B3

1.1 Osmosis

• osmosis is the diffusiom of water
• water diffuses from a dilute solution to a more concentrated soloution through a partially permeable membrane 
• water moves into or out of cells by osmosis throgh the cell membrane 

1.2 Active Tansport

• active transport allows clls to take in sunstances against a concentration gradient 
• active tansport uses energy from respiration 
• ions can from dilute solutions, and other substances such as sugar can be absorbed by active transport.

1.3 The Sports Drink Dilemma 

• most soft drinks contain: water to replace water when lost when sweating; sugar to replace sugar used for energy release in exercise; mineral ions to replace those lost in sweating 
• for normal levels of exercise, water is likely to be as effective as a sports drink.

1.4 Exchanging Materials - The Lungs

• large organisms need exchange surfaces
• exchange surfaces have features to make them efficient
• the lungs are adapted to be an efficent echange surface

1.5 Ventilating the Lungs

• the breathing system is designed to move air im and out of the lungs
• ventilation occurs due to changes of pressure inside the chest

1.6 Artificial Breathing Aids

• Reasons for artifical breathing aids: if the alveoli are damaged the surface area for gas exchange is reduced: if the tubes leading to the lungs are narrowed, less air can be moved through them: if the person is paralysed their muscles will not work to pull the ribcage up and out
•  breathing aids which force measured amounts of air in the lungs use positive pressure

1.7 Exchange in the gut

• the villi are an efficient exchange surface for the absorption of the soluble products of digestion by diffusion or active transport
• villi provide a large surface area and have a good blood supply.

1.8 Exchange in plants

• the stomata in plant leaves allow carbon dioxide to diffuse into the leaf from the atmostphere 
• leaves are flat and thin with internal aire spaces to increase the surface area for diffusion of gases
• root hair cells increase the surface area of roots.

1.9 Transpiration

• water is lost from the leaves be evaporation
• the water vapour escapes the leaf through the stomata when the open to allow carbon dioxide to enter the leaf
• wilting can protect the leaf from excessive water loss. 

2.1 The circulatory system and the heart

• the double circulation system in humans consists of blood vessels, blood and the heart
• the heart is the organ that pumps blood around the body
• valves prevent backflow of blood

2.2 Keeping the blood flowing 

• arteries, viens and capillaries are the main types of blood vessel
• substances diffuse between the blood and the cells in the capillaries 
• blocked or narrow arteries can be widened by stents, damaged heart valves can be replaced

2.3 Transport in the Blood

• blood plasma transports dissolved food molecules, Co2 and urea. Plasma also contains blood cells.
• the red blood cells carry oxygen from the lungs to the cells. the white cells are part of the defence system
• plateles are invloved in blood clotting.

2.4 Artifical or real?

• there are advantages and disadvantages when using artificial blood and artificial hearts
• they are useful when real blood or donor hearts are not available 

2.5 Transport systems in plants

• flowering plants have two transport tissues
• xylem transports water and mineral ions from the roots to the stems and the leaves
• phloem transports food, such as dissolved sugar, from the leaves to other parts of the plant.

3.4 Kidney transplants

• a diseased kidney can be replaced by a healthy kidney
• the donor kidney must be a very good 'match'
• the immune system has to be suppressed or it is likely to reject the new kidney.

3.5 Controlling body temperature

• enzymes work in a very narrow temperature range
• body temperature is monitored and controlled to kepp it within this narrow range.

3.6 Treatment and temperature issues

• both dialysis and kidney transplats have advantages and disadvantages 
• see AQA Science Biology Revision Guide for more information (page 86)

3.7 Controlling blood glucose 

• the level of glucose in the blood is controlled by hormones
• in type 1 diabetes the blood glucose level risesto high levels because it is not controlled properly.

3.8 treating diabetes

• type 1 diabetes is treated with insulin injections
• new methods are being tried or developed to treat diabetes. 

4.1 the effects of the population explosion

• the human poulation is increasig rapidly
• humans are using more resources and producing more waste and pollution

4.2 land and water pollution

• humans are responsible for pulling both land and waterways

4.3 air pollution

• sulfur dioxide dissolved in rain makes it more acid
• acid rain can effect organisms both directly and indirectly

4.4 deforestation and peat destruction

• forest are cut down to clear land for farming
• deforestation leads to a reduction in biodiversity and an increase in CO2 in the atmostphere
• destruction of peat bogs also releases carbon dioxide

4.5 Global warming

• the climate of the Earth is getting warmer
• global warming affects living organisms.

4.6 Biofuels

• ethanol based fuels can produced by anaerobic fermentation of sugars from plants
• the ethanol ditilled from the fermentation prduct can be used as fuel in motor vehciles

4.7 Biogas

• boigas is mainly methane. it is made by the anaerobic ferentation of a wide range of waste substances and plant material containing carbohydrates.
• biogas can be made on a large or a small scale
• many different microorganisms are involved in biogas production

4.8 making food production efficient 

• short food chains make food production more efficient
• food production can be controlled to reduce energy wastage

4.9 sustainable food production

• fish stocks can be maintained by controlling fishing quotas and net size
• the fungus fusarium produces mycoprotein

4.10 environmental issues

• human activities affet both local and global environments
• there is alot of evidence for environmental change
• scientists need to check the validity and the reproducibility of the data collected.