Proteins

Question 1

Name an example of a hydrophobic/non-polar amino acid.

Answer 1

Glycine, alanine, valine, leucine, isoleucine, methaoine, proline, phenylalanine, trytophan.

Question 2

Give an example of a polar, charged amino acid.

Answer 2

Asparte, Lysine, arginine, histidine, glutamate.

Question 3

Give an example of a polar, uncharged amino acid

Answer 3

Serine, theroine, glutamine, cystine, asparagine.

Question 4

What happens if the pH of a solution is lower than the pK value of an amino acid?

Answer 4

The amino acid will be protonated.

Question 5

What happens if the pH of a solution is greater than the pK value of an amino acid?

Answer 5

The protein will be deprotonated.

Question 6

Define the isoelectric point of a protein.

Answer 6

The pH at which there is no overall charge in a protein

Question 7

What are the characteristics of a basic protein?

Answer 7

Contain many positively charged, basic amino acids

Question 8

What are the characteristics of an acidic protein?

Answer 8

Contain many negatively charged, acidic amino acids. pI

Question 9

What is a conjugated protein?

Answer 9

Contains covalently linked chemical components in addition to amino acids?

Question 10

What are the four levels of protein structure?

Answer 10

Primary structure, Secondary Structure, Tertiary structure and quaternary structure

Question 11

What are the key features of an alpha helix?

Answer 11

Part of the secondary structure of a protein, 3.6aa/turn, 0.54nm pitch, right handed helix. Backbone c=o group is hydrogen bonded to a n-h group 4 amino acid residues away.

Question 12

What are the key features of a B-strand (or extended confirmation)

Answer 12

0.35nm between amino acids, r groups alternate between opposite sides of the chain.

Question 13

What are the 3 types of B-Strand?

Answer 13

Parallel (strands run in the same direction), antiparallel (strands run in different directions) and mixed (both parallel and anti-parallel parts)

Question 14

What are the two types of tertiary structure?

Answer 14

Fibrous (long strands or sheets, support, shape, protection) and globular (compact shape, catalysis and regulation)

Question 15

What two types of globular structures are there?

Answer 15

Domains (with a specific functional role) and motifs (folding patterns containing one or more elements of secondary structure)

Question 16

Name three of the forces involved in maintaining protein structure?

Answer 16

Three of: covalent (disulphide bonds), hydrophobic effect, van der walls forces, hydrogen bonds, ionic interactions.

Question 17

How do proteins fold?

Answer 17

All information for folding found in the primary sequence, not a random process, and sometimes chaperones are used to help with the folding of the proteins.

Question 18

What is an amyloid fibre?

Answer 18

Misfolded, charged form of normally soluble protein. Stabilised by lots of b sheets and hydrophobic interactions.

Question 19

Define a protein

Answer 19

Proteins are polypeptides made up of amino acids, which are joined covalently to determine the structure of the protein.

Question 20

What are some of the features of a peptide bond?

Answer 20

Planar, and with partial double bond characteristics so rigid.