Membranes Flashcards

1
Q

cell membrane: general features

A
  • selectively permeable
  • fluid mosaic
  • protects the cell
  • bind to cytoplasm and extracellular matrix
  • controls content of cytoplasm
  • sense molecules and other cells in the environment
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2
Q

lipids: general features

A
  • diverse class biological molecules
  • don’t mix well with water
  • non polar
  • fats, phospholipids, steroids
  • hydrophobic
  • consist of hydrocarbons
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3
Q

phospholipids: features

A
  • most abundant lipid in plasma membrane
  • amphipathic (has both hydrophobic and hydrophilic regions)
  • 2 fatty acids (tail) + phosphate group attached to glycerol (head)
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4
Q

micelles:

A
  • small objects forming naturally
  • hydrophobic tails point inwards
  • aid in transport and absorption of complex lipids and fat soluble vitamins (vit A)
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5
Q

fluid mosaic model:

A
  • membrane is a fluid structure with mosaic of various proteins embedded in it
  • phospholipids in plasma membrane can move around in bilayer
  • about as fluid as salad oil
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6
Q

significance: cholesterol in warm/cool temps

A
  • controls fluidity of membranes
  • 37˚ restrains movement of phospholipids
  • cool temp: prevents tight packing
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7
Q

Frye and Edidin’s experiment:

A
  • membrane fusion
  • human and mouse membrane proteins labelled with fluorescent antibodies
  • proteins intermixed
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8
Q

carbohydrates found:

A
  • exterior of membrane
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9
Q

significance: ER and Golgi apparatus in building membrane

A
  • determines asymmetrical distribution of proteins, lipids, associated carbohydrates in plasma membrane
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10
Q

molecules which pass through membrane easily:

A
  • gases (CO2, N2, O2)
  • water
  • small, uncharged nonpolar molecules (urea, ethanol)
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11
Q

molecules which pass through membrane difficultly:

A
  • charged polar molecules (amino acids, ATP)
  • ions (K+, Mg2+, Ca2+, HCO3-, H2PO4)
  • large uncharged nonpolar molecules (glucose)
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12
Q

list membrane proteins:

A
  • peripheral
  • integral
  • transmembrane
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13
Q

peripheral protein:

A
  • bound to surface f membrane
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14
Q

integral protein: what type

A
  • penetrate hydrophobic core

- amphipathic

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15
Q

transmembrane protein:

A
  • integral proteins which span membrane
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16
Q

membrane proteins: types

A
  • transport
  • structural
  • enzymes
  • cell-to-cell interaction proteins
  • cell communication
17
Q

hydrophobic domains in transmembrane proteins region of integral protein:

A
  • stabilise it within lipid bilayer
18
Q

list six major functions of membrane proteins:

A
  • transport
  • enzyme activity
  • signal transduction
  • cell-cell recognition
  • intercellular joining
  • attachement to cytoskeleton and extracellular matrix (ECM)
19
Q

osmosis:

A
  • diffusion of water across selectively permeable membrane

- moving from low solute conc. to higher

20
Q

hypotonic:

A
  • lower solute conc. than intracellular fluid

- lysed (burst)

21
Q

isotonic:

A
  • same solute conc. as intracellular fluid
22
Q

hypertonic:

A
  • higher solute conc. compare to intracellular fluid (shrivelled)
23
Q

diffusion:

A
  • small substances spread out evenly into available space
24
Q

facilitated diffusion:

A
  • transport proteins speed up passive movement of molecule across plasma membrane
  • channel proteins (ion channels) open/close responding to stimulus (gated channels)
25
transport protein: and eg.
- allow passage of hydrophilic substances across membrane - channel proteins: tunnel - carrier proteins: bind to molecules and change shape to shuttle them across membrane - specific to substance it moves
26
list types of transport proteins:
- uniport | - co-transport (symport, antiport)
27
uniport:
- single substance moved in single direction
28
co-transport:
symport: 2 different substanced moved together same direction antiport: 2 substances in both directions
29
significance: aquaporins
- normally lipid bilayer blocks/ slows flow of polar molecules (water) - aquaporins membrane channels allow water to cross cell membrane
30
gated channels: trigger eg.
- some need to be triggered - absence of acetylcholine, ion channel is closed - if acetylcholine binds to receptor, channel opens
31
active transport: eg
- requires energy ATP | - sodium potassium pump
32
membrane potential:
- voltage difference across a membrane
33
how is voltage created: and electrochemical gradient
- differences in distribution of positive/negative ions two combined forces drive diffusion of ions across a membrane: - chemical force (ionic conc. gradient) - electrical force (effect of membrane potential on ionic movement)
34
how ion pumps maintain membrane potential:
- electrogenic pump (transport protein) generates voltage across membrane - animal: sodium potassium pump - plants/bacteria/fungi: proton pump
35
sodium potassium pump:
- active transport - 3 sodium leave cell, 2 potassium enter - 3 NA bind to pump (cytoplasmic side) - ATP hydrolysis phosphorylates pump -> releases NA - 2 K bind on extracellular side - phosphate group released -> allow K in