Core Concepts; Cell Membranes and Transport
- Created by: Former Member
- Created on: 22-11-16 09:38
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- Cell Membranes & Transport
- Membrane Structure
- Phospholipids
- form bilayers, hydrophiliic heads out & hydrophobic tails in
- allow lipo-soluble molecules across
- Proteins
- extrinsic; on surface of membrane, provide support & form receptor sites
- intrinsic: across the mebrane as transport protiens; carrier or channel
- Cholesterol
- makes more rigid & stable
- Gylcoproteins/lipids
- hormone receptors, cell to cell recognition
- Fluid Mosaic
- Fluid= proteins & phospholipids can move
- Mosaic = proteins vary in size & shape
- Phospholipids
- Transport
- Facilitated Diffusion
- ions & charged particles through transport proteins
- passive as down gradient
- Diffusion
- passive as down gradient
- affected by gradient, travel distance, surface area
- Active transport
- active as moves up gradient so requires energy
- molecule enters carrier protein, phosphate group of ATP changes protein shape so molecule moves across & exits protein
- Co-transport
- brings molecules & ions in on same protein
- e.g. sodium & glucose
- Bulk transport
- Endocytosis
- material entering cell as engulfed by plasma & cytoplasm extension
- phagocytosis: large solid fuse with lysosomes which digest molecuke
- Pinocytosis: uptake of liquid
- Endocytosis
- Facilitated Diffusion
- Osmosis
- movement of water down conc gradient through partially permeable membrane
- Water Potential
- measure of water's free energy & tendency to move
- the more negative the WP, the more likely water will move there
- solutes decrease WP
- Solute Potential
- measures how easily water molecules move out of solution
- Plant Cells
- have pressure potential which is pressure when water enters & pushes cytoplasm against wall
- hypOtonic solution
- WP higher outside than in so water flows in cell
- cell becomes turgid
- hypERtonic solution
- WP lower outside than in so water flows out
- cytoplasm pulls away from wall (plasmolysis), cell is flaccid
- Isotonic solution
- Wp is equal so no net movement
- Animal Cells
- don't have cell walls so no pressure potential
- water enters but cell bursts if too full, haemolysis
- becomes crenated when water leaves
- Membrane Structure
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