8.4 Digestion

Question 1

What are nutrients?

Answer 1

Nutrients are important substances that your body needs to survive and stay healthy.

Question 2

What are the 7 types of nutrients?

Answer 2

Carbohydrates - which provide energy
Lipids (fats and oils) - which store energy
Proteins - which are used for growth and repair
Vitamins and Minerals - which keep you healthy
Fibre - important in the intestines, adds bulk to food.
Water - which is needed in all cells and body fluids.

Question 3

What are the 2 types of carbohydrates?

Answer 3

1. Sugars - found in foods such as sugar and fruit. Short term energy
2. Starch - found in foods such as bread and pasta. The energy is released more slowly.

Question 4

What are lipids?

Answer 4

They include fats and oils and provide you with a store of energy, keep you warm by providing a layer of insulation and protect organs like your kidneys and heart from damage.

Question 5

What are proteins needed for?

Answer 5

To repair body tissues and make new cells for growth. Muscles, organs and your immune systems are mostly made of proteins.

Question 6

What are vitamins and minerals?

Answer 6

They are essential substances for keeping you healthy, but you only need tiny amounts.

Question 7

How do you prepare a food solution?

Answer 7

1. Crush the food using a pestle and mortar.
2. Add a few drops of water, and mix well.

Question 8

How do you test for starch?

Answer 8

1. Add a few drops of iodine to the food solution.
2. If the solution turns a dark blue-black colour, the food contains starch

Question 9

How do you test for lipids?

Answer 9

For solid food:
1. Rub some of the food onto a piece of filter paper.
2. Hold the piece of paper up to the light. If the paper has gone translucent, the food contains lipids.
For a food solution:
1. Add a few drops of ethanol to the food solution.
2. Shake the test tube and leave for one minute
3. Pour the ethanol solution into a test tube of water. If it turns cloudy, the food contains lipids.

Question 10

How do you test for sugar?

Answer 10

1. Add a few drops of Benedict’s solution to the food solution.
2. Heat the test tube in a water bath.
3. If the solution turns orange-red, the food contains sugar.

Question 11

How do you test for protein?

Answer 11

1. Add a few drops of copper sulfate and sodium hydroxide to the food solution
2. If the solution turns purple, the food contains protein.

Question 12

What are vitamin and mineral deficiencies?

Answer 12

When a person doesn’t have enough of a certain vitamin/mineral. It can damage a person’s health.

Question 13

What is the digestive system?

Answer 13

The digestive system is a group of organs that work together to break down food and absorb nutrients into the blood so they can be used in the body.

Question 14

What happens during digestion?

Answer 14

During digestion, larger molecules are broken down into small molecules that then pass into the bloodstream.

Question 15

What are the main structures in the digestive system?

Answer 15

Mouth
Oesophagus
Stomach
Small intestine
Large intestine
Rectum
Anus

Question 16

What happens in the mouth?

Answer 16

Food is chewed and mixed with saliva. Teeth help to break the food down into smaller chunks.

Question 17

What happens in the oesophagus?

Answer 17

Food passes down this tube (25cm)

Question 18

What happens in the stomach?

Answer 18

Food is mixed with digestive juices and acids and churned around by the stomach muscles.

Question 19

What happens in the small intestine?

Answer 19

Bile is added to the food and digestion is completed. Small molecules of nutrients pass through the intestine wall into the bloodstream by diffusion.

Question 20

What happens in the large intestine?

Answer 20

Water passes back into the body, leaving faeces behind. Only food that cannot be digested gets this far.

Question 21

What happens in the rectum and anus?

Answer 21

Faeces is stored in the rectum before it passes out of the body through the anus (a muscular ring).

Question 22

How does food move along the intestines?

Answer 22

Muscles in the wall of the intestines contract, squeezing food along.

Question 23

What is the role of fibre?

Answer 23

Fibre adds bulk to the food, and is not digested. Muscles push against this forcing food along the gut. Eating lots of fibre rich foods is important for gut health and helps prevent constipation.

Question 24

How is the small intestine adapted to its function?

Answer 24

1. The wall of the intestine is very thin so molecules of food can pass through into the bloodstream.
2. The wall is covered in villi that provide the intestine with a larger surface area so nutrients can be absorbed quickly.

Question 25

What is the role of enzymes in the human body?

Answer 25

To break down larger molecules of nutrients into smaller molecules that can then be absorbed into the blood.

Question 26

Why are enzymes known as biological catalysts?

Answer 26

They speed up digestion without being used up.

Question 27

What are the main enzymes involved in digestion?

Answer 27

1. Carbohydrase - an enzyme that breaks down carbohydrates into sugar molecules.
2. Protease - an enzyme that breaks down proteins into amino acids
3. Lipase - an enzyme that breaks down lipids into fatty acids and glycerol.

Question 28

Where does the digestion of carbohydrates take place?

Answer 28

Carbohydrates are digested in the mouth, stomach and small intestine. Carbohydrase present in your saliva breaks down the starch into sugar (glucose).

Question 29

Where does the digestion of proteins take place?

Answer 29

Proteins are digested in the stomach and small intestine. Acid in the stomach helps digestion and kills harmful micro-organisms in food.

Question 30

Where does the digestion of lipids take place?

Answer 30

Lipids are digested in the small intestine and their digestion is helped by bile (made in the liver). The bile breaks the lipids into small droplets that are easier for the lipase to work on.