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Y Physiology I > Week 01 Transport > Flashcards

Week 01 Transport Flashcards

1
Q

What are the 3 main types of plasma membrane transport processes?

A
  • Simple Diffusion
  • Protein-mediated Membrane Transport
  • Vesicular Transport
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2
Q

What are 4 major types of protein-mediated membrane transport?

A
  1. Solute Carriers - facilitated diffusion
  2. ATP-Dependent Carriers - AKA pumps, active transport
  3. Ion Channels - forms a “pore” for ions
  4. Water Channels - aquaporins
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3
Q

How do carriers and channels differ in their…

energy usage?

transport mode?

speed?

kinetics?

A
  • Energy Usage:
    • carriers: active/passive
    • channels: passive
  • Transport Mode:
    • carriers: transport cycle
    • channels: gated
  • Speed:
    • carriers: slow
    • channels: fast
  • Kinetics:
    • carriers: saturatable
    • channels: unsaturable (at physio. concentrations)
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4
Q

What is Fick’s 1st Law of Diffusion?

More important than just the memorizing the equation… what are some important factors that affect direction and speed of diffusion?

A
  • Concentration Gradient (effects speed + direction, Δc)
  • Thickness of the Membrane (effects speed, Δx)
  • Solute Hydrophobicity (effects ability to diffuse/speed)
  • Solute Size (effects ability to diffuse/speed)

  • hydrophobicity + size are incorporated into the “diffusion coefficient”
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5
Q

What are some examples of molecules which diffuse easily through cell membranes?

A

O2

CO2

CO

NO

Urea

Hydrophobic Hormones

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6
Q

What are some examples of molecules which have more specialized modes of diffusion into cells?

And what kinds of molecules do not diffuse?

A

Specialized diffusion: water, ions, larger molecules such as glucose

Undiffusable molecules: peptides, proteins, disaccharides

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7
Q

In the case of glucose transport…

what kind of transport is it?

does it use energy?

does it effect electrical charge?

A

- facilitated transport with uniporter

- passive, no ATP use

- electroneutral (glucose is a neutral molecule)

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8
Q

Describe the general kinetics of GLUT transporters.

How is it affected by concentration?

A

- speeds up with increased concentration

- has a saturation point at which rate maxes out

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9
Q

Between GLUT-1 and GLUT-2, which one is at vmax in the physiological range of glucose concentration?

What is the consequence of this?

A

GLUT-1 has Vmax across whole range of physiological glucose concentrationand

  • leads to the cell always having glucose available
  • GLUT-2 has Vmax higher than any physiological glucose levels
  • leads to different transportation rates across all possible glucose concentrations
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10
Q

What are some places that you find GLUT-1?

GLUT-2?

GLUT-4?

A

1: Red blood cells
2: Beta cells of pancreas
4: skeletal muscle, adipocytes

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11
Q

What are the properties of the Cl-/HCO3- exchanger?

Energy usage?

Electrogenicity?

Location/function?

A
  • Cotransporter, anti-porter
  • passive
  • electroneutral (no change in charge)
  • in RBCs, transports CO2
  • goes in both directions
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12
Q

What are the propeties of Na/K-ATPase?

Transporter type?

Energy requirements?

Function?

Electrogenicity?

Inhibitors?

A

- is a pump

  • active transport requiring ATP
  • carries 3 Na+ out of and 2 K+ in to cell
  • electrogenic, net transport of +1 charge out
  • inhibited by Ouabain
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13
Q

What are the properties of the Ca2+-ATPase?

Transport type?

Electrogenicity?

Function/Location?

A

- Active Uniporter

- Electrogenic (due to calcium ion charge)

  • present in both plasma membrane and ER membrane (carries calcium into ER lumen)
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14
Q

What are the ABC transporters?

What are the two types?

A
  • a transporter superfamily standing for ATP-Binding Cassette
    types: primer pump and channel
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15
Q

What is the function of the primer pump type of ABC transporter?

Examples of this?

A
  • Active transport of mainly hydrophobic molecules

Examples:

  • cholesterol transport
  • bile secretion
  • drug removal (multi-drug resistance pumps)
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16
Q

What is an example of the channel type of ABC transporter?

A

CFTR - Cystic Fibrosis Transmembrane Regulator

  • works as a Cl- channel
  • mutations in its gene can result in cystic fibrosis
17
Q

How is water transported across the plasma membrane?

What drives this?

A
  • passively via aquaporin proteins
  • driven by osmosis
18
Q

What is van’t Hoff’s law for osmotic pressure?

A
19
Q

What is the reflection coefficient that is added to the van’t Hoff equation in physiological calculations?

What do its values represent?

A
  • a coefficient that indicates the diffusability of the solute in consideration
  • 0 means diffusable (ex: urea), 1 means undiffusable (ex: NaCl, sucrose)
20
Q

How would a 290 mOsm/l solution of urea affect a cell’s volume?

A
  • depsite the urea solution being at physiological osmolarity, the concentration gradient due to the lack of urea in the cell drives urea into the cell
  • water follows the urea due to osmosis

- cell volume increases

21
Q

What is oncotic pressure?

A

the osmotic pressure of large molecules (usually proteins)

22
Q

What is the total fluid volume in a 70 kg adult?

Intracellular?

Interstitial?

Plasma?

Transcellular?

A

Total: 42 L

Intracellular: 25 L

Interstitial: 13 L

Plasma: 3 L

Transcellular: 1 L

23
Q

How does receptor mediated endocytosis occur?

Give examples of proteins involved.

A
  • via receptor-coated pits in the cell membrane
  • clathrin, adaptin, and B-arrestin II
24
Q

What are the two types of exocytosis?

An example of one type?

A

Constitutive

Regulated - histmaine release from mast cells

25
Q

What are the 4 main compartments/spaces in relation to trans-epithelial transport?

A
  1. Luminal - within the epithelium-lined cavity
  2. Interstitial - beyond the basal membrane
  3. Paracellular - between epithelial cells
  4. Intracellular
26
Q

What is transport from the lumen to the interstitium called?

From the interstitium to the lumen?

A

- resorption

- secretion/excretion

27
Q

What are the 2 main types of transepithelial transport?

A

transcellular - thru cells from apical/basal or vice versa, passive/active

paracellular - thru tight junctions and then between cells, always passive

28
Q

What is ENaC?

Where can it be found?

What controls it?

A

Epithelial Sodium Channel

  • found in sweat glands + distal tubules of the kidney
  • controlled by aldosterone (can change # of ENaCs in a cell membrane)

Y Physiology I (17 decks)

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