Proteins and Enzymes

Question 1

Describe the induced fit model o enzyme action and how an enzyme acts as a catalyst.

Answer 1

• Substrate binds to active site
• Active site changes shape slightly so that it is complementary to substrate.
• Reduces activation energy

Question 2

In an experiment investigating the enzyme action of ATP synthase. Suggest a procedure scientists could have used to stop the reaction.

Answer 2

• Boil
• Denatures ATP synthase

Question 3

Explain the change in ATP concentration with increasing inorganic phosphate concentration.

Answer 3

• As Pi concentration increases, more enzyme complexes form
• Enzyme concentration becomes limiting factor

(refer to graph when necessary)

Question 4

A competitive inhibitor decreases the rate of an enzyme controlled reaction. Explain how.

Answer 4

• competitive inhibitor has a similar shape to the substrate
• binds to active site and occupies it.
• reduces the enzyme complexes that can form.

Question 5

Describe how the structure of a protein depends on the amino acids it contains.

Answer 5

• structure of protein is determined by the R group on amino acids.
• primary structure is a sequence of amino acids in a polypeptide
• secondary structure is formed by hydrogen bonds
• tertiary structure is formed by interactions
• Quaternary structure has more than one polypeptide chain

Question 6

Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.

Answer 6

• one amine group joins to a carboxyl group to form a peptide bond.
• So there is a free amine group and a free carboxyl group at the other end.

Question 7

Explain how the active site of an enzyme causes a high rate of reaction.

Answer 7

• Reduces activation energy
• Induced fit causes the active site to change shape
• enzyme-substrate complex causes bonds to form/break