GCSE AQA BIOLOGY UNIT 1 REVISION

GCSE AQA BIOLOGY UNIT 1 REVISION

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  • Created on: 08-06-12 10:27
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B1.1 Keeping Healthy
B1.1.1 Diet and Exercise
Summary
A combination of a balanced diet and regular exercise is needed to help keep the body
healthy.
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.
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.
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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 cardiovascular diseases, such
as strokes, heart attacks and thrombosis.…read more

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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.
Pathogens
Microorganisms that cause infectious disease are called pathogens.
Disease occurs when large numbers of pathogenic microorganisms enter the body.
Bacteria
Not all bacteria are pathogens.…read more

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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.…read more

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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.
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.…read more

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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.…read more

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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.…read more

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B1.2 Nerves and Hormones
Summary
The nervous system and hormones enable us to respond to external changes. They also help
us to control conditions inside our bodies. Hormones are used in some forms of contraception
and in fertility treatments. Plants also produce hormones and respond to external stimuli.
The nervous system
The nervous system enables humans to react to their surroundings and coordinate their
behaviour.
Central nervous system = brain plus spinal cord.
Stimuli = changes in the environment.…read more

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Receptors
Receptors and the stimuli they detect include:
o receptors in the eyes that are sensitive to light
o receptors in the ears that are sensitive to sound
o receptors in the ears that are sensitive to changes in position and enable us to keep
our balance
o receptors on the tongue and in the nose that are sensitive to chemicals and enable
us to taste and to smell
o receptors in the skin that are sensitive to touch, pressure, pain and to temperature
changes.…read more

Comments

daisy

very useful - quick and easy to read, gives you the basics  thank you

bec


Thank You

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