Biology AQA Unit 2

Cells

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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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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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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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, ** 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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