Active Transport, The Circulation System, Blood and Exercise

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Pages 76-79 of the GCSE AQA Biology Revision Guide

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  • Created by: jenny100
  • Created on: 15-05-12 18:50

Active Transport

Substances are absorbed against the concentration gradient, i.e. from a lower to a higher concentration and it requires energy

Root Hair Cells

  • Cells on the surface of plant roots grow into long hairs that stick into the soil
  • This gives the plant a big surface area for absorbing water and mineral ions from the soil
  • Most of the water and ions that enter the plant are absorbed by the root hair cells
  • The concentration of mineral is usually higher in the root hair cell so diffusion does not apply
  • Active transport allows the plant to absorb minerals against the concentration gradient which is essential for growth
  • The energy for active transport comes from respiration

Kidney Tubules

  • Active transport is used in the gut when there's a low concentration of nutrients in the gut, but a high concentration in the blood so the nutrients can still be taken into the blood despite the low concentration in the gut.
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The Double Circulation System

  • The heart is two pumps. The right side pumps deoxygenated blood to the lungs to collect oxygen and remove carbon dioxide. The left side pumps around the oxygenated blood around the body
  • Arteries carry blood away from the heart at a high pressure
  • Normally arteries carry oxygenated blood and veins carry deoxygenated blood but the Pulmonary vein and artery are in fact the opposite way round (exception to the rule)
  • Arteries eventually split off into thousands of capillaries which take blood to every cell in the body
  • Veins then collect the used blood and carry it back to the heart at a low pressure

All mammals and birds have a double circulation system 

Fish only have a single circulation system because the blood goes straight from the heart to the gills

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Blood

  • Capillaries use diffusion to deliver food and oxygen direct to body tissue and take CO2 and other waste materials away
  • Walls only one cell thick to make it easier for diffusion to occur

Blood consists of: White blood cells, red blood cells, plasma & platelets

Red Blood Cells carry oxygen, they have bio-concave disc shape to give a larger surface area for absorbing oxygen, they don't have a nucleus to make more room to carry oxygen. They contain haemoglobin, in the lungs the haemoglobin combines with oxygen to become oxyhaemoglobin. In body tissues the reverse happens to release oxygen to the cells.

Plasma carries everything in the blood:

  • Red and white blood cells and platelets 
  • Nutrients like glucose & amino acids
  • CO2 from organs to the lungs 
  • Urea from liver to kidneys
  • Hormones 
  • Antibodies and antitoxins produced by white blood cells
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Exercise

Exercise increases the heart rate because:

  • During exercise your muscles contract, for this to happen glucose and oxygen is needed
  • To obtain glucose and oxygen respiration and therefore breathing rate must increase
  • Now there's more in the blood so the heart rate increases so a higher rate of glucose and oxygen can reach the muscles 

Glycogen is used during vigorous exercise when the bodies glucose is used rapidly. The body must use its glycogen stores to provide more energy. If you continue to exercise then the glycogen stores run out and that's when the muscles don;'t get the energy they need to keep contracting and you start to fell tired.

Anaerobic Respiration is used if there's not enough oxygen:

  • Needed when your body can't supply enough oxygen to your muscles
  • Incomplete breakdown of glucose: glucose --> energy + lactic acid
  • The lactic acid builds up in the muscles which gets painful and causes the muscles to get tired
  • Does not release nearly as much oxygen as aerobic respiration
  • Leads to oxygen debt so your pulse & breathing rate will stay high until the brain detects the high levels of CO2 and lactic acid has decreased 
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Comments

anum

wow this is really good-must have t\ken you AGES!

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