Proteins

Question 1

Draw and label a diagram of an amino acid

Answer 1

Must include:

• amine group NH2
• carboxyl group - COOH
• variable R group
• H

Question 2

How many amino acids occur in life?

Answer 2

20

Question 3

What elements do all proteins contain?

Answer 3

Carbon, hydrogen, oxygen, nitrogen

Question 4

What are the 3 types of amino acids in life?

Answer 4

-5 non essential
Our body can make them from other amino acids
- 9 essential as they are only obtained by what we eat
- 6 conditionally essential
Only needed as children

Question 5

Draw a labelled diagram demonstrating condensation and hydrolysis of peptide bonds

Answer 5

• must show the water molecule removed

- use textbook to check

Question 6

Draw a dipeptide and label the bond

Answer 6

Use book to check

Question 7

Explain why there is a range of dipeptides and lots of variety in polypeptide chains

Answer 7

There are 20 amino acids
20x20 = 400 dipeptides

This quickly leads to a hugeee number of polypeptides

Question 8

Define polypeptide

Define protein

Answer 8

Polypeptide - a polymer of amino acids

Protein - one or more polypeptide chains arranged as a macromolecule with a specific function

Question 9

Define primary structure and describe how it is held together

Answer 9

• this is the sequence of amino acids in the polypeptide chain
• this is decided by DNA
• it is put together on ribosomes
• peptide bonds

Question 10

Define secondary structure

• what are the two types

- describe how it’s held in place

Answer 10

• chain folds or coils of polypeptide chain = secondary
• alpha helix or beta pleated sheets
• hydrogen bonds form between NH and CO of non adjacent amino acids

Question 11

Define tertiary structure

- describe how it is held in place

Answer 11

• further folding caused by bonds and interactions between R groups
• the secondary structure pulls R groups of amino acids closer
• weak hydrophobic / Philic interactions
• hydrogen bonds
• ionic bonds - oppositely charged R groups
• disulphide bridges - covalent and strong, but only between R groups containing sulphur

Question 12

Explain quaternary structure

- describe how it is held in place

Answer 12

Associations between separate polypeptide chains 
- uses all types of bonding 
Hydrophobic / Philic interactions
Hydrogen bonds
Ionic
Disulphide bridges

Question 13

Define globular protein

- properties

Answer 13

• compact
• water soluble
• spherical
• forms when hydrophilic R groups are on the outside of the protein, and hydrophobic are on the inside

Question 14

Define fibrous proteins

Answer 14

• long
• insoluble
• strong
• 2D ish
• high proportion of hydrophobic R groups
• repetitive primary structure

Question 15

Define prosthetic group

Answer 15

A non protein group that makes up the R group of an amino acid

Question 16

Define conjugated protein

Answer 16

• a globular protein that contains a prosthetic group

Question 17

Draw a table to show an example of

• a conjugated protein
• an enzyme
• peptide hormone

For each describe structure and function

Answer 17

Conjugated protein

• haemoglobin
• globular
• quaternary structure, 4 polypeptides
• transports oxygen

Enzyme

• catalase
• globular
• conjugated
• breaks down H2O2

Peptide hormone:

• insulin
• globular
• regulates blood glucose concentration

Question 18

3 examples of fibrous proteins

Answer 18

Keratin
Elastin
Collagen

Question 19

Compare structure properties and functions of 3 fibrous proteins

Answer 19

Keratin:

• strong disulphide bridges
• strong
• inflexible
• insoluble
• present in hair, skin and nails

Elastin:

• quaternary
• stretchy
• present in elastic fibres in blood vessels and alveoli

Collagen

• 3 polypeptide wound together
• strong, ropelike
• flexible
• connective tissue found in skin, tendons, ligaments