chapter 3 proteins

Question 1

enzymes

Answer 1

serve as catalysts, increasing the rates of chemical reactions

Question 2

Salivary amylase

Answer 2

digests starch in the mouth

Question 3

structural proteins

Answer 3

physical support and shape

Question 4

Collagen

Answer 4

in the skin

Question 5

Motility proteins

Answer 5

contraction and movement

Question 6

Microtubules

Answer 6

in a sperm’s flagellum

Question 7

Regulatory proteins

Answer 7

control and coordinate cell function. Peptide hormones

Question 8

Transport proteins

Answer 8

move substances into and out of cells. Hemoglobin

Question 9

Signaling proteins

Answer 9

communication between cells. Interferon

Question 10

Receptor proteins

Answer 10

enable cells to respond to chemical stimuli from the
environment. Beta-adrenergic receptor

Question 11

Defensive proteins

Answer 11

protect against disease. Antibodies

Question 12

Storage proteins

Answer 12

reservoirs of amino acids. Albumin

Question 13

Amino Acid Structure

Answer 13

• R group
• All amino acids except glycine have an asymmetric alpha carbon atom
• The specific properties of amino acids depend on the nature of their R groups

Question 14

Acidic amino acids are ___ changed whereas basic amino acids are ____ charged

Answer 14

neg, pos

Question 15

____ amino acids tend to be found on the surfaces of proteins

Answer 15

Polar

Question 16

The simplest amino acid is ___, with just a hydrogen as its R group

Answer 16

Glycine

Question 17

The end with the amino group is called the

Answer 17

N or amino terminus

Question 18

The end with the carboxyl group is calle dthe

Answer 18

C or carboxyl terminus

Question 19

The N terminus corresponds to the __ end of the mRNA that codes for it

Answer 19

5’

Question 20

Primary Structure

Answer 20

amino acid sequence

Question 21

Secondary Structure

Answer 21

local folding of polypeptide

Question 22

tertiary structure

Answer 22

3 dimensional conformation

Question 23

Quaternary Structure

Answer 23

interactions between monomeric proteins to form a multimeric unit

Question 24

By convention, amino acids sequences are written from the _ to _ terminus

Answer 24

N to C

Question 25

The first protein to have its amino acid sequence determined was the hormone

Answer 25

insulin

Question 26

Secondary Structure

Answer 26

local regions of structure that result from hydrogen bonding between NH and CO groups along the polypeptide backbone.

Question 27

Alpha Helix

Answer 27

spiral in shape, consisting of the peptide backbone, with R groups jutting out from the spiral.

Question 28

In the secondary structure of a triple helix

Answer 28

* three polypeptide chains are woven together * hydrogen bonds hold the chains together, giving the polypeptide the added strength typical of collagen, connective tissue, skin, tendons, and cartilage

Question 29

Beta sheet

Answer 29

* The β sheet is an extended sheet-like conformation with successive atoms of the polypeptide chain located at “peaks” or “troughs.” * The R groups jut out on alternating sides of the sheet. * Because of the formation of peaks and troughs, it is sometimes referred to as a β-pleated sheet.

Question 30

If the parts of polypeptides forming the β sheet have the same polarity (relative to the N- and C- termini), they are called

Answer 30

parallel

Question 31

If the parts of polypeptides forming the β sheet have opposite polarity, they are called

Answer 31

antiparallel

Question 32

In patients with Alzheimer's disease, beta amyloid proteins change from what to what?

Answer 32

a normal alpha helical shape to beta pleated sheets that stick together and form plaques

Question 32

Which amino acids tend to form alpha helices?

Answer 32

leucine, methionine, glutamate

Question 33

Which amino acids tend to form Beta sheets?

Answer 33

isoleucine, valine, phenylalanine

Question 34

Proline

Answer 34

cannot form hydrogen bonds and tends to disrupt α helix structures by introducing a bend in the helix.

Question 35

SECONDARY STRUCTURES ARE REUSED IN MANY PROTEINS BECAUSE

Answer 35

THE INTERACTIONS ARE BASED ON THE CARBOXYL/AMINO GROUPS

Question 36

Is tertiary structure easy to predict?

Answer 36

NO

Question 37

How is tertiary structure predicted?

Answer 37

It results from the sum of hydrophobic residues avoiding water, hydrophilic residues interacting with water, the repulsion of similarly charged residues, and attraction between oppositely charged residues. * SO many possibilities!!

Question 38

Sections of a protein interact to create the tertiary structure of a protein due to

Answer 38

* hydrophobic interactions between two nonpolar amino acids * hydrophilic interactions between the external aqueous environment and the R groups of polar amino acids * salt bridges, ionic bonds between ionized R groups of basic and acidic amino acids * hydrogen bonds between H of a polar R group and the O or N of another amino acid * disulfide bonds -S-S- between the -SH groups of cysteine amino acids

Question 39

The most stable possible three-dimensional structure of a particular polypeptide is called the

Answer 39

native conformation

Question 40

Fibrous proteins

Answer 40

have extensive regions of secondary structure, giving them a highly ordered, repetitive structure.

Question 41

Examples of fibrous proteins

Answer 41

* Fibroin proteins of silk * Keratin proteins of hair and wool * Collagen found in tendons and skin * Elastin found in ligaments and blood vessels

Question 42

globular proteins

Answer 42

folded into compact structures (most enzymes)

Question 43

quaternary structure

Answer 43

the level of organization concerned with subunit interactions and assembly

Question 44

A higher level of assembly is possible in the case of proteins (often enzymes) that are organized into

Answer 44

multiprotein complexes

Question 45

Denaturation

Answer 45

involves the disruption of bonds in the secondary, tertiary, and quaternary protein structures

Question 46

4 examples of denaturation

Answer 46

-heat and organic compounds that break apart H bonds and disrupt hydrophobic interactions - acids and bases that break H bonds between polar R groups and disrupt ionic bods -heavy metal ions that react with S-S bonds to form solids -agitation, such as whipping that stretches peptide chains until bonds break

Question 47

Example of denaturation

Answer 47

when an egg is cooked