Biological molecules and diet

Question 1

What are carbohydrates made of?

Answer 1

carbon, hydrogen, oxygen
carbohydrates are broken down in a chemical reaction, respiration, to release energy in the form of ATP
simple sugars (glucose and fructose)

Question 2

What is starch used for?

Answer 2

To store glucose in plants

Question 3

What is glycogen used for?

Answer 3

To store glucose in animals and fungi

Question 4

What are lipids (fats) made of?

Answer 4

Carbon, hydrogen, oxygen
Made of 3 fatty acids

Question 5

Functions of fats

Answer 5

energy storage
part of cell membranes
thermal insulation
electrical insulation around nerve cells
buoyancy

Question 6

What are proteins made of?

Answer 6

carbon, hydrogen, oxygen, nitrogen
many amino acids joined together

Question 7

What are the functions of proteins in the body?

Answer 7

structural molecules
controlling chemical reactions
messenger molecules
combating disease
transport

Question 8

What is the test for glucose?

Answer 8

Benedict’s solution

Question 8

Describe the benedict’s solution test.

Answer 8

1. Add benedict’s solution to a sample of food
2. Place in a water bath at 80 degrees for 5 minutes.
3. If glucose is present the colour will change from blue to brick red.

Question 8

What is the test for starch?

Answer 8

Iodine

Question 8

Describe the iodine test.

Answer 8

1. Add a few drops of orange iodine solution to the sample on a spotting tile.
2. A blue-black colour indicates the presence of starch

Question 9

What is the test for protein?

Answer 9

Biuret

Question 10

Describe the Biuret test.

Answer 10

1. Add 2cm3 water to a food sample and shake
2. Add an equal volume of dilute potassium hydroxide and shake.
3. Add two drops of 1% copper sulfate solution
4. If protein is present then a pale purple colour will develop.

Question 11

What is the test for lipids?

Answer 11

Emulsion

Question 12

Describe the emulsion test.

Answer 12

1. The food sample is placed in a test tube
2. Add a small volume of absolute ethanol and shake to dissolve any lipid in the alcohol.
3. Add an equal volume of water
4. A cloudy white colour indicates the present of lipids

Question 13

How can you calculate the amount of energy in food in joules per gram?

Answer 13

energy per gram of food in J/g = Energy in food (J) / Mass of food (in g)

Question 14

Describe an experiment to find the energy content in a food sample.

Answer 14

Use a dry food that will burn easily like a banana chip
Weigh a small amount of the food and then skewer it on a mounted needle
Next add a set volume of water to a boiling tube to measure the amount of energy that’s released when the food is burnt
measure the temperature of the water, then set fire to the food using a bunsen flame
Then hold the burning chip underwater until it goes out, then relight the food and hold under the tube again. keep doing this until the food won’t catch fire again
Then measure the temperature of the water again.

Question 15

How do you calculate the amount of energy in joules?

Answer 15

energy in food (J) = mass of water (g) x temperature change x specific heat capacity

Question 16

Why is the experiment for calculating energy in food not completely accurate?

Answer 16

Lots of heat energy is lost to the surroundings, insulating the tube with foil would minimise this heat loss

Question 17

What are examples of carbohydrates?

Answer 17

Pasta
Potatoes
Rice
(Main energy source)

Question 18

What are examples of proteins?

Answer 18

Nuts
Meats
Beans

Question 19

What are examples of fats?

Answer 19

Cheese
Oils
Chocolate

Question 20

Where is amylase made?

Answer 20

Salivary glands
Pancreas
Small intestine

Question 21

Where are proteases made?

Answer 21

Stomach (pepsin)
Pancreas
Small intestine

Question 22

Where are lipases made?

Answer 22

Pancreas
Small intestine