Polymers of Life 5: Proteins

Question 1

definition of alpha amino acid

Answer 1

• Molecules that contain an amino group and a carboxylic acid group that are separated by 1carbon
• carbon atom next to the COOH group ( therefore no. 2 in carbon chain staring from that functional group ) is called the alpha carbon dioxide

Question 2

What does alpha amino acid’s naming usually start with

Answer 2

2-amino

Question 3

What is an amino acid

Answer 3

• amine group NH2
• carboxylic acid
• R group
• H

Question 4

What happens when you join amino acids together

Answer 4

polypeptides are formed with the removal of water due to it being a condensation reaction

Question 5

How would you describe a peptide bond

Answer 5

A covalent bond that is rigid and cannot turn

Question 6

How would you describe different polypeptide

Answer 6

• Backbone of polypeptides is generally the same but with different R groups attached
• R groups will affect the shape of the polypeptide due to R groups being different sizes

Question 7

Describe a primary structure of a protein

Answer 7

Sequence of amino acids which is unique to each protein

Question 8

Describe secondary structure of a protein

Answer 8

• coiling & folding of the polypeptide because of hydrogen bonds into an alpha helix and a beta sheet

( - Spatial arrangement of sections of primary structure e.g. helixes or sheets

• held together by hydrogen bonds )

Question 9

Describe tertiary structure of a protein

Answer 9

Overall 3-D shape of protein Based on interactions between its various side chains

Question 10

Why is the sequence of amino acids not random

Answer 10

It is determined by genetic information DNA

Question 11

What is shapes kind of secondary structure of a protein take shape in

Answer 11

1. Alpha helix = held together by hydrogen bonds be

2. beta pleated sheet = held together by hydrogen bonds between amide + carbonyl group

Question 12

And a polypeptide folds in on itself from a secondary to tertiary what kinds of intermolecular forces are responsible for holding it together
( 4 )

Answer 12

1. Ionic bonds = NH3+ and COO- of exposed amino acids ( due to zwitterion form of amino acids )
2. Hydrogen bonds = amide + carbonyl groups or alcohols
3. instantaneous dipole - induced dipole = non polar side chains ( large hydrocarbon groups )
4. Disulphide bridges = covalent bonds between amino acid cysteine which includes sulphur atoms

Question 13

Describe the strength of the four intermolecular forces holding protein structures together

Answer 13

Srongest

• disulphide bridges
• hydrogen bonding
• ionic bonds
• instantaneous dipole - induced dipole

Weakest

Question 14

Describe the levels of organisation of a protein

Answer 14

1. Primary = Sequence of amino acids of the protein
2. Secondary = Hydrogen bonds in the peptide chain back pain = alpha helix and beta sheets
3. Tertiary = Mostly in noncovalent interactions between that our groups within the protein

Question 15

Describe haemoglobin

Answer 15

• Protein that carries oxygen and red blood cells
• 4 polypeptide chains = 2 identical alpha chains & 2 identical beta chains

= overall quaternary structure due to 2 secondary structures ( alpha & beta ) coming together