4.1 Cell-surface Membrane Structure Flashcards

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1
Q

How is the cell membrane partially permeable?

A
  • membranes control which substances enter and leave
  • let some molecules through but not others
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2
Q

What are the 3 ways substances can move across a cell-surface membrane?

A
  • diffusion
  • osmosis
  • active transport
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3
Q

Why is the structure of a cell membrane ‘fluid mosaic’?

A
  • bilayer made of constantly moving phospholipids =
    fluid
  • different components in a membrane = mosaic
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4
Q

What are the 4 types of molecules in a cell-surface membrane?

A
  1. phospholipids
  2. cholesterol
  3. proteins
  4. carbohydrates (attached to proteins or lipids)
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5
Q

What is the role of channel and carrier proteins in the bilayer

A
  • allow large molecules and ions to pass through the membrane
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6
Q

What is the role of receptor proteins in the membrane?

A
  • allows the cell to detect chemicals released from other cells
  • the chemicals signal to the cell to respond in some way
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7
Q

What are glycoproteins?

A
  • proteins with a polysaccharide chain
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8
Q

What are glycolipids?

A
  • lipids with a polysaccharide chain
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9
Q

Describe the role of phospholipids in the membrane

A
  • automatically arrange themselves in the bilayer with hydrophilic heads facing out to the water on either side of membrane
  • centre of bilayer is hydrophobic so membrane doesn’t allow water-soluble substances (ions) to enter
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10
Q

Describe the role of cholesterol in the membrane

A
  • type of lipid that is present in all cell membranes except bacteria
  • bind to the hydrophobic tails of phospholipids making membrane less rigid and more fluid
  • helps maintain the shape of cells especially those that aren’t supported by other cells
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11
Q

How does temperature below 0° affect membrane permeability?

A
  • phospholipids don’t have much energy so they can’t move
  • channel and carrier proteins deform and increase permeability
  • ice crystal may form and burst membranes
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12
Q

How does temperature between 0° and 45° affect membrane permeability?

A
  • phospholipids can move around and aren’t packed as tightly together = partially permeable membrane
  • increase temp = increase energy of molecules = increase permeability
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13
Q

How does temperature above 45° affect membrane permeability?

A
  • phospholipid bilayer starts to melt and membrane becomes more permeable
  • water inside the cell expands = increase pressure
  • channel and carrier proteins deform so they can’t control what enters the permeability of the membrane
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