Cell membranes

Functions
1. provide a partially permeable membrane
2. provide structural support
3. act as channels transporting water soluble substances
4. allow actrive transport through thorugh carrier proteins
5. form cell surface receptors for identifying cells
6. help cells adhere together
7. act as recpetors
fluid mosaic molecule
1. fluid
  1. individual phospholipids move around within their layer
2. mosaic
  1. pattern produced by scattered proteins when viewed from above
3. Phospholipid
  1. can form sheets (bilayer)
  2. form membrane bound compartments
  3. act as a barrier to water soluble substances
4. cholesterol
  1. prevent ions/molecules passing thorugh
  2. helps regulate fluidity
  3. stabilises phospholipid bilayer
5. proteins
  1. intrinisic
    1. channel
    2. carrier
  2. extrinsic
6. Glycolipids and glycoproteins
  1. short carbohydrate chains attach to lipids and proteins
  2. receptors
  3. antigens
  4. cells adhere
transport across cell membranes
1. diffusion
  1. net movement of molecules or ions from a region of high concentration to a gradient of low concentration
  2. occurs down a concentration gradients
  3. result= equilibrium
  4. simple diffusion
    1. molecules pass through the phospholipid bilayer
    2. polar moleculars or ions cannot pass through the bilayer
      1. or large molecules
    3. can get through...
      1. O2
      2. CO2
      3. lipid soluble molecules
        oestrogen
        testosterone
  5. facilitated diffusion
    1. protein molecules exists in membranes to facilitate diffusion
      1. channel protein
        transmembrance protein forms tunnel through bilayer
        Na+ Cl- K+
      2. carrier protein
        change shape to help molecules move in and out cells
        amino acids glucose
  6. factors effecting diffusion
    1. concentration gradients
    2. temperature
    3. surface area
2. active transport
  1. energy from respiration in the form ATP
  2. makes carrier proteins change shape
  3. reabsorption in kidneys
  4. digestion in gut
  5. loads sugar in to phloem
  6. inorganic ion uptake in root hairs
3. osmosis
  1. high water potential to low water potnetial
  2. measured in KPA
    1. pure water has 0KPA
      1. highest water potential
        hypotonic
        high WP low solute concentration
        hypertonic
        low WP high solute concentration
        isotonic
        equal [otential
        turgid
        plant cell where cell membrane exerts pressure on the cell wall
        plasmolysed
        cell membrane shrunk away from cell wall

Medienanhänge

7fb3a0b8-c3fa-40ba-ab35-70dd9e38ce27 (image/png)

Nächster

Cell membranes

Beschreibung

Zusammenfassung der Ressource

Medienanhänge

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	Erstellt von Katie Hughes vor mehr als 7 Jahre