Enzymes

Cell Metabolism

All the chemical reactions in an organism

Catalyst

Speeds up a reaction without being used up in the reaction

Enzymes

biological catalysts

Functions of an enzyme

Act on a substrate.

Form products.

are made of protein.

Are enzyme reactions reversable?

Yes

Examples of enzyme reactions (catabolic)

Amylase turns starch into maltose

Examples of enzyme reactions (Anabolic). 2

DNA Ligase joins 2 pieces of DNA together.

DNA polymerase repairs DNA.

Active site

The place on the enzyme that joins to the substrate.

Induced fit theory

When the substrate joins to the active site, its shape changes slightly to fit the substrate better.

Enzyme and substrate together = ?

The enzyme - substrate complex

Enzyme specificity

enzyme will only catalyse 1 reaction

Factors Effecting enzyme action

PH.

Temperature.

Bioprocessing

The use of living cells or their components to make useful products or to carry out useful procedures.

Examples of bioprocessing

Yeast to make beer.

Proteases in washing powder to break down food stains.

Immobilised enzymes

Enzymes that are attached to or trapped in an inert, insoluble material.

Uses of immobilised enzymes

To make lactose free milk by breaking down lactose into glucose into galactose.

Advantages of using immobilised enzymes

Makes a pure product.

More efficient.

more stable.

Bio-reactors (Batch Cultures)

The product is formed in cycles. Bioreactor is cleaned between cycles. product is removed before waste products build up.

Bio-reactors (continous flow cultures)

Nutrients, substrates and medium are fed continously into the bioreactor. product is continously removed at the bottom.

The effect of PH on the rate of action of an enzyme (Catalase)

Substrate = Hydrogen peroxide

Enzyme = Catalase

1. Prepare different buffer solutions at varying pH levels

2. Blend celery or use to extract catalase.

3. Place a fixed amount of hydrogen peroxide into test tubes containing the buffer solutions.

4. Measure Oxygen Production ,Add catalase to each tube and capture the released oxygen using a graduated cylinder or a gas syringe.

5. Record Results, Compare the rate of bubble formation or measure the volume of oxygen released over a set time.

6. Wear safety glasses to ensure safety.

Conclusion:

• The enzyme works best at its optimum pH (typically around pH 7).

The effect of temperature on the rate of action of an enzyme (Catalase)

Substrate = Hydrogen peroxide

Enzyme = Catalase

1. Label test tubes for different temperature conditions (e.g., 0°C, 20°C, 37°C, etc.).Add 5 cm³ of hydrogen peroxide to each test tube. Add a few drops of detergent to help capture oxygen bubbles.

2. Place the test tubes in water baths set at different temperatures. Allow hydrogen peroxide to reach the desired temperature.

3. Add a fixed volume of catalase solution (e.g., 1 cm³) to each test tube. Immediately start the stopwatch.

4. Record the height of foam produced. (e.g., 2 minutes).Repeat for each temperature condition.

Results:

• Low temperatures (0°C, 10°C): Slow reaction due to reduced enzyme activity.

• Optimum temperature (around 37°C): Fastest reaction rate as the enzyme functions best at body temperature.

• Higher temperatures (50°C+): Slower reaction or no reaction as the enzyme denatures and loses function.

Immobilizing Enzyme (Experiment)

Enzyme Used: Catalase

Substrate used: Hydrogen peroxide

Method:

1. Mix yeast (source of catalase) with sodium alginate.

2. Use a syringe to drop the mixture into calcium chloride solution.

3. Beads form—leave to harden for 10 minutes, then rinse with water.

4. Add the immobilised enzyme beads to hydrogen peroxide in a test tube.

5. In a separate test tube, add the free yeast (not immobilised) to hydrogen peroxide.

6. Measure the volume of oxygen gas released from both reactions using a graduated cylinder or gas syringe.

7. Compare the rate of reaction for the free and immobilised enzymes.

Result:

The free enzyme produced oxygen more quickly. The immobilised enzyme reacted slower but still broke down hydrogen peroxide.

Denature Enzyme (Experiment)

Enzyme Used: Catalase (from celery or yeast) Substrate Used: Hydrogen Peroxide (H₂O₂)

Method:

1. Blend celery (or use yeast) and filter to extract catalase.

2. Divide the catalase solution into two parts.

3. Boil one part for 5 minutes to denature the enzyme.

4. Allow it to cool.

5. Add equal volumes of hydrogen peroxide to two test tubes.

6. Add the unboiled catalase to one tube and the boiled catalase to the other.

7. Measure and compare oxygen production using a graduated cylinder or gas syringe.

8. Wear safety glasses for protection.

Result:

• The unboiled catalase produced bubbles (oxygen).

• The boiled catalase produced little or no bubbles.