Biology Additional Science

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Animal and Plants cells

Animals and plant cells have

  • Nucleus: controls cells activities
  • Cytoplasm: where many chemical reactions take place
  • Cell membrane: controls the movement of materials
  • Mitrochondria: where energy is released during aerobic respiration
  • Ribosomes: where proteins are made (synthesised)

Plant cells also have

  • Cell wall: for support
  • Chloroplasts: contain chlorophyll for photosynthesis
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Specialsed Cells

  • As organisms develop some of the celss chnage and become specialised to carry out particular jobs
  • This is called differentation
  • Differentation happens much earlier in the development of plants than it does in animals
  • In plants they may become xylem or root hair cells
  • In animals they may become nerve or sperm cells
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How do substances get in and out of cells

  • Diffusion is the random movement of molecules from an area of high concentration to low concentration
  • The larger the difference in concentration the faster the rate of diffusion
  • Examples of diffusion are oxygen in to the cells of the body from the blood strean as the cells are respiring
  • Also carbon dioxide in to actively photosynthesising plant celss
  • Also simple sugars and amino acids from the gut through the cell membranes
  • Diffusion does not require any energy from the cell
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  • Is the movement of water
  • A special case of diffusion involving a partially permeable membrane
  • Just like diffusion the movement of molecules is ransom and requires no energy from the cell
  • Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution to a more concentrated solution
  • No solute molecules can more across the membrane
  • Water is needed to support the celss and because chemical reactions take place in the solution
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  • The word equation is: carbon dioxide+water+light energy=glucose+oxygen
  • Photosynthesis can only be carried out in green plants
  • Chlorophyll traps the suns energy

The structure of a leaf

  • The upper epidermis contains a waxy layer which is waterproof so it stops water loss
  • The palisade layer contains the palisade cells that are at the top of the leaf, close to the light, tightly packed together and full of chloroplasts
  • The spongy layer contains cells that are not packed tightly together so they have a large surface area available for gas exchange, also some chloroplasts and air spaces
  • The lower epidermis contains guard cells that open and close the stomata to control water loss. Also the stomata that allows gases to move in and out of the leaf
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Limiting factors

  • The carbon dioxide concentration may be limited in an enclosed space, for example a greenhouse on a sunny day
  • Light intensity may be limited on the floor of a rainforest
  • The tempreture is a limiting factor becasue otherwise the enzymes will not work effectively
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How plants use glucose

  • The product of photosynthesis is glucose
  • Glucose is used in respiration
  • Glucose is combined with other nutrients by the plant to produce new minerals
  • Glucose is stored by the plant as an insoluble starch so it is not effected by osmosis
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Why do plants need minerals

  • Plants produce sugars through photosynthesis
  • Nitrates are taken from the soil to produce amino acids
  • These are used to make proteins for growth
  • A plant that is nitrate deficient will have stunted growth
  • Magnesium is essential to produce chlorophyll
  • A plant that is magnesium deficient will have yellow leave
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Pyramids of biomass

  • A pyramid of biomass represents the mass of all the organisms at each stage in the food chain
  • A pyramid of biomass is likely to give a more accurate picture than a pyramid of numbers
  • Becuase for example one bush may have many insects feeding on it but the mass of the bush is far greater than the mass of the insects
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Energy losses

  • Not all food eaten can be digested, some energy is lost ub faeces, respiration, movement and keeping a constant tempreture
  • Not all the energy taken in by an organism results in the growth of that organism
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Energy in food production

  • The shorter the food chain the less energy will be lost
  • It is more efficient for us to eat plants that animals
  • We can produce meat more efficiently by preventing the animals movement and keeping the animals at a constant tempreture
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  • Detritus feeders such as worms may start a process of decay by eating dead animals or plants and producing waste products
  • Then decay organisms break down the waste and dead plants and animals
  • Decay organisms are micro-organims
  • Decay works faster when it is warm and wet
  • All the materials from waste and dead animals are recycled
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The carbon cycle

  • Photosynthesis removes carbon dioxide from the atmosphere
  • Green plants and animals respire which returens carbon dioxide back in to the atmosphere
  • Animals eat green plants and they build the carbon up in their bodies
  • When animals and plants die the release carbon dioxide back in to the atmosphere
  • A stable community recycles all of the nutrients it takes up
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Enzyme structure

  • Enzymes are biological catalysts, they speed upo reactions
  • Enzymes are large proteins and each has a particular shape
  • The shape where the other molecules fit in is called the active site
  • When the tempreture is abov fourty degrees the enzymes will loose its shape and become denatured
  • Enymes lower the amount of energy needed for a reaction to take place, the activation energy
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Factors affecting enzymes action

  • Reactions take place faster when it is warmer
  • At a higher tempreture the molecules move around quicker and they collide with each other more often and with more energy
  • Tempreture affects the enzyme
  • If the Ph is too acidic or alkaline then the active site could change shape
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Aerobic respiration

  • Glucose+oxygen=carbon dioxide+water+energy
  • The process takes place in the mitrochondria
  • Aerobic respriration is the realase of energy from food when oxygen is availble
  • The energy released is used to build larger moleclules from smaller ones. Also enable muscle contractions in animals. Also maintain a constant body tempreture in mammals and birds and to build sugars, nitrates nutrients in plants. Which then turn in to amico acids which are proteins
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Enzymes in digestion

  • Digestion involes the breakdown of large insoluble molecules in to smalller soluble ones
  • Amayase is a carbohydrase that is produced by the salivary gland, pancreas and the small intestine
  • It catalyses the digestion of starch in to sugars in the mouth and small intestine
  • Protease is produced by the stomach, pancreas and small intestine
  • It catalyses the breackdown of proteins in to amino acids in the stomach and small intestine
  • Lipase is produced by the pancreas and the small intestine
  • It catalyses the break down of lipids which are fats and oils in to fatty acids and glycerol
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Speeding up digestion

  • Amylase and lipase work in the small intestine
  • They work best when the conditions are slightly alkaline
  • Protease works in the stomach and when the condition are acidic
  • Glands in the stomach wall produce hydrocloric acid to create very acidic conditions
  • The liver produces bile that is stored in the gall bladder
  • Bile is squirted in to the small intestine and neutralises the stomach acid
  • It makes the conditions slightly alkaline
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Making use of enzymes

  • Biological washing powder contains enzymes that digest food stains
  • They work at a lower tempreture which saves money and energy
  • Protease pre-digests proteins in baby foods
  • Isomerases converts glucose in to fructose
  • Fructose is much sweeter so less is need which makes it less fattening so it is used in diet foods
  • Carbohyrase converts starch in to sugar syrup for use in foods
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Controlling internal conditions

  • This is called homeostasis
  • Carbon dioxide is a waste product so it is excreted by the lungs
  • Some of the amino acids we take in are not used
  • These get converted in to urea by the liver and is excreted by the kidneys in the urine
  • Urine can be stored in the baldder
  • The water and ion content must be controlled
  • If they are not then to much or to little may move in and out of the cells by osmosis
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Controlling body tempreture

  • The thermoregulatory centre in the brain and the receptors in the sking detect changes in tempreture
  • The thermoregulatory centre controls the responses to internal tempreture

If the core tempreture rises:

  • Blood vessles near the surface dialte causing more blood to flow through the capillaries, vasodilation
  • Therfore heat is lost by radiation
  • Sweat glands produce more sweat which evaporates of the skin
  • The energy required for it to evaporate cones from the skins surface so we cool down

If the core tempreture falls:

  • Clood vessels near the surface constrict causing less blood to flow through the capillaries, vasocontstriction
  • Therefore less heat is radiated
  • We shives which make the muscles contract
  • This requires respiration and some of the energy produced is released as heat
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Controlling blood sugar

  • The pancreas monitors and controls the level of sugar in our blood
  • If there is too much sugar in our bllod the pancreas produces insulin
  • That results in the excess sugar being stored in the liver as glycogen
  • If insulin is not produced the blood sugar levek may become fatally high
  • If the pancreas is not producing enough insulin it is called type one diabetes
  • It can be controlled by diet or inslulin injections
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Cell devision and growth

  • Body cells need to divide to produce news cells for growth and repair
  • Mitosis results in two identical cells being produced from the original cell
  • A copy of each chromosome is made before the cells divides and one of each chromosome goes to each cell making them identical
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Stem Cells

  • Stem cells are unspecialsed
  • They can develop, differntiate in to many types of speacialised cells
  • Stem cels are found in the the embryo and in adult bone marrow
  • Many embryonic stem cellls are from aborted embryos or a spare embroyo from fertility treatments
  • This raises ethical issues
  • The use of stem cells from adult bone marrow is limited by the number of differnent types of specialised cells we can develop them in to
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Cell devison in sexual reproduction

  • Cells in reproduction organs diveide in to sex cells called gametes
  • Before devision a cope of each chromosome is made
  • The cell now divides twice to form four gametes
  • This is called meiosis
  • Sexual reproduction results in variation as the sex cells from each parent fuse
  • So half the genetic information if from your father and the other half from your mother
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From Mendel to DNA

  • Gregor Mendel was a monk who worked out how charteristics are inhrerited
  • Genes are short lengths of DNA (deoxyribonucleic acis)
  • These make up chromosomes and control our characteristics
  • Genes are a code of combinations of specific amino acids
  • Which make up proteins
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Inheritance in action

  • Humans have twenty-three pairs of chromosomes
  • Femals are **
  • Males are XY
  • Genes controlling the same characteristics are alleles
  • If am allele is masks the effect of another it is dominent
  • The allele wherer the effect is masked is a recessive
  • For example the allele for brown eyes is dominent over the allele for blue eyes
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Inherited conditions in humans

  • Huntingtons disease is a disorder of the nervous system
  • It is caused by a dominent allele
  • So evern if one parent has the disease it can be inherited by the child
  • Cystic fibrosis is a disorder of cell membranes
  • It is caused by a recessive allele
  • Only if both parents are either carriers of have the disorder can the child inherit it
  • Embroys can be screemed to see if the carry an alleles for one of these genetic disorders
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Maliha Yakub





Thank you!! This helps sooo much!!

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