c) Biological molecules

What elements are present in carbohydrates?

Carbon, hydrogen and oxygen.

What elements are present in proteins?

Carbon, nitrogen, hydrogen and oxygen.

What elements are present in lipids?

Carbon, hydrogen and oxygen.

Structure of carbohydrates?

Starch and glycogen are large, complex carbohydrates made from simple sugars(glucose/maltose).

Structure of proteins?

Long chains of amino acids.

Structure of lipids?

Built from fatty acids and glycerol.

What is the test for glucose, starch, protein and fat?

Glucose: Benedict’s test

Starch: Iodine solution

Protein: Biuret test

Fat: Sudan III test

How to investigate for the presence of glucose?

1. Prepare food sample and move 5cm3 to test tube.

2. Set water bath to 75 degrees celcius.

3. Add Benedict’s solution to test tube using pipette.

4. Place test tube in water bath.

5. If sample contains glucose it’ll change from blue to green/yellow in low concentration and brick red in high concentration.

How to investigate for the presence of starch?

1. Move 5cm3 of food sample into test tube

2. Add drops of iodine solution in tube and shake.

3. If it contains starch it’ll change from browny-orange colour to black or blue-back.

How to investigate for the presence of protein?

1. Transfer 2cm3 of food sample into test tube.

2. Add 2cm3 of biuret solution into test tube and shake.

3. If it contains protein it’ll change form blue to pink or purple.

How to investigate for the presence of fat?

1. Transfer 5cm3 of food sample into test tube.

2. Add 3 drops of Sudan III stain solution to test tube and shake.

3. If it contains lipids it’ll separate into 2 layers with the top being bright red.

Define catalyst?

A substance which increases the speed of a reaction, without being changed or used up.

Role of enzymes in metabolic reactions?

Reduce the need for high temperatures and speed up useful chemical reactions.

What happens to enzymes if you increase the temperature?

Increase rate of reaction

Enzyme and substrate have move energy.

They’ll move and more likely to collide and from enzyme-substrate complexes.

What happens to enzymes if it gets too hot?

The bonds holding the enzyme together will break.

This changes shape of the active site.

Substrate wont be able to fit.

Enzyme is denatured.

How to investigate on how temperature of enzyme affects how fast a product appears?

1. Add set amount of hydrogen peroxide to boiling tube.

2. Put boiling tube in 10 degrees celcius water bath.

3. Add source of catalase to hydrogen peroxide and attach bung.

4. Record how much oxygen is produced in first minute.

5. Repeat 3 times to find mean.

6. Repeat at 20, 30, 40 degrees Celsius.

How to investigate how temperature of enzyme affects how fast a substrate disappears?

1. Put drop of iodine solution in each well of spotting tile every 10 sec.

2. Drop sample of mixture into well.

3. When iodine solution remains bony-orange record time taken.

4. Repeat with water baths at different temperatures.

What happens if the pH of an enzyme is too high or too low?

The pH interferes with the bond holding enzyme together meaning it’ll change the shape of active site and denature the enzyme.