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1MB Principles > Physiology > Flashcards

Physiology Flashcards

1
Q

What are the functional differences between cell types are due to?

A

Variations in the composition of their plasma membranes - Different cells interact in different ways with essentially the same ECF

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2
Q

Two main components of membranes?

A

Lipids and proteins

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3
Q

Describe the glycerol background of phospholipids?

A 
Two hydroxyl groups of which are esterified to various
fatty acids (maybe saturated or unsaturated)

The third glycerol hydroxyl group is esterified
to a phosphate group which is attached to a head
group

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4
Q

What determines the thickness of the bilayer?

A

Length of the fatty acid chains (2-3nm).

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5
Q

What does the head group determine?

A

How densely packed adjacent phospholipid molecules are

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6
Q

What can dissolve phospholipids?

A

Detergents

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7
Q

What does cholesterol do?

A

Aids in rigidity

Constantly flip flops

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8
Q

T or F: The phospholipid composition of the two leaflets of the plasma membrane are identical

A

False

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9
Q

What is permeable to phospholipid layers?

A

Small uncharged polar molecules

E.g. O2, CO2, NH3, water

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10
Q

What is impermeable to phospholipid layers?

A

Almost any water-soluble substance

E.g. ions, proteins, and sugars

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11
Q

T or F: phospholipid layers is responsible for the fluidity of the membrane

A

True

Eg: RBC, skeletal muscle cell

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12
Q

T or F: phospholipids contain more lipids than proteins

A

False

Lipids

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13
Q

What are peripheral membrane proteins?

A

Not embedded within the membrane, instead they adhere tightly to the cytoplasmic or extracellular surfaces of the PM

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14
Q

What are integral membrane proteins?

A

Intimately associated with the lipid bilayer

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15
Q

What are the three different ways integral membrane proteins present themselves?

A

Span the lipid bilayer once or several times: transmembrane proteins

Some are embedded but do not cross the bilayer

Some are linked to a lipid component of the membrane or a fatty-acid derivative that intercalates into the membrane

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16
Q

Functions of integral membrane proteins

A

Ligand-binding receptors - hormones
Adhesion molecules - cadherins, integrals
Pores and channels - nerve cell (gated/leak channel)
Carriers
Pumps
Enzymes - carbonic anhydrase
Intracellular signalling - GTP binding proteins, kinases

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17
Q

What are dock-marker receptors?

A

Located on the inner membrane surface

Interact with secretory vesicles leading to exocytosis of the vesicle contents

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18
Q

Glycoproteins + glycolipids = ?

A

Glycocalyx

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19
Q

Cancer is an example of..

A

Abnormal surface marker

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20
Q

Role of carbohydrates?

A

Self-recognition

Cell-to-cell interactions

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21
Q

Two properties that influence whether a particle can

permeate the plasma membrane without assistance?

A

Solubility of the particle in lipid

Size of the particle

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22
Q

T or F: A Pathway and a driving force is required for movement across a membrane (applies for assisted or unassisted)

A

True

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23
Q

T or F: If impermeable diffusion will still takes place across the membrane even if a concentration gradient for that substance exists

A

False

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24
Q

Law’s of Fick’s diffusion

A

The magnitude of the concentration gradient

The larger the SA the greater the rate of diffusion it can
accommodate

The greater the lipid solubility the more rapidly the substance can diffuse through the membrane bilayer
down its concentration gradient

As molecular weight increases, the rate of diffusion will decrease

The greater the distance, the slower the diffusion

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25
Q

What is an example of a channel where diffusion takes place across?

A

Ion-specific channel proteins: Leak or gated

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26
Q

Define electrochemical gradient

A

The net effect of simultaneous electrical and

concentration gradients on a ion

27
Q

Water moves by osmosis to the area of…

A

Higher solute concentration

28
Q

Define Osmolarity and state its units

A

Concentration of osmotically active particles present in a solution (Osm/l)

Body fluids: ~300 mOsm/l

29
Q

Define Tonicity

A

Effect a solution has on cell volume

30
Q

Isotonic vs hypotonic vs hypertonic

A

Iso: No net movement
Hypo: Water diffuses into cell = swelling
Hyper: Water diffuses out of cell = shrinking

31
Q

Passive methods of transport

A

Ion channels: Movement along electrical gradients
Simple diffusion: Diffusion down concentration gradients
Osmosis

32
Q

What is carrier mediated transport?

A

Substance binds onto a specific carrier which undergoes a conformational change (shape change) which transports the substance

33
Q

What determines carrier mediated transport?

A

Specificity
Saturation (transport maximum eg renal glucose re-absorption)
Competition

34
Q

Two forms of carrier mediated transport?

A

Facilitated diffusion eg GLUT4 glucose transporter

Active transport

35
Q

Two forms of active transport?

A

Primary active transport - energy is directly required to move a substance against its concentration gradient

Secondary active transport - energy is required, but it is not used directly to produce ‘uphill’ movement. The carrier does not split ATP – instead it uses secondhand energy stored in the form of an ion concentration gradient

36
Q

What is need to induce a conformational change in active transport?

A

ATP splits - P binds to carrier
Change in shape reduces affinity to P
When carrier is released, so is P

37
Q

Na+ -K+ ATPase pump transports 3x___ out of the cell for every 2x___

A

3x Na+ out of the cell for every 2x K+ in

38
Q

Mechanisms of which secondary active transport occur?

A

Symport: move in the same direction.
E.g. glucose absorption at the apical membrane of
enterocytes

Antiport: move in opposite directions
E.g. Na+ -K+ ATPase pump

39
Q

Main intracellular ion is..

A

Potassium

40
Q

Main extracellular ion is..

A

Sodium

41
Q

Define membrane potential

A

Difference in charge between the thin layers of ECF and ICF located next to the outside and inside of the membrane

42
Q

Extracellular and intracellular conc. of K

A

E: 5
I: 150

43
Q

Extracellular and intracellular conc. of Na

A

E: 150
I: 15

44
Q

Extracellular and intracellular conc. of Cl-

A

E: 110
I: 7

45
Q

T or F: At resting potential the membrane is 100x more permeable to Na+ than K+

A

False

More permeable to K+ than Na+

46
Q

Two opposing forces acting on K+

A

The concentration gradient (tending to move K+ out
of the cell)

The electrical gradient (tending to move K+ into the
cell)

47
Q

The membrane potential at EK

is..

A

-90mV

48
Q

Measured Em for a typical nerve cell at rest is..

A

-70mV

Much closer to EK than ENa

49
Q

T or F: Passive movement an ion through an ion channel is driven by the concentration gradient for that ion

A

False

Electrochemical

50
Q

The driving force for Na+ influx

A

-130mV

51
Q

The driving force for K+ efflux

A

+20

52
Q

The ion channels responsible for the action

potential in neurones

A

Voltage-activated Na+ channels

Voltage-activated K+ channels

53
Q

K+ flows outwardly generating an outward current because…

A

The concentration gradient is outward and has an energy which exceeds that of the electrical gradient, which is inward

54
Q

What are action potentials

A

Brief electrical signals in which the polarity of the nerve cell membrane is momentarily (about 2 msec) reverse

55
Q

The activation of Na+ channels is..

A

Self-reinforcing – the opening of a few channels causes further channels to open, causes further depolarization. This is positive feedback

56
Q

The activation of K+ channels is..

A

Self-limiting – outward movement of K+ causes repolarisation which turns off the stimulus for
opening. This is negative feedback

57
Q

What is the state of voltage-activated N+ during maintained depolarization?

A

Inactivated stat

58
Q

Define Relative refractory period

A

A stronger than normal stimulus may elicit a second action potential

59
Q

What is passive conduction?

A

A factor in the propagation of the action potential (AP)

60
Q

T or F: The less ‘leaky’ the axon the greater the local current spread

A

True

61
Q

Why does backward current flow does not re-excite previously active area?

A

Because it’s in its refractory period

62
Q

How is current speed increased?

A

Increase axon diameter

Decrease leak of current across the axon (possible by adding an insulating material – myelin)

63
Q

What is upstroke, downstroke and overshoot due to?

A

U: Mediated by the opening of voltage-activated Na+
channels
D: Opening of voltage-activated K+ channels and the inactivation of voltage-activated Na+ channel
O: Delayed closure of voltage-activated K+ channels

1MB Principles (7 decks)

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