GCSE Biology Unit 3 - Gas and solute exchange, adaptations, heart & respiration.

Fairly comprehensive notes based around;

  • transportation
  • adaptations within the human body
  • the structure of the heart and associated blood vessels
  • respiration.

Created for the AQA 2011 unit 3 exam - any changes to the specification since then are not included.

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Page 1

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Gas and Solute Exchange

Remember, in diffusion the steeper the concentration gradient, the quicker the rate of
diffusion, eg

Summary of Adaptations to Assist Solute Exchange

1. In humans, the
surface area of the lungs is increased by alveoli
surface area of the small intestine is increased by villi

Page 2

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Adaptations in Humans

Alveoli and villi increase the
surface area of the lungs/intestine so
there is more available space in which
oxygen and carbon dioxide/nutrients can
be exchanged. They have a good blood
supply to keep the concentration gradient
steep and are moist to ease diffusion.
They have thin membranes…

Page 3

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Transportation around the Body

Substances are transported around the body by the circulation system, aka the
heart, blood vessels and the blood. The heart pumps the blood around the body, so that
required substances (glucose, oxygen etc) pass out of the blood and waste products
(carbon dioxide, urea etc) pass…

Page 4

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The Blood Vessels

Arteries have thick walls to prevent internal
bleeding and a thick layer of muscle and
elastic to help propel the blood along. It has
a large lumen. Blood sets out from the heart
along these.

Capillaries have very thin walls to
increase the rate of diffusion and…

Page 5

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When exercise is undertaken by the body
the muscle cells respire more quickly
the muscle cells use up oxygen and glucose more quickly
carbon dioxide is made more quickly
the heart rate increases
the arteries dilate
the depth and rate of breathing increases
In order that
the blood…


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