- Most animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
- Plant cells contain all the structures seen in animal cells as well as a cell wall and chloroplasts and a permanent vacuole filled with sap.
- Enzymes control the chemical reactions inside cells.
- Cells may be specialised to carry out a particular function. E.g fat cells, cone cells
- Diffusion is net movement of particles from an area where they are at a high concentration to an area where they are at a lower concentration.
- Osmosis if the diffusion/movement of water from a high concentration to a low water concentration through a partially permeable membrane.
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- carbon dioxide+water+(light energy)=glucose+oxygen
- During p/s light energy is absorbed by chlorophyll in chloroplasts. used to convert carbon dioxide and water into glucose. Oxygen released as by-product.
- Leaves are well adapted to allow maximum p/s to take place.
- Limiting factors=light, temp, carbon dioxide levels.
- We can artificially change the environment in which we grow plants. we can use this to observe the effect of different factors on the rate of p/s.
- Plant cells use some of the glucose the make in p/s for respiration.
- Some of the soluble glucose produced during p/s is converted into insoluble starch for storage.
- Plant roots absorb mineral salts including nitrate for healthy growth and magnesium for greenness.
- If mineral ions are deficient plant develops symptoms because it cannot grow properly.
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Pyramids of Biomass
- Radiation from the sun is the main source of energy for all living things. The Sun's energy is captured and used by plants during p/s.
- The mass of living material at each stage of a food chain is less then the previous stage. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass.
- The amount of biomass and energy gets less and less as some material lost in waste, some used up in respiration for movement and maintaining body temp.
- The efficiency of food production can be improved by reducin the number of stages in our food chains. It would be most efficient if we just ate plants.
- If you stop animals moving and keep them warm, they lose a lot less energy.
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Decay and Carbon
- Living organisms remove materials from the environment as they grow. they return them when they die through the action of decompose rs.
- Dead materials decay because they are broken down(digested) by microorganisms
- De composers work quickly in warm moist conditions and good oxygen supply
- The decay process releases substances which pants need to grow.
- In a stable community the processes remove materials and are balanced by the processes which return materials.
- The constant cycling of carbon in nature is known as the carbon cycle.
- Carbon dioxide is removed from the atmosphere by p/s and returned through respiration and combustion.
- The energy originally captured by green plants is eventually transferred back into plants, into decompose rs or as heart into environment.
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- Catalysts increase the rate of chemical reactions. Enzymes are biological catalysts.
- Enzymes are protein molecules made up of long chains of amino acids. the chains are folded to from active site where the substrate binds with the enzyme.
- Enzyme activity is affected by temp and PH
- High temp and wrong PH can affect shape of active site and stop it working.
- Enzymes catalyse processes such as respiration, p.s and protein synthesis.
- Aerobic respiration - glucose+oxygen=carbon dioxide+water +energy
- Enzymes catalyse the breakdown of large food molecules into smaller molecules during digestion.
- Digestive enzymes are produced inside cells but they work outside cells in gut.
- Enzymes in the ribosomes catalyse the build up of proteins from amino acids.
- The enzymes of the stomach work best in acid conditions.
- The enzymes made in pancrea and S.I work best in alkaline conditions.
- Bile produced by the liver neutralises acid and emulsifies fats.
- Biological detergents may contains proteases and lipase's.
- Proteases, carbohydrates and isomerase are used in food industry.
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- The internal conditions of your body have to be controlled to maintain a constant internal environment
- Poisonous waste products are made all the time and need to be removed.
- Carbon dioxide is produced during respiration and leaves body via lungs
- Urea is produced by your liver as excess amino acids are broken down and removed by kidneys in urine.
- Body temp must be mainted at level enzymes work best. monitored and conrollted my thermoregulatory centre in your brain.
- Body respons to coold you down or warm you up if core body temp falls.
- Blood glucose concentration is monitored and controlled by pancreas
- Insulin and glycogen are hormones involved in controlling blood sugar concentration. Insulin converts glucose to glycogen; glycogen- glycogen-glucose
- In diabetes the blood glucose may rise to fatally high levels because pancreas does not secrete enough insulin. can be treated by infections before meals.
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Cell division and growth
- Body cells divide by mitosis to produce identical cells for growth, repair and replacement.
- Most types of animal cells differentiate at an early stage of development. Many plant cells can differentiate throughout their life.
- Embryonic stem cells and adult stem cells can be made to differentiate into many different types of cells.
- Cells in reproductive organs divide to form gametes
- Body cells have two sets of chromosomes and gametes have only one
- Gametes are formed by meiosis
- Sexual reproduction gives rise to variety because genetic information from two parents is combined.
- Gregor Mendel was first person to suggest separately inherited factors (genes)
- Chromosomes are made up of large molecules of DNA. A gene is a small section of DNA which codes for a particular combination of amino acids which made a specific protein.
- In humans, XX femal XY mal. some features controlled by single gene. Genes have different forms called alleles, dominant/recessive.
- Huntington's disease is caused by dominant cystic fibrosis caused by recessive
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