Unit 1 AQA as biology summeries

This document is summeries of everything you need to know for unit 1 of AS AQA Biology.

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Revision notes biology
Enzymes and biological molecules
Contain 3 elements:
1. Carbon (C)
2. Hydrogen (H)
3. Oxygen (O)
Carbohydrates are found in one of three forms:
1. Monosaccharides
2. Disaccharides (both sugars)
3. Polysaccharides
Disaccharides and glycosidic bonds
These are formed when two monosaccharides are condensed together. One
monosaccharide loses an H atom from carbon atom number 1 and the other loses an OH
group from carbon 4 to form the bond.
The reaction, which is called a condensation reaction, involves the loss of water (H2O) and
the formation of a 1,4-glycosidic bond.
Examples of Disaccharides
Sucrose: glucose + fructose,
Lactose: glucose + galactose,
Maltose: glucose + glucose.
Maltose: glucose + glucose.
Functions of carbohydrates
1. Substrate for respiration (glucose is essential for cardiac tissues).
2. Intermediate in respiration (e.g. glyceraldehydes).
3. Energy stores (e.g. starch, glycogen).
4. Structural (e.g. cellulose, chitin in arthropod exoskeletons and fungal walls).
5. Transport (e.g. sucrose is transported in the phloem of a plant).
6. Recognition of molecules outside a cell (e.g. attached to proteins or lipids on cell
surface membrane).

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Lipids are made up of the elements carbon, hydrogen and oxygen but in different
proportions to carbohydrates. The most common type of lipid is the triglyceride Lipids can
exist as fats, oils and waxes. Fats and oils are very similar in structure (triglycerides).
These are made up of 3 fatty acid chains attached to a glycerol molecule.
Functions of lipids
1. Storage - lipids are non-polar and so are insoluble in water.
2.…read more

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Hydrolysis is the opposite of condensation and is the breaking of a peptide bond using a
molecule of water.
Fibrous proteins are made of long molecules arranged to form fibres (e.g. in keratin). Several
helices may be wound around each other to form very strong fibres.
Globular proteins are made of chains folded into a compact structure. One of the most
important classes are the enzymes.…read more

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2. pH
3. Enzyme Concentration
4. Substrate Concentration
Most enzymes require additional help from cofactors, of which there are 2 main types:
1. Coenzymes - these are organic compounds, often containing a vitamin molecule as
part of their structure.
2. Metal ions - most speed up the formation of the enzyme-substrate complex by
altering the charge in the active site e.g. amylase requires chloride ions, catalase
requires iron.
Inhibitors slow down the rate of a reaction.…read more

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Infection and disease
Your immune system is made up of cells that work with the body's physical and chemical
barriers. It helps prevent any pathogen (disease-causing organism) entering your body, and
your body therefore becoming infected. Note: Harmful bacteria is an example of a pathogen.
If the worst comes to the worst and any pathogens do get into your body, the immune
system tries to stop them from causing harm.…read more

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Inflammation happens because cells damaged by invading pathogens and particular white
blood cells release 'alarm' chemicals which makes blood vessels enlarge (vasodilate) and the
capillaries more 'leaky'.
Attack no 2: Phagocytes and lymphocytes
Inflammation attracts white blood cells to the area. The three types of white blood cell you
need to know for your exam are neutrophils, macrophages (these are both phagocytes,
which are engulfing cells), and lymphocytes.…read more

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Suppressor T cells
Memory cells
Humoral response (B cells)
As with T cells, a B cell will form a clone if it comes into contact with a complementary
shaped antigen. The clone contains mostly plasma cells for immediate use and some
memory cells for use in the future.
The plasma cells are highly developed and are able to make several thousand antibody
molecules every second.
Immunological memory
Plasma cells and most of T cells die after only a few days.…read more

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These are a result of an overreaction of the immune system to a harmless antigen, as in
asthma, hay fever and eczema. They are caused by allergens - for example, pollen, dust,
particles of animal skin, dustmites and their faeces.
Health and disease
Health can be defined as a person's physical, mental and social condition.
Disease is a disorder or malfunction of the mind or body, which destroys good health.…read more

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Lung disease
After heart disease and strokes, this is the most common cause of illness and death in the
Chronic bronchitis
Tar stimulates goblet cells and mucus glands to enlarge, producing more mucus. It destroys
the cilia inhibiting the cleaning of the airways and mucus (containing dirt, bacteria and
viruses) builds up blocking the smallest bronchioles.…read more

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blood pressure rises. This makes it difficult for the heart to receive the extra nutrients and
oxygen it requires during exercise.
Three forms exist: Angina, Heart Attacks, Heart Failure
These occur if an artery in the brain burstsand blood leaks into the brain tissue or when an
artery supplying the brain becomes blocked. The brain tissue becomes starved of oxygen and
dies. Strokes can be fatal or very mild and may affect speech, memory and control of the
body.…read more


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