Chapter 3.2.1 (Exam 1) Proteins + Amino Acids

Question 1

What do proteins consist of?

Answer 1

Proteins consist of one or more polypeptide chains—single, unbranched chains of amino acids

The chains are folded into specific 3-D shapes as defined by the sequence of amino acids

Question 2

Which functional groups do amino acids have?

Answer 2

Carboxyl and amino groups

Question 3

What is the structure of an amino acid?

Answer 3

Central carbon attached to a hydrogen, amino group, carboxyl group, and a side chain/R-group

Question 4

Do side-chains/R-groups have functional groups? What are amino acid groups based on?

Answer 4

Side chains or R-groups also have functional groups

Amino acids are grouped based on the side chains

Question 5

What is a result of the α carbon in amino acids (contains both amino and carboxyl group) being asymmetrical?

Answer 5

Amino acids can be optical isomers, D- and L-amino acids

Question 6

What is a result of amino acids having both carboxyl and amino groups? How is that so?

Answer 6

They function as both an acid and a base

Acids donate hydrogen ions (COOH releases its H⁺)

Bases accept hydrogen ions (NH₂ accepts an H⁺)

Question 7

What are the groupings of amino acids?

Answer 7

5 with electrically charged side chains (ionized, hydrophilic, and attracts opposite charge)

5 with polar side chains (hydrophilic, form H-bonds with water and other polar molecules)

7 with nonpolar side chains (hydrophobic)

3 special amino acids

Question 8

What are the 3 special amino acids?

Answer 8

Cysteine
-SH group, disulfide bridges

Glycine
R group consists of single H atom

Proline
Has a ring structure

Question 9

What are the 5 amino acids with electrically charged side chains?

Answer 9

3 positively charged:
Arginine
Histidine
Lysine

2 negatively charged:
Aspartic acid
Glutamic acid

Question 10

What are the 5 amino acids with polar, but uncharged side chains

Answer 10

GSTAT
Glutamine
Serine
Threonine
Asparagine
Tyrosine

Question 11

What are the 7 amino acids with nonpolar side chains?

Answer 11

VAMPLIT
Valine
Alanine
Methionine
Phenylalanine
Leucine
Isoleucine
Tryptophan

Question 12

How does cysteine form disulfide bridges?

Answer 12

The terminal —SH group can react with another cysteine side chain to form a disulfide bridge, or disulfide bond (—S—S—)

Question 13

Why are the disulfide bridges that cysteine can form important?

Answer 13

These are important in protein folding but most cysteines in a protein are not involved in disulfide bridges