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BIOLOGY 130 > Unit 6 - Biological Membrane > Flashcards

Unit 6 - Biological Membrane Flashcards

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1
Q

Membrane Functions

A
  1. Provides selectively permeable barrier
  2. Transports solutes
  3. Responds to external signals
  4. Energy Transduction
  5. Compartmentalization
  6. Scaffold for biochem. activities
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2
Q

Membrane Phospholipids

A
  • polar head group
  • phosphate group
  • glycerol
  • fatty acid chains/tails
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3
Q

Amphipathic

A

-molecule with both hydrophobic & hydrophilic parts

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4
Q

Movement of Phospholipids within Membrane

A
  • constantly moving
  • spinning in place
  • travelling laterally within leaflet
  • occasionally ‘flipped’ to opposite leaflet during membrane synthesis
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5
Q

Membrane Fluidity

A

-how easily lipid molecules move rotationally and laterally within a membrane leaflet

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6
Q

Membrane Fluidity is affected by…

A
  1. Temperature

2. Changes in lipid composition which affects alignment of phospholipid tails

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7
Q

Transition Temperature (Tm)

A
  • temp. at which membrane transitions between fluid and gel phase
  • above Tm –> membrane ‘melts’
  • below Tm –> membrane gels, incompatible with life
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8
Q

Tm is affected by

A
  1. altering length of fatty acid chains: longer chains –> less fluid
  2. altering degree of saturation of fatty acids: more double bonds –> more fluid
  3. altering amount of sterol: cholesterol acts as ‘buffer’, inhibits phase transitions when temp. changes
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9
Q

Homeo-viscous Adaptation

A

-maintaining membrane fluidity at temps low enough to cause membrane to enter gel phase, through altering the membrane lipid composition

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10
Q

Low Temperatures

A

-enzymes which cut fatty acid chain length

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11
Q

Difference between Membrane phospholipids in eukaryotic cells & archaebacteria

A
  1. Eukaryotic: fatty acid chains ester-linked to D-glycerol

2. Archaebacteria: fatty acid chains ether-linked to L-glycerol

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12
Q

Role of ER in Membrane Assembly

A
  1. Free fatty acids in cytosol are catalyzed by enzymes bound to cytosolic side of ER
  2. new phospholipids added to cytosolic side
  3. Scramblases transfers random phospholipids to other leaflet
  4. membrans with ‘scrambled’ phospholipids emerge from ER
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13
Q

Role of Golgi in MA

A
  1. Membranes with evenly distributed phospholipids arrive from ER
  2. Flippases move PS and PE to cytosolic leaftlet
  3. membrane asymmetry maintained from this point on
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14
Q

Why is the Human RBC a Model Organism for the plasma membrane?

A
  • best understood plasma membrane
  • cells inexpensive and available in large numbers
  • already present in single-cell suspension
  • simple, pure preps of plasma membrane
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15
Q

Types of Membrane Proteins (TARE)

A
  1. Transport
  2. Anchors
  3. Receptors
  4. Enzymes
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16
Q

polypeptide chains usually cross as…

A

alpha helices

17
Q

hydrophilic channels are formed via…

A

several alpha helices

18
Q

proteins folded into pleated sheets can form…

A

pores!!

19
Q

Diffusion

A
  • dissolved solutes in constant, random motion
  • solutes ‘spread out’ until conc. in all regions are equal
  • water moves down concentration gradient, if solute cannot move, water will move to even out solute conc.
20
Q

Osmosis

A
  • diffusion of water across semi-permeable membrane down conc. gradient
  • once water conc. equal on both sides, no net movement of water
21
Q

Hypotonic Solution

A
  • net water gain
  • cell swells
  • Animal: bursts (lyses)
  • Plant: normal state, turgid
22
Q

Isotonic Solution

A
  • no net loss or gain
  • Animal: normal state
  • Plant: shrivels
23
Q

Hypertonic Solution

A
  • net water loss
  • cell shrinks
  • Animal: shrivels
  • Plant: plasmolysis
24
Q

Osmoconformers

A

-adjustment of internal salt conc. to match seawater/outside environement

25
Q

Osmoregulators

A

-single-celled eukaryotes have contractile vacuoles that periodically pump out water

26
Q

Turgor

A

-water pulled into cell, presses membrane out to cell wall

27
Q

Order to Molecules’ ability to pass directly through membranes?

A
  1. O2,CO2,N2, steroid hormones
  2. H20, ethanol, glycerol
  3. amino acids, glucose, nucleosides
  4. ions
28
Q

Ion Channel Functions

A
  • allow movement of ions down conc. gradient

- critical in many cell activities

29
Q

Ion Channel Features

A
  • discriminate on both charge and size
  • usually highly selective
  • much faster than carriers
  • bidirectional
  • electrochemical gradient
30
Q

What determines whether channels are open or closed?

A
  1. Voltage
  2. Ligand (extracellular/intracellular)
  3. mechanical
31
Q

Carrier Proteins

A
  • mediate facilitated diffusion
  • binding solute at specific site
  • solute moves down conc. gradient
32
Q

GLUT1

A

-gluose transporter on mammalian cells

33
Q

Features of Membrane Carrier Proteins

A
  1. Specificity
  2. Passive
  3. Saturable
  4. Can be inhibited/blocked
34
Q

Active Transport

A
  • transport against a gradient
  • using energy (directly/indirectly) to move ions
  • transport closely coupled to hydrolysis of ATP, absorption of light, and movement of electrons
35
Q

Sodium-Potassium ATPase

A
  • first pump discovered
  • only present in animal cells
  • move 3 NA+ out for every 2 K+ in
  • coupled to hydrolysis of ATP
36
Q

Hydrogen-Potassium ATPase

A
  • on parietal cells lining stomach

- enables cells to secrete high conc. of H+

37
Q

Coupled Transport

A
  • membrane carrier proteins use driving force of ion moving down conc. gradient to move a solute across membrane against solute gradient
  • indirect active transport

BIOLOGY 130 (11 decks)

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