L10- Membrane transport Flashcards

1
Q

What is a membrane?

A

A thin pliable layer of tissue covering surfaces, enveloping a part or separating or connecting structures or organs

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2
Q

What is the structure of membranes?

A
  • Phospholipid bilayer with polar head groups (hydrophilic) and hydrophobic fatty acid tails made of hydrocarbons.
  • Hydrophilic surface and hydrophobic core of bilayer
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3
Q

What are the major lipid components of biological membranes?

A
• Glycerophospholipids
• Sphingolipids
• Glycosphingolipids
• Glycoglycerolipids
All contain glycerol attached to phosphates in head groups and fatty acid tails
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4
Q

What are integral membrane proteins?

A

Largely buried within the membrane but are usually exposed on both faces

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5
Q

What are peripheral membrane proteins?

A

Exposed at only one membrane face

Have oligosaccharides attached to their membrane proteins that project into the aqueous surroundings of the cell

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6
Q

What does it mean if a protein is glycosylated?

A

It means it is found in the membrane (facing out)

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7
Q

What is the fluid mosaic model?

A

Lateral movement within the phospholipid bilayer occurs but diffusion across the membrane is slow

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8
Q

What is the transition temperature of a membrane?

A

The temperature at which a phospholipid bilayer changes from the (solid) gel state to crystalline liquid state

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9
Q

What does the Tm depend on?

A

The nature of the hydrocarbon tails (saturated or unsaturated) and the head groups.
Unsaturated hydrocarbon tails have lower melting points than saturated phospholipid

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10
Q

How can organisms protect membranes from thermal stress?

A

Alteration of membrane lipids to maintain optimal conditions at a given temperature

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11
Q

What are key characteristics of integral membrane proteins?

A
  • High percentage of hydrophobic residues, particularly in parts embedded in membrane
  • Segments of protein that span the membrane are alpha helical
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12
Q

What are the ways in which transport occurs across membranes?

A
  1. Simple diffusion
  2. Carrier-mediated transport
  3. Endo/exocytosis
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13
Q

What are examples of hydrophobic molecules?

A

Easily diffuse through membrane

O2,CO2,N2, benzene

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14
Q

What are examples of small uncharged polar molecules?

A

Mostly diffuse through membrane

H2O, urea, glycerol

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15
Q

What are examples of large uncharged polar molecules?

A

Some diffuse through membrane

Glucose, sucrose

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16
Q

What are examples of ions?

A

Cannot diffuse through membrane

H+, Na+, K+, Ca2+

17
Q

What is the definition of passive diffusion?

A

Random movement of molecules through a semi-permeable membrane from an area of high concentration to low concentration

Rate of transport depends on concentration gradient

18
Q

What is the equation for the rate of passive diffusion?

A

P= KD1/l

J=-P(C2-C1)

19
Q

What is the equation for Gibbs free energy?

A

ΔG= RT ln (C2/C1)

20
Q

What do different values of ΔG mean?

A

C2>C1 means ΔG is negative and the reaction is thermodynamically favourable

C2=C1 means ΔG is zero and the reaction is at equilibrium

C2

21
Q

What are 3 cases where membrane potential will not reach equilibrium?

A
  1. Membrane electrical potential may be maintained across the membrane and influence ion distributions
  2. Coupling transport to a process with negative ΔG
  3. Binding of the substance to a molecule or modification

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