Chapter 18

Question 0

Proteins

Answer 0

> polymers of amino acids
long chains of amino acids
fold to make 3d structures

Question 1

Most abundant organic molecule @ about 15% of human body mass:

Answer 1

Proteins

Question 2

Amino acids that link together by forming an Amide between carb. Acid & amino acid are:

Answer 2

Peptide bond

Question 3

How many standard amino acids are there?

Answer 3

20

> named by abbreviations

Question 4

Classification of amino acids

Answer 4

> Non polar- hydrocarbon side chain
polar neutral-alcohol,Amide,phenol side chain
Polar acidic-Carboxylic acid side chain
Polar basic-amine side chain

Question 5

Intermolecular forces & water effects of amino acids

Answer 5

> Non polar- London forces (hydrophobic)
polar neutral- hydrogen bonding (hydrophilic)
acidic- negative amino acids are attracted to basic

Question 6

Acid base properties

Answer 6

Amino acids are acids and bases
>amino group as a base [pka 9-10]
> Carboxylic acid as acid [pka 2-3]

Question 7

Zwitterions

Answer 7

In water @ pH amino acids exist with positive charge on amine & negative charge on Carboxylic acid

Question 8

pH changes

Answer 8

On amino acids:
>Negative charge is lost at low pH
>Positive charge is lost at high pH

Question 9

Isoelectric

Answer 9

Where the pH of the overall charge is zero
> all amino acids and all
Proteins have an isoelectric point

Question 10

Chiral

Answer 10

Molecules that have handedness
>mirrored
> the alpha carbon in all amino acids is chiral
(Different)

Question 11

Achiral

Answer 11

Molecules are symmetrical and have no mirror image

Same

Question 12

L-amino acids

Answer 12

All alpha amino acids in humans are left handed.

Question 13

Enantiomers

Answer 13

Right & left hand isomers of a chiral molecule
>mirror image isomers
>pairs have same boiling point, water solubility, & isoelectric point, differ in biological activity

Question 14

Peptides; etc:

Answer 14

Short polymers of amino acids
>oligopetide: 10-20aa
>polypeptide: 20-50aa
>protein: 50 or more aa

Question 15

Interactions that determine shape

Answer 15

> H-bond in backbone
H-bond between polar neutral side chains
ionic attractions between acidic and basic
hydrophobic interactions
covalent disulfide bonds

Question 16

4 levels of protein structure:

Answer 16

• primary:
• secondary:
• tertiary:
• quaternary:

Question 17

Alpha helix

Answer 17

Amino acids twist into a spiral like a spring; Coiled w/hollowed center; 4aa per turn

Question 18

Beta sheet

Answer 18

Protein chains are side by side; hydrogen bonding to both sides of a chat & forms a rigid sheet

Question 19

Fibrous proteins:

Answer 19

>long & thin
>insoluble in water
>ridgid
>proteins for hair, skin,nails, muscle
>mostly alpha-helix

Question 20

Globular proteins:

Answer 20

>globe shape 
>soluble in water
>enzymes, antibodies
>hydrophilic on the outside & hydrophobic on the inside 
>circulates in blood

Question 21

Random folding is an area of _____.

Answer 21

Flexibility

Question 22

Native protein

Answer 22

A protein in its correct functional shape

Question 23

Simple protein

Answer 23

Functional by themselves

Ex: insulin

Question 24

Hemoglobin

Answer 24

> globular protein that transports oxygen in the blood
conjugated (flat)
-can carry 4 oxygen molecules

Question 25

How hemoglobin works:

Answer 25

Oxygen binding to one hemoglobin subunit causes a shape change» proteins chains rotate to open all oxygen binding sites»>oxygen delivered to tissues and hemoglobin goes back to its shape!

Question 26

Denaturation

Answer 26

> proteins has a loss of function because of unfolding

> lose water solubility

Question 27

Reasons protein denature:

Answer 27

Heat, detergents, alcohol, acids/bases, Hg2+ and Pb2+