Biology Unit 3

AQA Biology unit 3 GCSE

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  • Created by: Emily
  • Created on: 11-05-12 19:55

What is active transport

  • The movement of a substance from an area of low to high concentration (against a gradient)
  • requires energy
  • energy comes from cellular respiration
  • happens in plant for the uptake of water and mineral ions from the soil as they are found in dilute solutions in the soil, however in plant cells there is a high concentration
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Adaptations of the roots to make uptake efficient

  • root hair cells have a large surface area for more active transport to take place in a shorter amount of time
  • root hair cells have thin walls for the mineral ions to pass through much quicker
  • root hair cells have microvilli and lots of mitochondria (for respiration)
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Properties of alveoli to improve gas exchange

  •  Rich blood supply - maintains a concentration gradient
  • moist
  • large surface area - more diffusion/active transport can occur in a shorter space of time
  • thin walls - less space for molecules to diffuse across
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Water loss from the surface of the leaf

  • happens through small openings called the stomata, which open and close to allow water out and CO2 in (for photosynthisis)
  • factors that increase evaporation - increase transpiration
  • Hot, dry, and windy conditions increase the rate of transpiration

Transpiration Stream

As water is lost from the surface of the leaves, it was also taken in through the xylem

  • if water is lost quicker than it is gained - leaves can "wilt" this decreases surface area, therefore, water loss
  • the leaves have a "waxy cuiticle" - this is gas proof and water proof















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circulatory system

Consists of:

  • Arteries - carry oxygenated blood away from the heart to the organs in the body - these create our pulse as they stretch to allow blood through and then return to their normal shapes
  • Veins - carry deoxygenated blood towards the heart - these have valves to stop the back flow of blood
  • Cappilaries - found in junctions between the arteries and veins - walls are 1 cell thick to allow diffusion to happen quickly
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The Blood

  • Blood Plasma = a yellow liquid that transports substances around the body, it contains red blood cells, white blood cells (immune system) and platetets (blood clotting). it can carry co2 back to the lungs and can carry urea from the liver to the kidney where it is excreted via urine
  • Red Blood cells contain haemaglobin - this can carry oxygen around the body (hence the bloods red colour)
  • red blood cells are specially designed:
  • they are shaped like bioconcave discs - increases surface area
  • have no nucleus - more room for oxygen/haemaglobin
  • and are packed full of haemaglobin
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Excercise and the body

When we excercise, glucose is broken down by aerobic respiration, to provide energy for the excercising muscles.

we we excercise:

  • Breathing rate increases - allowing more oxygen in and more co2 out, so that more respiration is able to take place in the body
  • heart rate increase and arteries dialate - allowing more blood flow to the excercising muscles of respiration

During vigorous excercise, our body cannot get sufficient oxygen and our muscles being to fatigue, so our body switches to anaerobic respiration and lactic acid builds up in the muscles. Oxygen debt is the amount of oxygen required to break down all of this lactic acid and transform it into co2 and water vapour, which is excreted when we breate out

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  • Vital in maintaining homeostasis
  • When these organs fail it can cause a dangerous build up of substances in the blood stream,such as urea and mineral ions, this must be treated otherwise the person would be unable to survive. it can be treated in two ways:
  • Dialysis
  • this requires the patients blood to leave their bodies and flow through a partially permeable membrane, on the other side of this the the dialysis fluid containing certain concentrations of certain substances to control what leaves the blood and what is reabsorbed. for example - the fluid contains no urea so this leaves the blood entirely as it is so dangerous, but contains a certain level of mineral ions, so some of these mineral ions are reabsorbed by selective reabsorbion. glucose stays in the blood as it is very important. The patient has a restricted life as dialysis must be carried out every few days, and must have a healthy diet to avoid build up.
  • Another alterative is a kidney transplant
  • this could be attacked and rejected by the patients immune system due to the different antigen on the surface, so they must try to find a donor of the same blood type to  avoid this. The patient could also take immunosupressant drugs to shut down the immune system. after a kidney transplant the patient can usually live a normal life and eat whatever they wish.
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yoghurt production

made anaerobically (fermentation)

  • add a bacteria culture to warm milk
  • this bacteria breaks down lactose into lactic acid
  • lactic acid gives the yoghurt a tangy taste and causes it to clot
  • flavourings may be added to make yoghurt taste more pleasant
  • bacteria stops it from going off as quickly
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Growing bacteria or microbes in a culture, which acts as a energy source as it is a carbohydrate. This allows us to see the behavior of different microbes as a cologny.

Safety precautions much be taken such as:

  • avoiding much exposure to the air (keep the lid on)
  • sterilize all equiptment
  • wash hands regularly

This must be done to avoid cross contamination and to stop microbes from becoming pathogenic (dangerous)

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  • Used in the production of bread
  • Respires aerobically and produces CO2 and water, the CO2 causes the bread to rise and gives it a light and fluffy texture
  • yeast is killed when the bread is baked so it isn't dangerous

also used in the production of ethanol. In beer production, barley grains are malted into a sugary solution, which is then added to yeast which ferments it, yeast also ferments the natural sugars used to make wine.

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  • mostly methane
  • produced from waste materials and dead animals and plants in biogas generators
  • exothermic reaction
  • optimum temperature = 30 degrees
  • cheap
  • environmentally friendly
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Industrial microbe production

  • large vessels called fermenters
  • they have a constant oxygen supply to ensure all microbes respire
  • stirrer to keep contents in suspension and ensure all materials are mixed
  • water cooled jacket absorbs any heat given out in the reaction and maintains a constant temperature
  • PH monitor ensures it remains at the correct PH

can be used to make penicillin

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  • mixture of petrol and ethanol used as fuel
  • ethanol is "carbon neutral"
  • ethanol doesn't give out toxic gases
  • not enough maize to create this on a large scale
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wow tanxs i really wanted sum short but useful nd important  key points tanxs  xxxx

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