Chapter 3 Biochemistry

Question 1

_________ are macromolecules composed of amino acids that participate in nearly all cellular activities.

Answer 1

Proteins

Question 2

Any protein in the human body can be created from permutations of only ____________.

Answer 2

20 Amino Acids

Question 3

What is the basic structure/groups of an amino acid?

Answer 3

A central alpha carbon with an acidic carboxyl group, a basic amino group, alpha hydrogen, and unique R-group/side chain.

Question 4

Each of the 20 amino acid’s unique chemical structure dictates its ______, ______, _______, and _______.

Answer 4

Size, Charge, Polarity, Hydrophobicity

Question 5

How many possible stereoisomers do amino acids have? What is this due to?

Answer 5

2 possible stereoisomers due to tetrahedral arrangement of amino acids.

Question 6

9 amino acids are essential. What does this mean?

Answer 6

Must consume these from our diet.

Question 7

Depending on their R substituents, what are the 6 categories that amino acids can be placed in?

Answer 7

Nonpolar Aliphatic, Nonpolar
Nonpolar Aromatic
Polar
Polar (+) Charged, Polar (-) Charged

Question 8

Which 7 amino acids have ionizable side chains?

Answer 8

Tyrosine, Cysteine, Lysine, Histidine, Arginine, Aspartate, Glutamate

Question 9

LQ: Which amino acid(s) has three pKa values?
A) Leucine
B) Proline
C) Lysine
D) Threonine
E) Cysteine

Answer 9

C) Lysine
E) Cysteine

Question 10

Describe properties of Nonpolar Aliphatic R Groups and how they stabilize proteins.

Answer 10

Nonpolar side chains want to cluster together within proteins in center, with polar groups on the outside exposed to aqueous solution. Stabilize the protein through the hydrophobic effect.

Question 11

Describe properties of Aromatic R Groups.

Answer 11

R groups absorb UV light at 270-280nm. Exploit this property to characterize proteins. Can contribute to the hydrophobic effect.

Question 12

Describe properties of Polar Uncharged R Groups. What is special about cysteine?

Answer 12

R groups can form hydrogen bonds. Hydrophilic in nature. Cysteine can form disulfide bonds (modest polarity).

Question 13

Describe the properties of (+) Charged R Groups.

Answer 13

Have significant positive charge at pH 7.0. Some of the most hydrophilic side chains (charged).

Question 14

Describe the properties of (-) charged R groups.

Answer 14

Have a net negative charge at pH 7.0.

Question 15

LQ: Which amino acid would most likely be found in the interior of a globular protein?
A) Val
B) D
C) Aspartate
D) Cysteine
E) Y

Answer 15

A) Val