Chapter 4 - Enzymes

Question 1

What are enzymes

Answer 1

Biological catalysts
Globular proteins

Question 2

What type of reactions do enzymes catalyse

Answer 2

Anabolic and catabolic

Question 3

Anabolic reactions

Answer 3

Building up eg. Condensation reactions

Question 4

Catabolic reactions

Answer 4

Breaking down eg. Digestion

Question 5

What is the active site

Answer 5

An area within the tertiary structure of the enzyme that is complementary to the shape of a specific substrate

Question 6

How does enzyme bind to the subrate

Answer 6

R-groups in the tertiary structure in the active site form temporary bonds with the substrate

Question 7

Lock and key hypothesis

Answer 7

The specificity of the active site to the substrate

Question 8

Induced fit hypothesis

Answer 8

The active site changes shape to fit the substrate after it binds
The initial reaction is weak but it induces a change to the tertiary structure of the enzyme to strengthen the binding

Question 9

Intracellular enzymes

Answer 9

Enzymes that catalyse reactions inside cells

Question 10

Example of intracellular enzyme

Answer 10

Catalase breaks down H2O2 into O2 and H2O to prevent accumulation in cells as it is toxic

Question 11

Extracellular enzymes - amylase

Answer 11

• starch molecules to large to be absorbed into blood
• amylase (in saliva) breaks starch down partially into maltose
• maltase in the small intestine breaks maltose into glucose which can be absorbed

Question 12

Extracellular enzymes - trypsin

Answer 12

Trypsin (a protease) in pancreas breaks down proteins into smaller peptides which can be easier broken down into amino acids by other proteases for absorption into the blood

Question 13

Temperature coefficient

Answer 13

Q10 - how much rate increases per 10 degree Celsius rise (usually 2)

Question 14

Vmax

Answer 14

The maximum rate
When all enzyme active sites are occupied or no more substrate

Question 15

What is an inhibitor

Answer 15

Molecules that prevent enzymes from carrying out their normal function

Question 16

Competitive inhibitor

Answer 16

• Same shape as substrate to fit into the active site
• blocks substrate and prevents catalysis which slows rate
• normally temporary and reversible
• can still reach Vmax by increasing substrate concentration

Question 17

Non-competitive inhibitors

Answer 17

• bind to allosteric site
• changes tertiary structure of enzyme and active site
• specificity lost
• irreversible
• cannot reach Vmax

Question 18

End product inhibition

Answer 18

Non-competitive reversible inhibition
Prevents excess product being formed

Question 19

What do co-factors and co-enzymes do

Answer 19

Non-protein helper components that help enzymes carry out their function

Question 20

Co- factors

Answer 20

Inorganic molecules or ions

Question 21

Examples of co-factors

Answer 21

• Cl- for amylase
• Zn2+ prosthetic group for carbonic anhydrase

Question 22

Co-enzymes

Answer 22

Organic molecules

Question 23

Where do coenzymes come from

Answer 23

Usually found in vitamins