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Foundations Of Medicine > Forces acting across membranes > Flashcards

Forces acting across membranes Flashcards

1
Q

What is the basic structure of the membrane

A
  1. Double layer of phospholipids
  2. Embedded with proteins (aquaporin)
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2
Q

What are the characteristics of a membrane

A
  1. Selective barrier
  2. Permeability can vary
  3. Dynamic
  4. Very thin bilayer
  5. Very flexible because of fatty acids
  6. Insulators against ion movement
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3
Q

What is the function of the membrane

A

Selectively permeable barrier between ICF and ECF
Provide binding sites for chemical signals
Differences in membrane proteins responsible for varied charteristics

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4
Q

What are the different types of membrane proteins

A
  1. Integral - Span hydrophobic core of phopholipid bilayer
  2. Periphrial - interact only with phosphates of bilayer and do not penetrate hydrophobic region
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5
Q

What are the functions of membrane proteins

A
  1. Receptors
  2. Transport
  3. Enzymes
  4. Maintenence of cell structure
  5. Communication
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6
Q

What are the concentrations of ions in cellular fluid

A
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7
Q

What are the differences in membrane protein content

A

Myelin - low protein content 18%, high lipid content good insulator
Plasma membrane - protein content 50%
Membranes for energy transduction - high protein content 75%

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8
Q

What is the elctrochemical gradient

A

Combination of chemical gradient and electrical gradient

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9
Q

What are the mechanisms of movement across membranes

A
  1. Diffusion
  2. Active transport
  3. Osmosis
  4. Filtration
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10
Q

What is Endocytosis

A

Invagination of cell membrane to form a vesicle which disintegrates on inisde, releasing contents that migrate to destination
Common mechanism to terminate signals from extracellular ligands

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11
Q

What is exocytosis

A

Vesicles merge with plasma membrane on inside and release contents outside of cell
Many proteins synthesized inside cell are released this way

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12
Q

What is diffusion across membranes

A

Molecules move from high concentraition to low concentration down concentration gradient

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13
Q

What types of diffusion is there

A
  1. Passive
  2. Facilitated
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14
Q

Describe passive diffusion

A

Substances move directly through lipid bilayer
Molecules need to be: small, uncharged and Lipophilic

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15
Q

Describe facilitated diffusion

A

Substances require assistance from membrane proteins to cross lipid bilayer
Membrane proteins can be channels or mediated transport proteins

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16
Q

What type of channels proteins are there

A

Voltage gated - electric potential
Ligand gated - ligand binding

17
Q

Describe Transporters

A

Open to one side of ECF or ICF at a time

18
Q

What is active transport

A

Movement of molecules against concentraition gradient with energy

19
Q

Describe the Na+/K+ pump

A

1.Maintains high Na+ outside cell and high K+ concentration inside
2.Pumps 3 Na+ out and 2 K+ inside
3.Net movement of positive charge out cell = electrogenic pump
4.40% of resting energy is used by pump

20
Q

What is osmosis

A

Net movement of H2O from high concentrations to low concentrations of water

21
Q

What is the difference between osmosis and diffusion

A

Osmosis - Net movement of water form high concentration to low
Diffusion - Net movemet of solutes from high solute concentration to low

22
Q

Describe osmosis

A

Membranes permiable to only water will have equal concentrations on both sides of membrane but different volumes

23
Q

Describe diffusion

A

Membranes permiable to water and a solute will have equal concentrations on both sides and equal volume

24
Q

What is osmolarity

A

Total number of solute particles in solution (after they dissociate), not nature of particles

25
Q

What is Tonicity

A

Total number of non-penatrating particles in solution (particles unable to cross membrane)

26
Q

What is the importance of tonicity

A

If a solute cannot cross a membrane, a change in its concentration will cause osmotic flux and change volume of cell

27
Q

Describe an isosmotic solution

A
28
Q

Describe an isotonic solution

A
29
Q

Give examples of penetrating and non-penetrating particles

A

Penetrating - water, urea
Non-penetrating - ions

30
Q

What is the Osmolarity of human plasma

A

285mosmol/l, same as osmolarity of cells

31
Q

What happens to cells in hypotonic and hypertonic solutions

A

Hypotonic - swell because water enters cell down conc. gradient
Hypertonic - shrink because water leaves down a chemical gradient

32
Q

Why is osmosis important when prescribing fluids

A

Cause cells to burst
Lysed cells introduce proteins to ISF, uncontrolled increase of ECF tonicity
Fluids must have the appropriate tonicity
Brain is most sensative to change in tonicity

Foundations Of Medicine (28 decks)

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