Plasma membranes Flashcards

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1
Q

True or False.
Plasma membranes only surround cells.

A
  • False.
  • Plasma membranes also surround membrane- bound organelles (ie. mitochondria/ nucleus.)
    -note: membrane of any organelles of eukaryotes
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2
Q

Why are plasma membranes described as a “fluid mosaic model?”

A
  • Mosaic: due to the mixture of molecules/ proteins found (vary in shape and size. )
  • Fluid: The proteins, phospholipids, glycoproteins, glycolipids can move around.
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3
Q

How are molecules (ie glycoproteins, channel proteins, glycolipids) arranged in the phospholipid bi- layer ? What does this create?

A
  • They are either within or on the outside of the bi- layer.
  • Creates the partially- permeable membrane (only certain molecules can pass through other molecules in bi- layer. )
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4
Q

What does an unsaturated fatty acid chain look like in comparison to a saturated fatty acid?

A
  • It has a kink ( bends) due to the double bond between carbon atoms.
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5
Q

What is the role of cholesterol in plasma membranes?

A
  • Restricts movement of other molecules (making up membrane.)
  • Makes plasma membrane more rigid.
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6
Q

What 4 molecules are found in plasma membranes that can move?

A

1.) Phospholipids
2.) Proteins (ie. channel/ carrier.)
3.) Glycoproteins
4.) Glycolipids.

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7
Q

What are the 2 types of proteins in plasma membranes? What is the difference between the two?

A
  • Intrinsic: proteins that span across from one side of the bi- layer to the other.
  • Extrinsic: Do not extend completely across/ through the membrane.
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8
Q

What are extrinsic proteins used for in the plasma membrane?

A
  • Provide mechanical support or they are connected to proteins or lipids to make glycoproteins/ glycolipids.
  • Function of glycoproteins/ glycolipids —> cell recognition (ie. receptors. )
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9
Q

In what case is it useful for cholesterol to make plasma membranes more rigid/ less fluid?

A
  • Useful: makes membrane less fluid at high temperatures and prevents water/ dissolved ions from leaking out of the cell (could cause dehydration/ cells bursting.

(more fluid membrane is = more gaps in membrane.)
() - extra info for clarification.

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10
Q

What are intrinsic proteins used for in the plasma membrane?

A
  • Protein carriers/ channel proteins involved in transport of molecule across the membrane.
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11
Q

What sort of molecules are transported by channel proteins?

A
  • Water/ amino acids/ potassium/ sodium.
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12
Q

How exactly do carrier proteins transport molecules into the cell?

A
  • Larger molecules will bind to the carrier protein.
  • The carrier protein will change shape to transport molecules to other side of membrane.
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13
Q

What are the molecules that can pass easily through the plasms membrane? Give examples?

A
  • Lipid-soluble substances (ie. hormones.)
  • Non-polar, very small molecules (ie. O₂, CO₂,)
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14
Q

What molecules cannot pass through the plasma membrane by simple diffusion? Give examples?

A
  • Polar molecules (water)
  • And large molecules (glucose.)
  • Water-soluble substances (ie. sodium/ potassium/ amino acids.)
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15
Q

If you have more unstaured fatty acids in a plasma membrane, what does this do to the membrane?

A
  • More unssaturated fatty acids = increase in fluidity/ flexibility/ lower melting point.
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16
Q
A