Cells

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Cells

  1. 1. Robert Hooke [1665] examined thin sections of a bottle cork under a crude microscope found hexagonal boxes or chambers packed together like a honeycomb
  2. 2.  Robert Hooke used the word cells to describe these structures
  3. 3. Cell TheoryAll living things are made up of cells.Cells are the smallest working units of allliving things.All cells come from preexisting cells throughcell division.
  4. 4. Definition of Cell A cell is the smallest unit that is capable of performing life functions.
  5. 5. Examples of Cells Plant cellAmoeba Red blood cells BacteriaNerve cell
  6. 6. A typical animal cell
  7. 7. Animal cells are spherical
  8. 8. A typical plant cell
  9. 9. Plant cells are cylindrical
  10. 10. Which structures are common to both cells?
  11. 11. Cell membrane is a very thin, flexible layer round the cell
  12. 12. Functions of the cell membrane1. keeps the cell contents together (like the sack)2. controls what substances go in and out of the cell as it is semi-permeable
  13. 13. Cytoplasm is a thick liquid with particles in it contains ENZYMES which control the chemical changes taking place in the cell may contain food reserves e.g.  starch grains  oil droplets
  14. 14. Cell Parts:Organelles
  15. 15. What are ‘organelles’? subunits in the cytoplasm that carry out a particular function such as the:  nucleus  mitochondria
  16. 16. Nucleus each cell has one nucleus a cell cannot live for long without a nucleus the nucleus controls the activities of the cell Nucleus in a cheek cell.
  17. 17. The nucleus contains: thread-like structures called: CELL chromosomes  chromosomes Chromosome contain DNA (deoxyribonucleic acid) DNA
  18. 18. The nucleolus is a dark region in the nucelus Function of the nucleolus:  certain chemicals are made e.g. RNA (ribonucleic acid) which then work in the cytoplasm nucleolus
  19. 19. VacuolesAnimal cells: have small vacuoles that are temporary Amoeba engulfs food. Phagocyte engulfs bacteria.
  20. 20. Plant cells: have a large central, permanent vacuole full of SAPSAP is a mixture of: sugars salts water pigments
  21. 21. Mitochondria are structures in which aerobic respiration occurs are called the ‘power houses’ of the cell as they release energy are usually sausage-shaped
  22. 22. Mitochondriaare seen only by an electron microscope
  23. 23. Explain why there are more mitochondria in muscle cells than in skin cells. Moremitochondria in musclecells as they use more energy.
  24. 24. Structures ONLY in plantsCell wallChloroplasts
  25. 25. The cell wall is: a non-living structure surrounding the cell membrane made of cellulose fully permeable i.e. substances pass freely through it cell membrane cell wall
  26. 26. Functions of the cell wall1. gives rigidity to the cell2. together with the central vacuole, it provides support
  27. 27. Chloroplasts contain the greenpigment: CHLOROPHYLL
  28. 28. Function of chlorophyll  traps light for photosynthesis chloroplast
  29. 29. QUESTION: SEP, 2011Give a reason for each of the followingobservations.i) Large permanent vacuoles are present in plant cells. (2) Gives shape and rigidity to the plant cells.
  30. 30. QUESTION: SEP, 2011Give a reason for each of the followingobservations.ii) Animal cells tend to have irregular shapes. (2) Cells are surrounded by a thin cell membrane which is not stiff.
  31. 31. QUESTION: SEP, 2011Give a reason for each of the followingobservations.iii) Sperm cells are haploid. (2)After fertilisation, the diploid number of chromosomes is restored.
  32. 32. CELL SPECIALISATION specialisation is the process by which cells change their shape to carry out a particular task specialisation happens in multicellular organisms
  33. 33. Examples of specialised animal cells: white blood cells  change their shape to engulf bacteria nerve cell  contains a long fibre to conduct impulses
  34. 34. Examples of specialised animal cells: muscle cell  elongated cell which can shorten red blood cell  has no nucleus to have more space to carry more oxygen
  35. 35. Examples of specialised plant cells:1. guard cells bean-shaped cells with a pore in between to allow gas exchange2. palisade cells elongated cells with many chloroplasts to carry out photosynthesis
  36. 36. Examples of specialised plant cells:3. epidermal cells transparent to let light pass through them
  37. 37. Tissues, Organs & Systems
  38. 38. Unicellular Multicellular organism organismone cell:  cells become carries out all the differentiated vital functions into tissues is capable to live on its own
  39. 39. Differentiated means cells become adapted during development to a specific function
  40. 40. Cells in a tissuehave the same structure and functiona tissue cannot live on its own
  41. 41. Examples of animal tissues muscle tissue  blood tissue nerve tissue  bone tissue
  42. 42. Examples of plant tissuesPhotosynthetic tissue Vascular tissue: xylem & phloem Epidermal tissue: Protects from water loss & pathogens
  43. 43. QUESTION: SEP, 2011Blood is an animal tissue.List TWO plant tissues and give thefunction of each. (6)Epidermal tissue:Photosynthetic tissue:Vascular tissue:
  44. 44. Question: MAY, 2010Write the appropriate plant or animal tissue for eachof the following descriptions. (6) Description Name of tissue Tissue used in the translocation of organic solutes. Tissue conducts nerve impulses. Tissue contracts to support and move the body. Tissue found in leaf containing numerous chloroplasts. Tissue acts as the living protective layer in leaf. Tissue carries substances round the body.
  45. 45. Question: MAY, 2010Write the appropriate plant or animal tissue for eachof the following descriptions. (6) Description Name of tissue Tissue used in the translocation of organic solutes. Phloem Tissue conducts nerve impulses. Nervous Tissue contracts to support and move the body. Muscle Tissue found in leaf containing numerous chloroplasts. Photosynthetic Tissue acts as the living protective layer in leaf. Epidermis Tissue carries substances round the body. Blood
  46. 46. Organism Levels of cellular organisationSystem Organ Tissue Cell
  47. 47. Organs  are made up of groups of tissues
  48. 48. Examples ofanimal organs Heart Lungs Kidneys Brain Skin Ear Eye Uterus
  49. 49. Four plantorgans: Flower Leaf Stem Root
  50. 50. Systems are made up of a group of organs e.g. heart + blood vessels make up the circulatory system
  51. 51. Examples of SystemsSkeletalCirculatoryImmuneRespiratoryDigestiveExcretoryReproductiveNervousEndocrineMuscular
  52. 52. QuestionTo which systems of the body do the followingorgans belong? Chose from the list: circulatory nervous reproductive breathing skeletal excretory digestivea) Gut: digestive b) Bladder: excretoryc) Skull: skeletal d) Heart: circulatorye) Ears: nervous f) Ovaries: reproductiveg) Lungs: breathing h) Spinal cord: nervous
  53. 53. Organism results from many systems working together I am an organism.
  54. 54. Surface area to volume ratio
  55. 55. Why does an amoeba NOT require a circulatory system?An amoeba has a LARGE surface area tovolume ratio. Materials can move within theamoeba quickly enough due to its smallvolume.
  56. 56. What happens to the SA:Vol ratio as the cube increases?
  57. 57. SA:Vol ratio limits cell sizeExchange of materials across surface can happen only in the (small / large cube).
  58. 58. SA:Vol ratio limits cell sizeExchange of materials across surface can happen only in the (small / large cube).
  59. 59. Large organisms need a:1. respiratory system  to take in O2 & remove CO21. circulatory system  to transport materials to all cells in the body
  60. 60. T HE END

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