AQA Science © Nelson Thornes Ltd 2006 1 B3 2 Summary Transporting substances around the body Chapter review.

AQA Science © Nelson Thornes Ltd 2006  1

B3 2 Summary

Transporting substances around the body

Chapter review

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  2

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.

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  3

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)

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  4

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.

B3 2 Summary

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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.

B3 2 Summary

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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 using oxygen.

• Demand for oxygen stays high until lactic acid is all gone – oxygen needed is oxygen debt.

Higher

Photo: Photodisc 51 (NT)

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  7

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.

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  8

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

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  9

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.

B3 2 Summary

AQA Science © Nelson Thornes Ltd 2006  10

Which is best – dialysis or transplant?

Dialysis: • Machines usually

available.• No problems with

tissue matching.• Has to happen at least

twice aweek for life.

• Expensivelong-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

immunosuppressantdrugs for life.

• Surgery every ten years or so.