Biology Unit 2

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  • Created by: YOIMO
  • Created on: 01-06-17 12:28

B2.1 cells, tissues and organs part1

  • mitochondria- where energy is released during aerobic respiration eg muscle/sperm cell
  • ribosomes- where protein synthesis takes place eg gland cells producing enzymes
  • human/animal cells contain: Normally MR Clark Makes **** Profiteroles - Nucleus Mitochondria Ribosomes Cell Membrane CytoPlasm
  • plants and algal also have: Cell Walls, CHloroplasts and a Permanent Vacuole - Canary Wharf CHose Various People And Peasants
  • a rigid cell wall is made of cellulose for support
  • Bacteria cell: Cell Membrane, Cell Wall, CytoPlasm, Genetic Material- General/nuclear power stations
  • Yeast cell: Nucleus, Cytoplasm, Cell Wall, Cell membrane- more intelligent as code is in XY
  • root hair cell: nucleus, large permanent vacuole
  • sperm cell: nucleus, mitochondria, acrosome
  • diffusion examples: oxygen into the cells of your body from the blood stream, diffusion of carbon dioxide into actively photosynthesising plant cells, diffusion of simple sugars and amino acids from the gut through cell membranes
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B2.1 cells, tissues and organs part2

  • animal tissues: muscle tissue- contract to bring about movement, glandular tissue- produce hormones and enzymes, epithelial tissue- covers some parts of the body
  • plant tissues: epidermal tissue- covers the plant, mesophyll- can photosynthesise, xylem and phloem- transport substances around the plant
  • stomach is made of tissue: muscular- churn stomach contents, glandular- produce digestive juices, epithelial- cover the outside and inside of the stomach
  • food we eat must change from insoluble molecules into soluble molecules, then it gets absorbed into the blood
  • digestive system is a muscular tube which includes: glands such as the pancreas and salivary glands which produce digestive juices, the stomach and small intestine where digestion occurs, the liver which produces bile, the small intestine where the absorption of soluble food occurs, the large intestine where water is absorbed from the undigested food producing faeces
  • plant organs include stems, roots and leaves
  • differentiation of cells- process of cells becoming specialised. They become specialised for a particular function and cannot change into different types of cells
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B2.2 organisms in the environment

  • some of the glucose from photosynthesis is converted into insoluble starch for storage
  • the iodine test on leaves shows us if there is starch and that photosynthesis has occurred. variegated leaves have patches of green (with chlorophyll) and white (without chlorophyll). only the green patches will turn the iodine solution blue-black to show that starch has been made
  • independent variable- one being tested
  • dependent variable- the one you measure
  • glucose produced by photosynthesis may be: converted into insoluble starch for storage, used for respiration, converted into fats and oils for storage, used to produce cellulose which strengthens cell walls, used to produce proteins
  • plant and algal cells also need a supply of mineral ions such as nitrate ions in order to produce protein. plants absorb nitrate ions from the soil. algae absorb nitrate ions from the water they live in
  • physical factors affecting the distribution of organisms are: temperature, nutrients, light, water, oxygen, carbon dioxide
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B2.3 enzymes part1

  • protein molecules are made from long chains of amino acids
  • the shape of the protein depends on its function
  • proteins can be: structural components of tissues, hormones, antibodies, catalysts
  • chemical reactions in cells are controlled by proteins called enzymes
  • enzymes are biological catalysts
  • enzymes have areas called the 'active site' where other molecules can fit
  • the substrate in a reaction can be held in the active site and either be connected to another molecule or be broken down
  • enzymes can: build large molecules from many smaller ones eg building starch from glucose molecules, change one molecule into another one eg convert one type of sugar into another, break down large molecules into smaller ones eg all the digestive enzymes do this
  • stomach enzymes work best in acidic conditions
  • amylase- (a carbohydrase) produced by the salivary glands, pancreas and small intestine. catalyse the digestion of starch into sugars in the mouth and small intestine
  • protease- produced by the stomach, pancreas and small intestine. catalyses the breakdown of proteins into amino acids in the stomach and small intestine
  • lipases- produced by the pancreas and small intestine. catalyses the breakdown of lipids (fats and oils) to fatty acids and glycerol
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B2.3 enzymes part2

  • protease enzymes in the stomach work best in acidic conditions. glands in the stomach wall produce hydrochloric acid to create very acidic conditions
  • amylase and lipase work in the small intestine in slightly alkaline conditions
  • liver produces bile that is stored in the gall bladder. the alkaline bile is squirted into the small intestine and neutralises the stomach acid. bile makes the conditions in the small intestine slightly alkaline
  • biological detergents contain proteases and lipases which digest food stains
  • proteases are used to pre-digest proteins in some baby foods
  • isomerase is used to convert glucose syrup into fructose syrup. fructose is much sweeter, so less is needed in foods- less fattening
  • advantages of enzymes: lower temp, less energy, reduces cost, some enzymes are used in medicine to diagnose, control or even cure diseases
  • disadvantages of enzymes: enter waterways via sewage, allergic reactions, costly to produce enzymes, enzymes denature at high temps which are needed to remove pathogens, fabrics like wool are digested by proteases, very effective at removing stains
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B2.4 energy for respiration

  • energy released from aerobic respiration may be used by the organism to: build larger molecules from smaller one, enable muscle contraction in animals, maintain a constant body temp in colder surroundings, build sugars, nitrates and other nutrients into amino acids and then proteins in plants
  • when you exercise, your muscles need more energy so they can contract: need to increase the rate oxygen and glucose reach the muscle cells for aerobic respiration, remove the waste carbon dioxide, heart rate increases, blood vessels dilate (widen) to increase blood flow, breathing rate increases and so does the depth, muscles store glucose as glycogen
  • glucose is not completely broken down in anaerobic respiration therefore lactic acid is produced
  • less energy is released from the glucose in anaerobic respiration
  • one cause of muscle fatigue is the build up of lactic acid
  • blood flowing through the muscles removes the lactic acid
  • when muscles respire they build up an oxygen debt
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B2.5 simple inheritance in animals and plants part

  • cell division is necessary for the growth of an organism, or for the repair of damaged tissues
  • Mitosis results in two identical cells being produced from the original cell
  • the chromosomes contain the genes (alleles) which must be passed on to each new cell
  • a copy of each chromosome is made before the cell divides and one of each chromosome goes to each new cell
  • stem cells are unspecialised
  • plant cells can differentiate throughout the life of the plant as it grows
  • cells of offspring produced by asexual reproduction are produced by mitosis from the parent cell. they contain the same alleles as the parents
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Mitosis

                                        

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B2.5 simple inheritance in animals and plants part

  • gametes (sex cells) are produced by meiosis. in humans the gametes are the sperm and ova
  • each gamete has only one chromosome from each original pair. all of the cells are different from each other and the parent cell
  • sexual reproduction results in variation as the gametes from each parent fuse
  • when gametes join at fertilisation, a single body cell with new pairs of chromosome is formed
  • a new individual then develops by this cell repeatedly dividing by mitosis
  • before division, a copy of each chromosome is made
  • the cell now divides twice to form four gametes
  • each gamete has a single set of chromosomes each with a different combination of genes
  • embryo screening- tests are carried out on the embryo to diagnose possible disorders
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Meiosis

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B2.5 simple inheritance in animals and plants part

  • stem cells are found in human embryo and in adult bone marrow
  • stem cells differentiate
  • Mendel worked out how characteristics are inherited. his idea took a long time to be accepted because scientists did not know about chromosomes and genes until after he died
  • genes are found on chromosomes
  • chromosomes are made of DNA which is a very long molecule with a double helix structure
  • genes are short sections of DNA
  • each gene code for a particular combination of amino acids which make a specific protein
  • humans have 23 pairs of chromosomes
  • genes controlling the same characteristics are called alleles
  • phenotype- physical appearance of the characteristic
  • genotype- the genetic make up
  • polydactyly- where a baby is born with extra fingers (dominant)
  • cystic fibrosis- the allele affects cell membranes and causes the production of thick sticky mucus. the mucus can affect several organs, including the lungs and pancreas (recessive)
  • adult stem cells eg bone marrow cells are useful in treating disorders such as leukaemia
  • embryonic stem cells are taken from spare embryos
  • additionally, they can be used to grow new tissues and organs for transplants
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B2.6 old and new species

  • the Earth is about 4500 million years old
  • life began 350 million years ago
  • fossils are formed by: hard parts of animals which don't decay easily eg teeth and bones, parts of organisms that have not decayed due to weather conditions, parts of the organisms are replaced by other materials, preserved traces of organisms eg footprints
  • most organisms when they died did not form fossils because the exact conditions for fossil formation were not present
  • many early life forms had soft bodies so few traces were left behind
  • reasons for extinction: new diseases, environment changes (climate change), new predator, new competitor, single catastrophic event, natural changes in species
  • geographical isolation occurs if an island separates or a river intervenes. organisms left on the island may be exposed to different environmental conditions, food availability or predators. natural selection will occur in both areas, but different characteristics will be beneficial in the two populations. each population has a wide range of alleles that control their characteristics. this is genetic variation
  • if the environment, competitors, food supply and predators are different for each population they will evolve differently
  • speciation has occurred when the two populations can no longer successfully interbreed
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