post lab 5

What is an enzyme?

A protein that acts as a catalyst for chemical reactions.

What does a catalyst do?

Speeds up a chemical reaction without being used up.

What is the substrate?

The molecule an enzyme acts on.

Where does the substrate attach to an enzyme?

The active site.

What is an enzyme-substrate complex?

The enzyme and substrate temporarily joined together.

What is enzyme specificity?

An enzyme's active site fits only certain substrates.

What is a product?

The substance formed by an enzymatic reaction.

What is catalysis?

The speeding up of a chemical reaction by a catalyst.

What is catabolism?

A reaction that breaks down a substrate.

What is anabolism?

A reaction that combines substrates to form a product.

What enzyme breaks down hydrogen peroxide?

Catalase.

What does catalase break down?

Hydrogen peroxide (H₂O₂).

What are the products of catalase's reaction?

Water (H₂O) and oxygen gas (O₂).

What is the catalase reaction?

2 H₂O₂ → 2 H₂O + O₂.

Why is catalase important to cells?

It protects cells from oxidative damage caused by hydrogen peroxide.

Where is catalase found?

In most living things.

What enzyme catalyzes catechol oxidation?

Catechol oxidase.

What is the substrate of catechol oxidase?

Catechol.

What is the product of catechol oxidation?

Benzoquinone.

What color is benzoquinone?

Red-brown.

Why do cut fruits and vegetables turn brown?

Catechol oxidase converts catechol into brown benzoquinone.

Where is catechol oxidase found in plant cells?

In the chloroplasts.

Where is catechol stored in plant cells?

In the vacuoles.

What happens when a plant cell is damaged?

Catechol mixes with catechol oxidase, forming benzoquinone.

What chemical was tested as a similar substrate to catechol?

Hydroquinone.

Is hydroquinone the normal substrate for catechol oxidase?

No. It is structurally similar but not the normal substrate.

What factors affect enzyme activity?

Temperature, pH, and salt concentration.

What happens outside an enzyme's normal conditions?

Enzyme activity decreases and the enzyme may denature.

What does denatured mean?

The enzyme's 3D shape changes so it can no longer function normally.

Why does enzyme shape matter?

The substrate must fit the enzyme's active site.

What did Experiment 1 test?

Whether different foods contain enzymes that break down hydrogen peroxide.

What enzyme activity causes bubbling in Experiment 1?

Catalase breaks down H₂O₂ and releases oxygen gas.

Why was sand used in Experiment 1?

Sand does not contain the enzyme catalase.

Why was water used in Experiment 1?

It serves as a comparison/control without the enzyme-containing food.

What did Experiment 2 test?

The effect of pH on catechol oxidase activity.

What did Experiment 3 test?

The effect of temperature on catechol oxidase activity.

What indicates more catechol oxidation?

A darker red-brown color.

What does a color score of 0 mean?

No detectable catechol oxidation.

What does a higher color score mean?

More catechol was oxidized and more product formed.

What is the independent variable in Experiment 2?

pH.

What is the independent variable in Experiment 3?

Temperature.

What is the dependent variable in Experiments 2 and 3?

Amount of catechol oxidation, measured by color.

What happens to enzymes at very high temperatures?

They may denature and lose their function.

Why can extreme pH reduce enzyme activity?

It can change the enzyme's shape and active site.

What is the color guide used to measure?

Catechol oxidation, from 0 (none) to 5 (most).