transport membranes
- Created by: gsemma
- Created on: 11-01-19 13:22
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- 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
- Partially permeable membranes between:
- 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.
- Glycolipids
- carbs attached- recognition sites and cell-cell attachment sites (formation of tissue
- Phospholipids
- built of many components which move relative to each other.
- 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
- role
- 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.
- the rate of diffusion is proportional to the conc' gradient and number of proteins available.
- alternatively, small polar molecules can diffuse though pores called channel proteins.
- 3. molecule detaches and protein goes back to original shape.
- the rate of diffusion is proportional to the conc' gradient and number of proteins available.
- alternatively, small polar molecules can diffuse though pores called channel proteins.
- 3. molecule detaches and protein goes back to original shape.
- 2. protein changes shape and the molecule is transported through to inside the cell
- faster than narmal diffusion and use to transport large and polar moleucles like:
- diffusion
- 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.
- 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.
- 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.
- 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.
- 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.
- co-transport and absorption in the ileum
- effects of solutions of different water potentials on cells
- membranes
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