2.1.5 Biological Membranes Flashcards

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1
Q

what are the membranes like between the cell and its environment?

A
  • partially permeable
  • plasma membrane allows transfer of substances in and out of the cell
  • e.g water, ions
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2
Q

what is the role of the membrane between organelles and cytoplasm?

A
  • compartmentalisation
  • in a lysozome, the hydrolytic enzymes need to be kept seperate from other organelles
  • controls what enters and leaves organelle
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3
Q

what is the role of membranes within organelles?

A
  • allows for concentration gradients to be created
  • site of attatchment of enzymes into the membrane
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4
Q

what are the other roles of membranes inside a cell?

A
  • sites of chemical reactions
  • sites of cell communication
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5
Q

what happens in cell communication?

A
  • communication between cells
  • cell identification
  • cells working together
  • to trigger a response
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6
Q

why do phospholipids arrange themselves in a bilayer at the cell surface?

A
  • hydrophilic heads orientate towards water and form hydrogen bonds
  • hydrophobic tails orientate away from water
  • water is present both outside and inside of the cell
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7
Q

what makes up a phospholipid bilayer in a fluid mosaic model?

A
  • glycoproteins and glycolipids
  • proteins
  • cholesterol
  • phospholipids
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8
Q

what is the function of glycolipids/glycoproteins?

A
  • cell recognition
  • cell signalling
  • acts as antigens
  • acts as receptors
  • involved in cell adhesion (cells bind together)
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9
Q

what do carrier proteins do?

A

transports large and polar substances

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10
Q

what do channel proteins do?

A

transports polar substances

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11
Q

where is cholesterol found in the model and what does it do?

A
  • found between the tails of the phospholipid
  • it regulates fluidity of the membrane
  • more cholesterol = less fluid
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12
Q

what factors affect membrane permeability?

A
  • temperature
  • solvent
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13
Q

what happens to permeability when you increase temperature?

A
  • phospholipids gain kinetic energy
  • causes gaps to appear between phospholipids
  • membrane becomes more permeable
  • at high temperatures, the proteins will denature
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14
Q

what happens to the permeability when temp decreases and water freezes?

A
  • water expands and forms ice crystals
  • break and pierce cell membrane making it more permeable
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15
Q

what is diffusion?

A

the net movement of molecules down a concentration gradient until equilibrium is reached

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16
Q

what factors affect the rate of diffusion?

A
  1. temperature
    —> higher temperature = more KE so particles move faster
  2. thick membrane
    —> thicker membrane = more distance so slower rate of diffusion
  3. surface area
    —> larger SA = faster rate of diffusion
  4. conc gradient
    —> higher conc gradient = faster rate of diffusion
17
Q

what is facilitated diffusion?

A

using carrier or channel proteins for diffusion

18
Q

how do carrier proteins work in diffusion?

A
  1. large molecule attaches to carrier proteins
  2. protein changes shape
  3. releases molecule on the other side of the
19
Q

how do channel proteins help in facilitated diffusion?

A

form pores for charged particles to diffuse through