W1 - Amino acids

Question 1

How many aa are there?

Answer 1

20

Question 2

What is special about the carbon centre of an aa?

Answer 2

It is chiral

Question 3

At neutral pH, what are the amino acids called?

Answer 3

Zwitterions

Question 4

When the pH is low, what happens to the aa?

Answer 4

Amine groups become protonated, creating a positive charge

Question 5

When the pH is high, what happens to the aa?

Answer 5

The carboxyl group(s) become deprotonated, creating a negative charge

Question 6

What is the most common form of aa found in proteins?

Answer 6

L-isomer

Question 6

Which way does L/D isomers spin plane polarised light?

Answer 6

L - left (anticlockwise), D - right (clockwise)

Question 6

What determines the properties of the aa?

Answer 6

The chemical nature of the R groups

Question 7

What is the smallest aa and what does it’s side chain consist of?

Answer 7

Glycine, H only

Question 8

What two things can D isomers not do?

Answer 8

Can’t be digested or interact with tRNA

Question 9

How many amino acids are hydrophobic?

Answer 9

10

Question 10

What is the relation between size and hydrophobicity in G, A, V, L, I and M

Answer 10

As size increases, hydrophobicity increases

Question 11

What is the characteristic of GAVLIM hydrophobic aa side chains?

Answer 11

They are aliphatic

Question 12

Where are the hydrophobic R groups typically found and what is the exception?

Answer 12

Inside proteins, exception = external surface of integral/transmembrane proteins (channel)

Question 13

What can give an aa hydrophilic properties?

Answer 13

If it is charged/polar or both

Question 14

What groups in side chains can give hydrophilicity?

Answer 14

-OH and -NH-

Question 15

Which amino acid is an important buffer in blood?

Answer 15

Histidine

Question 16

What other characteristics do acidic and basic aa have? (@ physiological pH)

Answer 16

Acidic are negatively charged and polar, basic are positively charged and polar

Question 17

What are the uncharged derivatives of aspartate and glutamate?

Answer 17

Asparagine + Glutamine

Question 18

What makes asparagine and glutamine uncharged compared to aspartate/glutamate?

Answer 18

The O- is replaced by a neutral NH2

Question 19

Why is proline unique?

Answer 19

The R group is bound to both the chiral C centre and the NH2+

Question 20

Where is proline usually found?

Answer 20

In bends in proteins

Question 21

Are SH (thiol) and OH (hydroxyl) unreactive or reactive?

Answer 21

Reactive

Question 22

Where is histidine often found and why?

Answer 22

Active sites of enzymes because it can bind and release protons

Question 23

What are the three aromatic amino acids?

Answer 23

Phenylalanine, tryptophan, tyrosine

Question 24

How many +vely/-vely charged aa are there?

Answer 24

3 +ve, 2-ve

Question 25

How many uncharged hydrophilic aa are there?

Answer 25

5

Question 26

How many hydrophobic aa are there?

Answer 26

10