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Similar to GCSE AQA BIOLOGY UNIT 2
GCSE AQA BIOLOGY UNIT 2
- 1. Energy and Cells Photosynthesis biomass Genetics Unit 2 Biology Nutrient cycling Homeostasis Genes and cell Enzymes division
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- 3. Animal Cells Nucleus: controlseverything in the cell, contains the information to make new cells Cytoplasm: A jelly like substance in which chemical reactions in the cell take place, the chemical reactions are controlled by enzymes Cell membrane: gives the cell its shape and controls which substances enter and leave the cell Ribosomes: Where proteins are made Mitochondria: Releases energy from respiration for the cell to use- found in the cytoplasm, small sausage shaped structures
- 4. 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
- 5. Differences between plantand 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
- 6. Specialised cells Leaf palisade cells- found in the leaf of the plant, contain lots of chloroplasts for photosynthesis: Xylem cells- small tubes that carry water up the stem Root hair cells- are long and thin to absorb water from the soil
- 7. Nerve cells- arelike wires to carry messages around the body Sperm cells have a tail to swim to the egg Red blood cells have a substance that carries oxygen
- 8. Tissues and organs Tissuesare 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.
- 9. Diffusion and osmosis Diffusion is the movement of particles from a region of high concentration 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.
- 11. What is theuse 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 both State the differences between animal and plant cells SLIDE 4 What is the mitochondria and where is it found? SLIDE 4 Name 3 cells found in the plant and their uses SLIDE 3 Define: • Tissues • Organs • Diffusion SLIDES 7 + 8 • Osmosis
- 12. Describe the roleof enzymes inside the cell Suggest 2 factors that increase the rate of diffusion Name the substance that moves across a partially permeable membrane during the process of osmosis Explain 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
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- 14. What is photosynthesis? •Photosynthesis is the process where plants make their own food • The equation = Light energy + chlorophyll Carbon 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
- 15. Water is absorbedthrough 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 respiration Carbon dioxide enters the leaf by to give plants their own energy diffusion through the stomata Excess glucose can be stored in the leaves as insoluble starch
- 16. Limiting factors • Limitingfactors 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
- 17. The products ofphotosynthesis • 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
- 18. Healthy growth Plants needmineral ions and nutrients to stay healthy. They are found in the soil and absorbed through the plant’s roots. Magnesium and nitrate are vital for a plant to remain healthy: Nitrate Magnesium Nitrate is needed to produce Magnesium is needed to amino acids, which then produce chlorophyll- to be form proteins for the plant used in photosynthesis to absorb the sunlight If Nitrate is lacking the Without magnesium the plant’s growth will be leaves will turn yellow, due stunted and older leaves will to the lack of chlorophyll urn yellow which is green
- 19. Leaves • Leaves arewell 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
- 20. Leaf Structure Cuticle: waterprooflayer that also cuts water loss by evaporation Upper epidermis: single layer of cells, no chloroplasts present, sunlight goes straight through to palisade cells Palisade mesophyll: Where cuticle photosynthesis takes place, as lots of chloroplasts Spongy mesophyll: Lots of air space between them, for gas exchange to occur Vein: contains xylem tubes and phloem tubes Xylem tubes: brings water and salt to leaf through stem Phloem tubes: takes dissolved foods away
- 22. Why do plantsneed 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’ use Name 3 limiting factors of photosynthesis What 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 lacking Why are leaves well adapted for photosynthesis? What do the following do in the leaf:- Cuticle? Spongy mesophyll? Lower epidermis? Upper epidermis? Palisade layer? Vein?
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- 24. Energy Theoriginal source of energy for all communities of living organisms is radiation from the Sun Green plants capture this solar energy, transferring it into chemical energy and stored in starch and other substances that make up plant cells Only about 10% of the solar energy reaching the plant is transferred into chemical energy by photosynthesis. Most of the energy is: • Reflected by the leaf • Passes straight through the leaf • Simply heats the leaf up
- 25. Biomass • Biomass isthe 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 20g We can use these biomass figures to draw a pyramid of biomass to scale bird snails grass
- 26. Food production • Ifthere 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.
- 27. Only 10% isused for growth 90% 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.
- 28. Ways to improvethe 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
- 29. • Plants aretreated 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 effects of managing food production there has to be a compromise between : Maximising food production from the available land, plants and animals and protecting the environment from damage by pollution or over use and treating animals as humanely as possibly
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- 31. Decomposition • Useful materialslike 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
- 32. The ideal conditionsfor decomposition by microorganisms are warm and moist Many bacteria are also more active when there is plenty of oxygen. consumers feeding breakdown breakdown producers decomposers photosynthesis Nutrients in environment
- 33. Decomposers • Fungi andbacteria 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
- 34. 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
- 35. Photosynthesis and respiration •Respiration and photosynthesis dominate the carbon cycle Photosynthesis takes carbon dioxide out of the atmosphere and provides the input for carbon into food chains Light energy + chlorophyll Carbon dioxide + water glucose + oxygen Respiration, by animals, plants and microbes releases carbon dioxide back into the atmosphere
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- 37. How Enzymes Work •Enzymes are BIOLOGICAL CATALYSTS
- 38. Hotting up • Hightemperatures can destroy the shape of an enzyme – DENATURE • The substrate can then no longer fit and the reaction can no longer take place
- 39. Enzymes and respiration •Enzymes inside living cells catalyse processes such as respiration, photosynthesis and protein synthesis • Aerobic respiration= Glucose +oxygen carbon dioxide + water + ENERGY The 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
- 40. OR.. Woman GoneMad! Warmth Growth Movement
- 41. Enzymes and digestion Enzyme Where found Substrate it acts Product on Amylase Mouth Insoluble starch glucose Protease Stomach, small Proteins Amino acids intestine Lipase Small intestine Lipids Fatty acids/ glycerol
- 42. In the stomachand 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.
- 43. 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).
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- 45. 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
- 46. Diabetes • Our bloodglucose 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.
- 47. 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
- 48. 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
- 49. 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 evaporates Getting 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.
- 50. Waste products • Wasteproducts 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 and removed as urine, which is temporarily stored in the bladder.
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- 52. Cell division • Insidethe 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
- 53. Mitosis • Mitosis isa 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
- 54. Meiosis • Is atype 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
- 55. Fertilisation 2 gametes fusetogether A sperm with 23 chromosomes joins with an egg with 23 chromosomes making 46.
- 56. 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
- 57. Stem cells • Mosttypes of animal cells differentiate at an early stage- specialised cells • Cell division is usually for repair and replacement
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- 59. 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
- 60. Hereditary diseases • CysticFibrosis- 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.
- 61. Genetic crosses • Homozygous=both alleles are the same, e.g. AA/ aa (think homosexual- the SAME sex) • Heterozygous= different alleles e.g. Aa
- 62. DNA • Is amolecule, containing coded information that determines inherited characteristics.