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BCH 4024 Exam 2 > Lecture 17- Membranes and Membrane Proteins > Flashcards

Lecture 17- Membranes and Membrane Proteins Flashcards

1
Q

Membrane dynamic State?

  • Below Tm (<– ?)
  • Noncovalent interactions lock lipids into a semisolid gel phase
  • Motion of individual lipids is limited
A

Liquid-ordered state (Lo)

Tm: Melting Temperature- switch/transition bw ordered & disordered state

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2
Q

Membrane Dynamic State?

  • Above Tm
  • Lipids are fluid w/ rapid motion in the plane of the membrane
  • More motion w/in lipid interior
A

Liquid-disordered state (Ld)

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3
Q

Why is lipid membrane composition regulated and how?

A

To keep the transition/Tm BELOW the body temp of the organism

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4
Q

Why must the lipid composition of membranes adjust?

A

To maintain membrane fluidity (Remember: Tm is transition state bw Lo and Ld)

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5
Q

___________ fatty acids (FA) = high Tm

___________ FA = decreased Tm

A

Saturated FA = high Tm

Mixture of saturated & unsaturated FA = decreased Tm

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6
Q

Fluidity is affected by?

  1. ?
  2. ?
  3. ?
A

Fluidity is affected by?

  1. Temperature
  2. FA content
  3. Sterol Content
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7
Q

What is the process that maintains the same membrane fluidity even when external temp changes?

A

Bacterial Adaptation

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8
Q

What maintains membrane fluidity over a broader range of lipid composition?

A

Cholesterol

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9
Q

Cholesterol interacts w/ phospholipids w/ unsaturated fatty acyl chains that have a ______ Tm which will _______ the Tm and cause them to _______ to drive them to a more ________ state.

A

Cholesterol interacts w/ phospholipids w/ unsaturated fatty acyl chains that have a lower Tm which will increase the Tm and cause them to compact to drive them to a more ordered state.

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10
Q

Cholesterol interacts w/ phospholipids w/ saturated fatty acyl chains that have a ______ Tm will _______ the Tm and cause them to become more _______ to drive them to a more ________ state.

A

Cholesterol interacts w/ phospholipids w/ saturated fatty acyl chains that have a higher Tm which will decrease the Tm and cause them to become more fluid to drive them to a more disordered state.

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11
Q

Lipid Movement in the Bilayer:

  • Lateral diffusion in the _____ of the bilayer occurs very rapidly
A

Lateral diffusion in the plane of the bilayer occurs very rapidly

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12
Q

Lipid Movement in the Bilayer:

  • ___________ movement req’s a charged _____ group to leave the _________ environment and move into the ___________ interior of the bilayer
  • What type of change is required for movement to proceed?
A
  • Transbilayer movement req’s a charged head group to leave the aqueous environment and move into the hydrophobic interior of the bilayer
  • Large (+) free energy change input required
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13
Q

Asymmetric distribution of lipids predicts the existence of enzymes that catalyze ____-____ _________.

A

Asymmetric distribution of lipids predicts the existence of enzymes that catalyze flip-flop diffusion.

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14
Q

What regulates lipid movement between leaflets?

A

Membrane Proteins

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15
Q

What type of catalyzed transbilayer translocation occurs w/ ATP and involves the movement of a lipid from the outer leaflet to the cytosilic interior leaflet?

A

Flippase

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16
Q

What type of catalyzed transbilayer translocation occurs w/ ATP and involves the movement of a phospholipids from the cytosilic interior leaflet to the outer leaflet?

A

Floppase

17
Q

What type of catalyzed transbilayer translocation is an exchange that moves a lipid from the outer leaflet to the inner leaflet and a lipid from the inner leaflet to the outer leaflet towards equilibrium?

A

Scramblase

18
Q

What are membrane microdomains enriched w/ cholesterol and sphingolipids in the outer leaflet?

Microdomains are slightly thicker and have a more ___ state.

A

Lipid Rafts

Lo

19
Q

What are lipid rafts rich in and where does the cholesterol fill up? (2 locations)

A

GPI proteins

  1. Under the head group of sphingolipids
  2. Crowds around the fatty acyl chains in the apposing leaflet
20
Q

What requires changes in membrane curvature and results in the fusion of 2 membranes without losing membrane continuity?

A

Membrane reorganization

21
Q

Membrane Fusion during NT Release at a Synapse:

  1. ________ ________ loaded w/ __, approaches plasma membrane
  2. _& _-snares bind to ____ _____, zip up into ______ from ______ terminal
  3. ________ & _________ bilayers draw together and _______ initiates
  4. Complete fusion results in ___ released into ________ cleft.
A

Membrane Fusion during NT Release at a Synapse:

  1. Synaptic vesicle loaded w/ NT, approaches plasma membrane
  2. V& T-snares bind to each other, zip up into helices from amino terminal
  3. Vesicle & membrane bilayers draw together and fusion initiates
  4. Complete fusion results in NT released into synaptic cleft.
22
Q
A
23
Q

Transport across intact membranes:

  • ________ ________ leads to electro-chemical gradient.
  • A few ________ compounds (__,___) can dissolve in the lipid bilayer and cross the membrane unassisted.
  • For transmembrane transport of any _____ compound/ion a _______ _______ is reqd.
  • Direction of transport determined by?
  • Transport against a gradient requires? (2)
    • Happens spontaneously (?) or gated (? ?)
A

Transport across intact membranes:

  • Membrane barrier leads to electro-chemical gradient.
  • A few nonpolar compounds (O2,CO2) can dissolve in the lipid bilayer and cross the membrane unassisted.
  • For transmembrane transport of any polar compound/ion a membrane protein is reqd.
  • Direction of transport determined by electrochemical gradient for diffusion.
  • Transport against a gradient requires either energy or ion exchange down a gradient (active transport)
    • Happens spontaneously (porins) or gated (ion channels)
24
Q

Chemical Gradients

  • Net movement of an electrically ______ solute is toward the side of _______ concentration.
  • Rate of movement is __________ to concentration ratio (C2/C1)
A
  • Net movement of an electrically neutral solute is toward the side of lower concentration.
  • Rate of movement is proportional to concentration ratio (C2/C1)
25
Q

Electrochemical Gradients

  • Net movement of an electrically _______ solute is dictated by a combo of 1.) The _______ gradient or membrane _________ (Vm) and 2.) The _____ of the chemical concentrations (C2/C1)
  • Ions will move ______ the membrane until the electrochemical potential reaches _____
A
  • Net movement of an electrically charged solute is dictated by a combo of 1.) The electrical gradient or membrane potential (Vm) and 2.) The ratio of the chemical concentrations (C2/C1)
  • Ions will move across the membrane until the electrochemical potential reaches zero
26
Q

Energetics of Transport Across Membranes

  • ​_______ lower the barrier (energy of activation for diffusion)
    • _______ of water (________ ______)- protein forms ___________ interactions w/ dehydrated solute to replace __-bonding with ______
    • Movement thru opening in _______
    • Barrier bw ______ and __________ lipids
    • ________ & ________: membrane proteins that speed the movement of a solute across a membrane by facilitating diffusion
A
  • ​Proteins lower the barrier (energy of activation for diffusion)
    • Removal of water (Hydration shell)- protein forms noncovalent interactions w/ dehydrated solute to replace H-bonding with water
    • Movement thru opening in protein
    • Barrier bw solute and hydrophobic lipids
    • Transporters & Channels: membrane proteins that speed the movement of a solute across a membrane by facilitating diffusion
27
Q

Transmembrane Transport: Channel

  • Allow transmembrane transport approaching?
  • Pump functioning and # of gates?
  • Saturable?
A

Transmembrane Transport: Channel

  • Allow transmembrane transport approaching the limit of free diffusion
  • Pump functioning? NO, single gate
  • Saturable? NO, doesn’t obey saturation kinetics
28
Q

Transmembrane Transport: Transporters

  • Bind substarates with?
  • Transport at rates…?
  • Pump functioning and # gates?
  • Saturable?
A
  • Bind substarates with high specificity
  • Transport at rates below that limits of free diffusion
  • Pump functioning? YES, can move a substrate against a gradient (alternating gates)
  • Saturable? Yes, obeys saturation kinetics

BCH 4024 Exam 2 (15 decks)

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