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AS Biology: Edexcel - Unit 1: Topic 1
Circulatory systems
Closed circulatory systems:
Blood leaves heart under pressure arteries arterioles
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 veins ensure that blood only flows in one
Single circulatory system: (e.g.…read more

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SAN / Sino Atrial Node /
pacemaker/ AVN /Atrioventricular Node /
Purkinje fibres /Purkyne fibres / Bundle of
His/eq } ;
(b) Giraffes are very tall mammals found roaming the plains of
Using the information in the photograph and your own
knowledge, explain the
importance of the heart and circulation to the giraffe (4)
1. idea that the heart has to pump blood a long
way around the body of the giraffe ;
2.…read more

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Explain the importance of water as a solvent in
transport, including it dipolar nature
In the circulatory system all the particles it contains are transported in
one direction in a process known as mass flow.
Properties of water that make it a good transport medium:
Water is a very good transport medium.
Water is liquid at room temperature.
The hydrogen's in the water push away from each other making
the molecule V shaped.…read more

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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
Veins: have valves
Capillaries: Are only one cell think and join the small arteries
(arterioles) and small veins (venules)
How does blood move through the vessels?
Every time the heart contracts (systole) blood is forced…read more

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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
Phase 2: Ventricular systole
Ventricles contract from base upwards increasing the pressure.
this pushes blood up and out through the arteries.…read more

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Stages of atherosclerosis:
Endothelium becomes damaged (e.g. due to high blood
pressure, or cigarette smoke)
Damage causes inflammatory response.…read more

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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 reliable results
Rick factors that increase the chance of getting CVD:
High blood pressure
Blood cholesterol and other dietary factors
Genetic inheritance
The risk of CVD is higher for men than women in…read more

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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 suitable for storage
because they are compact molecules.
Starch, glycogen and cellulose
Starch is made up of a mixture of two molecules, amylose and
amylopectin.…read more

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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
The (1)
A R groups
B R group and the amino group
C R group and the carboxyl group
D carboxyl group and the amino group
Lipids enhance the flavour and palatability of food.…read more


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