Amino Acids

Question 1

Name the 3 groups making up an amino acid

Answer 1

Side chain (R)

Primary amine (NH3+)

Carboxylate (COO-)

Question 2

Amino acid has no net charge due to opposite charges, what is this called

Answer 2

Zwitterion

Question 3

Name the ends of the amino acids

Answer 3

N terminus. And C terminus

Question 4

What is the carbon in the middle of an amino acid called

Answer 4

Alpha carbon

Question 5

What is the importance of the position of amino acids (CORN)

Answer 5

To be used in a protein they all need to be the L isomer Eg L alanine instead of D isomer

This follows the CO R N rule

Question 6

Peptide bonds are rigid due to partial double bonds. What gives it its double bond

Answer 6

The carbonyl oxygen gives the double bond between N = C. And the single bond swaps to the carbonyl oxygen

Question 7

Bonds can sometimes rotate in amino acids. The trans bond is the common one with the hydrogen on bottom of N, what is it called when hydrogen swaps to the top of nitrogen to be aligned with oxygen ?

Answer 7

Cis bond

Question 8

Why is the alpha carbon called asymmetric?

Answer 8

Different elements on each side of it. Eg side chain, NH3, coo

Question 9

Give the name of the 4 hydrophobic amino acids (due to hydrocarbon chains)

Answer 9

Valine - val V
Leucine - Leu L
Isoleucine - IIE I
Methionine - Met M

Question 10

3 aromatic amino acids

Answer 10

Phenylaline - Phe - F

Tryptophan - trp - W

Tyrosine - Tyr - Y

Question 11

Why is proline amino acid special?

Answer 11

It’s side chain joins back to the primary amine

Question 12

Give the codes for asparagine amino acid

Answer 12

Asn

N

Question 13

What is the one letter code for glutamine

Answer 13

Q

Question 14

Name the 2 negatively charged amino acids

(Due to the O-) and carboxylate chain

Answer 14

Aspartate - Asp - D

Glutamate - Glu - E

Question 15

Name the 2 positive amino acids (due to NH3+) side chains

Answer 15

Lysine - K - Lys

Arginine - Arg - R

Question 16

What makes hydrophobic amino acids hydrophobic? (Made of hydrocarbon chains)

Answer 16

Electro negativity is the same in carbon and hydrogen - ability to attract electrons

Electrons spread which gives them no overall charge (non polar) - can’t mix in water

Question 17

Aspartate and glutamate are negative, what gives them negative charge when in water

Answer 17

The carboxylate OH loses the H proton leaving it with just O-

Question 18

What happens to lysine and arginine to give them a positive charge

Answer 18

They start off as NH2 but a proton H associates in water and becomes NH3+

Question 19

Why is glycine not an L or D isomer

Answer 19

The side chain is H, this is the same as another chain meaning 2 same chains = no isomer

Question 20

Why is glycine in flexible regions of proteins

Answer 20

Because of the small side chain

Question 21

Cysteine contains SH which is unique. Why is this side chain so important for proteins

Answer 21

When SH oxidised. Sulfur makes cross links in proteins via DISULFIDE BONDS- needed in extra cellular proteins

Also can bind to metals like ZN++ to form a protein metal binding site

Question 22

Why is SH called a Thiol group?

Answer 22

Because the H is lost so easily. Ie allowing disulfide bonds

Question 23

Why is histidine partially positive charged

Answer 23

It is ionising like the others Eg glutamate- this is because it can accept or donate a positive proton.

Question 24

Can histidine bind to metals like ZN++?

Answer 24

Yes if there are 2 histidine in the case of ZN

Question 25

Why are aromatic amino acids hydrophobic

Answer 25

CH rings, electro negativity is equal which means floating electrons. No charge