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B3 2 Summary
Transporting substances around
the body
Chapter review
AQA Science © Nelson Thornes Ltd 2006
1
B3 2 Summary
How does your circulatory
system work?
• Three elements: blood vessels, heart and blood.
• Three types of blood vessels: veins, arteries and
capillaries.
• Heart acts as a pump, moving blood around the
body.
• Double circulation:
– heart to lungs to heart.
– heart to body to heart.
AQA Science © Nelson Thornes Ltd 2006
2
B3 2 Summary
How does your blood transport
substances?
• Blood consists of plasma, red
blood cells, white blood cells
and platelets.
• Plasma is a yellow liquid.
• Plasma transports all of the
blood cells, carbon dioxide,
urea, soluble products of
digestion, e.g. glucose.
• Red blood cells carry oxygen.
Photo: Photodisc 59 (NT)
AQA Science © Nelson Thornes Ltd 2006
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B3 2 Summary
How are red blood cells adapted
to carry oxygen?
• Large numbers – five million per
1 mm3.
• Biconcave discs for increased
surface area.
• Packed full of haemoglobin – red
pigment that can carry oxygen.
• No nucleus – makes more space
for haemoglobin.
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B3 2 Summary
How does exercise affect your
body?
• Muscles use oxygen for aerobic respiration,
to provide energy as glucose is broken down.
• When you exercise, muscles work – they
need more oxygen.
• Heart rate increases.
• You breathe more deeply.
• More oxygen in, more carbon dioxide out.
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B3 2 Summary
Higher
What is an oxygen debt?
• Lots of exercise causes muscle
fatigue.
• The body switches to anaerobic
respiration – not as efficient, so
it gives less energy.
• Lactic acid is produced.
• When exercise is over, the body
has to break down lactic acid
Photo: Photodisc 51 (NT)
using oxygen.
• Demand for oxygen stays high until lactic acid is all gone –
oxygen needed is oxygen debt.
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B3 2 Summary
Why are your kidneys so
important?
• Important for homeostasis.
• Remove urea from blood.
• Remove excess water from blood or
conserve water.
• Remove excess mineral ions from blood or
conserve mineral ions.
• Filter blood and reabsorb everything needed,
e.g. glucose, by selective reabsorption.
• Produce urine.
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B3 2 Summary
What is kidney dialysis?
• Kidney failure means death,
unless the function of the
kidneys is replaced.
• Dialysis replaces kidney
function – filters and cleans
blood.
• Depends on diffusion along
concentration gradients from
blood to dialysis fluid.
Photo: SPL BSIP/Beranger
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B3 2 Summary
What is a kidney transplant?
• Failed kidneys replaced by single healthy
kidney from donor.
• Donor usually dead, but may be living.
• To prevent rejection by the immune
system:
– The kidney is as close a tissue match as
possible.
– The recipient takes immunosuppressant
drugs for life.
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B3 2 Summary
Which is best – dialysis or transplant?
Dialysis:
• Machines usually
available.
• No problems with
tissue matching.
• Has to happen at least
twice a
week for life.
• Expensive
long-term.
• Have to watch diet.
Transplant:
• No special diet.
• No sessions of dialysis.
• Relatively inexpensive,
particularly after surgery.
• Need donor, often not available.
• Need tissue match.
• Have to take
immunosuppressant
drugs for life.
• Surgery every ten years or so.
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