B3

B3

1. Exchange of materials

   • Osmosis
     • Diffusion of water down a concentration through a semi-permeable membrane
     • Causes net water movement into and out of cells
   • Active transport
     • Against concentration gradient
     • Uses energy from respiration
     • Cells absorb ions, sugar and salt this way
   • Sports drinks
     • Contains sugars and ions
     • Reseach shows that water is as effecive for normal amounts of exercise
     • Replaces sugars, ions and water lost in exercise and through sweating
   • Lungs
     • Large surface area, thin walls and steep concentratn gradients all help with the diffusion of oxygen.
     • Alveoli increase the surface area so that there is more space for diffusion to happen across
     • Adapted to make gaseous exchange as efficient as possible
     • The intercostal muscles move the ribcage up and out and your diaphragm moves down making your thorax bigger, this makes your lungs expand
   • Breathing aids
     • There are negative pressure breathing aids such as the iron lung and positive pressure breathing aids which force air into your body
     • All breathing aid have advantages and disadvantages
   • The gut
     • Villi and microvilli give the gut a large suface area
     • Villi have a good blood supply close to the surface
   • Exchange in plants
     • Plants have stomata which allows them to get carbon dioxide
     • Most water and ions needed are absorbed through the roots
     • Transpiration is loosing water vapour through the plants stomata

2. Trasporting materials

   • Circulatory system
     • Blood vessels, the heart and the blood
     • Humans have a double circulation
     • The heart pumps blood around the body
     • Valves make sure blood flows in the right dirrection
     • Arteries, veins and capillaries are all types of blood vessels
     • Damaged heart valves can be replaced and stents can reopen blood vessels
   • Transport in the blood
     • Blood plasma transports dissolved food molecules, carbon dioxide and urea.
     • Red blood cells carry oxygen
     • White blood cells are part of the immune system
     • Platelets are used in clotting of blood
   • Artificial
     • Artificial blood can be used to replace real blood that is lost
     • No blood group matching is needed for artificial blood
     • Artificial bood is very expensive and doesnt carry much oxygen
     • Artificial hearts are good as there is no wait for a donor
     • Artificial hearts can cause problems with blood clotting
   • Transport systems in plants
     • Flowering plants have seperate transport systems
     • Xylem tissue transports water and mineral ions
     • Phloem tissue transports dissolved sugars from the leaves to the rest of the plants

3. Keeping internal conditions constant

   • Controling internal conditions
     • Internal conditions must be kept constant to maintain the efficient use of organs and to prevent enzymes being denatured
     • Carbon dioxide leaves the body through the lungs
     • Urea is produced in the liver when excess amino acids are broken down
   • Kidneys
     • Kidneys are important for homeostasis
     • Kidneys produce urine by filtering the blood
     • Excess ions, water and urea are removed in urine
   • Kidney replacements
     • Dialysis does the job of a kidney but is not as effective
     • Dialysis machines restore levels of dissolved substances to normal levels
     • In kidney transplants, the old kidneys are left in the body
   • Body temperature
     • Body temperature is controlled in the thermoregulatory center in the brain
     • Body temperature must be kept at the level in which enzymes work best
     • Blood vessels dilate and constrict to control blood flow to the skin and therefore heat loss
     • Shivering heats up the body as blood goes to the muscles to move
   • Blood glucose
     • Controlled by the pancreas
     • Insulin allows glucose to move from the blood into cells
     • Type 1 diabetes can be treated with injections of insulin before meals
     • Type 2 diabetes can be treated with a careful diet and exercise

4. How humans can affect the environment

   • Population explosion
     • The human population is growing rapidly and the standard of living is increasing
     • We are using non renewable resources, taking over land and producing loads of waste
   • Polution
     • Toxic chemicals can pollute the land, rivers and the air
     • Carbon dioxide, sulfur dioxide and nitrogen oxide is realeased when fossil fuels are burnt
     • Acid rain damages trees
     • Air pollution contributes to global warming
   • Deforestation and peat destruction
     • Large scale deforestation has led to an increase in cabon dioxide in the atmosphere
     • The destruction of peat bogs releases carbon dioxide into the atmosphere
   • Global warming
     • Carbon dioxde and methane levels are rising which is causing an increasd greenhouse effect
     • Global warming is the increase in temperature of the surface of the earth
     • Global warming causes climate change, rise in sea levels and loss of biodiversity
   • Biofuels
     • Biofuels can be made using crops and fermenting them to make ethanol
     • Biogas can be made by the anaerobic fermentation of plants and waste containing carbohydrates
     • Biogas generators can be small to supply a family or big enough to supply a whole city
   • Sustainable food production
     • Increasing efficiency of food production can be done by decreasing the number of stages in the food chain
     • If you keep animals warm and stop them moving then they waste less energy
     • Controlling net size and setting limits for the amount of fish that can caught conserves fish stocks
     • The fungus fusarium is grown in sugar syrup to produce mycroprotein foods
   • Environmental issues
     • Methods to produce food and water can have short and long term effects on the environment
     • There is alot of data on effects on the environment