GCSE Biology B3 AQA

Just more b3 revision!

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  • Created by: Anisah
  • Created on: 13-10-10 18:00

The Heart / Circulatory System

The heart pumps blood round the body through arteries and veins. An artery carries blood away from the heart and a vein carries blood towards the heart.
The major vessels taking blood to and from the heart are:

 

  • the vena cava - this vein brings deoxygenated blood (with high levels of CO2) from the rest of the body to the heart
  • the pulmonary artery - this carries the deoxygenated blood from the heart to the lungs where it will be oxygenated
  • the pulmonary vein - this returns the now oxygenated blood (with low levels of CO2) to the heart
  • the aorta - this artey carries the oxygenated blood from the heart around to the rest of the body.
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Inhaling + Exhaling

The ventilation of lungs is the process of inhaling (breathing in) and exhaling (breathing out).
To inhale, the diaphragm contracts and flattens, while the intercostal muscles contract, lifting the ribs upwards and outwards. Both these actions increase the thorax volume and reduce the pressure in the lungs. Air is forced into the lungs by the higher air pressure outside.
Exhaling is the exact reverse process.

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Villi

The villi are tiny little folds in the surface of small intestine. In cross-section they look finger-shaped. You need to know how the structure of villi relates to their function:

  • they increase the surface area of small intestine so that small molecules can diffuse into the bloodstream more efficiently
  • they have very thin walls, only one cell thick so that small molecules can pass through easily
  • they have a plentiful supply of capillaries so that these small molecules can be carried away to the rest of the body
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Avtive Transport

mineral salts are taken up in the roots by active transport using energy from respiration.

Normally, ions will diffuse from high concentrations to low concentrations. This is known as the concentration gradient. For plants to absorb mineral ions like nitrates and magnesium from very dilute concentrations in the soil into cells with much higher concentrations, they have to "pull" against the concentration gradient. This requires energy, which is provided by respiration (using up glucose and oxygen).
Over-watering plants makes this more difficult as the concentration gradient is made worse.

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Kidneys

  • the glomerulus - this is a bundle of tiny capillaries that increase the pressure on the blood forcing small particles like much of the water, all the urea, all the glucose and ions through the capillary walls in a process called ultra filtration. None of the larger particles such as proteins or the red and white blood cells pass through
  • the Bowman's capsule - this collects the filtrate
  • the first coiled tube - here all of the glucose, some of the water and some of the ions are passed back through the capillary network into the blood in a process called re-absorption
  • the second coiled tube - more water is reabsorbed here increasing the concentration of the filtrate
  • the collecting tubule - these collect the filtrate from different nephrons, water continues to be re-absorbed here passing into the ureter as urine

 

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i didn't actually type this all out. 

Reference ; www.logonscience.com

Just for those that don't have a username

Hope it helps.

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Jack

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