C3 - Food Matters

Question 1

How is dead animal and plant matter turn into compounds that plants can use?

Answer 1

Dead animal and plant matter (and animal waste) is broken down by microbes. They convert it into compounds that are taken up by other plants and the whole process starts again

Question 2

Give three ways that nitrates are added to the soil in the nitrogen cycle

Answer 2

• Nitrogen fixing bacteria in the soil can make nitrates directly from nitrogen in the air
• Energy from lightning can also make nitrogen and oxygen in the air react to give nitrates in the soil
• Nitrifying bateria turn the ammonium compounds produced by the microbes into nitrates in the soil

Question 3

Give two ways that nitrates are removed from the soil in the nitrogen cycle

Answer 3

• Denitrifying bacteria break down nitrates in the soil to give nitrogen in the air again
• Plants absorb nitrogen in the from of nitrates from the soil

Question 4

Explain why the nitrogen cycle does not happen in a field of crops

Answer 4

When the field gets harvested and removed from the field they are removed for good instead of being returned to the soil when the plants die and decay. This means that it can’t turn into compounds to then be taken up by other plants to start the whole process again.

Question 5

Give three ways that organic farmers can replace the nutrients that are lost from their soil

Answer 5

• Manure, sewage and compost all contain waste plant material, so they replace the elements that plants take out of the soil in the same way as a natural cycle would
• Organic farmers also grow “green manure”. Plants are grown on the fields and then ploughed in and left to rot. Plants like clover are often used because they have nitrogen-fixing bacteria in their roots which add nitrates to the soil
• Also they use crop rotation to help keep their soil fertile. They grow different crops each year in a cycle. For example, peas might be grown first year as they contain nitrogen-fixing bacteria to help prepare the soil for the cabbage on the second year which needs lots of nitrates. Carrots would be third year as they don’t need much nitrogen

Question 6

Give two advantages of using artificial fertilisers on crops

Answer 6

• Because they are pure chemicals (i.e. they’re not full of plant matter), it’s easy to use just the right amount
• Farmers can use small volumes of artificial fertilisers, as they contain much higher percentages of the elements the crops need than manure does
• The amount of each nutrient can be chosen to be exactly right for a particular plant’s need

Question 7

Give two disadvantages of using artificial fertilisers on crops

Answer 7

• If too much fertiliser is used it can pollute water supplies
• It may also lead to eutrophication, a situation where there is not enough oxygen dissolved in the water for aquatic organisms to survive

Question 8

Give two ways that an organic farmer can limit the number of diseases affecting his or her crops

Answer 8

• Crop rotation is used to prevent pests and disease causing the organisms of one particular plant building up in an area
• Varieties of plants that are best able to resist pests and diseases are chosen

Question 9

Explain the advantages of using chemical pesticides to kill pests

Answer 9

• More effective than organic methods as they usually kill all of the pests and disease-causing organisms, which organic methods can’t
• Means a bigger yield of crops with fewer blemishes

Question 10

Explain the disadvantages of using chemical pesticides to kill pests

Answer 10

• The spraying leaves a chemical residue on the crop. This could harm humans eating the plants, as week as the pests
• Chemical pesticides kill indiscriminately, this means that not only pests are killed but also other organisms that could be beneficial

Question 11

What must a farmer who grows crops and produces animals for meat do for the food to be classed as organic?

Answer 11

The national rules ban the use of virtually all artificial chemicals and set standards for the way that pests and diseases are controlled.
The animals must be allowed to move around freely, can only be fed an organic feed and can’t be given artificial hormone to make them grow more quickly.

Question 12

Name two carbohydrates polymers

Answer 12

Starch

Cellulose

Question 13

Which element is found in proteins but not in carbohydrates

Answer 13

Nitrogen

Question 14

Name the monomer molecules that make up a protein polymer

Answer 14

Amino acids

Question 15

Why can the starch in food not be absorbed straight into the blood?

Answer 15

They are insoluble and too big to diffuse into the blood

Question 16

Where are excess amino acids broken down into the body? How are the products of this process excreted?

Answer 16

Excess amino acids in the blood are taken to the liver to be broken down. They are converted into a soluble substance called urea which is then released into the blood. As the blood passes through your kidneys, the dissolved urea is removed and passes out of the body in the urine

Question 17

How is type 1 diabetes usually treated?

Answer 17

Daily injections of insulin and by controlling the diet to help control the blood sugar levels

Question 18

Explain why type 2 diabetes is increasing in young people

Answer 18

Because of increasing obesity due to poor diet and lack of exercise

Question 19

Explain why the South American plant, cassava, should not be eaten raw

Answer 19

In the root are compounds that produce lethal cyanide in the liver if eaten

Question 20

What is aflatoxin? What problem can it cause if eaten by humans?

Answer 20

A poisonous substance that is produced by a mould that can grow on nuts, creaks and dried fruit if they’re not stored correctly. Aflatoxin can cause liver cancer.

Question 21

What health problem might be caused by eating burnt foods?

Answer 21

Cause cancer in animals by altering their DNA

Question 22

Why is sodium benzoate added to food?

Answer 22

To preserve food

Question 23

Why is saccharin added to food?

Answer 23

Used as an artificial sweetener

Question 24

Ice cream contains two different kinds of chemicals to prevent it separating out. What are they?

Answer 24

Emulsifiers

Stabilisers

Question 25

Give two examples of problems that have been linked to additives passed as safe to use by the EU

Answer 25

• Some artificial food colourings have been linked with allergies and hyperactivity
• Sulfur dioxide in dried fruit has been linked with asthma
• Artificial sweeteners have been linked with hyperactivity and behavioural problems

Question 26

Why can no food ever be guaranteed to be completely safe?

Answer 26

There are many ways that the food could have become accidentally contaminated (e.g. pesticides and herbicides). You can’t predict with absolute certainty your body’s reaction to it. High temperature cooking can produce PAHs and HAs

Question 27

Explain what the ‘precautionary principle’ is

Answer 27

An idea used by governments and individuals to help limit risks. If you’re not sure about something, and you know it could potentially cause serious harm, you’d best avoid it

Question 28

Explain how scientific advisory committees and the FSA limit the risks from food

Answer 28

Scientific advisory committee carry out risk assessments to help set safe limits for the levels of chemicals allowed in food
FSA check that legislation on food safety, labelling, diet, farming and hygiene is being followed properly, for example by supporting food sampling programmes

Question 29

Suggest three ways that individuals can limit the risks from their food

Answer 29

• Choose food produced in a way that minimises the amount of artificial chemicals applied to it (organic foods).
• Wash the food carefully or peel it before eating it
• Store and cook the food in the way recommended on the packaging

Question 30

What kinds of information can consumers get from food labels?

Answer 30

• Detailed information on things like the amounts of each type of fat and sometimes whether it is high, medium or low compared to other foods
• How and where the food was produced
• What it contains and whether it contains substances that people might be allergic to
• Recommended daily amounts and how much of that daily amount the product contains

Question 31

Outline the risks and benefits of eating intensively produced vegetables

Answer 31

The risks:
Mainly concern the chemicals used in the production of these foods. Residues of pesticides should only exist in small amounts but nobody is certain of the long-term effect of eating small amounts repeatedly. Some residues has been linked with diseases (Parkinsons)
The benefits:
Include price, choice and convenience. Some people also prefer the unblemished appearance and uniformity of intensively farmed foods

Question 32

How is dead animal and plant matter turn into compounds that plants can use?

Answer 32

Broken down by microbes. They convert it into compounds that are taken up by other plants and the whole process starts again