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Cell membranes + Transport (1.3) - Coggle Diagram
Cell membranes + Transport (1.3)
Membrane structure (Lipid bilayer)
Main function - Controls the movement of substances in and out of cells
Fluid mosaic model
Describes the fluidity
Also describes the mosaic arrangement of the protein
All cells + organelles surrounded by a partially permeable membrane
Composed of a sea of phospholipids with protein molecules between phospholipid molecules
It contains receptors for other molecules (Hormones) and allows adjacent cells to stick together.
Factors affecting the permeability
Heat
Ethanol
pH
Phospholipid molecule
Fatty acid tails
Hydrophobic
Hydrophilic head
Charged, as it is phosphate
Intrinsic proteins
Found across the membrane
Hydrophobic + Hydrophilic parts
Can be channel proteins
Diffusion
High to low concentration, until equilibrium
Occurs in phospholipid bilayer
limited to small, non-polar or lipid-soluble molecules
Oxygen, Carbon dioxide, fat soluble vitamins (A, D, E, K)
Factors affecting diffusion
Surface area
Length of diffusion pathway
Steepness of concentration gradient
Temperature
Membrane permeability
Salt concentration
Detergents
Organic solvents
Passive
Osmosis
High water potential > low water potential
Selective permeable membrane
Passive
If water potential is equal on both sides = no movement
Solute P (-) + Pressure P = Water P (-)
kPa
Hypotonic
Low solute concentration
High water potential
Cells expand + burst
No cell wall
Hypertonic
High solute conc.
Low water potential
Cells shrink
Isotonic
Same solute conc.
Same water potential
Plant cells
Cytoplasm / Vacuole, Shrinks / Expands
Plasmolysis
Plasmolysed
Incipient plasmolysis
50% of cells = plasmolysed
Facilitated Diffusion
Passive
Carrier proteins + channels used
Transports charged particles + polar molecules
Usually too big to cross by simple diffusion
Co-transport
Two different particles through a protein at the same time
Example - Glucose and Na+ transported into cells together
Factors affecting
Number of protein carriers
Temperature
Active transport
Low to high
ATP
Protein carriers
Rate affected by respiration rate