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Foundations of Medicine > Week 2 Forces acting across membranes > Flashcards

Week 2 Forces acting across membranes Flashcards

1
Q

Explain the composition of ICF and ECF

A

ICF

K in intracellular, protein and phosphates/sulphates in ECF

ECF na+, Cl-, HCO3- (bicarbonate).

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2
Q

Volumes of fluid in ICF and ECF

A

plasma 3L

ISF - 11L

ICF 28L

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3
Q

what can pass freely between all components?

ECF and ICF

how?

A

Water

presence of aquaporins channels - osmosis

Gases

across cell membrane etc 02, c02

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4
Q

Where can Ions pass in ECF and ICF

A

readily between plasma and ISF

not as easily ICF - regulated - mainly impermeable

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5
Q

7 important things on the cell membrane:

A
  1. selective permeability

2 permeability can vary - various cell function e.g. transmission of nerve impulse

  1. dynamic constantly formed, maintained, dismantled
  2. thin double layer sheet of lipid (bilayer) hydrophilic and hydrophobic
  3. membranes are very flexible due to fatty acid - if overstretched will rupture.
  4. excellent insulators against movement of electrical charge.
  5. embedded with proteins (and associated with carbohydrates)
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6
Q

Explain membrane carbohydrates

A

Molecules may attach phospholipid or protein embedded ALL ARE extracellular

important role - if the cell is self vs non-self for recognition by the immune system.

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7
Q

Function of membrane protein

integral protein

A

SPAN the hydrophobic core of lipic bilayer

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8
Q

The function of membrane protein

peripheral protein

A

associated only with phosphate head (internal or external) of the lipid bilayer and does not penetrate hydrophobic core

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9
Q

The function of membrane protein

5 function list

A
  1. receptor

2 transport (transporter and channel protein)

3 enzyme

4 maintenance of cell structure (anchorage)

5 communication

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10
Q

Role receptor

A

Integral to membrane structure - penetrace from ECF to ICF. allow communication of extracellular signal (LIGAND) e.g. neurotransmitter or hormone for cellular response.

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11
Q

What is a Ligand?

A

ligand refers to substances that bind to receptors.

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12
Q

receptor proteins specific?

A

yes cells will present receptors react certain chemicals e.g. gonads folicle stimulating hormone

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13
Q

Are there any receptors inside cell?

A

YES

(intracellular receptors)

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14
Q

Proteins

explain transporters

A

two forms

Channel protein - move ions across membranes

can be open (water) aquaporin or gated (ion) usually closed

transporters don’t create continuous pore from ECF to ICF - move larger molecules. open only one side at a time (ECF and ICF)

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15
Q

Explain glucose transporters

A

permanently percent in the cell membrane

is INSULIN INDEPENDENT

e.g. nerve cells. insulin only requred for glucose reuptake in muscle and adipose tissue.

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16
Q

Explain enzymes as membrane protein

A

membrane enzyme catalyse chemical reaction on cell membrane.

Enzymatic part may be on:

external side of membrane e.g. found small intestine break nutrients into smaller units

internal side converting signals carried from receptirs into an intracellular response

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17
Q

Explain structural protein on the membrane

A

Anchor cell membrane to intracellular skeleton to extracellular matrix (collagen) or other cells. if dysfunctional cause disability - e,g, lack dystrophin protein in Duchennes Muscular Dystrophy.

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18
Q

Explain protein-membrane communication

A

Can be within or out of cell

Glycoprotein act marker tell the immune system if self or non-self

carry hormone (or drug) to intracellular

Peripheral protein (inside) relay signal along membrane from integral receptor protein (span bilayer) to an integral enzyme protein.

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19
Q

Explain how membrane differ in protein content

A
  1. Myelin - specialist membrane insulator around myelinated nerves - low content protein (18%) major component is lipid.
  2. plasma membrane have greater activity protein content (typically 50%)
  3. membranes involved in energy transduction (inner membrane mitochondria) highest content - 75%
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20
Q

What is an electrochamical gradient?

A

Ions creating concentration gradient are charged

as they move across membrane - creats electrical gradient.

drives direction of passive movement.

any movement against this gradient requires energy (active transport)

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21
Q

What drives the direction of passive movement?

A

movement of ions down the electrochemical gradient

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22
Q

What is active transport

A

any movement against the concentration gradient requires energy (active transport)

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23
Q

Mechanism of movement across membranes

what is diffusion?

A

Diffusion is the net movement of anything from a region of higher concentration to a region of lower concentration down a gradient in concentration

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24
Q

Mechanism of movement across membranes

what is passive diffusion

A

Directly through the lipid bilayer

The movement of substances in the direction of the concentration gradient without any energy input.

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25
Q

Mechanism of movement across membranes

what is facilitated diffusion

A

i) protein channels or;
ii) protein transporters

Facilitated diffusion is the process of spontaneous passive transport of molecules or ions across a biological membrane via specific transmembrane integral proteins.

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26
Q

Mechanism of movement across membranes

what is Active transport

A

movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient.

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27
Q

What is endocytosis and exocytosis. what is the purpose?

A

Mechanisms for moving macromolecules across membranes without disrupting them

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28
Q

Describe endocytosis

A

invagination of the cell membrane form a vesicle which disintegrates on the cytoplasmic (inside) surface of the membrane, releasing contents which then migrate within the cell to their destination

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29
Q

Describe Exocytosis

A

involve the reverse of endocytosis

Proteins manufactured in the cell are released from those cells by exocytosis.

proteins packed in Golgi apparatus - travel up to membrane and then excreted

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30
Q

LO:

Define what is meant by diffusion

list factos which favour diffusion through lipid bilayer

define difference between passive diffusion and facilitated diffusion

define difference between facilitated diffusion and active transport

describe different typed of membran proteins and their functions

explain what is meant by carrier mediated transport system (i,e transporters)

A
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31
Q

Describe filtration

A

The movement of substance across the capillary wall

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32
Q

The three types of passive transport are

A

Diffusion

Osmosis

Facilitated diffusion

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33
Q

Active transport is different from passive transport because it allows .

A

molecules to be transported against the concentration gradient

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34
Q

Passive transport is driven by the .

A

concentration gradient

.

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35
Q

(Primary/Secondary) active transporter proteins use the concentration gradient of one molecule to move a different molecule across the membrane against its concentration gradient.

A

Secondary active transporter proteins

use the concentration gradient of one molecule to move a different molecule across the membrane against its concentration gradient.

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36
Q

(Primary/Secondary) active transporter proteins use ATP directly to move molecules across the membrane against the concentration gradient.

A

Primary active transporter proteins use ATP directly to move molecules across the membrane against the concentration gradient.

37
Q

In diffusion, if substances move from one compartment to another can it go back?

A

As long as the membrane is permeable to the substance for both ways, it allows it to come back. The net flux will move in the direction from high concentration to low, but some will come back.

38
Q

Are cell membranes permeable to intracellular proteins?

A

NO

the membrane is effectively impermeable to intracellular proteins and organic anions. These cannot diffuse in any capacity and stay inside the cell.

39
Q

For smaller molecules passing membrane what is it important to distinguish?

A

Whether they are passing through the lipid bilayer (passive diffusion) or via proteins embedded in membrane (facilitated diffusion)

40
Q

An example of a substance that crosses via Passive diffusion

A

02 and c02 - needs to be lipophilic to diffuse across

although c02 is not lipophilic it’s small enough it still crosses

41
Q

An example of a substance hat crosses via facillitated diffusion

A

Glucose, ions can cross through ion channels

42
Q

Passive diffusion what do molecules need to be

A

molecules need to be:

1. small

2. uncharged

3 ideally lipophilic (hydrophobic)

gases - small and uncharged. 02, c02, and nitrogen.

(large molecule e.g. glucose or small charged particles like ions do not cross membrane without assistance from membrane protein,, facilitated diffusion)

43
Q

Facilitated diffusion

A

ions (charged)

nutrients e.g. glucose (large)

slow movement

na+ slower than c02 movement.

44
Q

name some membrane proteins to help transport proteins through facilitated diffusion

A

i) channel proteins
ii) mediated transport proteins

45
Q

What are membrane channels

A

need to be in solution (water) to transport. water and ion molecules move together

Na+, K+, Cl-, Ca2+, H+

aquaporins (only allow water)

46
Q

What opens ion channels?

A

Ligand response trigger change through signal

Electric charge signal

47
Q

How do ions cross the membrane

A

Using channels (usually GATED)

remain closed until stimulus (chemical or electrical charge change) cause to open

48
Q

What channels open due to electrical potential., where are these found extensively

A

Voltage-gated channels

extensively in muscle and nerve cells

49
Q

What channels open when chemical (neurotransmitter or hormone) channel?

A

Ligand-gated

open bind chemical binding site to the channel protein. act transporter and receptor.

50
Q

What happens if there are conflicting electrical and concentration gradients?

A

both electrical charge and chemical concentrations cause a conformational change in channel protein to cause open or close.

The direction of diffusion depends on concentration/electrical gradient (in charged particles)

Sometimes forces cooperate, sometimes they oppose. The net direction depends on the dominant force

51
Q

How do molecules that are too big to move through channel proteins or lipid bilayer?

A

facilitated diffusion through a carrier-mediated transport protein

molecules too big to move through channel proteins use carrier-mediated transport protein (transporters)

52
Q

Active transport

A

molecules being moved against electrochemical gradient.

53
Q

Example of active transporter (pump)

A

Na+/K+ATPase or Na+/K+​​ pump

54
Q

Na+/K+​​ pump purpose?

A

Help maintain different of Na+ outside cell and K+​​ inside.

continuously purple 3 Na+ out cell and 2 K+​​ ions inside cell.

Produces net movemen of positive charge out of the cell electrogenic pump creates charge difference across membrane

40% resting energy og body used by Na+/K+​​ ATPase

55
Q

Na+/K+​​ ATPase or Na+/K+​​ pump - distrubutes how much of Na+ and K+​​ to where?

A

continuously pump 3 Na+ out cell and 2 K+​​ ions inside the cell.

Produces net movement of positive charge out of the cell electrogenic pump creates charge difference across the membrane

40% resting energy of body used by Na+/K+​​ ATPase

56
Q

The ratio of Na+ and K+​​ in/out of cell does what with charge across membrane

A

continuously pump 3 Na+ out cell and 2 K+​​ ions inside the cell.

Produces net movement of positive charge out of the cell electrogenic pump creates charge difference across the membrane

40% resting energy of body used by Na+/K+​​ ATPase

57
Q

How much resting energy does the Na+ /K+​​ pump use

A

40% of resting energy

58
Q

What is osmosis?

A

Net movement of H2O from regions of high concentration of H2Oto regions of low concentration of H2O

59
Q

difference osmosis and diffusion

A

Osmosis: Net movement of H2O from regions of high concentration of H2Oto regions of low concentration of H2O

Diffusion: the net movement of solute from regions of high solute concentration to low concentration

water can move freely between ICF and ECF body is osmotic equilibrium Not all solutes move freely

60
Q

How is H2O concentration related to concentration of solute

A

H2O is inversely related to solute concentration.

more solute particles in solution, the more they will displace H2O molecules, lowering the concentration of H2O

61
Q

what is osmotic pressure

A

oppose increase of volume in pressure when cell is permeable to water but not solute on both sides.. this will mean ncrease unequal volume but equal water. so the pressure to oppose

62
Q

What will happen with osmosis with no diffusion

A

change in cel volume

63
Q

What is osmolarity describe it inclusing moles from a solute (e.g. NaCl)

A

1-mole substance dissolved in a litre mol/l

a mole consists of 6/02x1023 molecules

The number of solute particles not molecules which determine osmotic effect.

1 mole glucose added to h20 - 1 mole/l

1 mole NaCL added to H20 - 2 mole/l as 1 molecule Na+ and 1 molecule Cl-

64
Q

Term osmolarity

A

measures concentration biological solution in units of OSMOLES - describe number particles/L of solution (use miliosmoles)

NORMAL human plasma has osmolarity 285 mOsmol/l which is same within cells (often taken as 300 for ease)

65
Q

What is normal osmolarity in plasma

A

NORMAL human plasma has osmolarity 285 mOsmol/l which is same within cells (often taken as 300 for ease)

66
Q

For osmosis, the volume of the cell is dependant on the concentration of what on either side of the membrane?

A

Concentration of non-penetrating solutes

67
Q

What act as non- penetrating soluted in the

ECF

ICF

A

ECF - Na+ and Cl-

ICF - K+ and organic anions)

68
Q

Osmolarity described ___

A

total number of particles in solution

including penetrating and non penetrating

69
Q

Tonicity describes__

A

A number of the non-penetrating particles in solution.

70
Q

what does isoosmotic mean

A

same TOTAL number of solute particles.

71
Q

Hypo-Osmotic

A

Solutions with fewer total solute particles

72
Q

Hyper osmotic

A

Solutions with greater number of total solute particles

73
Q

Isotonic

A

Solution has same number of nonpenetrating particles as normal ECF (plasma)

74
Q

Hypotonic

A

solutions with fewer number of nonpenetrating solute particles as normal ECF (PLASMA)

75
Q

Hypertonic

A

Solutions with greater number of nonpenetrating solute particles as ECF (plasma)

76
Q

Non-penetrating particles determine ___

penetrating particles PLUS non penetrating particles determine ____

give examples

A

nonpenetrating particles (ions) determine tonicity.

penetrating particles (e.g. urea) PLUS non-penetrating particle determine osmolarity

77
Q

What determines tonicity

what determines osmolarity

A

nonpenetrating particles (ions) determine tonicity.

penetrating particles (e.g. urea) PLUS non-penetrating particle determine osmolarity

78
Q

what happens to a cell when put in hypotonic solution

A

swell, maybe burst

79
Q

What happens to a cell when put in hypertonic solution

A

Shrink

80
Q

Why do we need to know a cell will swell in hypertonic solution

A

haemolysis which can kill

81
Q

what happens when cells have lysed (burst)

A

proteins will be introduces to interstitial fluid (ISF) increasing tonicity of extracellular fluid ECF in an uncontrolled manner making management very complicated

82
Q

what should you NEVER transfuse a patient with

what are they usually transfused?

what in rare occasions can a solution be prescribed?

A

Never transfuse with pure water

Usually transfused an ISOTONIC solution of sodium chloride Nacl

a hypotonic transfusion controlled in a drip. never injected

83
Q

If a solution is hypotonic it is ____ osmotic

A

Hypoosmotic

84
Q

If a solution is hyperosmotic it can be ________

A

Hypertonic, isotonic, hypotonic.

85
Q

if a solution is isoosmotic it can be ______

A

isotonic or hypotonic

86
Q

only changes in osmolarity/tonicity will change cell volume

A

tonicity

87
Q

what organ is most sensitive to changes in tonicity?

A

Brain

88
Q
A

Foundations of Medicine (12 decks)

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