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AS Biology Revision Notes ­ Unit 1

Topic 1: Lifestyle, Health, and Risk
* Water molecules are non-linear and polar molecules because the H
and O atoms are different in size and electronegativity.
* They form hydrogen bonds with other water molecules.
* Some properties include...

Property Explanation

Page 2

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AS Biology Revision Notes ­ Unit 1

(Glucose and galactose)

Oligosaccharides - 3-10 sugar units. Found in vegetables e.g. leeks,
lentils, beans


Page 3

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AS Biology Revision Notes ­ Unit 1

Polysaccharides (polymers) are long chains of glucose molecules.
Found in muscle and liver cells for energy storage.
Made of poly alpha glucose linked together.
Insoluble because it has 1,4 and some 1,6 links, which form branches in the chain.
Very compacted, thus…

Page 4

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AS Biology Revision Notes ­ Unit 1

* Saturated fatty acids contain the maximum number of hydrogen atoms and no carbon-carbon double
bonds. They are found in animal fats and dairy products.
* Monounsaturated fats contain 1 double bond, for example olive oil.
* Polyunsaturated fats contain a larger number…

Page 5

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AS Biology Revision Notes ­ Unit 1

returning from the veins.
Increased pressure opens the atrioventricular valves allowing blood to enter the
The atria contract to force remaining blood into ventricles.

Ventricular systole Ventricles contract from the base up, increasing the pressure and closing the
atrioventricular valves.
The semilunar…

Page 6

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AS Biology Revision Notes ­ Unit 1

- Large lumen (decreases effect of friction).
Capillaries - Walls are one cell thick (cells are called
Adapted for exchange of endothelial cells).
substances. - Lumen is the same width as one RBC
(therefore more of RBC in contact with wall,
therefore smaller…

Page 7

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AS Biology Revision Notes ­ Unit 1

- Nicotine stimulates adrenaline release, increasing heart rate and blood pressure.
- Chemicals damage endothelium, triggering atherosclerosis.
- Decreased levels of HDLs.
Inactivity - Most common risk factor.
- Exercise can halve the risk of developing CHD.
- Reduces blood pressure.
Stress Leads…

Page 8

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AS Biology Revision Notes ­ Unit 1

* Determining Risks:
Risk is the probability of occurrence of some unwanted event or outcome.
A time period is always quoted.
Not all individuals are at risk to the same degree.
Risk factors increase the chance of the harmful outcome.
Factors that contribute…

Page 9

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AS Biology Revision Notes ­ Unit 1

Topic 2: Genes and Health
Cell Membrane:
* Cell membrane is made up of a phospholipid bilayer.
* The phosphate head of the phospholipid is a polar molecule and
attracts water ­ it is hydrophilic.
* The fatty acid tails are non-polar and…

Page 10

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AS Biology Revision Notes ­ Unit 1

Secondary structure: the shape the molecule folds because of hydrogen bonding between the C=O
of one amino acid and the N-H of the amine group of another ­ an helix or a pleated sheet.
Tertiary structure: the final 3D shape of the molecule,…




Brilliant resource very detailed. 



Pretty well oriented...Thanks alot IIwellyne!



thankq so much it is so useful ! But some questions were empty , can anyone tell me how to find answers for those ?

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