Wonderful world of cells


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Wonderful world of cells

  1. 1. The wonderful world of cells!A fascinating insight into the world ofcells, who discovered them, thedifferent types and what they aremade up of.
  2. 2. Microscopes Light microscope Electron microscopeUses light rays Uses electron ‘beams’Magnification – x2000 Magnification – x500,000Resolving power – 200nm Resolving power – 1nmFocused by glass lenses Focused by electromagnetsSpecimens can be living or Specimens must be deaddeadSmall, portable and Large, static and veryrelatively inexpensive expensive
  3. 3. Microscopes Magnification – to make an image appear bigger To calculate the magnifying power of a microscope:eye piece lens magnification X objective lens Resolution – the minimum distance between 2 points at which they are still visible as 2 separate points
  4. 4. Robert HookeHe looked at corkcells under amicroscope andused the term‘cell’. The holesthat he observedwhere once filledwith living material(cytoplasm)
  5. 5. Robert Hooke’s cells
  6. 6. Theodor Schwann
  7. 7. Matthias Schleiden
  8. 8. Cell theory with the cellSchwann and Schleiden came up theory.They proposed that all plants and animals were made up of cells and that cells were the basic units of lifeAnother scientist, Rudolf Virchow discovered that new cells can only arise from the division of pre-existing ones.
  9. 9. Prokaryotic and Eukaryotic cells No true nucleus  Distinct nucleus Few organelles except for surrounded by a nuclear envelope small ribosomes  Many membrane bound Single strand of genetic organelles material free in the cell  Genetic material is stored Simple structure in the nucleus Small in size  Highly organized to carry Include bacteria and out complex functions blue/green algae  Large in size  Include plants, animals and fungi
  10. 10. Eukaryotic cell
  11. 11. Animal cells: these are cheek cells asseen with a compound microscope,compare these cells to the next onesseen through an electron microscope.
  12. 12. Plant and animal cells Cellulose cell wall  No cell wall Chloroplasts  No chloroplasts Large permanent  Small, temporary vacuole with cell sap vacuoles No centrioles  Centrioles present Starch grains for  Glycogen granules storage for storage
  13. 13. Plant cell
  14. 14. Animal cell
  15. 15. Cytoplasm Watery, jelly-like material Contains many substances for metabolism The other organelles are suspended in it
  16. 16. Cellulose cell wall Many cellulose fibers glued together Strong to resist expansion of the cell as water enters – this supports the cell Provides mechanical strength to the cell Freely permeable
  17. 17. Vacuole Large permanent vacuole in plant cells is called a central vacuole. It contains cell sap, a solution of sugar and minerals. They are food stores They accumulate waste products Some contain pigments to give color Vacuoles in animal cells are small and temporary
  18. 18. Nucleus Largest cell organelle Surrounded by a double membrane that allows materials to pass in and out Contains genetic material (DNA) which is used to make proteins Controls the metabolic activity of the cell
  19. 19. Nucleolus Found in the nucleus Dense, spherical structure Contains RNA for the production of ribosomes
  20. 20. Ribosomes Small, dense organelles Can be free in the cytoplasm or attached to rough endoplasmic reticulum They are made in the nucleolus They are the site of protein synthesis
  21. 21. Endoplasmic reticulum Complex system of double membranes with fluid-filled sacs in between called cisternae Connected with the nuclear membrane and the cell membrane It collects, stores and distributes materials Rough endoplasmic reticulum has ribosomes on it. It packages and transports proteins made by ribosomes Smooth endoplasmic reticulum is the site of lipid (fat) synthesis.
  22. 22. Golgi complex Also known as golgi body or apparatus Made from small pieces of rough ER pinched off at the end to form vesicles which fuse together Site of protein modification Vesicles pinch off at the ends to carry the new chemicals away (some vesicles become lysosomes)
  23. 23. Lysosomes Small vesicles formed when pieces of the golgi body pinch off Contain hydrolytic enzymes that can digest cell material They destroy worn out organelles They can destroy material brought into the cell (e.g. bacteria) They can release enzymes out of the cell to digest other cells They can cause the cell to self destruct
  24. 24. Mitochondria Has a double membrane. The outer one controls entry of materials and the inner one has many folds called cristae Has a matrix containing DNA, ribosomes and enzymes Site of aerobic respiration The more active the cell, the more mitochondria it has
  25. 25. Chloroplasts Found in plants cells that carry out photosynthesis They are the site of photosynthesis They have a double membrane filled with fluid (stroma) where the photosynthesis reactions take place The stroma contains piles of flattened scas (grana) where chlorophyll is found and light is absorbed
  26. 26. Cytoskeleton This is a network of fibrous proteins It allows movement and gives the cell shape and support It is made up of microtubules and microfilaments
  27. 27. Centrioles These are 2 short bundles of microtubules positioned at right angles to each other. They are found just outside the nucleus in animal cells During cell division, they move to opposite ends of the cell and produce the spindle
  28. 28. Flagella Also made up of microtubules Often used to help cells move (e.g. sperm)
  29. 29. Cell membrane Made up of a bilayer of phospholipids that allows some materials through but not others (semi-permeable) Contains proteins that can act as pores, carriers or be involved in cell recognition The main function is to regulate the movement of molecules and ions
  30. 30. Cell membrane structure Made up of a bilayer of phospholipids. They have a polar end (water liking) and a non-polar end (water hating) Protein carrier molecules are found embedded in the cell membrane; these molecules form specific bridges allowing specific molecules to pass through
  31. 31. Transport across membranes The cell membrane is thin and provides a large surface area for diffusion to occur Diffusion is the movement of molecules or ions from a region of high concentration to a region of low concentration until they are spread out evenly (down a concentration gradient) A big difference in concentration, an increase in temperature, small molecules and a short diffusion distance makes the rate of diffusion faster
  32. 32. Facilitated diffusion This allows faster movement It involves the use of proteins to assist (facilitate) diffusion Specific channel proteins form pores for specific molecules Carrier molecules bind to specific molecules, change shape and deliver the molecule to the other side of the membrane
  33. 33. Osmosis This is the diffusion of water molecules They move from where they are in a high concentration (a dilute solution) to where they are in a low concentration (a concentrated solution)
  34. 34. Osmosis in plant cells As water enters a plant cell, the cell starts to swell. The cell wall starts to resist the stretching which creates pressure When no more water can enter the cell, it is said to be TURGID. This provides strength and support to the cell If water leaves a cell, the membrane can pull away from the cell wall. This causes a plant to wilt
  35. 35. Different solutions Solution – a mixture of 2 or more substances Solvent – the liquid that a substance dissolves in Solute – the substance that dissolves in a solvent Hypotonic – a weak solution: weaker in solute concentration than cell Hypertonic – a strong solution: stronger in solute concentration than cell Isotonic – a solution with the same concentration as cell.
  36. 36. Active transport Moving molecules against a concentration gradient (from low to high concentration) It requires special carrier proteins called membrane pumps It uses energy in the form of ATP
  37. 37. Endocytosis and exocytosis For molecules too large to pass through the membrane Endocytosis – taking materials into the cell by closing the cell membrane around it to form a vesicle (There are 2 types, pincytosis and phagocytosis) Exocytosis – material in vesicles in the cell fuse with the cell membrane and are released