transport membranes

  • Created by: gsemma
  • Created on: 11-01-19 13:22
View mindmap
  • Biological membranes and movement across them
    • membranes
      • role
        • Partially permeable membranes between:
          • cell and environment
          • organelle and cytoplasm
          • within organelle
        • sites of chemical reactions
          • e.g. respiratory enzymes on inner mitochondria membrane
        • sites of cell communication and signalling
      • The fluid mosaic model (add image)
        • built of many components which move relative to each other.
          • Phospholipids
            • form bilayer- allow lipid soluble substances in and out- harder for water-soluble in and out- flexible and self-sealing.
          • Cholestrol
            • regulates membrane fluidity and flexibility- prevents water and ions leaking form cell
          • Protiens
            • complex functions and chemical reactions. regulating across membrane. form channels and carriers.
          • Glycoprotien
            • carbs attached- recognition sites and cell-cell attachment sites (formation of tissue
              • Glycolipids
                • lipids attached- helps stabilise membrane.
      • membrane permeabity
        • molecules that cannot diffuse- too large, not soluble, same charge of channel proteins, polar or other electrical charge.
        • increased temperature has effects which increase fluidity and permeability.
          • phospholipids have more Kinetic energy so move more- fatty acids less compressed- proteins denature reducing ability to control transport.
        • changes in pH affects function and solvents like ethanol will damage membrane by dissolving lipids
    • movement
      • effects of solutions of different water potentials on cells
        • When the water potential outside the cell is higher then inside, the solution is hypotonic- the water moves in via osmosis- lysis may occur in animal cell but plant cells have a cell wall which prevents this.
        • isotonic- conc' is the same inside and out.
        • hypertonic- water pot. is higher inside than out- water moves it- can cause crenation in animal cells and plasmolyis plant cell.
      • Passive transport
        • diffusion
          • movement of molecules or ions form a low to a high area of conc' until equal- dynamic equilibrium
          • rate depends on Surface area, thickness and strength of diffusion gradient.
          • small, non-polar can diffuse through membranes- O2, CO2, steroids and fat-soluble vitamins.
        • osmosis
          • net movement of water molecules form an area of high water potential to low water potential.
          • through partially permeable membrane
          • pure water has a WP of 0 so adding solutes decreases it.
        • Facilitated Diffusion
          • faster than narmal diffusion and use to transport large and polar moleucles like:
            • glucose, fructose, non-fat-soluble vitamins, urea and ions.
          • three steps- 1. molecules binds to carrier protein on cell surface
            • 2. protein changes shape and the molecule is transported through to inside the cell
              • 3. molecule detaches and protein goes back to original shape.
                • alternatively, small polar molecules can diffuse though pores called channel proteins.
                  • the rate of diffusion is proportional to the conc' gradient and number of proteins available.
                    • 3. molecule detaches and protein goes back to original shape.
                      • alternatively, small polar molecules can diffuse though pores called channel proteins.
                        • the rate of diffusion is proportional to the conc' gradient and number of proteins available.
        • co-transport and absorption in the ileum
          • villi and microvilli line the end of the small intestine called the ileum- this provides a much larger surface area for diffusion of digested molecules.
            • as theses are continually being digested, there is  higher conc' in the lumen of gut than blood. diffusion alone would lead to equilibrium.
        • active transport
          • co-transport and absorption in the ileum
            • villi and microvilli line the end of the small intestine called the ileum- this provides a much larger surface area for diffusion of digested molecules.
              • as theses are continually being digested, there is  higher conc' in the lumen of gut than blood. diffusion alone would lead to equilibrium.
          • movement of molecules against the conc' gradient.
            • carrier protein like potassium pumos, use ATP to transport molecules. upon binding a carrier protein undergoes conformational change that pushes the molecules into the cell.
            • bulk transport- large molecules that can't fit through the plasma  membrane.
              • Endocytosis- into cell- cell dimples engulf the substance- the membrane surround the substance forming a vesicle . liquids- pinocytosis.
              • exocytosis- into cell-membrane bound vesicle moves to plasma membrane then fuses to it realising the contents out.

    Comments

    No comments have yet been made

    Similar Biology resources:

    See all Biology resources »See all Cellular processes and structure resources »