aqa biology gcse b3 n.
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AQA Biology GCSE - B3

AQA Biology GCSE - B3

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AQA Biology GCSE - B3

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  2. The Exchange of Materials • ACTIVE TRANSPORT= the movement of a substance against a concentration gradient. Uses up energy from respiration, and is found in the intestines and the kidney (for absorption and re-absorption) • IT REQUIRES ENERGY from respiration (mitochondria) • Allows cells to absorb ions from very dilute substances

  3. Lungs • Breathing system takes air in + out of body • Lungs are protected by ribcage and contain lots of alveoli • ALVEOLI= tiny air sacs in the lungs well adapted to gaseous exchange because: • They create a large surface area • They are moist • They have very thin walls- less distance for gases to travel • The constant movement of the blood and the breathing of the lungs keeps a high concentration gradient perfect for diffusion • The blood capillaries are right next to the alveoli, meaning easy access for the oxygen to diffuse into the blood, and the CO2 into the lungs. • Breath out= ribcage down, diaphragm up • Breath in= ribcage up, diaphragm down

  4. The Intestine • VILLI= tiny protrusions in the intestine which help to absorb the products of digestion • Use active transport + diffusion to gain as much of the valuable materials, especially sugar, as possible • Villi help increase absorption because they: • Have a large surface area (squashed up) • Are moist • Are very close to a large network of capillaries (absorbed straight into blood stream)

  5. Exchange in Organisms • All organisms need large, moist SA, large conc. grad. and short diffusion distance • Fish Gills – rich blood supply, constantly moist (in water) and thin. Constant supply of water means large conc grad so diffusion is constant. When taken out of water, gills stick together – smaller SA – and suffocate. • Tadpoles/Frogs Tadpoles work same as fish, when turn into frogs they develop simple lungs + can breathe in air AND water • Insects Have no blood supply due to impermeable cover or insects. Instead O2 and CO2 are pumped directly to cells, so no need for blood. Also have spiracles (insects version of stomata).

  6. Exchange in Plants • Need osmosis in roots (for water) and diffusion near stomata (for CO2) • Leaves thin + flat to increase SA for light and a waxy cuticle to prevent evaporation • Root hair cells increase SA because of long, thin hairs • Most minerals + ions needed taken through roots

  7. Transpiration • Transpiration = loss of water from surface of plants + leaves • Water is often lost through stomata • Waxy cuticle minimises it • Water is pulled up through XYLEM to replace lost water vapour • Occurs more in hot, dry, sunny, windy conditions

  8. Exchange of Materials in Plants • STOMATA= holes in the underside of leaves that allow carbon dioxide in, and oxygen and water vapour out for gaseous exchange. Guard cells can close off the stomata in order to stop transpiration. • TRANSPIRATION= the loss of water vapour through the stomata, resulting in the movement of water through osmosis through the plant due the change in concentration gradient at the top of the plant. This brings needed ions etc up the plant. • Transpiration happens more quickly in hot, windy and dry conditions • Plants may wilt when they lose water faster than they gain it from the roots- cells become less rigid due to they fact they aren’t full of water.

  9. The Circulatory System Circulation system contains BLOOD VESSELS, HEART and BLOOD. • Oxygenated blood is pumped to the heart from the lungs, and to the body from the heart • De-oxygenated blood is pumped from the heart to the lungs, and from the body back to the heart • VEINS= carry blood to the heart • ARTERIES= carry blood away from the heart • CAPILLARIES= tiny blood vessels found near organs and tissues of the body that exchange substances with the cells eg glucose, CO2 VERY THIN (1 cell thick) THE HEART Right side= pumps low O2 blood to lungs Left side= pumps high O2 blood to body • Double circulation = two transport systems in body, one to carry blood TO heart, other to carry AWAY from heart. • Humans have this.

  10. BLOOD • WHITE BLOOD CELLS- fight infection • PLATELETS- help blood to clot • PLASMA- holds dissolved substances, glucose (taken from the small intestine to the body organs), CO2, waste products (urea from the kidneys) • RED BLOOD CELLS- • No nucleus- more room for haemoglobin • Special shape with a lowered centre- greater surface area to absorb gas • HAEMOGLOBIN- substance which gains oxygen from the lungs to form OXYhaemoglobin. Then releases oxygen into cells. Reversible  Oxygen + Haemoglobin ↔OXYhaemoglobin

  11. Effect of Exercise • Energy from respiration used to make muscles contract • When this happens, you need more respiration to take place (ie more O2 + glucose, quicker CO2 release) • Causes increased heart/breathing rate • Arteries dilate  more blood for muscles increases oxygen/glucose supply CO2 is removed quicker

  12. Anaerobic Respiration • Your everyday muscle movements are made possible by AEROBIC respiration • If heart rate is increased, blood cant supply O2 quick enough • Anaerobic respiration doesn’t involve O2 and is less efficient • Glucose  Lactic Acid (+ energy) • Lactic acid needs to be got rid of (by reacting with O2 to form CO2 + water) = OXYGEN DEBT

  13. Human Kidney • Vital for homeostasis • Works by filtering everything from blood and then reabsorbing all the sugar, as well as the mineral ions and water needed. • Active transport ensures ALL sugar is reabsorbed and diffusion makes sure mineral ions and water is reabsorbed in the right amounts • Hot day with little water intake = little urine (concentrated) • Cold day with large water intake = lots of urine (dilute)

  14. Dialysis • Kidney failure results in toxins such as urea building up + salt/water balance being lost – certain death without dialysis • In a dialysis machine, blood thinners prevent clotting, dialysis fluid containing right amounts of minerals allows blood to diffuse to normal levels (urea etc go into dialysis fluid and are removed) and then passed through a bubble trap to get rid of any bubbles

  15. Kidney Transplants • New kidney is placed inside the person, and the old kidneys are left in the body • If everything goes well, it will function as a normal kidney • The donor kidney may be rejected by the recipient’s immune system • To minimise this, immunosuppressant drugs are used, as well as finding very close matches • Despite this, it is very hard to find donors

  16. Dialysis Vs Transplants

  17. Growing Microbes • Micro-organisms grow in an agar culture medium with a carbohydrate energy source and various other vitamins, minerals and proteins • You need to take careful safety measures and use sterilized equipment to ensure the growth of uncontaminated cultures

  18. Food Production + Yeast • Yeast is a single celled organism which can respire both aerobically and an anaerobically • Aerobic respiration produces CO2 and water and is used to make bread rise • Anaerobic respiration produces CO2 and ethanol, the process is known as fermentation • This is used in the production of beer, wine and other alcoholic drinks

  19. Food Production + Bacteria • Bacteria are used to make cheese abd yoghurt • Yoghurt is formed when bacteria act on lactose (sugar in the milk), producing lactic acid and changing the texture and taste of the milk • Different type of bacteria is added for cheese, making much more lactic acid is made and it is thicker (curds) • This is cooled and left in moulds to set and then more bacteria is added to give different flavours

  20. Large Scale Microbe Production • Can be grown on a large scale using fermenters • Fermenters have features such as an oxgen supply, stirrer to keep microorganisms in suspension and maintain an even temp, water-cooler jacket to remove excess heat and measuring instruments such as pH and temperature gauges • Mycoprotein is produced by allowing the fungus ‘Fusarium’ to grow on sugar syrup in aerobic conditions

  21. Antibiotic Production • Discovery of penicillin was made by Alexander Fleming, however he could mass produce it • Howard Florey + Ernst Chain discovered a way to mass produce by being able to store the penicillin for a long time • Penicillium is now used as it provides more penicillin, as it is made in a fermenter • Mould only starts making penicillin after all nutrients are used up, so there is a lag time between the production of the mould and antibiotic

  22. Biogas • Biogas – mainly methane – produced by anaerobic fermentation of a wide range of plants and waste materials that contain carbohydrates • Gets rid of waste, solves energy needs and is renewable, however hard to do it on a large scale • Different types of biogas plants (floating-drum Vs. fixed dome) mainly built underground for insulation

  23. Other Biofuels • Ethanol based fuels can be produced from anaerobic fermentation of sugar cane juices by the enzyme carbohydrase • +ves = doesnt produce toxic gases, muych cleaner and can be mixed with petrol, carbon neutral • -ves = needs lots of space, poor countries grow cash crops instead of feeding people  starvation

  24. I downloaded this resource but it was very detailed, so I decided to improve it with more detail and covering the entire B3 syllabus