Amino Acid Structures and Properties

Question 1

What is the average weight of one amino acid?

Answer 1

110g/mol or 110 Da

Question 2

What is the only achiral amino acid?

Answer 2

Glycine

Question 3

What are the basic building blocks of proteins?

Answer 3

Amino acids

Question 4

How many types of amino acids can our body encode for?

Answer 4

20

Question 5

What is the basic structure of an amino acid.

Answer 5

It has a carboxylic acid, hydrogen, amine group, and R side chain all attached to an Alpha carbon.

Question 6

Are all of the chiral amino acids L-amino or D-amino acids? (based on the rotation of plane-polarized light)

Answer 6

L-amino (Living)

Question 7

Which chiral amino acid is the only one with a R configuration? (based on structure)

Answer 7

Cysteine

Question 8

What is a tetrapeptide?

Answer 8

A protein formed by 4 amino acids

Question 9

Define a chiral center.

Answer 9

It is a carbon with 4 different substituents and has superimposable mirror images (enantiomers). It can also rotate plane polarized light.

Question 10

Do most amino acids have an R or S configuration?

Answer 10

S

Question 11

Define aliphatic amino acids

Answer 11

hydrocarbon side groups

Question 12

How many non-polar and non-aromatic amino acids are there and what are they?

Answer 12

7
Glycine (Gly) G
Alanine (Ala) A
Valine (Val) V
Leucine (Leu) L
Isoleucine (Ile) I 
Methionine (Met) M 
Proline (Pro) P

Question 13

What makes methionine unique in the non-polar and non-aromatic group?

Answer 13

It is one of two amino acids with a Sulfur (S) atom. It is also found in eggs and is involved in DNA methylation.

Question 14

Why is proline unique?

Answer 14

It is the only amino acid that has a cyclic component that links back with the amino acid itself. The N in the amine group is part of proline’s side chain. It is rarely found in the middle of regular secondary structure of proteins because it has the ability to break the secondary structure up by introducing proline kinks. Common in turns between peptide strands in beta-pleated sheets.

Question 15

How many non-polar and aromatic amino acids are there and what are they?

Answer 15

3
Phenylalanine (Phe) F - found in aspartame
Tyrosine (Tyr) Y
Tryptophan (Trp) W -precursor of serotonin and melatonin

Question 16

What is aspartame?

Answer 16

Artificial sweetener

Question 17

What is a precurser?

Answer 17

It is a substance from which another is formed, especially by metabolic reaction.

Question 18

How many polar uncharged amino acids are there and what are they?

Answer 18

5
Serine (Ser) S - targeted by phosphorylation, primary -OH
Threonine (Thr) T - secondary -OH
Asparagine (Asn) N - amide
Glutamine (Gln) Q - amide
Cysteine (Cys) C

Question 19

Why is cysteine a unique amino acid?

Answer 19

It is the only chiral amino acid with and R configuration. It is one of two amino acids with a sulfur atom. It contains a thiol group S-H. Two cysteine residues can for covalent disulfide bonds which are very important in tertiary structure of protein.

Question 20

How many positively charged/basic amino acids are there and what are they?

Answer 20

3
Lysine (Lys) K
Arginine (Arg) R - most basic amino acid
Histidine (His) H - uncharged in physiological conditions

Question 21

How many negatively charged/acidic amino acids are there and what are they?

Answer 21

2
Aspartic Acid (Asp) D - helps make aspartame
Glutamic Acid (Glu) E - important neurotransmitter

Question 22

What is a bronsted-lowry base

Answer 22

A proton acceptor

Question 23

What is a bronsted-lowry acid

Answer 23

A proton donor

Question 24

What is a proline kink?

Answer 24

How proline breaks up the helical and sheet motifs of secondary structure of proteins.