Proteins

Question 1

Describe what amino acids are.

Answer 1

Amino acids are the monomers that make up proteins

Question 2

Describe the formation and products of a peptide bond?

Answer 2

• A condensation reaction between 2 amino acids forms a peptide bond
• Dipeptides are formed by the condensation of 2 amino acids
• polypeptides are formed by the condensation of many amino acids

Question 3

Describe the different levels in protein structure

Answer 3

Primary
- the specific sequence of amino acids in a polypeptide chain - peptide bond

Secondary
- the curling or folding if the polypeptide chain into a alpha helice or a beta pleated sheet due to the formation of hydrogen bonds - hydrogen bonds

Tertiary
- the overall 3D shape of a protein, which is determined by interactions between r groups - hydrogen/ionic/covalent bonds

Quaternary
- the specific 3D shape of a protein that is determined by the multiple polypeptide chains or the prosthetic groups bonds together - hydrogen/ionic bonds

Question 4

what is the biuret test for proteins?

Answer 4

1) Add biuret solution - sodium hydroxide + copper (II) sulfate
2) If present, it turns purple. If there is none, it stays blue
- it also detects the presence of peptide bonds

Question 5

Describe the nature and function of enzymes

Answer 5

• Enzymes are biological catalysts that catalyse intracellular and extracellular reactions that determine strictures and functions from cellular to whole organism level
• It lowers the activation energy of a reaction and speeds up the rate of reaction

Question 6

What is the Lock and Key model?

Answer 6

• Active site is a fixed shape, and is complementary to only 1 substrate
• after a successful collision, an enzyme substrate complex is formed, leading to a reaction

Question 7

What is the Induced Fit Model?

Answer 7

1) Before reaction, enzyme active site is not complementary to substrate
2) Active site shape changes as the substrate binds and an enzyme substrate complex forms
3) This distorts bonds in the substrate, leading to a reaction

Question 8

How does temperature affect rate of reaction

Answer 8

• Increasing temperature causes an increase in kinetic energy
• molecules move around faster and therefore more collisions and E S complexes.
• Increasing temperature above optimum causes enzymes to denature. The tertiary structure and active site changes shape, and so there is a lower rate of reaction