Movement of molecules in Cells
- Created by: Zoe
- Created on: 17-05-13 16:54
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- Movement through Cell Membranes
- Diffusion
- movement of molecules from a region of high concentration to a region of low concentration
- Net Movement:
- no overall movement of molecules in one direction
- Rate Factors
- Larger surface area
- Temperature
- thin membrane
- steep concentrationgradient
- small or lipid based molecules through the bilayer
- Facilitated Diffusion
- diffusion of larger, charged molecules which cannot pass through the bilayer.
- Two proteins used
- Carrier Proteins
- shaped so specific molecules fit into them. Protein changes shape when it does, to allow molecule through to other side of membrane
- Channel Proteins: form water filled channels across membrane allowing water soluble ions to pass through
- Carrier Proteins
- Osmosis
- movement of water from a high water potential to a low water potential through a partially permeable membrane
- In Animal Cells
- Cells bathed in tissue fluid to avoid haemolysis
- When water potential is higher
- water enters cell
- In Plant Cells
- Higher Water Potential
- cell becomes turgid from entering water
- Equal water potential
- incipient plasmolysis
- Negative water potential
- cell becomes plasmolysed as water leaves cell.
- Higher Water Potential
- Active Transport
- Movement of molecules from a low to a high concentration using ATP
- Carrier proteins (pumps) are complimentary to molecule they cary
- Carry specific molecules one way using ATP against conc gradient
- One way Flow:
- energy used to pump changes shape of protein so molecule can only fit in one way
- Bulk Transport
- Endocytosis
- bringing materials into the cell
- cytoplasm enclose bacterium, forming a vesicle.
- Exocytosis
- moving material out of cell
- substances are released when vesicular membrane fuses with plasma membrane.
- Endocytosis
- Diffusion
- bringing materials into the cell
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