AQA GCSE Science

Biology

Keeping Healthy

Name: ……………………………………….

Steve Bishop

October 2013

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B1.1 Keeping Healthy

Summary

A combination of a balanced diet and regular exercise is needed to help keep the body

healthy.

You should be able to:

■ evaluate information about the effect of food on health

■ evaluate information about the effect of lifestyle on development of disease

■ analyse and evaluate claims made by slimming programmes, and slimming products.

B1.1.1 Diet and Exercise

Key terms

Diet

Nutrients

Carbohydrate

Fat

Energy

Insulation

Protein

Vitamins

Minerals

Malnourishment

Overweight

Deficiency

Diabetes

Inherited

Metabolic rate

Obese

Healthy Diet

A healthy diet contains the right balance of the different foods you need and the right

amount of energy.

These foods should provide the following nutrient groups:

o Carbohydrates for energy and to make cell structures

o Fat for energy and insulation and cell structures

o Protein to control cell reactions (as enzymes) and to build cell structures

o Vitamins and minerals to help our bodies function well.

Malnourishment

A person is malnourished if their diet is not balanced.

This may lead to a person being overweight or underweight.

An unbalanced diet may also lead to diseases.

Lack of essential nutrients in the diet can lead to deficiency diseases.

Excess intake of high energy foods can lead to type 2 diabetes.

o This is a disease where the person is unable to control the levels of sugar in

their blood.

o This is very dangerous, and the person must carefully control their diet and

monitor their blood sugar levels regularly.

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Slimming programmes

A person gains mass when the energy content of the food taken in is more than the

amount of energy expended by the body.

A person loses mass when the energy content of the food taken in is less than the

amount of energy expended by the body.

An effective slimming programme advises people to reduce the energy content of their

food, and to increase the amount they exercise.

Some slimming programmes encourage people to consume a low proportion of one of

the nutrient groups in their diet. This may enable them to lose weight, but it will not

necessarily be a sensible, healthy diet.

Exercise

Exercise increases the amount of energy expended by the body.

People who exercise regularly are usually healthier than people who take little exercise.

They expend more energy and their circulatory system becomes more efficient.

They are likely to have lower blood pressure, and less likely to be overweight.

Metabolic rate

This is the rate at which all the chemical reactions in the cells of the body are carried out.

One major set of metabolic reactions is respiration.

The rate of these reactions vary with the amount of activity you do.

The more activity, the more energy is required by the body.

Metabolic rate also varies with respect to the proportion of muscle to fat in your body.

The higher the proportion of muscle to fat, the higher the metabolic rate.

Exercise increases the proportion of muscle to fat.

Inheritance

Inherited factors can influence our health.

We can inherit genes from our parents which can influence our metabolic rate.

We can also inherit genes which influence our cholesterol level.

Cholesterol is a substance that our body creates from fat that we consume in our diet.

Cholesterol is needed to make cell membranes.

However, too much cholesterol can increase the chance of cardio-vascular diseases,

such as strokes, heart attacks and thrombosis.

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A healthy diet

Look at the food labels and complete this table

Type of food Energy (kJ/

100g)

Nutrient per 100 g

Carbohydrate Fats Protein Fibre

For a healthy diet we need these important nutrients

Protein – needed for cell growth and repair

Carbohydrates – provides energy

Fats and oils – provides energy and warmth

Vitamins and Minerals - needed for health, to fight diseases

Water – keeps the body hydrated

Fibre – helps digestion

Without a balanced diet we can become malnourished. We can have a lack of important

nutrients.

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Obesity

If someone is obese they are extremely overweight.

Obesity can lead to heart problems, to high blood pressure, to diabetes type 2 and to

arthritis.

To lose weight we need more exercise and to reduce the amount of food we eat; particularly

fats such as in chips, crisps and biscuits.

Metabolic rate

Our metabolic rate is how quickly our bodies use up our energy resources.

Metabolism is the chemical reactions in our body’s cells.

The higher the metabolic rate the more we use up our energy resources.

We can increase our metabolic rate by exercising.

We all have different metabolic rates. Men usually have a higher metabolic rate than women.

Now try these

Use a dictionary and / or the Internet to make your own definition of these terms:

Obese

Malnourished

Nutrient

Metabolic rate

What is meant by the term a ‘healthy diet’?

Fill in the blanks with the correct terms

Complete the table

Needed for: Found in:

Vitamins and

minerals

Fruits, vegetables, eggs, milk,

meat

Carbohydrates

Protein cell growth and repair

Fibre

Fats and oils

Research

How many calories a day can a

man eat?

How many calories a day can

women eat?

Why the difference?

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Food Test Practical

Iodine Test for Starch

Crush a small amount of the food sample using a pestle and mortar.

Put some of the sample in the well of a dimpled tile.

Add a few drops of Iodine Solution.

If the food contains STARCH the solution will go blue/black.

Biuret Test for Protein

Place small amount of the sample in a test tube.

Add 2ml of Sodium Hydroxide.

Add Copper Sulphate drop by drop.

If the pale blue colour turns purple, PROTEIN is present.

Benedict’s Test for Sugar

Place a small amount of sample in a Boiling tube.

Add 2ml of Benedict’s solution.

Place Boiling tube in water bath for 2-3 mins.

If the food contains SUGAR an orange/red precipitate is produced.

Emulsion Test for Fat

Place a small bit of the sample into a test tube and add 3ml of ethanol.

Mix together and add 3ml of water.

Shake gently.

If a milky white suspension is formed this indicates the presence of FAT.

Food Starch? Protein? Sugar? Fat?

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Diet and exercise questions

1. List the main food groups in a healthy diet

2. What might happen to a person if their diet is not balanced?

3. Name three deficiency diseases

4. How can exercise help in losing weight?

5. What inherited factors may affect our health?

6. What is the term metabolic rate?

7. The table shows six different meals A-F

Which meal contains the least sugar?

Which meal contains most energy?

Which meal contains the most salt?

The recommended daily amount of fat for a woman is 80g

A woman eats meal D.

What proportion of the recommended daily amount of fat does she get?

Which meal is the healthiest?

Give two reasons for your answer.

Key terms Deficiency Inherited Metabolic rate Obese

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8. Many people are obese (very overweight).

Obesity can lead to heart disease.

Other than heart disease, name two conditions which are linked to obesity.

9. The graph shows the number of deaths from heart disease each year in the UK.

(a) The pattern for deaths from heart disease in men is different from the pattern in women.

Give two differences between the patterns for men and women.

(b) Suggest two reasons for the difference in the number of deaths from heart disease in

men and women between the ages of 40 and 60.

10. Scientists estimate that about one third of cancers in the UK may be linked to obesity.

Name two other diseases linked to obesity.

The graph shows the changes in the cancer rate and the changes in the percentage of

obese adults in the UK from 1995 to 2006.

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(a) Does the data in the graph prove that obesity causes cancer?

(b) Explain the reason for your answer.

(c) Exercise helps a person to lose weight.

Explain why.

11.

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B 1.1.2 Infectious Disease

Summary

Our bodies provide an excellent environment for many microbes which can make us ill once

they are inside us. Our bodies need to stop most microbes getting in and deal with any

microbes which do get in. Vaccination can be used to prevent infection.

You should be able to:

■ relate the contribution of Semmelweiss in controlling infection to solving modern problems

with the spread of infection in hospitals

■ explain how the treatment of disease has changed as a result of increased understanding

of the action of antibiotics and immunity

■ evaluate the consequences of mutations of bacteria and viruses in relation to epidemics

and pandemics

■ evaluate the advantages and disadvantages of being vaccinated against a particular

disease.

Key terms Pathogens Disease Microorganisms Bacteria Viruses Toxins Antibiotics Agar

Vaccine Immunity Antibody Antigen Pandemic Epidemic Mutation

Fighting disease Classify these statements into True, not sure, false.

True Not sure False

Some pathogens make you ill. [ ] [ ] [ ]

All pathogens are bacteria. [ ] [ ] [ ]

Infectious diseases are not caused by living organisms. [ ] [ ] [ ]

Some pathogens can be spread between organisms [ ] [ ] [ ]

very easily.

Infectious diseases are not caused by living organisms. [ ] [ ] [ ]

Vaccinations can wear off after time. [ ] [ ] [ ]

Painkillers kill off pathogens. [ ] [ ] [ ]

Antibiotics are helpful to destroy viruses. [ ] [ ] [ ]

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Pathogens

Microorganisms that cause infectious disease are called pathogens.

Disease occurs when large numbers of pathogenic micro-organisms enter the body.

Bacteria

Not all bacteria are pathogens.

Pathogenic bacteria reproduce rapidly inside the body and may produce poisons (toxins)

which make us feel ill.

Example: E.coli produces toxins that cause fever symptoms when we have food

poisoning.

Viruses

Viruses are much smaller than bacteria.

All viruses are pathogens.

Viruses also produce toxins and they damage the cells in which they reproduce, leading

to illness.

Viruses replicate by invading cells, reproducing inside them and bursting them.

This causes damage to tissues, leading to illness.

Examples:

o HIV damages white blood cells, reducing immunity and leading to AIDS.

o Influenza virus released toxins which cause aches and fever symptoms.

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Virus replication

Use the information above to complete the diagram and table

stage Description

1

2

3

4

5

6

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Virus or bacteria?

Are the following viruses or bacteria?

TETANUS TB AIDS COMMON COLD CHICKEN POX MUMPS

FOOD POSIONING SORE THROAT RUBELLA

Virus Bacteria

Adapted from http://www.curriculumbits.com/prodimages/details/biology/microbes-and-disease.html

Which goes where?

Look at these statements – do they apply to both bacteria and viruses or only one?

single-celled microorganisms

require living hosts

killed by antibiotics

can cause infections or diseases

doesn’t have a nucleus

too small to be seen by the naked eye

Place them in the correct box

Same

Only virus

Only bacteria

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The immune system

The body has different ways of protecting itself against pathogens.

White blood cells defend our internal environment from pathogens

These form part of our immune system.

There are various types of white blood cells:

Cells that ingest and destroy microorganisms

Cells that produce antitoxins that destroy toxins released by pathogens

Cells that produce antibodies that destroy specific pathogens:

o They produce specific antibodies to kill a particular pathogen.

o This leads to immunity from that pathogen.

o The body is able to rapidly produce large numbers of the specific antibodies if

it is exposed to the same pathogen in the future.

o In some cases, dead or inactivated pathogens stimulate antibody production.

o This also leads to immunity.

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The skin: defend and protect

Watch this clip:

http://www.bbc.co.uk/learningzone/clips/skin-defend-and-protect/12226.html

and answer these questions

What is the body’s first line of defence?

What is on the surface of the skin that could cause infection?

How many skin cells a day do we loose?

How does this help the body’s defences?

What is dehydration?

What is sebum secretion?

How does it help stop dehydration?

How Humans heal themselves

Watch this clip and answer the questions

http://www.bbc.co.uk/learningzone/clips/how-humans-heal-themselves/12229.html

How does the body help to defend us?

What helps stop bleeding?

What stringy protein helps form scabs

What produces the purple colour of the black eye?

What do macrophages do?

What give red blood cells their colour?

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Dr Ignaz Semmelweiss – death on their hands

Who was Dr Semmelweiss

Watch these video clips and answer the questions.

http://www.youtube.com/watch?v=U6-FjtpdePA&feature=relmfu

http://www.youtube.com/watch?v=T73PYNyyeiI&feature=relmfu

In which country was Semmelwiess born?

Why did more mothers die when delivered by doctors than by midwives?

What was his simple life-saving idea?

Why did it take a long time for his ideas to become accepted?

What is septicemia?

GCSE-style question

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In the 19th century, Dr Semmelweiss investigated infection in a hospital.

He compared the number of deaths of mothers on two maternity wards (see above)

• On Ward 1, babies were delivered mainly by doctors. These doctors worked on many

different wards in the hospital.

• On Ward 2, babies were delivered by midwives. The midwives did not work on other

wards.

The bar chart shows the results of his investigations.

600 mothers gave birth on Ward 2 in 1845.

How many mothers died from infections on Ward 2 in 1845?

Which was the safer ward on which to have a baby?

In January 1848, Dr Semmelweiss asked all doctors to wash their hands before delivering

babies.

The table shows the number of deaths on the two wards in 1848.

What was the effect on the death rate on Ward 1 of doctors washing their hands before

delivering babies?

What might the reason be?

Preventing transmission

In the 1850s Semmelweiss recognised the importance of hand-washing in the prevention

of spreading some infectious diseases.

He insisted that medical students washed their hands before delivering babies.

This resulted in doctors washing their hands before and after examining patients.

This greatly reduced the number of deaths from infectious diseases in his hospital.

This idea was not readily accepted – people were not aware of microorganisms.

Nowadays, it is standard practice for people to wash hands after treating patients, to

prevent disease being transmitted to other patients.

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Using drugs to treat disease

Some medicines, including painkillers, help to relieve the symptoms of infectious

disease, but do not kill the pathogens.

Antibiotics are medicines that help to cure bacterial disease by killing infective bacteria

inside the body. Eg penicillin

Antibiotics cannot be used to kill viral pathogens, which live and reproduce inside cells.

It is difficult to develop drugs which kill viruses without also damaging the body’s tissues.

It is important that specific bacteria should be treated by specific antibiotics.

Antibiotics kill bacteria inside the body.

The use of antibiotics has greatly reduced deaths from infectious bacterial diseases.

Antibiotic resistance

Overuse and inappropriate use of antibiotics has increased the rate of development of

antibiotic resistant strains of bacteria.

Pathogenic bacteria mutate, producing resistant strains.

Antibiotics kill individual pathogens of the non-resistant strain.

Individual resistant pathogens survive and reproduce, so the population of the resistant

strain increases.

Antibiotics and vaccinations may no longer be effective against a new resistant strain of

the pathogen.

The new strain will then spread rapidly because people are not immune to it and there is

no effective treatment.

Many strains of bacteria, including MRSA, have developed resistance to antibiotics as a

result of natural selection.

These bacteria can enter the body through wounds and cuts.

Healthy people’s white blood cells would quickly destroy these bacteria.

People who are ill in hospital are likely to have reduced immunity to bacterial disease,

and become infected more easily.

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What can be done?

Doctor’s should only prescribe antibiotics when necessary – and not for viruses.

It is important that if you are prescribed antibiotics you take the whole course.

o A lot of people will stop taking the antibiotic when they feel better.

o If you do this, you leave a few bacteria inside your body.

o These will reproduce, increasing the chance of some developing resistance.

Scientists are trying to develop new versions of the antibiotics.

Some antibiotics are developed but not used – just in case.

Epidemics and Pandemics

Epidemics – diseases that spread widely through one country.

Pandemics – diseases that spread through several countries.

Eg Influenza

A viral disease.

Most people recover in a week.

People who are old or very young or already ill can die.

Different strains of influenza affect other animals.

These rarely affect humans, because humans need to directly contact an infected

animal.

Humans that are infected may be more likely to die than if they had human influenza.

Most of these viruses cannot be transmitted from human to human.

However, there are concerns that the viruses could mutate and become able to be

transmitted between humans.

If it does this, it will start off by causing an epidemic, which may spread to become a

pandemic.

Many people could die, particularly very old people, very young people, and people who

are already ill.

Immunisation

If a large proportion of the population is immune to a pathogen, the spread of the

pathogen is very much reduced.

Eg small pox was completely eradicated by the 1970s.

People can be immunised against a disease by introducing small quantities of dead or

inactive forms of the pathogen into the body (vaccination).

Vaccines stimulate the white blood cells to produce antibodies that destroy the

pathogens.

This makes the person immune to future infections by the microorganism.

The body can respond by rapidly making the correct antibody, in the same way as if the

person had previously had the disease.

An example is the MMR vaccine used to protect children against measles, mumps and

rubella.

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Growing Microoganisms

Microorganisms = organisms that can only be viewed with a microscope.

Eg bacteria, viruses and fungi.

Uncontaminated cultures of microorganisms are required for investigating the action of

disinfectants and antibiotics.

It is important that the culture is not contaminated with other microorganisms that may

compete for nutrients or produce toxins.

Careful procedures are required to prevent potentially pathogenic microorganisms being

released into the environment.

Culturing microorganisms

To study microorganisms, they need to be cultured.

They need to be provided with the conditions they need to reproduce quickly:

o Nutrients

o Warmth

o Moisture

Bacteria and fungi can be grown in special media called agar.

This provides them with:

o Carbohydrate

o Protein or amino acids

o Water

When agar is heated up it is liquid.

It can be poured into a Petri dish.

o A circular plastic or glass dish with a lid:

The agar solidifies when left to cool.

Petri dishes and culture media must be sterilised before use to kill unwanted

microorganisms

Inoculating loops are used to transfer microorganisms to the media.

These must be sterilised by passing them through a flame:

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The lid of the Petri dish should be secured with adhesive tape to prevent microorganisms

from the air contaminating the culture.

In school and college laboratories, cultures should be incubated at a maximum

temperature of 25oC.

This greatly reduces the likelihood of growth of pathogens that might be harmful to

humans.

In industrial conditions higher temperatures can produce more rapid growth.

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Questions

1. What is a pathogen?

2. What is an antibiotic?

3. Use these three terms to make the sentence correct:

Diseases Germs Microbes

_______________ are _______________ that causes _______________ .

4. What is meant by a ‘mutation’ of a pathogen?

5. How is a pandemic different from an epidemic?

6. What are antibiotics?

7. Why don’t doctors give antibiotics for mild throat infections?

8. How can bacteria develop antibiotic resistance?

9. Why are antibiotics not used to kill viruses?

10. What is meant by vaccination?

11. How does a person develop immunity form a vaccination?

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12. What three things do white blood cells do to defend the body?

13. Why do industrial laboratories use 35°C instead of 25°C as in schools to grow cultures?

14. Why are cultures not grown at 100°C?

15. Vaccines like MMR, give people immunity against infectious diseases.

Which three diseases does MMR vaccine protect against?

Explain how vaccinations help to protect the body against a disease.

16. What are the advantages of vaccination?

17. What are the disadvantages of vaccination?

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GCSE Style questions

1.

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2. Influenza is caused by a virus.

(a) How do viruses cause illness?

(b) A British company making a reality television show in the Peruvian Amazon has been

accused of starting an influenza epidemic.

This epidemic allegedly killed four members of a remote Indian tribe and left others seriously

ill.

The members of the television crew did not show symptoms of influenza, but members of

the Indian tribe died from the disease.

Suggest an explanation for this

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Influenza is an infectious disease. The influenza virus often mutates.

This has made the World Health Organisation worried about another influenza pandemic.

(a) What is meant by a pandemic?

(b) Explain why a mutation of the influenza virus might cause another influenza pandemic.

The MMR vaccine is used to protect children against measles, mumps and rubella.

(a) Complete the sentences about vaccination.

Vaccines stimulate white blood cells to produce .......................................... .

This makes children ....................................................... to the pathogen.

3.

Describe how the percentage of children vaccinated with the MMR vaccine changed

between 1990 and 1995.

Does the data in the graph support a link between MMR vaccination and autism? Explain

your answer.

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MICROBES What they

are

Where they're

found

How they

get around

Examples of

diseases they

cause

What does one look like –

find and copy labelled

diagram of one of these

Bacteria

Viruses

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