Biology - B3.1 - Exchange of Materials
0.0 / 5
- Created by: Katatatitee
- Created on: 04-05-14 11:28
B3.1.1 - Osmosis
- Osmosis - movement of water
- Like diffusion, osmosis is random and requires no energy
- Osmosis - diffusion of water across partially permeable membrane - cell membrance is partially permeable
- Moves from area of high concentration (dilute solution) to lower concentration (concentrated solution)
1 of 9
B3.1.2 - Active Transport
- Cells may need to absorb substances in short supply: against concentration gradient - use active transport to absorb substances across partially permeable membrane against concentration gradient
- Active transport requires energy released in respiration
- Cells able to absorb substance from dilute solutions - eg. root cells absorb mineral ions from soil
- Glucose reabsobed in kidney tubules by active transport
2 of 9
B3.1.3 - The Sports Drink Dilemma
- Exercise - muscles release energy through respiration, using glucose - body gets hot: sweat to cool down -> sweat a lot: dehydrated - need to replace sugar, mineral ions and water that have been used or lost after exercise
- Sports drinks: sugar and mineral ion solutions - helps rehydrate cells
- Drinks designed to help balance body fluid concentration and concentrations inside cells - if drink concentration = body fluid concentration: isotonic
- Evidence of sports drinks benefits is varied - some think water is just as good, others think sports drinks are better as they replace sugar and minerals ions as well as water
3 of 9
B3.1.4 - Exchanging Materials - The Lungs
- Large, complex organisms have special exchange surfaces to obtain food and oxygen needed - intestines absorb soluable food materials (solutes), lungs absorb oxygen and CO2 is removed
- Efficient exchange surfaces need: large surface area, thin wall/short diffusion path, efficient transport system - eg. blood supply
- Lungs contain gaseos exchange surface - surface area is increased by alveoli
- Alveoli have thin walls, large surface area and good blood supply
- Lungs ventilated to maintain steep diffusion gradient
- Oxygen diffuses into capillaries surrounding alveoli and CO2 diffuses back out into lungs to be breathed out
4 of 9
B3.1.5 - Ventilating the Lungs
- Lung - contain exchange surface of breathing system - situated in thorax, in ribcage, above diaphragm: separates lung from abdomen
- When we breathe in:
- intercoastal muscles between ribs and diaphragm contract
- ribcage moves up and out and diaphragm flattens
- volume of thorax increases
- pressure in thorax decreases: air is drawn in
- When we breathe out:
- intercoastal muscles of ribcage and diaphragm relax
- ribcage moves down and in and diaphragm becomes domed
- volume of thorax decreases
- pressure in thorax increases: air is forced out
- Ventilation: movement of air in and out of lungs
5 of 9
B3.1.6 - Artificial Breathing Aids
- People can't get enough in their lungs because: alveoli are damaged: surface area decreased, tubes leading to lungs are narrow: less air can be moved through, paralysis: muscles don't work to pull ribcage up and out
- Breathing aids have been developed:
- Iron lung - used for people paralysed by polio - person lays with chest sealed in metal cylinder - air is drawn out: vacuum formed inside cylinder creates negative pressure: breathe in - air pumped back into cylinder: creates pressure on chest: breath out
- Breathing aids force measured amounts of air into lungs use positive pressure - bags of air linked to masks force air down trachea
- Positive pressure aids are smaller, easier to manage and can be linked to computers to control
6 of 9
B3.1.7 - Exchange in the Gut
- Food is digested in the gut into small, soluable molecules that are absorbed into blood in small intestine - villi line inner surface: exchange surface for food molecules
- Villi - finger-like projections - increase surface area for absorbtion to take place
- Walls of villi are thin with many capillaries close to them
- Soluable products of digestion can be absorbed into villi by either diffusion or active transport
7 of 9
B3.1.8 - Exchange in Plants
- Gases diffuse in and out of plants through stomata - tiny holes, size controlled by guard cells
- Gases are: oxygen and CO2 - movement of gases depends on which process is happening faster - respiration or photosynthesis
- Plants lose water through stomata due to evaporation
- Leaves are flat and thin - don't need to diffuse very far, also internal air spaces
- Water and mineral ions taken up by roots - root hair cells increase root surface area
- Stomata close to prevent wilting if water is being lost faster than being replaced
8 of 9
B3.1.9 - Transpiration
- Plants take up water through roots - water passes through plant to leaves - in leaves, water evaporates from leaf cells and water vapour diffuses through stomata
- Transpiration stream: movement of water through plant
- Plant can dehydrate if rate of evaporstion > root water uptake
- Evaporation is faster in hot, dry, windy or bright conditions
- Guard cells - close to prevent excess water loss
- Wilting prevents water loss - leaves collapse and hang down: reduces surface area
9 of 9
Related discussions on The Student Room
- Pearson Edexcel Law »
- The University of Edinburgh vs NUS for Engineering? »
- Website for Aero, Thermo »
- Which a level teaches this and exambaord »
- help - a level history cousework »
- Modern Greek A-level »
- Losing job before exchanging contracts on a house »
- Economics doubt »
- Semester Abroad @ Uni of Edinburgh vs Trinity College Dublin »
- feeling frustrated bc my brother is privately educated and i wasn't »
Similar Biology resources:
0.0 / 5
2.0 / 5 based on 1 rating
2.5 / 5 based on 3 ratings
1.0 / 5 based on 1 rating
3.0 / 5 based on 1 rating
3.5 / 5 based on 2 ratings
0.0 / 5
2.5 / 5 based on 4 ratings
3.5 / 5 based on 3 ratings
0.0 / 5
Comments
No comments have yet been made