Cell membranes Flashcards

1
Q

function of membrane proteins

A

Signaling, protection, structure and movement, transport and general homeostasis

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2
Q

3 components of a lipid (glycerophosholipids)

A
  1. fatty acid tail
    - ~16-18 carbon (even #), unbranched, saturated or unsaturated
  2. glycerol backbone
    - ester linkage to fatty acid tails
  3. phosphate head
    -“R” is linked (ester) to another molecule
    -choline, ethanol amine, glycerol, inositol, serine

i.e. phosphatidylcholine (PC) and phosphatidylethanolamine (PE)

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3
Q

what is cholesterol? where is it found? what does it do to cell membranes?

A

-type of steroid
-intercalates between phospholipid with the OH- closest to the aqueous interface
-small amounts = decrease fluidity, “Stiff”
-large amounts= increase fluidity, interfere with interactions between lipid tails

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4
Q

sphingolipids; components; cellular function, what structure it contributes to

A

-sphingosine backbone, NOT glycerol like other lipids therefore membrane fluidity is decreased
-sugar residues with many functions
–> cellular functioning: form lipid rafts and myelin
–> contribute to glycocalyx which signal to other cells

“Sphingosine is formed by an amino alcohol head group, with two hydroxyls, and one amino group attached to a long unsaturated hydrocarbon chain of typically 18 carbon atoms”

in sphingolipids the glycerol component is replaced by a long-chain amino alcohol known as sphingosine, which is amide-linked to a fatty acid and phosphate group

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5
Q

types of sphingolipids

A

ceramide
sphingomyelin
cerebroside
ganglioside

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6
Q

what is the bond between a fatty acid tail and the glycerol backbone

A

ester linkage

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7
Q

what can sphingolipids form?

A

lipid rafts and myelin

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8
Q

what is a glycocalyx

A

-glycocalyx signal to other cells
-they are proteins (glycoproteins) and lipids that are bound to carbohydrates that vary in size
-outer leaflet of the cell; protect structure and singaling functions
-sphingolipids contribute to them

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9
Q

membrane lipids characteristics

A

-amphipathic- micelle or phospholipid bilayer
–> both thermodynamically favourable (i.e. hydrophilic head in aqueous environment on outside)
-increase [ ] of phospholipids then bilayer formation more favourable then micelles

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10
Q

what membrane lipids inside the cell dont need to do

A

-membrane lipids inside the cell dont need to:
-signal to other cells
-protect cells from harsh environments or microbes
-form a glyocalyx
–> therefore dont need sphingolipids
-less cholesterol in membrane of organelles
–> Golgi or smooth ER might have more cholesterol and sphingolipids because they are made or modified there

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11
Q

diffusion

A

diffusion: high to low [ ], spread out molecules; spontaneous (Gibbs)

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12
Q

osmosis

A

osmosis: water diffuses through semi-permeable membrane (allows water to pass through, but is impermeable to at least 1 solute)

i.e. if add sugar to a semipermeable system then water will go to where sugar [ ] is higher to balance it out

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13
Q

what are membrane lipids a barrier to?

A

-charged and polar molecules
-medium and large non polar molecules

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14
Q

integrity of membrane via membrane lipids

A

-ionic and fluid homeostasis, cell movement, and shape
-less integrity = threaten cell survival

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15
Q

membrane permeability and concentration gradients and osmosis

A

-cell membranes are semi-permeable
-aquaporins in plasma membrane –> high water conductance
-membranes impermeable to larger solutes
-interior of cell has high [ ] of large solutes therefore must expend energy to regulate solute concentration and cell volume
–> concentration gradients

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