Unit 2

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  • Created on: 17-04-13 18:57
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  • Biology - Unit 2
    • Enzymes
      • Enzyme Structure
        • Enzymes are biological catalysts – they speed up reactions
        • Enzymes are large proteins which have a particular shapes depending on their function
        • The shapes have an area where molecules can fit in – called an active site
        • If the temperature is to high the enzyme will become denatured and no longer work
        • Enzymes can help build small molecule into larger ones or break down large molecules into smaller ones
        • Enzymes lower the amount of energy needed for a reaction to take place – the activation energy
      • Factors effecting enzyme action
        • Reactions work faster in warmer conditions – the molecules move around quicker so they collide with each other more often with more energy
        • If the temperature gets to hot the enzymes active site changes shape and it becomes denatured
        • Enzymes work at different PH’s depending on where they are naturally found – if the ph is to alkali or acidic it can cause the active site to change shape
      • Aerobic Respiration
        • Glucose + Oxygen  Carbon Dioxide + Water (+ energy)
        • The process takes place mostly in the mitochondria
        • The energy released can be used for building larger molecules from smaller ones; enabling muscle contraction in animals; maintaining constant body temperature in mammals and birds; and building sugars and other nutrients in plants into amino acids then proteins
        • Aerobic respiration is the release of energy from food when oxygen is available
      • Enzymes in digestion
        • Digestion is the breaking down of large insoluble molecules into smaller soluble molecules
        • Without enzymes digestion would be to slow
        • There are specific conditions in different parts of the gut that help enzymes to work effectively
        • Amylase – produced by the salivary glands, pancreas and small intestine – used to catalyse the breakdown of starch into sugars – used in the mouth and small intestine
        • Protease – produced by the stomach, pancreas and the small intestine – catalyses the breakdown of proteins into amino acids – used in the small intestine and stomach
        • Lipase – produced by the pancreas and small intestine – catalyses the breakdown of lipids (fats and oils) into fatty acids and glycerol
        • Isomerases – turns glucose into fructose
      • Speeding up digestion
        • Protease enzymes in the stomach work best in acidic conditions
        • Glands in the stomach wall produce hydrochloric acid to create acidic conditions
        • Amylase and Lipase work best in slightly alkali conditions
        • The liver produces bile which is stored in the gall bladder – it then gets squirted into the small intestine to neutralise the stomach acid and create the alkaline conditions necessary
      • Making use of enzymes
        • Enzymes can be used in products in the home and in industryEnzymes can be used in products in the home and in industry
        • Biological washing powders contain enzymes that digest food stains – they work at lower temperatures than ordinary washing powders which save money
        • Protease enzymes can be used to pre-digest proteins in some baby foods
        • Isomerases are used to convert glucose to fructose – fructose is sweeter so less is needed in foods – making the foods less fattening
        • Carbohydrases convert starch into sugar syrup for use in foods
    • Energy Flows
      • Pyramids of biomass
        • Biomass is the mass of living material in plants and animals
        • It gives a more accurate picture than a pyramid of numbers
        • A pyramid of biomass represents the mass of organisms at each stage of a food chain
      • Energy Losses
        • Energy is lost between each stage of the food chain
        • Not all food can be digested so energy is lost through faeces
        • Some is used for respiration – which releases energy for living processes like movement – the more something moves, the more energy it uses
        • Some animals require a constant temperature so some of the energy is used to maintain this temperature
      • Energy in Food Production
        • The shorter the food chain the less energy will be lost – it is more efficient to eat plants than animals.
        • Meat can be artificially produced more efficiently by limiting the animal from movement so it doesn’t waste energy – this is seen as cruelty by most people and is very controversial
        • Keeping the animal at a warmer temperature means it doesn’t use as much energy to keep itself warm
      • Decay
        • Detritus feeders – like some types of worm – start the process of decay by eating dead animals/plants and producing waste materials containing the nutrients from the organism
        • Decay organisms – bacteria/fungi etc – then break down the waste and dead plants/animals
        • Decay is faster in warm and wet conditions
        • All of the materials from the dead organisms and waste are recycled
      • The Carbon Cycle
        • The recycling of carbon involve photosynthesis and respiration
        • Photosynthesis removes Carbon Dioxide from the atmosphere
        • Green plants and animals respire returning Carbon Dioxide to the atmosphere
        • A stable community recycles all of the nutrients it takes up
        • Animals build carbon into their bodies by eating green plants and when plants/animals die/produce waste microorganisms release the Carbon Dioxide back into the atmosphere through respiration
    • How Plants Produce Food
      • Photosynthesis
        • Carbon Dioxide + Water (+ Light Energy)  Glucose + Oxygen
        • Carbon dioxide is taken in by the leaves and Water by the roots
        • The chlorophyll traps the energy required for photosynthesis
        • Photosynthesis can only be carried out by green plants – chlorophyll makes the leaves green
      • Limiting Factors
        • If things like Sunlight, Water and Carbon Dioxide are in short supply, or the temperature is not right it slows down the rate of photosynthesis
        • If plant growers are unaware of one these limiting factors they will quickly lose money
        • Not enough sunlight slows down the rate of photosynthesis because light provides the energy for the reaction to take place
        • If it is to cold the enzymes lose energy and won’t work effectively, if it is to hot the enzymes become denatured – lose their shape
        • If there is too little carbon dioxide then it lowers the rate of photosynthesis
        • There is no point increasing one of the factors if photosynthesis is still limited by another one.
      • How plants use glucose
        • Photosynthesis produces a sugar called glucose, which is used for respiration
        • Glucose is combined with other nutrients by the plant to create new materials#
        • Most plants store glucose as starch
        • Starch is an insoluble substance, therefore it has no effect on osmosis
      • Why do plants need minerals?
        • Plant roots take up minerals for healthy growth
        • Nitrates are needed to produce amino acids
        • These amino acids are used to make proteins for growth
        • A plant deficient in nitrates will have stunted growth
        • Plants need magnesium to make chlorophyll
        • Chlorophyll is what makes the leaves green
        • A plant with a lack of magnesium has yellow leaves
    • Cells
      • Animal cells
        • A nucleus to control the cells activities
        • Cytoplasm where many chemical reactions take place
        • Cell Membrane to control the movement of materials
        • Mitochondria where energy is released during aerobic respiration
        • Ribosome’s where protein synthesis happens – proteins are made
      • Plant cells also have
        • A rigid cell wall for support
        • Chloroplasts which contain chlorophyll for photosynthesis
        • A permanent vacuole containing cell sap
      • Specialised cells
        • As organisms develop some of their cells become specialised to carry out different jobs, this is called differentiation
        • Differentiation happens earlier in the development of animals than plants
      • How substances get in and out of cells
        • Molecules move randomly because of the natural energy they contain
        • Diffusion is the random movement of molecules from an area of high concentration to an area of lower concentration.
        • Diffusion requires no energy from the cell
        • The larger the difference in concentration, the faster the rate of diffusion
        • One example is the diffusion of oxygen into cells of the body from the blood stream as the cells respire – use up oxygen
        • Carbon Dioxide diffuses into actively photosynthesising plant cells
      • Osmosis
        • Osmosis is the movement of water across a semi/partially permeable membrane, it is a special kind of diffusion
        • Like diffusion it is the random movement of molecules which requires no energy from the cell
        • The water moves from a more dilate solution to a more concentrated solution.
        • No solute molecules can cross the partially permeable membrane
        • Water is needed to support cells because chemical reactions take place in solution.
        • Some water will pass through the partially permeable membrane from low to high concentration but the net movement of water is from high to low concentration
    • Homeostasis
      • Controlling internal conditions
        • We must remove the waste products produced through chemical reactions from the body
        • Homeostasis is the processes in the body which help to maintain a constant internal environment
        • Carbon Dioxide is a waste product of respiration and is excreted through the lungs
        • Some of the amino acids we take in are not used so they are converted into urea by the liver and excreted by the kidneys in urine which is stored in the bladder
        • The water and ion content of the cells has to be carefully monitored because if they aren’t then too much or not enough water can move in and out of them by osmosis#
      • Controlling body temperature
        • The thermoregulatory centre of the brain and receptors in the skin detect changes in temperature – it also controls the body’s response to change in internal temperature
        • If core body temperature rises – Blood vessels near the surface of the skin dilate allowing more blood to flow through the skin capillaries so heat is lost through radiation (Vasodilatation) – sweat glands produce more sweat which evaporates from the skins surface taking energy from the skin and cooling the body down.
        • If core body temperature falls – blood vessels near the surface of the skin constrict and less blood flows through the skin capillaries so less heat is lost through radiation (Vasoconstriction) – shivering is where muscles contract quickly which requires respiration which produces some energy as heat.
      • Controlling blood sugar
        • The pancreas monitors and controls the level of sugar in our blood
        • If there is too much sugar in the blood the pancreas produces insulin which causes excess sugar to be stored in the liver as glycogen
        • If insulin isn’t produced the blood sugar level may become fatally high
        • If the pancreas isn’t producing enough insulin it has a condition called diabetes – this can be controlled by diet but in more serious cases the person mat need insulin injections
    • Inheritance
      • Cell Division and Growth
        • Cell division is necessary for the growth and repair of an organism
        • Mitosis is the type of cell division which create to identical cells produced from the parent cell
        • A copy of each chromosome is made before the cell divides and one of each chromosome goes into each new cell
      • Stem Cells
        • Stem cells are unspecialised so they can develop (differentiate) into many different types of specialised cell
        • Stem cells are found in embryos and in adult bone marrow
        • Most embryonic stem cells that we carry out research on are from aborted embryos or spare embryos from fertility treatment – this causes ethical issues because some people argue that you are destroying life to obtain these stem cells for research
        • Most embryonic stem cells that we carry out research on are from aborted embryos or spare embryos from fertility treatment – this causes ethical issues because some people argue that you are destroying life to obtain these stem cells for research
      • Cell division in sexual reproduction
        • Sex cells are produced by meiosis
        • Cells in reproductive organs divide into sex cells – gametes
        • Before division a copy of each chromosome is made then the cell divides into 4
        • Each gamete has one chromosome from the original pair so all of the cells are different from each other and the parent cell
        • This means that when the gamete fuse during reproduction half the genetic information comes from the mother and half from the father
      • From Mendel to DNA
        • Gregor Mendel was a monk who worked out how characteristics were inherited
        • Genes are short lengths of DNA (Deoxyribonucleic Acid)
        • Genes make up Chromosomes which control our characteristics
      • Inheritance in action
        • Human beings have 23 pairs of Chromosomes
        • Genes controlling the same characteristic are called Alleles
        • In each pair of alleles there is a dominant and recessive allele
      • Inherited conditions in humans
        • Huntington’s disease is a disorder of the nervous system caused by a dominant allele – even if only one parent has it, it can be inherited by a child
        • Cystic fibrosis is a cell membrane disorder caused by a recessive allele – each parent must be a carrier or sufferer of the disease for the child to inherit it.
        • Embryos can be screened for these disorders and many other genetic disorders

Comments

Anisa -Team GR

wow this is too much!

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