GCSE AQA Biology 'Unit 1' Revision Guide

Revision guide for GCSE AQA Biology 'Unit 1' / 'B1'. Please ignore all the random writing around the sides of the page, I was a rather weird person in Year 10 (not that there's much writing anyway).

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Biology One By Applequestria (applequestria.deviantart.com)
Diet and exercise:
A healthy diet consists of the right amount of different foods and the right amount of energy. Being
malnourished means your diet isn't balanced, and can lead to a being overweight or underweight. An
unbalanced diet can also lead to deficiency diseases, or conditions such as Type 2 diabetes.
Carbohydrates ­ to release energy
Fats ­ to keep warm and release energy
Proteins ­ growth and cell replacement
Fibre ­ to help keep digestion running smoothly
Mineral ions and vitamins ­ needed in small amounts to keep a healthy body
A person can lose mass by taking in less energy than what they use. When we take exercise, we use energy,
which then helps use up the energy we took in. People who exercise regularly are usually healthier than
people who take little exercise. The speed at which the chemical reactions take place in the body is called your
metabolic rate. This varies from person by person, and can be affected by inherited factors; for example
cholesterol level.
Defence against infectious diseases:
Microorganisms that cause disease are called pathogens. When inside the body, bacteria and viruses may
reproduce rapidly. Bacteria may damage cells, and produce poisons (toxins) that make us feel ill. Viruses
damage cells, and use the cell's mechanism to reproduce. Luckily, our bodies have different ways of protecting
itself against these pathogens. White blood cells are part of the immune system and help defend against
pathogens by:
1. Ingesting pathogens (not eat or digest)
2. Producing antibodies, which lock on and destroy specific bacteria or viruses.
3. Producing antitoxins, which neutralise toxins released by pathogens.
Our immune system produces specific antibodies to kill a particular pathogen. The immune system then
`remembers' the specific antibody used to kill the pathogen, so when the pathogen enters our body again, we
can activate antibody production and kill off the pathogen. If most people in a population are immune to a
pathogen, it is more difficult for the pathogen to spread. This is called herd immunity.
Ignaz Semmelweis believed that doctors were spreading diseases by not washing their hands. By insisting that
doctors washed their hands before entering his ward, he greatly reduced the number of deaths from infectious
diseases in his hospital.
Some medicines, including painkillers help to make us feel better, but do not kill the pathogens. However,
antibiotics (such as penicillin), can help to cure bacterial disease by actually killing the bacteria in the body.
Unfortunately, antibiotics cannot be used to kill viruses. This is because viruses live, and reproduce inside cells,
so it is difficult to kill the virus without damaging the cell.
Unluckily for us, many strains of bacteria (including MRSA), have developed resistance to antibiotics as a result
of natural selection. This is because bacteria can mutate. Useful mutations can allow individual pathogens to
survive, while the non-resistant strain is killed. These resistant bacteria then reproduce, so the population of
the resistant strain increases. This can mean that our antibiotics and vaccines will no longer work against these
strains, so we have to develop more new antibiotics. Luckily, there are a few ways to slow down the
development of resistant strains:

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1. Antibiotics are only used to treat serious infections.
2. An antibiotics course has to be completely finished.
In research made to investigate the action of disinfectants and antibiotics, uncontaminated cultures of
microorganisms are required. To do this, the Petri dishes and culture media must be sterilised to kill unwanted
microorganisms. Inoculating loops used to transfer the microorganisms must be sterilised by passing them
through a flame.…read more

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Now you need to know about the menstrual cycle. Firstly, a hormone called FSH is secreted by the pituitary
gland which causes the development and maturation of the eggs in the ovaries. This also stimulates oestrogen
to be secreted by the ovaries which inhibits further production of FSH. This stimulates LH to be secreted by the
pituitary gland, which finally causes the release of the eggs from the ovaries.
You may also be asked to describe how hormones are used in controlling fertility.…read more

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However, the overall impact of legal drugs on health is much greater than illegal drugs because much more
people use them.
Some athletes use drugs to enhance performance. Even though all drug use in to gain an advantage in sport is
banned, some people still use them to boost their bodily functions such as heart rate, and use anabolic
steroids which stimulate muscle growth.
To survive and reproduce, organisms require materials from their surroundings and other living organisms.…read more

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Waste material
Decay processes
Organisms have to remove and use materials from the environment or growth and other purposes. These
materials are eventually returned back to the environment in either the form of waste materials or when
organisms die. Both of these materials are decayed by microorganisms. This means it is broken down and
digested. Microorganisms are more active and digest faster in warm, moist, aerobic conditions. This decay
process releases substances that plants need to grow, things like nutrients.…read more

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1. Tissue culture - using a small group of cells taking from a part of the plant.
2. Embryo transplants - taking cells from an animal embryo, before transplanting them into host mothers.
3. Adult cell cloning - this is often asked for in exams because it is the most complex, so learn the steps
carefully. The nucleus is first removed from an unfertilised egg. The nucleus from an adult body cell (for
example, a skin cell), is then inserted into the egg cell.…read more


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