Full Revision Notes, Edexcel, Unit 1 Biology

Complete revision notes, based on each individual specification point, core practicals not included.

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Genes & Health 05/12/2013 09:34
2) Explain the importance of water as a solvent in transport, including its dipole nature
- Water is vital to living organisms
makes up 80% of a cell's content
water is a solvent which means some substances dissolve in it.
Most biological relations take place in solution
water transports substances. Substances can be transported more easily if they're
dissolved in a solvent
- Water molecules have a simple structure
one atom of oxygen joined to two atoms of hydrogen by shared electrons
shared negative electrons are pulled towards the oxygen atom, other side of hydrogen
is left slightly positively charged
unshared negative electrons on oxygen give it a slightly negative charge
makes water a dipolar molecule
(negative charge on one side and
a positive charge on the other)
3) Distinguish between monosaccharides, disaccharides and polysaccharides (glycogen and
starch ­ amylose and amylopectin) and relate their structures to their roles in providing and
storing energy
Made up of 1 sugar molecule only
Glucose, Fructose and Galactose
No bond
2 monosaccharides joined together
condensation reaction
joined by a glycosidic bond
can be split through hydrolysis reactions
used for energy/food source in seeds
alpha glucose + alpha glucose
form in which sugars are transported in plants
alpha glucose + fructose
carbohydrate source in mammalian milk
alpha glucose + galactose
Many monosaccharides joined together
Condensation reaction
Glycosidic bonds
Starch = polymer of glucose

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Genes & Health 05/12/2013 09:34
Glycogen = polymer for alpha glucose
Cellulose = polymer of beta glucose
Starch and Glycogen:
o Energy stores
o Animals store glucose as glycogen
o Plants store glucose as starch
o Compact molecules
o Low solubility in water (don't effect water concentration in cytoplasm, so
doesn't effect osmosis)
o Large molecules
o Uncharged
o Easily broken down
Starch ----------->maltose
Maltose ----------->glucose
Make from 2 molecules in combination, amylose & amylopectin
Both made from alpha glucose
Found in…read more

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Genes & Health 05/12/2013 09:34
High melting point
Solid at room temp (butter)
Unsaturated fatty acids
Low melting point
Liquids at room temp (fish oil)
6) Explain why many animals have a heart and circulation (mass transport to overcome
limitations of diffusion in meeting the requirements of organisms)
Unicellular organism don't need transport system, as they rely on diffusion to excrete waste and
absorb nutrients due to their high SA:Vol ratio
2 types of circulatory system:
open (mollusks, anthropods) : blood leaves vessels and moves…read more

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Genes & Health 05/12/2013 09:34
Ventricles fill with blood
Valvles in vena cava & pulmonary veins snap shut to prevent backflow of blood from
atria to viens
Ventricular Systole:
Ventricles contract from apex (base) upwards
Pressure inside ventricles increases
as pressure in ventricles > pressure in atria blood pushes against atrioventricular valves,
shutting them and preventing back flow (first heart sound)
Semilunar valves open under pressure and blood leaves the heart
Ventricle relaxed (diastole) and the semilunar valves snap shut behind the blood (second
heart…read more

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Genes & Health 05/12/2013 09:34
Base on aorta
Prevents backflow
Open during atrial systole
Elastic fibres
In the muscle layer
Allows stretching
Prevent damage of aorta
10) Describe the blood clotting process (thromboplastin release, conversion of prothrombin to
thrombin and fibrinogen to fibrin) and it's role in CVD (cardiovascular disease)
11) Explain the course of events that leads to atherosclerosis (endothelial damage,
inflammatory response, plaque formation, raised blood pressure)
Atherosclerosis is the degeneration of artery walls.…read more

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Genes & Health 05/12/2013 09:34
A fatty deposit that builds up along the artery wall
o takes many years to develop
o can lead to CHD or myocardial infarction
more likely to develop if an artery has been damaged in some way
more likely if high blood pressure
often in artery branches
Foam Cells:
Macrophages engulf cholesterol droplets by phagocytosis these appear white and foamy. Foam
cells invade artery walls and form fatty plaques.…read more

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Genes & Health 05/12/2013 09:34
If you have thrombotic disorder & need to stop clotting.
Interrupts part of the process involved in blood clotting
Reduces risk of intracranial bleeding
Older patients may be susceptible to bleeding complications
Increased risk of arterial calcification
Statins: e.g.…read more

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Genes & Health 05/12/2013 09:34
The higher your blood cholesterol, the greater the risk of CHD. Cholesterol isn't soluble in water, so
in order for it to be transported around the blood, insoluble cholesterol must combine with proteins
to form soluble phospholipids. Obesity and diabetes increases risk of CHD.…read more

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Genes & Health 05/12/2013 09:34
Risk = number of people with disease at any one time
number of people who could develop the disease
Risk factors ­ anything that increases chance of developing disease. They are correlational not
necessarily causal.…read more

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Genes & Health 05/12/2013 09:34
2) Explain how models such as the fluid mosaic membrane of cell membranes are
interpretations of data used to develop scientific explanations of the structure and properties
of cell membranes
Components of the plasma membrane:
Phospholipids ­ act as a
barrier to most molecules,
made from 2 fatty acid chain
`tails' attached to a phosphate
group `head'. Head is polar and
hydrophilic, tails are non-polar
and hydrophobic.
Cholesterol ­ type of lipid that
controls membrane fluidity.…read more


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