Transport across membrane Flashcards

1
Q

Describe the fluid mosaic model of membranes

A

Fluid:Phospholipid bilayer in which individual phospholipids can move=membrane has flexible shape
Mosaic:Extrinsic and intrisinic proteins of different size and shapes are embedded

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2
Q

Explain the role of chloestrol and glycolipids in membranes

A

Chloesterol:Steriod molecule in some plasma membranes;connects phospholipids and reduces fludity to make bilayer more stable
Glycolipids:Cell signalling and cell recognition

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3
Q

Explain the functions of extrinsic and transmembrane proteins in membranes

A

Exteinsic:
* binding sites/receptors e.g for hormones
* Antigens (glycoproteins)
* binds cells together
* involved in cell signalling

Intrinsic:
* electron carriers (respiration/photosynthesis)
* channel proteins (facilitated diffusion)
* carrier proteins (facilitated diffusion/ active transport)

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4
Q

Explain the functions of membranes within cells

A
  • provide internal transport system
  • selectively permeable to regulate passage of molecules into/out of organelles
  • provide reaction surface
  • isolate organelles from cytoplasm for specific metabolic reactions
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5
Q

Explain the functions of the cell surface membrane

A

isolates cytoplasm from extracellular enviroment
selectively permeable to regulate transport of substances
involved in cell signalling recognition

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6
Q

Name 3 factors that affect membrane permeability

A
  • temperature: high temperature dentaures membrane proteins/phospholipid molecules have more kinetic energy and move further apart
  • Ph: changes tertiary structure of membrane proteins
  • use of a solvent: may dissolve membrane
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7
Q

Outline how Colorimetery can be used to investigate membrane permeability

A
  1. Use Plant tissue with soluble pigement in vacuole. Tonoplast and cell surface membrane disrubted= increase permeability =pigment diffuses into solution
  2. select colorimeter filter with complementary colour
  3. use distilled water to set colirmeter to 0. measure absorbance/ % transmission value of solution.
  4. High absorbance/lowtransmission =more pigment in solution
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8
Q

Define Osmosis

A

Transport of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential until a dynamic equilibrium is established

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9
Q

How does Osmosis affect plant and animal cells

A
  • Osmosis into cell Plant protoplast swells=cells turgid
    animal: lysis (breaking of cellmembrane release of cellular components)
  • Osmosis out of cell: Plant:protoplast shrinks=cell flaccid
  • animal:crenation (shrinkage of cell causing it to wrinkle and condense)
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10
Q

Define simple diffusion

A

Net movement of small lipid-soluble molecules directly through the bilayer from an area of high concentration to an area of lower concentration (down conc gradient)

Passive process requires no energy from ATP hydrolysis

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11
Q

Define Facilitated Diffusion

A

Specific channel or carrier proteins with complementary binding sites transport large and polar molecules/ions down concentration gradient

Passive process:requires no ATP

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12
Q

Explain how channel and carrier proteins work

A

channel:Hydrophillic channels bind to specific ions=one side of protein closes and the other opens

Carrier:Binds to complementary molecule=conformational change releases molecule on other side of membrane
(in fd passive ) (in at requires atp hydrolysis)

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13
Q

5 Factors that affect rate of diffusion

A
  • temperature
  • diffusion distance
  • surface area
  • size of molecule
  • difference in conc gradient (how steep conc gradient is)
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14
Q

State Ficks Law

A

Surface area xdifference in conc/diffusion distance

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15
Q

How cells adapted to maxmise the rate of transport across their membranes

A
  • mny carrier proteins/channel proteins
  • folded membrane increase surface area
  • lots of mitrochondria for energy release atp hydrolyisis
  • micro villi
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16
Q

Explain the difference between the shape of graph of concentration (x-axis) against rate (y-axis) for simple vs facilitated diffusion

A
  • Simple diffusion:straight diagonal line; rate of diffusion increases proportionally as conc increases
  • Facilitated diffusion: Straight diagonal line later levels of when all channel/carrier proteins are saturated
17
Q

Define active transport

A

Active Process ATP hydrolysis releases phosphate groups that bind to carrier protein causing it to change shape

Specific carrier protein transports molecules/ions from area of low conc to an area of high conc (against conc gradient)

18
Q

Define Co-transport

A

Movement of a substance against its conc gradient is coupled with movement of another substance down its conc/electro chemical gradient

Substances bind to complementary intrinsic protein:symport transports in same direction antiport: transports substances in opposite direction e.g sodium ppotassium pump

19
Q

Describe how co-transport is involved in the absoptioon of glucose/amino acids in the small intestine

A
  1. Na+ transported out of epithelial cells and into the blood stream
  2. Na+ concentration is lower in epithelial cells than lumen of gut
  3. transport of glucose/amino acids from lumen to epithelial cells is ‘couples’ to facilitated diffusion of Na+ down electrochemical gradient