IGCSE Biology - Enzymes Flashcards

Flashcards for IGCSE Biology covering Enzymes topic, based on lecture notes.

What is a catalyst?

A substance that increases the rate of a chemical reaction and is not changed by the reaction.

Define enzymes.

Proteins that function as biological catalysts.

Why are enzymes important in living organisms?

Enzymes increase reaction speeds necessary to sustain life.

Describe enzyme action.

Enzymes have complementary shapes to their substrates, allowing for the formation of a product.

What happens during enzyme denaturation?

Enzymes lose their shape and can no longer catalyse reactions.

What is the active site of an enzyme?

The specific region of an enzyme where the substrate binds.

What is the enzyme-substrate complex?

The intermediate structure formed when a substrate binds to the active site of an enzyme.

What is meant by 'specificity of enzymes'?

Enzymes are specific because their active site has a complementary shape to fit a specific substrate.

How does temperature affect enzyme activity?

Temperature affects the kinetic energy of enzymes and substrates, influencing collision frequency. High temperatures can lead to denaturation.

How does pH affect enzyme activity?

Changes in pH can alter the shape and fit of the active site, potentially leading to denaturation.

List five properties of enzymes.

1. They are all proteins, 2. Each enzyme catalyses one reaction only, 3. They can be reused again, 4. They are affected by pH, 5. They are affected by temperature.

Explain the concept of 'complementary shapes' in enzyme-substrate interaction.

The active site of an enzyme has a shape that is complementary to the shape of its specific substrate, like pieces of a jigsaw puzzle.

Give three examples of what enzymes can do.

Enzymes can: i) break down large molecules into smaller ones, ii) build up smaller molecules into large ones, iii) convert small molecules into other molecules.

What happens to enzyme activity at temperatures above the optimum temperature?

Enzyme activity will decrease; enzymes can denature.

What happens to enzyme activity at pH levels significantly away from the optimum?

Enzyme activity decreases; the enzyme loses its shape and denatures.

Explain why plateau is reached in substrate concentration graph.

All enzyme active sites are occupied, so the reaction rate does not increase with additional substrate

Define enzyme denaturation.

An irreverisible change in the enzymes shape

Why is it incorrect to say an enzyme is 'killed'?

Enzymes are not living things; they are proteins. The term 'denatured' should be used instead.

List four factors that affect enzyme activity.

1. Temperature, 2. pH, 3. Substrate concentration, 4. Enzyme concentration

What happens to particles as temperature increase in stage 1 of temperature graph description?

Particles gain more kinetic energy as temperature increases.