ESAT Biology B8

What is the active site of an enzyme?

A specific 3D region where the substrate binds and the reaction occurs.

What is enzyme specificity?

Each enzyme only reacts with a particular substrate that fits its active site.

What is the enzyme-substrate complex (ESC)?

The temporary combination of an enzyme and its substrate during a reaction.

Are enzymes used up in reactions?

No, enzymes are unchanged and can be used again.

What is a hydrolysis reaction?

A reaction where water breaks down a substrate into smaller molecules.

What is a condensation reaction?

A reaction where water is removed to join molecules together.

What is the induced fit theory?

The enzyme slightly changes shape to fit the substrate more closely, increasing reaction efficiency.

What happens when an enzyme is denatured?

Its active site changes shape, so the substrate can no longer bind, and the reaction stops.

How does temperature affect enzyme activity?

Increasing temperature increases kinetic energy and collisions until the optimum; above this, enzymes denature and activity decreases.

How does pH affect enzyme activity?

Each enzyme has an optimum pH; moving away from it causes denaturation and reduced activity.

What are optimum conditions for enzymes?

The temperature and pH at which an enzyme works fastest without denaturing.

Give an example of an enzyme that digests carbohydrates.

Amylase, which breaks down starch into sugars.

Give an example of an enzyme that digests proteins.

Protease, which breaks down proteins into amino acids.

Give an example of an enzyme that digests fats.

Lipase, which breaks down lipids into fatty acids and glycerol.

What are intracellular enzymes?

Enzymes that work inside cells, e.g., those involved in respiration or photosynthesis.

What are extracellular enzymes?

Enzymes secreted outside cells to digest molecules, e.g., digestive enzymes in the stomach or small intestine.

Why are digestive enzymes extracellular?

They must break down large molecules outside cells so that the smaller products can be absorbed.

Give an example of a commercial use of enzymes.

Biological washing powders contain proteases and lipases to remove stains.

Why are biological washing powders recommended to be used at a maximum of 40°C?

Higher temperatures denature the enzymes, making them ineffective. :: What happens to enzyme activity as temperature increases?

What happens to enzyme activity above the optimum temperature?

The enzyme denatures, the active site is altered, and the reaction rate decreases.

What happens to enzyme activity when pH moves away from the optimum?

The enzyme denatures, and the reaction rate decreases.

Why do different species have enzymes with different optimum conditions?

Enzymes adapt to the species’ habitat, e.g., hot springs enzymes have higher optimum temperatures than Arctic enzymes.

What is catalase?

An enzyme that breaks down hydrogen peroxide into water and oxygen.

How can the effect of temperature on catalase be measured?

By measuring the height of foam formed from oxygen release when hydrogen peroxide is broken down.

What did the potato catalase experiment show?

Optimum temperature for potato catalase was around 35°C; above this, enzyme shape started to change and activity decreased.

How can the effect of pH on amylase be tested?

By incubating starch-agar with amylase at different pH levels and flooding with iodine to see the clear zone of starch digestion.

Why was the clear zone small at pH 11 in the amylase experiment?

The enzyme was denatured and could not digest starch effectively.

What are carbohydrases?

Enzymes that break down carbohydrates into smaller, soluble sugars.

What are proteases?

Enzymes that break down proteins into amino acids.

What are lipases?

Enzymes that break down lipids (fats) into fatty acids and glycerol.

Why are intracellular enzymes important?

They catalyze reactions inside cells, such as respiration and photosynthesis, essential for cell metabolism.

Give examples of extracellular enzyme use.

Digestive enzymes in food digestion, commercial use in baby food, washing powders, sugar syrups, ethanol, beer, and wine production.

Why are catalysts necessary in organisms?

Reactions would occur too slowly without enzymes to sustain life processes.

Why does only enzyme Y catalyse a reaction with a specific substrate?

Enzymes are specific; only substrates with a complementary shape fit the enzyme’s active site.

Why are digestive enzymes extracellular in humans?

They are secreted outside cells to break down food so nutrients can be absorbed in the small intestine.

Are enzymes used by decomposers intracellular or extracellular?

Extracellular; they break down dead organic material outside the cells.

Why should biological washing powders be used at a maximum of 40°C?

High temperatures can denature the enzymes, reducing their effectiveness.

What is an enzyme-substrate complex (ESC)?

A temporary structure formed when a substrate binds to the active site of an enzyme.

Does an enzyme get used up in a reaction?

No, the enzyme remains unchanged and can catalyse multiple reactions.

What type of reaction breaks substrates by adding water?

Hydrolysis reaction.

What type of reaction forms products by removing water?

Condensation reaction.

What is the lock-and-key model of enzyme action?

The substrate fits perfectly into the active site, like a key fitting into a lock, showing enzyme specificity.

What is the induced fit model of enzyme action?

The active site slightly changes shape to fit the substrate better, improving reaction efficiency.

What factors affect the rate of enzyme action?

Temperature, pH, substrate concentration, enzyme concentration, and inhibitors.

What happens to an enzyme when it denatures?

Its 3D shape is altered, the active site is lost, and it can no longer catalyse the reaction.

Why do enzymes from organisms in extreme habitats have different optimum conditions?

They adapt to extreme temperatures, pH, or other environmental factors to maintain activity.

What is the role of amylase?

To break down starch into simple sugars.

What is the role of protease?

To break down proteins into amino acids.

What is the role of lipase?

To break down lipids into glycerol and fatty acids.