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OCR 21 st Century Science Unit B4a Revision

OCR 21 st Century Science Unit B4a Revision . Animal and Plant cells Respiration and Photosynthesis . mitochondria contain enzymes for the reactions in aerobic respiration (in animals, plants and yeast)

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OCR 21 st Century Science Unit B4a Revision

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  1. OCR 21st Century Science Unit B4a Revision Animal and Plant cells Respiration and Photosynthesis

  2. mitochondria contain enzymes for the reactions in aerobic respiration (in animals, plants and yeast) • cell membrane allows gases and water to pass in and out of the cell freely while presenting a barrier to other chemicals • nucleus or circular DNA in bacteria contains DNA which carries the genetic code for making enzymes used in the chemical reactions of respiration • cytoplasm where enzymes and proteins are made • chloroplasts contain chlorophyll and the enzymes for the reactions in photosynthesis Animal and Plant Cells

  3. Respiration

  4. Uses for respiration summary • Animals and plants have many uses for the energy they generate from respiration: • To perform the life processes, such as moving, _____ etc • To build up body _______ • To maintain a constant body ___________ (warm-blooded mammals only) • To build up sugars, ________ and other nutrients in plants • Active __________ • Words – nitrates, tissue, proteins, transport, growing

  5. Synthesis Glucose molecules Starch molecule Glucose molecules Proteins “Synthesis” means “making large molecules out of small ones”. Two examples: 1) Glucose (sugar) can be used to make long chains of insoluble starch… 2) Glucose can be combined with nitrates to make proteins (for growth)…

  6. all living things depend on chemical reactions within cells that require energy released by respiration • Respiration is a series of chemical reactions that release energy by breaking down large food molecules in all living cells Aerobic Respiration glucose + oxygen  carbon dioxide + water (+ energy released) C6H12O6 + 6O2 6CO2 + 6H2O

  7. Aerobic respiration summary All living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy: Glucose + oxygen  water + carbon dioxide + ENERGY The glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells. Words – breathing, energy, grow, respiration, food, mitochondria

  8. anaerobic respiration takes place in animal, plant and some microbial cells in conditions of low oxygen or absence of oxygen, to include: Anaerobic Respiration In Animal Cells: glucose  lactic acid (+ energy released) In Yeast glucose  ethanol + carbon dioxide (+ energy released) • Happens in • roots in waterlogged soil • bacteria in puncture wounds • human cells during vigorous exercise

  9. Anaerobic respiration summary Unlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________: Glucose  lactic acid + a bit of energy This happens when the body can’t provide oxygen quick enough for __________ respiration to take place. Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much. Anaerobic respiration can also take place in other low-oxygen conditions, such as plant roots in _________ soil or bacteria in ________ wounds. Words – oxygen, aerobic, quicker, puncture, waterlogged

  10. Respiration in cells In bacteria cells, this job is done by circular DNA 1) Cytoplasm - where enzymes are made 2) Nucleus – carries genetic info for making enzymes Cell Membrane – controls what comes in and out 3) 4) Mitochondria – contain enzymes for respiration reactions

  11. OCR 21st Century Science Unit B4b Revision Enzymes, Osmosis and Diffusion

  12. Enzymes in respiration and photosynthesis Enzymes are proteins that speed up chemical uses. Here are two important natural uses for them: Cells use glucose to generate energy – this process is called “respiration”. Respiration happens in mitochodria and is catalysed by enzymes. • Photosynthesis is catalysed by enzymes in the cells.

  13. Enzymes- The lock and Key Model Enzyme • enzymes are proteins that speed up chemical reactions • cells make enzymes according to the instructions carried in genes • molecules have to be the correct shape to fit into the active site of the enzyme (the lock and key model) Substrate

  14. heat pH normal denatured Factors affecting enzyme action (Denaturing) • The shape of the enzyme is vital to its function. • The main factors affecting enzyme action are 1.) temperature and 2.) pH • 1.) High temperatures can destroy the enzymes ‘special shape’ so it becomes denatured. • 2.) Different enzymes work best at different pH values.

  15. Optimum conditions Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity 400C Temp pH pH Enzymes work best in certain conditions: • Enzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.

  16. high concentration low concentration Diffusion and concentration gradients • Diffusion is the spreading of the particles of a gas, or of any substance in solution. • This results in a net movement from a region where they are of • a higher concentration to a region of lower concentration • The greater the difference in concentration, the faster the • rate of diffusion.

  17. Diffusion Summary Diffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______. Words– faster, low, gradient, temperature, energy

  18. Osmosis

  19. Osmosis

  20. Osmosis summary Osmosis is a “special kind of ___________”. It’s when water diffuses from a __________ area to a less concentrated area through a partially permeable _________ (i.e. one that allows water to move through but not anything else): In this example the water molecules will move from left to right (along the concentration ______) and gradually _____ the sugar solution. Plants use osmosis to take in water through their roots. Words – membrane, concentrated, dilute, diffusion, gradient Water

  21. Strong sugar solution Medium sugar solution Which way does movement take place? Potato cells Weak sugar solution

  22. Active transport

  23. Active transport summary In diffusion substances moved along a concentration gradient. In active transport, substances move against this gradient: This process takes ______ and this comes from ___________. It enables cells to take in substances even though there are in very small __________. Root hair cells take in ______ using active transport. Words– concentration, energy, respiration, nutrients Outside cell Inside cell Cell membrane

  24. OCR 21st Century Science Unit B5a Revision Animal & Plant cells and Stem cells

  25. Specialisation of animal cells Ciliated epithelial cell White blood cell Nerve cell (neurone) Egg cell (ovum) During the development of a multi-celled organism cells differentiate to form specialised cells:

  26. 2. Sperm cell – long tail providing movement s it can swim to and fertilise egg. Nucleus contains genetic material 1. Guard cell – can open and close to control exchange of gases and water loss 3. Red blood cell – concave disc shape - increases area to carry more oxygen 4. Egg cell (ovum) – large – maximum exposure for sperm, has a large food store 6. White blood cell – can change shape to digest microbes 7. Neurone – long like wires to carry messages around the body 5. Root hair cell – large surface area to absorb water and minerals. Thin cell wall so minerals can pass through easily. Positioned close to xylem tissue.

  27. Cells, tissues and organs Basically, all living things are made up of cells… A group of CELLS makes up a TISSUE A group of TISSUES makes up an ORGAN A group of ORGANS makes up a SYSTEM A group of SYSTEMS make up an ORGANISM

  28. Adult stem cells Ciliated epithelial cell White blood cell Nerve cell (neurone) Egg cell (ovum) It is also possible to have adult stem cells – these are unspecialised cells that can become specialised later (but they can’t form ALL types of cell) Adult stem cells can be found in places like bone marrow.

  29. Adult stem Cells Cells inside an organism contain the same genes. So how can cells specialise if they have the same genes and make the same proteins? The reason is that many of the genes in the nucleus are “switched off” so that the cell only produces the proteins it needs. It is possible to “switch on” different genes to make the cell produce different proteins – this is the basis of stem cell research.

  30. Adult Stem cells As well as adult stem cells from bone marrow, stem cells can also come from... These stem cells have the potential to develop into any kind of cell. The rest of the embryo is destroyed. Most of these embryos come from unused IVF treatments. Embryo Egg and sperm Cloned embryos The ethical issue: Should these embryos be treated as humans?

  31. Meristems Plant growth occurs in areas called meristems. These meristems are “mitotically active”: • This meristem causes the plant to grow upwards. • This meristem causes the plant to grow in width. Cells from the meristem behave like stem cells – they can develop into any kind of cell. Cloned plants can be produced from these cells.

  32. Phototropism ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

  33. Plant hormones In the shoots the hormone auxin is “destroyed” by light, so the shoot will bend towards the light as the cells on the shaded side grow quickest. In the roots hormones slow down growth of the cells in the lower region, which makes the root bend down. Shoots grow towards light (positive phototropism) and against gravity (negative geotropism). Roots grow away from light (negative phototropism) and in the direction of gravity (positive geotropism). The growth of roots and shoots is controlled by hormones:

  34. Phototropism summary

  35. Cuttings ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

  36. OCR 21st Century Science Unit B5b Revision DNA and Mitosis & Meiois

  37. Inside the nucleus the genetic code is in the cell nucleus of animal and plant cells but proteins are produced in the cell cytoplasm

  38. DNA • DNA has a double helix structure • both strands of the DNA molecule are made up of four different bases which always • pair up in the same way: A with T, and C with G • the order of bases in a gene is the genetic code for the production of a protein

  39. DNA and coding for proteins • the order of bases in a gene is the code for building up amino acids in the correct order to make a particular protein

  40. Building proteins 1) DNA “unravels” and a copy of one strand is made 2) The strand copy is made to produce RNA 3) The copy (with its code) then moves towards the ribosome 4) The ribosome “decodes” the code which tells the ribosome how to make the protein In other words, genes do NOT leave the nucleus but a copy of the gene (the mRNA) carries the genetic code to the cytoplasm.

  41. Building proteins ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

  42. DNA summary Some facts: - DNA has a “double ______” structure - This contains instructions on what a cell does, how the organism should work etc - The instructions are in the form of a ______ - The code is made up from the four ____ that hold the strands together with hydrogen bonds; A always pairs with T and C with G - The bases represent the order in which _____ acids are assembled to make specific ________ Words – helix, amino, code, bases, proteins

  43. Chromosomes in body cells • In body cells the chromosomes are in pairs • Body cells have two sets of chromosomes; • Sex cells (gametes) have only one set. • Sex cells (gametes) are made by meiosis

  44. Asexual and sexual reproduction

  45. Mitosis parent cell daughter cells • cell division by mitosis produces two new cells that are genetically identical to each other and to the parent cell • a fertilised egg cell (zygote) divides by mitosis to form an embryo mitosis

  46. Mitosis The chromosomes are copied… Each daughter cell has the same number of chromosomes and genetic information as the parent – it’s a “clone”. The chromosomes separate… The nucleus divides…

  47. Mitosis summary

  48. Meiosis • meiosis is a type of cell division that produces gametes • in meiosis, it is important that the cells produced only contain half the chromosome number of the parent cell • a zygote contains a set of chromosomes from each parent.

  49. Meiosis Each daughter cell has half the number of chromosomes of the parent.

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