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Cell Membranes
Fichas del conjunto (36)
- 1What are the roles of the cell surface membrane?1. Permanently excludes certain substances
2. Permanently retains some substances
3. Allows some substance to freely enter and leave cell.
4. Allows some substances to pass freely through membrane at one moment but to prevent on another occasion - 2what are the two types of passage that can occur in a cell?Active
Passive - 3what is the plasma membrane made up of?1. phospholipids
2. cholesterol
3. glycolipids
4. glycoproteins
5. proteins - 4What is a phospholiid?A phospholipid joined with two fatty acid tails
- 5What is Micelle?1. When the phospholipid is shaken in water.
2. When the hydrophillic heads face outwards towards the aqueous solution and the hydrophobic tails face inwards. - 6how wide is a typical membrane?7.5nm
- 7What is the role of microvilli?1.transport of substances
2. Increases the surface area - 8where are microville found?In the small intestine
- 9what is the role of plasmodesmata?so that two cells are able to communicate with each other and past substances between them
- 10what is the role of phospholipids?1. Provides a barrier tp water amd pther polar/ charged molecules/ ions.
2. Helps determine fluidity - 11what is the role of cholesterol?1. reduces the rate that polar molecules diffuse through the membrane
2. increases that stability of the membrane
3. St low temperatures decreases the fluidity, at high temperatures, increases the fluidity. - 12what are Glycoproteins?protein molecules linked to a carbohydrate sugar chain
- 13what are the roles of Glycoproteins/ Glycolipids?1. act as specific recognition and binding for the absorption of molecules by pinocytosis.
2. cell to cell recognition/communication
3. act as antigens for the immune system.
4. Receptors for hormones and neurotransmitters - 14What are the roles of Proteins?1. Form hydrophillic channels to enable polar molecules to pass more rapidly.
2. Substance carriers
3. Structural- reduces membrane fluidity.
4. enzymes
5. Act as electron carriers in photosynthesis and respiration. - 15what are the effects of temperature on cell membranes?Increasing the temperature makes the membrane more permeable.
The molecules have more kinetic energy and vibrate more.
50°C- lipid bilayer will become so fluid= more permeable. - 16What is cell signaling?The transfer of information by chemical signaling molecule from one cell to another.
- 17How does cell communication occur?By:
1. Direct contact
2. nerve impulse
3. Chemical signals - 18what is simple diffusion?The net movement of molecules/ions from a region where they are highly concentrated to a region where they are less concentrated.
- 19what are the factors that increase diffusion?1. High concentration gradient
2. Increase in temperature
3. Large surface area
4. small size of diffusion substance
(fastest when in gases) - 20What is facilitated diffusion?passive transport of molecules or ions across the membrane with the use of channel or carrier proteins.
- 21What is osmosis?The movement of water molecules from a region of high concentration to a region of low concentration through a partially permeable membrane.
- 22What does Turgid mean?When a cell is filled with water so that it is firm
- 23What does Flaccid mean?When a cell has lost turgidity and longer has a pressure potential
- 24What does plasmolysed mean?When the cytoplasm has shrunk away from the cell wall in a plant cell.
- 25What is solute?A substance that is dissolved in another substance = a solution
- 26What is a solvent?A substance in which other substances are dissolved. (e.g. water)
- 27What is water potential?The tendency of water to move from one area to another.
Pure water= 0 Pa - 28What are the characteristics of Active transport?1. requires energy
2. Involves large membrane carrier proteins
3. enables molecules/ ions to be moved against their concentration gradient. - 29What is primary pumping?When the energy is directly involved in movement of ions across the membrane.
- 30What are sodium ion pumps and Calcium ion pumps used for in primary pumping?Sodium ion pumps Na+ out of animal cell= prevents them bursting
Calcium ions pumps are needed for muscles and nerves to function - 31What is secondary pumping?Energy is not directly involved in movement of a particular substance.
- 32What are the steps of the transport of sucrose into the phloem sieve tubes?H+ is pumped out of a companion cell in phloem by a primary pump using ATP. It returns without the need for ATP, via a second carrier protein bringing then sucrose with it.
- 33What is the evidence for active transport?1. substances move against concentration gradient.
2. If cyanide is added, it stops respiration, and therefore stops active transport. - 34What are the sub categories in Bulk transport?Endocytosis
Exocytosis - 35What is Endocytosis?Transport of materials into the cell.
1. Phagocytosis- solids
2. Pinocytosis- liquids - 36What is Exocytosis?Transport of material out of the cell.
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- A Levels (F211) Biology Fichas sobre Cell Membranes, creado por megan.radcliffe16 el 23/11/2014.
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- megan.radcliffe16
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