C) biological molecules and enzymes

What are the functions of water in living organisms

• water carries nutrients

• chemical reactions

• temperature regulation

What types of carbohydrates are there?

monosaccharides, disaccharides, polysaccharides

2 examples of polysaccharides

glyogen + starch

2 examples of disaccharides

maltose + lactose

2 examples of monosaccharides

glucose + fructose

What atoms make up carbohydrates?

carbon, hydrogen, oxygen

Uses of carbohydrates

• Dietary energy

• short term energy store

• plant structure (cellulose)

What is Benedicts test

test for reducing sugars

how to carry out Benedict's test

1. Place two spatulas of the food sample into a test tube or 1 cm³ if the sample is liquid.

2. Add about 1 cm³ depth of water to the tube and stir to mix.

3. Add an equal volume of Benedict's solution and mix.

4. Place the tube in a water bath at about 95°C for a few minutes.

5. Record the colour of the solution

6. if sugars are present, the solution will go blue —> brick red

Uses of fats

• Provide the building blocks to form cell membranes

• long term energy store

What are fats

they are lipids

Structure of fats

Glycerol and three fatty acids.

How do you test for starch?

iodine turns blue/black in the presence of starch

What are proteins used for

Growth and repair of cells

what is the structure of proteins

long chains of amino acids

How many types of amino acids are there?

20

how do you test for fats

1. Place two spatulas of the food sample into a test tube or 1 cm³ if the sample is liquid.

2. Add 2 cm³ of ethanol to the tube. Cover the end of the tube and shake the tube vigorously.

3. Allow the contents to settle.

4. Pour the liquid from the top of the mixture into a test tube half-filled with water.

5. Record the level of the food and whether the water is cloudy or clear

How do you test for proteins?

1. Place one-two spatulas of the food sample into a test tube or 1 cm³ if the sample is liquid. Add about 1 cm³ depth of water to the tube and stir to mix.

2. Add an equal volume of potassium hydroxide solution to the tube and stir.

3. Add two drops of copper sulfate solution and stir for two minutes.

4. If protein is present, blue —> purple

What are enzymes

Enzymes are biological catalysts that speed up reactions without being used up

Why are enzymes referred as "Biological?"

Because they are made in cells

How enzymes function, using the terms active site, substrate and product

• Enzymes use a lock and key method so they can only lock with a specific "Substrate" to make the products

• Bind together in the active site.

e.g. - the enzyme amylase will lock with the substrate starch to produce the product maltose

What is the optimum pH for enzymes?

pH of 7

What is the optimum pH for enzymes in the stomach?

pH of 2

What is the optimum pH for enzymes in high acidic places?

pH of 9

What is the optimum temperature of enzymes?

The human bodys temperature is around 37°C

How does temperature affect enzyme activity?

• Enzyme activity increases as temperature increases, and in turn increases the rate of the reaction.

• This also means activity decreases at colder temperatures.

• There are certain temperatures where they work optimally.

• after exceeding their optimum temperature they denature

describe how temperature increases enzyme activity

• As temperature is increased the enzymes and substrate gain kinetic energy (move more quickly)

• This increases the frequency of collisions

How does pH affect enzyme activity?

• Extreme pH values can cause enzymes to denature.

• Changing the pH of its surroundings will also change the shape of the active site of an enzyme.

• This is called denaturation and it is irreversible

How to investigate the effect of temperature and pH on enzyme activity (11 steps)

1. Set up a Bunsen burner, heatproof mat, tripod and gauze.

2. Place a beaker of water on the gauze and adjust the flame to keep the water at about 35°C.

3. Now put two drops of iodine solution into each spot of a spotting tile.

4. Add 2 cm3 of amylase enzyme solution to a test tube.

5. Place 2 cm3 of starch solution into the same tube.

6. Add 1 cm3 of pH solution to the tube. This will keep the pH constant.

7. Mix the solution in the test tube and place it into the beaker of water on the Bunsen burner.

8. Use a pipette to remove a few drops of solution every 20 seconds from the test tube and put them into a different well of the spotting tile.

9. Repeat until the iodine solution stops turning black.

10. Record the time this takes.

11. Repeat with different pH solutions.

(repeat each 3 times and find the mean of each result for accuracy)

carbohydrates

starch + amylase =

maltose

carbohydrates

maltose + maltase =

glucose

proteins

protein + protease =

amino acids

fats

lipids + lipase =

glycerol + 3 fatty acids

2 examples of protease

pepsin

tripsin

how to test for starch

1. Place one spatula of the food sample on a dish or 1 cm³ if the sample is liquid.

2. Using a dropper, place a few drops of iodine solution onto the food.

3. Record any change in the colour, orange —> blue-black means starch is present