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AS Biology: Edexcel - Unit 1: Topic 1


Circulatory systems
Closed circulatory systems:
Blood leaves heart under pressure arteries arterioles
capillaries
Capillaries come in large numbers. They exchange substances
between the blood and cells.
After passing through capillaries blood goes back to the heart
via Venules veins
Valves in the…

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7. correct reference to position of
{atrioventricular valves / eq} ;

8. correct reference to position of semilunar
valves ;

9. reference to position of {tendons / tendinous
cords / papillary muscles / eq} ;

10. correct reference to position of {aorta /
pulmonary artery} ;

11. correct reference to…

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8. idea of diffusion not meeting the requirements
of the giraffe ;

9. reference to low surface area to volume ratio ;

10. idea that circulatory system helps
regulation of body temperature ;


Explain the importance of water as a solvent in
transport, including it dipolar nature
In the circulatory…

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Semi-lunar valve (separates the ventricles from the aorta)
Inferior vena cava (from lower body)
Superior vena cava (from head and arms)
Arteries and veins:
Arteries: narrow lumen
Veins: wide lumen
Arteries: thick walls
Veins: thinner walls
Arteries: more collagen, elastic fibres and smooth muscle
Veins: has less
Arteries: no valves…

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Phase 1: Atrial systole
Blood under low pressure flows into the left and right atria from
the pulmonary veins and vena cava.
As atria fill pressure against atrioventricular valves pushes them
open and blood starts leaking into the ventricles.
the atria walls then contract forcing more blood into the
ventricles.…

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Stages of atherosclerosis:
Endothelium becomes damaged (e.g. due to high blood
pressure, or cigarette smoke)
Damage causes inflammatory response. White blood cells
move into the artery wall, they accumulate chemicals from
the blood (cholesterol)
A deposit then builds up called an atheroma
Calcium salts and fibrous tissue build up at…

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Cohort study - a group of people are followed over time to see who
develops the disease
Case-control studies - a group of people who have the disease are
compared with a group who do not have the disease


Features of a good study:
clear aim
representative sample
valid and…

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Sucrose - Glucose + fructose - 1-2 glycosidic bond - form in
which sugar is transported in a plant
There are three main polysaccharides that are found in food: starch and
cellulose in plants, and glycogen in animals. Starch and glycogen act as
energy storage molecules within cells. They are…

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(c) The role of starch is to (1)

A be a source of energy to plants
B store energy in all living organisms
C store energy in plants
D store energy in animals

(d) Proteins are polymers of amino acids joined by peptide bonds formed
between
The (1)

A R…

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