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GCSE AQA BIOLOGY UNIT 2
 

GCSE AQA BIOLOGY UNIT 2

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    GCSE AQA BIOLOGY UNIT 2 GCSE AQA BIOLOGY UNIT 2 Presentation Transcript

    • Energy and Cells Photosynthesis biomass Genetics Unit 2 Biology Nutrient cycling HomeostasisGenes and cell Enzymesdivision
    • Cells
    • Animal CellsNucleus: controls everything in thecell, contains the information to makenew cellsCytoplasm: A jelly like substance inwhich chemical reactions in the celltake place, the chemical reactions arecontrolled by enzymesCell membrane: gives the cell itsshape and controls which substancesenter and leave the cellRibosomes: Where proteins aremadeMitochondria: Releases energy fromrespiration for the cell to use- found inthe cytoplasm, small sausage shapedstructures
    • Plant Cells Cell wall: outside the cell membrane, made of cellulose and strengthens the cell Chloroplasts: found in the cytoplasm. They absorb light energy to make food by photosynthesis Vacuole: a large sac in the centre of the cytoplasm. It contains a watery fluid called cell sap
    • Differences between plant and animal cells Plant cells Animal cells Have tough cell walls for No cell wall support A large PERMENANT vacuole Some with small vacuoles, containing cell sap however no cell sap Chloroplasts, absorb sunlight No chloroplasts for photosynthesis Box-like shape SHAPE VAIRES
    • Specialised cells Leaf palisade cells- found in the leaf of the plant, contain lots of chloroplasts for photosynthesis:Xylem cells- smalltubes that carrywater up the stem Root hair cells- are long and thin to absorb water from the soil
    • Nerve cells- are like wires to carry messages around the bodySperm cells have a tail to swim to theeggRed blood cells have a substance thatcarries oxygen
    • Tissues and organsTissues are groups of cells that all do the same job Organs are made up of groups of tissues.A number of organs working together make a system.
    • Diffusion and osmosis Diffusion is the movement of particles from a region of highconcentration to a region of lower concentration until they are evenly spread out. Osmosis is the diffusion of water molecules from a dilute solution to a more concentrated one through a partially permeable membrane.
    • What is the use of the:• Nucleus?• Cytoplasm?• Cell membrane?• Ribosomes? SLIDES 2 + 3• Cell wall?• Chloroplasts?• Vacuole?Also state whether they are in Plant (P) cells/ Animal (A) cells or bothState the differences between animal and plant cells SLIDE 4What is the mitochondria and where is it found? SLIDE 4Name 3 cells found in the plant and their uses SLIDE 3Define:• Tissues• Organs• Diffusion SLIDES 7 + 8• Osmosis
    • Describe the role of enzymes inside the cellSuggest 2 factors that increase the rate of diffusionName the substance that moves across a partially permeable membrane during theprocess of osmosisExplain what cell specialism means answers CONTROL CHEMICAL REACTIONS CONCENTRATION, TEMPERATURE WATER CELLS BEING CHANGED TO DO A SPECIFIC JOB; NERVE CELLS, SPERM CELLS, RED BLOOD CELLS
    • PHOTOSYNTHESIS
    • What is photosynthesis?• Photosynthesis is the process where plants make their own food• The equation = Light energy + chlorophyllCarbon dioxide + water glucose + oxygen• Sunlight is absorbed by the green chlorophyll which are found in chloroplasts• Light energy is used to convert carbon dioxide and water into glucose
    • Water is absorbed through the roots from the soil and Oxygen is released as a by product carried up the stem to the of photosynthesis leaves in the xylem vessels Light energy + chlorophyll Carbon dioxide + water glucose + oxygen Glucose is used through respirationCarbon dioxide enters the leaf by to give plants their own energydiffusion through the stomata Excess glucose can be stored in the leaves as insoluble starch
    • Limiting factors• Limiting factors decrease the rate of photosynthesis, they include:• Shortage of sunlight• Shortage of CO2• Low temperature• The rate of photosynthesis would increase if these factors increased
    • The products of photosynthesis• The glucose produced can be used in respiration to release energy.• This energy can be used to build large molecules from small ones:• Sugars can be converted into insoluble starch, stored in the roots• Sugars can be changed into cellulose to form new cell walls• Sugars can combine with nitrates and other nutrients to form amino acids- build proteins for plant growth• Sugars can be converted into lipids (fat and oils) and stored in seeds
    • Healthy growthPlants need mineral ions and nutrients to stay healthy. They arefound in the soil and absorbed through the plant’s roots.Magnesium and nitrate are vital for a plant to remain healthy:Nitrate MagnesiumNitrate is needed to produce Magnesium is needed toamino acids, which then produce chlorophyll- to beform proteins for the plant used in photosynthesis to absorb the sunlightIf Nitrate is lacking the Without magnesium theplant’s growth will be leaves will turn yellow, duestunted and older leaves will to the lack of chlorophyllurn yellow which is green
    • Leaves• Leaves are well adapted to carry out photosynthesis. They have:• A large surface area- to absorb light rays• A thin shape- to allow gases to diffuse in and out of the leaf easily• Chloroplasts- containing chlorophyll that absorb light energy• Veins- to carry substances to and from all of the cells of the leaf
    • Leaf StructureCuticle: waterproof layer that also cuts water loss by evaporationUpper epidermis: single layer of cells, no chloroplasts present, sunlight goes straight through to palisade cellsPalisade mesophyll: Where cuticlephotosynthesis takes place, as lots ofchloroplastsSpongy mesophyll: Lots of air spacebetween them, for gas exchange tooccurVein: contains xylem tubes andphloem tubesXylem tubes: brings water and salt toleaf through stemPhloem tubes: takes dissolved foodsaway
    • Why do plants need the process photosynthesis?How is sunlight absorbed?Light energy is used for what?Explain the job of chlorophyll during photosynthesis?Write the equation for photosynthesis and explain each gases’ useName 3 limiting factors of photosynthesisWhat are the 5 products and uses of photosynthesis?What do plants need for healthy growth?Name 2 gases that are needed and what would happen if they were lackingWhy are leaves well adapted for photosynthesis?What do the following do in the leaf:-Cuticle?Spongy mesophyll?Lower epidermis?Upper epidermis?Palisade layer?Vein?
    • ENERGY AND BIOMASS
    • Energy The original source of energy for all communities of living organisms is radiation from the SunGreen plants capture this solar energy, transferring it into chemicalenergy and stored in starch and other substances that make up plant cellsOnly about 10% of the solar energy reaching the plant is transferred intochemical energy by photosynthesis.Most of the energy is:• Reflected by the leaf• Passes straight through the leaf• Simply heats the leaf up
    • Biomass• Biomass is the mass of living material, and as you go along the food chain it gets less and less.• A pyramid of biomass shows the mass of all the organisms at each point in a food chain 2500g 400g 20gWe can use these biomass figures to draw a pyramid of biomass to scale bird snails grass
    • Food production• If there is less biomass at each stage in a food chain then there must also be less material and less energy. The efficiency of food production can be improved by reducing the number of stages in food chains• If we want an energy efficient diet we should eat from low down the food chain- eating the plants rather than the plant eaters.
    • Only 10% is used for growth90% is used for:• Lost in food that is uneaten• Lost in faeces and urine Energy losses• Used in respiration 30% lost as heat in respiration Energy consumed 60% lost in urine 10% for growth and faeces The cow is a mammal, and mammals must keep their body temperature constant. This results in a lot of energy being lost as heat to their surroundings.
    • Ways to improve the efficiency of food production• Intensive animal farming involves taking steps to reduce energy losses from food animals• Animals such as poultry are kept indoors, in a temperature controlled environment• Their movement is also restricted to reduce heat loss from respiration, and to ensure they put weight on quickly
    • • Plants are treated with hormones• These chemicals ensure that they ripen as they appear on supermarket shelves, rather than on the plant or during transport.When discussing the positive and negative effectsof managing food production there has to be acompromise between : Maximising food production from the available land, plants and animals and protecting theenvironment from damage by pollution or over use and treating animals as humanely as possibly
    • NUTRIENT CYCLING
    • Decomposition• Useful materials like carbon and nitrogen are removed from the environment from living things.• Eventually they are released when dead organisms are broken down (digested) by microorganisms- we call these microorganisms decomposers• These decomposers are bacteria and fungi
    • The ideal conditions fordecomposition by microorganisms are warm and moist Many bacteria are also more active when there is plenty of oxygen. consumers feeding breakdown breakdownproducers decomposers photosynthesis Nutrients in environment
    • Decomposers• Fungi and bacteria use enzymes to digest their food DEAD MATERIALS• These work in the same way as enzymes do in your gut• The soluble products are taken up by the bacteria and fungi BACTERIA AND FUNGI• The decomposers absorb the food and (CARRY OUT use it for growth and energy DECOMPOSITION)• These bacteria and fungi may be eaten by other organisms and so the nutrients are passed on RESPIRATION GROWTH AND CELL DIVISION CYCLING• Decomposers food chain:Dead leaves  fungus  beetle  frog RELEASE OF CARBON DIOXIDE NEW DECOMPOSER MATERIAL NUTRIENTS RETURNED TO SOIL
    • The carbon cycle• Carbon dioxide is removed from the atmosphere by green plants for photosynthesis• The carbon from the carbon dioxide is used to make carbohydrates , fats and proteins which make up the body of plants• Some of the carbon dioxide is returned to the atmosphere when green plants respire• When green plants are eaten by animals and these animals are eaten by other animals , some of the carbon becomes part of the fat and proteins which make up their bodies• When animals respire some of this carbon becomes carbon dioxide and is released into the atmosphere• When plants and animals die or release waste, microorganisms feed on their bodies and the waste• Carbon is released into the atmosphere as carbon dioxide when these microorganisms respire
    • Photosynthesis and respiration• Respiration and photosynthesis dominate the carbon cyclePhotosynthesis takes carbon dioxide out of theatmosphere and provides the input for carbon intofood chains Light energy + chlorophyllCarbon dioxide + water glucose + oxygen Respiration, by animals, plants and microbes releases carbon dioxide back into the atmosphere
    • ENZYMES
    • How Enzymes Work• Enzymes are BIOLOGICAL CATALYSTS
    • Hotting up• High temperatures can destroy the shape of an enzyme – DENATURE• The substrate can then no longer fit and the reaction can no longer take place
    • Enzymes and respiration• Enzymes inside living cells catalyse processes such as respiration, photosynthesis and protein synthesis• Aerobic respiration=Glucose +oxygen  carbon dioxide + water + ENERGYThe energy released during respiration is used:• To build larger molecules from small ones• In animals, to make muscles contract• In mammals + birds to maintain a constant body temp• In plants, to build up sugars, nitrates and other nutrients into amino acids= proteins
    • OR.. Woman Gone Mad! Warmth Growth Movement
    • Enzymes and digestionEnzyme Where found Substrate it acts Product onAmylase Mouth Insoluble starch glucoseProtease Stomach, small Proteins Amino acids intestineLipase Small intestine Lipids Fatty acids/ glycerol
    • In the stomach and small intestine• Hydrochloric acid is produced in the stomach, gives best pH for protease to work at• The liver produces bile, which is stored in the gall bladder, before passing down the bile duct into the small intestine.• Bile neutralises the acid that was added to the food in the stomach- providing alkaline conditions for the enzyme in the small intestine to work best.• Bile also emulsifies.
    • Enzymes in industry• Microorganisms produce enzymes that pass OUT of cells.• Biological detergents contain proteases and lipases to digest protein and fat stains.• In industry:• Proteases: pre-digest the protein in baby foods• Carbohydrases: convert starch into glucose• Isomerase: convert glucose syrup into fructose syrup (fructose is sweeter, therefore less is needed, used in SLIMMING FOODS).
    • HOMEOSTASIS
    • What is homeostasis?• Homeostasis means keeping conditions inside the body constant• Conditions such as temperature, water level, sugar level, pH of the blood (ion content) and carbon dioxide level.• These constant conditions are controlled by hormones• Hormones are produced by glands and are transported to their target organs in the bloodstream
    • Diabetes• Our blood glucose level is controlled by two hormones: insulin and glucagon.• Both of these hormones are released by the pancreas.• Diabetics are unable to control their blood sugar level properly. They can not make enough insulin and so the concentration of glucose in their blood may become dangerously high- ‘hypos’ may occur.• This can make them tired and thirsty.• Sometimes the blood sugar level can fall too low.• The person can feel weak, irritable and confused- may even faint.• Diabetes can be treated by following a low glucose diet or by injecting with exactly the right dose of insulin.
    • Controlling blood sugar• It is the pancreas that monitors and controls blood glucose level• After a high carbohydrate meal, blood glucose will be too high.• The pancreas detects this and releases insulin into the blood• Insulin causes the liver to convert glucose to insoluble glycogen. The liver removes the glycogen from the blood and stores it and so your blood sugar level returns to normal.• After a lot of exercise your blood sugar will be too low. The pancreas detects this and releases a different hormone, glucagon, into the blood.• Glucagon causes the liver to convert glycogen into glucose and release it into the blood.• So your blood sugar returns to normal
    • Controlling body temperature• Your body temperature is controlled by receptors in the brain- forming the thermoregulatory centre.• This part of the brain monitors the temperature of the blood running through it.• This is your core body temperature• Also temperature receptors in the skin send impulses to this centre, giving it information about skin temperature
    • When it’s hot• Blood vessels supplying the capillaries at your skin surface dilate, so that your blood reaches the surface of your skin and more heat is lost by radiation- so you look flushed• Sweat glands in your skin release more sweat, which cools the body as it evaporatesGetting colder• Blood vessels supplying the capillaries at your skin surface constrict, so that less blood reaches the surface of your skin and less heat is lost by radiation- so you look pale• Sweat glands stop making sweat• Your muscles may start to shiver/ contract.• These contractions need respiration which produces extra heat energy and these warm your body.
    • Waste products• Waste products must be removed from the body because they are toxic.They include:• Carbon dioxide produced during respiration and removed from the body by the lungs when we breathe out;• Urea produced in the liver by the breakdown of excess amino acids – the process deamination.Urea is filtered out of the blood by the kidney andremoved as urine, which is temporarily stored inthe bladder.
    • GENESAND CELLDIVISION
    • Cell division• Inside the nucleus are thread like chromosomes• These chromosomes carry genes along their length• A gene codes for a certain characteristic e.g. eye colour• Genes are made up of the chemical DNA• In body cells, chromosomes are found in pairs• Humans have 46 chromosomes which can be separated into 23 identical pairs• The only human cell that does not have 46 chromosomes is the gametes (sex cell)• The sperm and the egg each have 23 chromosomes
    • Mitosis• Mitosis is a type of cell division which makes all the body cells except the gametes• Before a cell can divide by mitosis, it must make a second set of chromosomes• Each chromosome makes a copy of itself, so when the cell divides into two, each cell has a copy of each of the original chromosome set• Each of the new cells will have exactly the same genetic information• Body cells divide by mitosis:• To produce additional cells during growth• To produce replacement cells if some are damaged• During asexual reproduction to produce clones, that are genetically identical to the parent
    • Meiosis• Is a type of cell division which results in gametes• Cells in reproductive organs divide to form gametes• Cells in the testes divide by meiosis to form sperm• Cells in the ovaries divide by meiosis to form eggs• When a cell divides by meiosis:• Copies of each of the chromosomes are made• Then the cell divides twice to form four gametes, each with a single set of chromosomes
    • Fertilisation2 gametes fuse togetherA sperm with 23 chromosomes joins with an eggwith 23 chromosomes making 46.
    • Variation in offspring• The cells of an offspring produced by asexual reproduction are formed by mitosis from parental cells. Identical genes as the parent• Offspring from sexual reproduction vary:• meiosis= both parental cells mixed• Obtain different alleles• Different characteristics
    • Stem cells• Most types of animal cells differentiate at an early stage- specialised cells• Cell division is usually for repair and replacement
    • GENETICS
    • Chromosomes and alleles• There are 46 chromosomes in human body cells.• Chromosomes are thread like structures and are made up of long proteins called DNA.• A gene is a length of DNA that codes for protein, by combining with amino acids.• Some genes have 2 different forms- alleles.• Dominant alleles and recessive alleles
    • Hereditary diseases• Cystic Fibrosis- disorder of the cell membrane- caused by the recessive allele• Huntington’s Disease- disorder of the nervous system- caused by the dominant allele.• Embryo Screening= taking cells from embryos and analysing them for diseases/ genetic disorders.
    • Genetic crosses• Homozygous= both alleles are the same, e.g. AA/ aa (think homosexual- the SAME sex)• Heterozygous= different alleles e.g. Aa
    • DNA• Is a molecule, containing coded information that determines inherited characteristics.