proteins 1

Question 1

What do proteins do?

Answer 1

provide structure (bone, skin, tendon)
Transport molecules (LDL-cholesterol, haemoglobin-oxygen)
Defence (antibodies)
Biological catalysts (enzymes, eg lysosomes)
Regulation of genes (lac repressor)

Question 2

Hypercholesterolemia

Answer 2

mutation histadine residue in LDL receptor

Question 3

What do the functions of protein really come down to?

Answer 3

Specific binding which depends on conformation

Question 4

What changes the activity of a protein?

Answer 4

A change in conformation

Question 5

What are proteins?

Answer 5

Linear polymers: amino acids joined by peptide bonds

Question 6

What defines the structure and function of a protein?

Answer 6

The R group of it’s amino acids

Question 7

Classification of hydrophilic amino acids

Answer 7

Basic
Acidic
Polar with uncharged R groups

Question 8

Basic amino acids (hydrophillic)

Answer 8

Lysine
Arginine
Histidine

Question 9

Acidic amino acids (hydrophillic)

Answer 9

Aspartate and Glutamate

Question 10

Polar amino acids with uncharged R groups (hydrophillic)

Answer 10

Serine, Threonine, Asparagine, Glutamine

Question 11

Hydrophobic amino acids

Answer 11

Alanine, Valine, Isoleucine, Leucine, Methionine, phenylalaline, Tyrosine, Tryptophan

Question 12

Special amino acids

Answer 12

Cysteine (covanent S-S)
Glycine (smallest)
Proline (ring R, kink)

Question 13

what do we mean by acid

Answer 13

a molecule that tends to release a hydrogen ion

Question 14

what do we mean by base

Answer 14

ion that readily binds to H

Question 15

How is the pH of a reaction calculated?

Answer 15

Henderson hasselbach equation

pH=pKa + log [A-]/[HA]

Question 16

What is the pKa of an acid?

Answer 16

The pH at which half the molecules are disassociated.

Question 17

Why is pH relevant?

Answer 17

Affect disassociation(mainly over 2 units of pH centred on pKa) 
Changes charge of overall aminoacid.
Means local environment affect pKa.

Question 18

Give an example where a reduction in pH affects proteins

Answer 18

histadine residues -on LDL acting as carriers (cholesterol)- change conformation with change in pH, release cholesterol in endosomes

Question 19

Peptide bond

Answer 19

condensation reaction, carbon from carboxylate shares electron with N from amino

Question 20

Why is there a limit to the number of 3D conformations possible for a peptide?

Answer 20

peptide bond does not permit rotation, bulky R groups positioned on either side of backbone

Question 21

What is secondary structure of a protein? (Stabilised by H bonds)

Answer 21

periodic repeats, initial folding patter.

a helix, b sheet, bend/loop

Question 22

What groups are capable of hydrogen bonding?

Answer 22

H and oxygen, nitrogen or fluorine