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Year 1 MBChB Principles > Membrane Transport > Flashcards

Membrane Transport Flashcards

1
Q

2 properties that influence whether a particle can permeate a plasma membrane without assistance?

A

Size of the particle

Permeability of the molecule in lipid

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2
Q

What is required for movement across a membrane?

A

A pathway and a driving force

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3
Q

Types of driving forces?

A

Passive

Active- requires cell to expend ATP

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4
Q

What must a substance be, for a membrane to be permeable to it in passive diffusion?

A

Small, lipid soluble molecule

There also must be a concentration gradient

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5
Q

Factors in Fick’s law of diffusion?

A

1) Magnitude of concentration gradient
2) Surface are of membrane across which the diffusion is happening
3) Lipid solubility of the substance
4) Molecular weight of the substance
5) Distance through which diffusion must take place

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6
Q

As molecular weight increases, rate of diffusion..?

A

Decreases

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7
Q

Effect of an Increased concentration gradient on Fick’s law rate of net diffusion?

A

Increases it

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8
Q

Effect of an increased SA of membrane on the rate of net diffusion according to Fick’s Law?

A

Increases it

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9
Q

Effect of Increasing Lipid solubility on rate of net diffusion across a membrane according to Fick’s law?

A

Increases net diffusion

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10
Q

Effect of increasing molecular weight on rate of net diffusion across a membrane according to Fick’s law?

A

Decreases rate

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11
Q

Effect of increasing thickness of membrane on rate of net diffusion according to Fick’s law?

A

Decrease rate

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12
Q 
Symbols for 
Conc gradient 
SA of membrane 
Lipid solubility 
Molecular Weight 
Thickness of membrane
A 
(Triangle )C 
A
B
MW
(Triangle) X
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13
Q

Fick’s Equation

A

Q∝ △C . A . P

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14
Q

Types of ion specific channel proteins?

A

Ligand-Gated or leak

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15
Q

How an Electrochemical Gradient is produced?

A

Difference in charge between two adjacent areas generates an electrical gradient

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16
Q

What does an electrochemical gradient promote?

A

Movement of ions towards areas of opposite charge

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17
Q

Electrochemical Gradient Definition

A

The net effect of electrical and concentration gradients on an ion.

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18
Q

Definition of Diffusion

A

The net diffusion of water down it’s own concentration gradient through a selectively permeable membrane

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19
Q

Where does water move to in osmosis?

A

Area of higher solute concentration

20
Q

Osmolarity

A

Concentration of osmatically active particles present in a solution

21
Q

Tonicity

A

Effect a solution has on cell volume

22
Q

Units of tonicity?

A

NO UNITS

23
Q

Ways to describe a solution

A

Isotonic
Hypertonic
Hypotonic

24
Q

Units of osmolarity?

A

Osmoles of solute per litre (Osm/l)

25
Q

Normal cell volume?

A

Intracellular Fluid= 300mOsm

26
Q

2 different mechanisms for selective transport?

A

Carrier-mediated transport

Vesicular transport

27
Q

Passive transport mechanisms?

A 
Simple diffusion (down a conc gradient)
Movement along electrical gradients (Ion channels)
Osmosis
28
Q

What do all passive transport mechanisms depend on?

A

Lipid solubility of molecule
or
Ability to fit through specific ion channels

29
Q

3 important characteristics of carrier-mediated transport?

A

Specifity
Saturation
Competition

30
Q

Comparing transport rates between a carrier mediated transport & simple diffusion down a concentration gradient.

A
  • Simple diffusion gets a higher rate of transport of molecule into the cell but a lower concentration of transported molecules in the ECF than Carrier mediated transport
  • Facilitated diffusion has a lower rate of transport of molecule into cell however reaches a higher concentration of transported molecules in the ECF
31
Q

2 forms of carrier mediated transport?

A

Facilitated diffusion

Active Transport

32
Q

Facilitated Diffusion definition?

A

Uses a carrier protein to facilitate the transfer of a substance across a membrane ‘downhill’ from high to low concentration

33
Q

Active Transport Definition?

A

Requires the carrier to expend energy to transfer a substance ‘uphill’ across a membrane against a concentration gradient

34
Q

Two forms of Active transport?

A

Primary

Secondary

35
Q

Primary AT?

A

Energy is directly required to move a substance against it’s concentration gradient

36
Q

Secondary AT?

A

Energy is required, but it is not used directly to produce ‘uphill’ movement.
The carrier does not split ATP – instead it moves a molecule ‘uphill’ by using secondhand energy stored in the form of an ion concentration gradient (usually a Na+ gradient)

37
Q

What is a Na+/K+ pump?

A

More complicated Primary active transporter

38
Q

Where is a sodium/Potassium pump found?

A

Plasma membrane of all cells

39
Q

3 important roles of Na+/K+ Pump?

A
  1. Helps establish Na+/K+ concentration gradients across plasma membrane of all cells
  2. Helps regulate cell volume by controlling concentration of solutes inside cell
  3. Energy used to drive the pump indirectly serves as the energy source for secondary AT.
40
Q

Secondary AT definition

A

The transfer of a solute across the membrane is always coupled with the transfer of the ion that supplies the driving force (typically Na+)

41
Q

2 mechanisms which 2AT could occur by?

A

Symport or Antiport

42
Q

Symport

A

Solute and Na+ move in same direction

43
Q

Why does Vesicular transport need energy?

A

Vesicular formation and movement within the cell

44
Q

Endocytosis?

A

Pinching off of membrane to engulf substance
or
extracellular environment engulfed into intracellular environment

45
Q

Exocytosis

A

A vesicle fuses with the plasma membrane, releasing its contents to the ECF

Year 1 MBChB Principles (5 decks)

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