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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  • Created by: Sarah
  • Created on: 03-01-12 18:24
Preview of GCSE Biology Unit 3 - Gas and solute exchange, adaptations, heart & respiration.

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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
lungs are protected by the ribcage
lungs are divided by abdomen by diaphragm
breathing system expels and takes in air
thus oxygen can diffuse into bloodstream
carbon dioxide can diffuse out of bloodstream
2. In plants
surface area is increased by root hairs
surface area is increased by flattened leaf shape
stomata conserve water
carbon dioxide enters through diffusion
water and ions absorbed by roots

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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 to decrease
the distance of diffusion.
Adaptations in Plants
The surface area is increased
by root hair cells. These absorb nitrates
and minerals through diffusion and
active transport.…read more

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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 through the capillaries back to the blood.
The blood tissue is a complex mixture of cells. It has four main parts
1.…read more

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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 are very small.
The lumen is narrow. These are how the blood
flows through organs to deposit its load.…read more

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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 flow to muscles is increased
oxygen and glucose is supplied more quickly
the rate of removal of carbon dioxide is increased
We respire glucose to provide energy for our muscles to contract.…read more


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