Cell Membrane Structure

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  • Created by: samya_
  • Created on: 09-12-17 21:17
What are Cell-surface Membranes?
* barrier between the cell and its environment * partially permeable
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What is an Organelle Membrane?
Membranes around organelles that act as barriers between the organelle and the cytoplasm
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What was the Fluid Mosaic Structure?
Created 1972, MODEL suggested to describe the arrangement of molecules in the membrane
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Describe the "Fluid Mosaic" model?
*Phospholipid molecules form a bilayer *Bilayer is fluid since the phospholipids are constantly moving
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What do Cell Membranes Include?
* proteins scattered around like "tiles in mosaic" *e.g. Channel + Carrier Proteins * Receptor proteins
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What do Receptor Proteins on cell-surface membrane do?
Allow the cell to detect chemicals released from other cells. Chemical signals the cell to respond in some way
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What are some Proteins + Lipids like?
* Some Proteins able to move sideways through bilayer, while others are in a fixed position * some Proteins have polysaccharide chain attached( glycoproteins) *some lipids also have this polysaccharide chain attached (glycolipids)
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What do Channel and Carrier proteins do?
allow large molecules and ions to pass throught the membrane
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Describe Structure of Phospholipid Molecule?
Have Head And Tail *Head is hydrophilic( attracts water) * Tail is hydrophobic( repels water)
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How do Phospholipids Form a Barrier to Dissolved Substances?
* Molecules automatically arrange themselves into a bilayer ** Center of bilayer is hydrophobic so membrane doesn't allow water-soluble substances (like ions) through it therefore acts as barrier to dissolved substances
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What is cholesterol?
* Lipid * Present in all cell membranes( except bacterial celll membranes)
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How does cholesterol give the membrane stability?
* Cholesterol molecules fit between the phospholipids. Bind to the hydrophobic phospholipid tails, causing them to pack more closely together. Thus restricts movement of phospholipids. * Making membrane less fluid and more rigid
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How to Investigate the permeability of Cell Membrane in a Lab?
Beetroot= leaking coloured Pigment 1) use scalpel to cut 5 equal pieces, rinse to remove pig 2)add to diff texts tubes contains 5cm^3 water 3) place in diff water baths 10-40 Celsius 4) remove pieces leave water 5) Use colorimeter, the connect
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Increasing Temperature increases membrane permeability : Below 0 degree Celsius?
*Phospholipids don't have much energy so can't move much, packed closely, membrane rigid * channel+ Carrier Proteins deform * Thus increases permeability and no control of substance in and out * ICE CRYSTALS MAY FORM AND PIERCE MEMBRANE
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What is a Colorimeter?
Machine that passes light through liquid and measure how much light is absorbed. **HIGHER THE ABSORBANCE, THE MORE PIGMENT ABSORBED, THUS HUGHER PERMEABILITY OF MEMBRANE
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Increasing Temperature increases membrane permeability : Between 0 - 45 degree Celsius
* Phospholipids can move, not tightly packed * membrane partially permeable * As temp increases Phospholipids move more since have more energy thus increases membrane permeability
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Increasing Temperature increases membrane permeability : Above 45 degree Celsius?
* Phospholipd Bilayer starts to melt and membrane becomes more permeable * water inside cell expands putting pressure on membrane * Channel+ Carrier Proteins deform , so no control * increases permeability
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What is the Effect of Solvents on the Permeability of Cell Membranes?
* Surrounding cells in an increasing conc of a solvent (alcohol/acetone) Increases memb permeability because solvent dissolves the lipids in cell membrane, causing it to lose Structure
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WHAT IS ADVANTAGE OF SOMETHING INSOLUBLE⁉️
⭕️ IF INSOLUBLE DOSENT AFFECT WATER POTENTIAL ⭕️ REDUCES OSMOSIS
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What is Tissue Fluid?
The environment around the cells of a multicellular organism
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How do you calculate the Surface Area to Volume ratio?
SA: 4 pie r squared Volume: 4/3 pie r cubed
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What are the 5 features of specialised exchange surfaces?
1) large SA to VOL ratio of the organism thus increases rate of exchange 2) Very Thin so diffusion distance shorter, so materials cross exchange surface rapidly 3) partially permeable 4) Movement of environmental medium AND transport system
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Difference between external and internal cell Membranes?
Internal cell Membranes are ones surrounding organnneles (e.g. Plasma membrane)
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Other cards in this set

Card 2

Front

What is an Organelle Membrane?

Back

Membranes around organelles that act as barriers between the organelle and the cytoplasm

Card 3

Front

What was the Fluid Mosaic Structure?

Back

Preview of the front of card 3

Card 4

Front

Describe the "Fluid Mosaic" model?

Back

Preview of the front of card 4

Card 5

Front

What do Cell Membranes Include?

Back

Preview of the front of card 5
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