

Answer 60

Quaternary Structure

Question 61

The number peptides possible from the __________ amino acids is enormous.

Answer 61

20 protein-derived

Question 62

There are __________ dipeptides possible.

Answer 62

20 × 20 = 400

Question 63

There are ___________ tripetides possible.

Answer 63

20 × 20 × 20 = 8000

Question 64

The number of peptides possible for a chain of n amino acids is ______.

Answer 64

20n

Question 65

For a small protein of 60 amino acids, the number of proteins possible is __________

Answer 65

20^60 ≈ 10^78

Question 66

The hormone insulin consists of (1) __________, held together by (2) __________.

Answer 66

(1) two polypeptide chains (A and B) (2) two disulfide bonds

Question 67

Amino acid sequence of Human Insulin: • A chain positions 8-9-10 : (1) __________ • B chain position 30 : (2) __________

Answer 67

(1) -Thr-Ser-Ile (2) -Thr

Question 68

Amino acid sequence of Cow Insulin : • A chain positions 8-9-10 : (1) __________ • B chain position 30 : (2) __________

Answer 68

(1) -Ala-Ser-Val- (2) -Ala

Question 69

Amino acid sequence of Hog Insulin : • A chain positions 8-9-10 : (1) __________ • B chain position 30 : (2) __________

Answer 69

(1) -Thr-Ser-Ile- (2) -Ala

Question 70

Amino acid sequence of Sheep Insulin : • A chain positions 8-9-10 : (1) __________ • B chain position 30 : (2) __________

Answer 70

(1) -Ala-Gly-Val- (2) -Ala

Question 71

Is a nonapeptide and an antidiuretic hormone.

Answer 71

Vasopressin

Question 72

A nonapeptide that affects contractions of the uterus in childbirth and the muscles of the breast that aid in the secretion of milk.

Answer 72

Oxytocin

Question 73

Conformations of amino acids in localized regions of a polypeptide chain.

Answer 73

Secondary Structure

Question 74

The most common types of secondary structure are (1) __________ and (2) __________.

Answer 74

(1) a-helix (2) b-pleated sheet

Question 75

A type of secondary structure in which a section of polypeptide chain coils into a spiral, most commonly a right-handed spiral.

Answer 75

a-Helix

Question 76

A type of secondary structure in which two polypeptide chains or sections of the same polypeptide chain align parallel to each other; the chains may be parallel or antiparallel.

Answer 76

b-Pleated sheet

Question 77

In a section of a-helix • The six atoms of each peptide bond lie in the (1) _________. • The (2) __________ groups of peptide bonds point in the same direction, roughly parallel to the axis of the helix. • The (3) __________ groups of peptide bonds point in the opposite direction, also roughly parallel to the axis of the helix.

Answer 77

(1) same plane (2) N–H groups (3) C=O groups

Question 78

In a section of a-helix • The C=O group of each peptide bond is (1) __________ to the N–H group of the peptide bond __________ units away from it. • All (2) __________ groups point outward from the helix.

Answer 78

(1) hydrogen bonded; four amino acid (2) R–

Question 79

In a section of b-pleated sheet; • The six atoms of each peptide bond of a b-pleated sheet lie in the (1) __________. • The C=O and N–H groups of the peptide bonds from adjacent chains point (2) __________ each other and are in the same plane so that __________ is possible between them. • All (3) __________ on any one chain alternate, first above, then below the plane of the sheet, etc.

Answer 79

(1) same plane (2) toward (3) R–groups

Question 80

Many __________ contain all three kinds of secondary structure in different parts of their molecules: a-helix, b-pleated sheet, and random coil.

Answer 80

globular proteins

Question 81

The overall conformation of an entire polypeptide chain.

Answer 81

Tertiary Structure

Question 82

Tertiary structure is stabilized in four ways: • (1) __________ as for example, the formation of disulfide bonds between cysteine side chains. • (2) __________ between polar groups of side chains, as for example between the –OH groups of serine and threonine. • (3) __________, as for example, the attraction of the –NH3+ group of lysine and the –COO– group of aspartic acid. • (4) __________, as for example, between the nonpolar side chains of phenylalanine and isoleucine.

Answer 82

(1) Covalent bonds (2) Hydrogen bonding (3) Salt bridges (4) Hydrophobic interactions

Question 83

The –SH (sulfhydryl) group of __________ is easily oxidized to an –S–S– (disulfide).

Answer 83

cysteine

Question 84

The (1) __________ group of cysteine is easily oxidized to an (2) __________.

Answer 84

(1) –SH (sulfhydryl) (2) –S–S– (disulfide)

Question 85

The arrangement of polypeptide chains into a noncovalently bonded aggregation.

Answer 85

Quaternary Structure

Question 86

The individual chains of quaternary structures are held together by (1) __________, (2) __________, and (3) __________.

Answer 86

(1) hydrogen bonds (2) salt bridges (3) hydrophobic interactions

Question 87

Type of hemoglobin with two alpha chains of 141 amino acids each, and two beta chains of 146 amino acids each.

Answer 87

Adult Hemoglobin

Question 88

Type of hemoglobin with two alpha chains, two gamma chains, and has a greater affinity for oxygen.

Answer 88

Fetal Hemoglobin

Question 89

Form quaternary structures in which the outer surface is largely nonpolar (hydrophobic) and interacts with the lipid bilayer

Answer 89

Integral Membrane Proteins

Question 90

The process of destroying the native conformation of a protein by chemical or physical means.

Answer 90

Denaturation

Question 91

Some denaturations are (1) __________, while others (2) __________ the protein.

Answer 91

(1) reversible (2) permanently damage

Question 92

Can disrupt hydrogen bonding; in globular proteins, it can cause unfolding of polypeptide chains with the result that coagulation and precipitation may take place.

Answer 92

Heat

Question 93

Disrupts hydrogen bonding.

Answer 93

6 M aqueous urea

Question 94

Detergents such as sodium dodecylbenzenesulfate (SDS) disrupt hydrogen bonding.

Answer 94

Surface-Active Agents

Question 95

2-Mercaptoethanol (HOCH2CH2SH) cleaves disulfide bonds by reducing –S–S– groups to –SH groups.

Answer 95

Reducing Agents

Question 96

Transition metal ions such as Pb2+, Hg2+, and Cd2+ form water-insoluble salts with –SH groups; Hg2+ for example forms –S–Hg–S–.

Answer 96

Heavy Metal Ions

Question 97

70% ethanol penetrates bacteria and kills them by coagulating their proteins. It is used to sterilize skin before injections.

Answer 97

Alcohols