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Physiology 2 (Y2,S1) > Transport 1 > Flashcards

Transport 1 Flashcards

1
Q

Why is it important that solutes cross membranes

A
  • Absorb oxygen for respiration
  • Absorb food through gut
  • Maintain membrane potential
  • Change membrane potential
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2
Q

Steps glucose takes from intestine to blood to muscle

A
  • GLucose leaves intestine & enters blood (crossing 4 lipid membranes & interstitial space)
  • Circulates in blood stream to desired location
  • Leaves blood & enters muscle cell (crossing 3 more lipid membranes & interstitial space)
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3
Q

Chemical gradient

A

Substances move from high concentration to low concentration by diffusion

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4
Q

What happens if gradient is outwards

A

If gradient is outwards, there is a force to leave a cell

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5
Q

What happens if gradient is inwards

A

If gradient is inwards, there is a force to enter a cell

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6
Q

Electrical gradient

A

Inside of cell is negative relative to outside

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7
Q

Where are positive & negative ions forced due to electrical gradient

A
  • Negative ions are forced outwards
  • Positive ions are forced inwards
    (Inside of cell negative -70mV)
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8
Q

what will cross membrane spontaneously in the direction of the electrochemical gradient

A
  • Gases (O2/CO2/NO)
  • Hydrophobic substances (steroid hormones & ethanol)
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9
Q

What cannot spontaneously cross membrane even if there is an electrochemical gradient

A
  • Ions (K+/Na+/Cl-)
  • Hydrophilic substances (Glucose/Amino Acids/Water)
  • Proteins & DNA (negatively charged)
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10
Q

What is Fick’s Law of Diffusion

A

Rate of diffusion= (permeability coefficient) (electrochemical gradient)

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11
Q

Is diffusion rapid or slow over short distance

A

Diffusion is rapid over short distance
(Diffusion slow over long distance)

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12
Q

What are membrane channels

A

Pores in the membrane with specificity for a single substance e.g.: Na+ only or H2O only

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13
Q

2 subdivisions of channels

A
  • Regulated (gated)
  • Non regulated (constitutive - always open)
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14
Q

What do uniporters do

A

They bind & move larger molecules (e.g: glucose) down concentration gradient across the membrane without creating a pore that is completely open at any one time

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15
Q

What are uniporters regulated by

A

Insertion/removal of the uniporter from the cell membrane

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16
Q

Example of a uniporter

A

GluT1 - glucose transporter in kidneys

17
Q

Why is there a glucose transporter rather than a glucose channel

A

A glucose channel would allow other ions & H2O through so transporter needed

18
Q

Active transport

A

Ions or molecules can move up/against conc gradient, but this requires additional energy - spontaneous diffusion won’t occur

19
Q

What is primary active transport carried out by

A

By ion pumps

20
Q

What is secondary active transport carried out by

A

Secondary active transport is carried out by symporters & antiporters

21
Q

Where does the energy used in secondary active transport come from

A

uses energy stored in concentration gradient established by primary active transport

22
Q

Which transporters are secondary active transport

A
  1. symporter
  2. antiporter
23
Q

What is the cells resting membrane potential

A

-70mV (milliVolts)

24
Q

Why is the RMP -70mV (2)

A
  1. Ficks law (ATP7 & proteins17 cannot leave to neutralise)
  2. The Na+/K+ pump (Na+ cannot enter cell to neutralise)
25
Q

Na+/K+ pump: what happens

A
  • Uses ATP to:
  • Pump 3 Na+ out of cell
  • And simultaneously pump 2 K+ into the cell
26
Q

What is osmolarity

A

The amount of solute dissolved in 1 litre of water

27
Q

Why is there no net movement of water between ICF & ECF

A

No net movement because osmolarity is the same in both

28
Q

What happens osmotically to rbcs in plasma if ICF of rbc = 280mOsm and plasma = 280mOsm

A
  • There is no osmotic gradient (solutions are isosmotic)
  • There is no net osmosis, therefore rbc maintains size & function
29
Q

What happens osmotically to rbcs in pure water if ICF of rbc = 280mOsm and pure water = 0 mOsm

A
  • There is an osmotic gradient as the osmolarity is greater inside
  • There is net osmosis, water rushes into cell & it explodes, losing function
30
Q

What happens osmotically to rbcs in sea water if ICF of rbc = 280mOsm and sea water = 1000 mOsm

A
  • There is an osmotic gradient as the osmolarity is greater outside the cell
  • There is net osmosis, water rushes out of the cell & it implodes, losing function

Physiology 2 (Y2,S1) (3 decks)

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