2. Enzymes

Question 1

What are enzymes?

Answer 1

Enzymes are catalyst molecules that change the rate of chemical reactions

Question 2

Explain the Enzyme Cycle

Answer 2

Catabolic reaction:
Substrate + enzyme —> enzyme-substrate complex —> enzyme + products

Anabolic reaction:
Enzyme + products —> enzyme substrate complex —> enzyme + substrate

Question 3

What is the active site?

Answer 3

The active site of an enzyme is where the substrate fits. The specific nature of an enzyme is due to this fit. A chemical reaction cannot occur if the active site of an enzyme does not fit a particularly shaped substrate

Question 4

What are inhibitors?

Answer 4

Competitive inhibitors compete with the substrate to block the active site (and therefore stop the reaction)

Non-competitive inhibitors don’t approach the active site, but change its shape, so specific substrates can no longer fit

Question 5

What are factors that affect enzyme action?

Answer 5

• temperature: excessive heat can denature enzymes, obstructing them from interacting with the substrate
• pH: certain enzymes require acidic or alkaline environments
• enzyme concentration: the greater enzyme concentration, the greater the rate of reaction
• substrate concentration: higher substrate concentrations may limit the rate of reaction

Question 6

What are metabolic pathways?

Answer 6

Metabolic pathways alter molecules in a series of steps, to either build them up or break them down

Catabolic pathways: give off energy by breaking down complex molecules (e.g. respiration)

Anabolic pathways: consume energy to build complex molecules (e.g. photosynthesis)