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Block 1 > Cell Membranes And Transport > Flashcards

Cell Membranes And Transport Flashcards

1
Q

How do cells communicate with the extracellular fluid?

A

Semi-permeable barrier of the plasma membrane

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2
Q

Describe the structure of cell membranes.

A 
Fluid lipid structure
2 layers (bilayer): hydrophilic external layer + hydrophobic internal layer
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3
Q

What organelles in the cell have double membranes?

A

Nucleus

Mitochondria

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4
Q

What organelles in the cell have single membranes?

A

ER
Golgi apparatus
Others

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5
Q

What can the endoplasmic reticulum membrane be continuous with?

A

Outer nuclear membrane

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6
Q

How do organelles communicate with the intracellular fluid i.e. cytoplasm?

A

Membranes

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7
Q

What is the most important feature of cell membranes?

A

Semi-permeable - allow some substances to pass across easily but not others

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8
Q

What type of molecules can go across the cell membrane? How do they move across?

A

Small, uncharged and/or fat-soluble things e.g. O2, water + steroids via simple diffusion down a concentration gradient

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9
Q

What is diffusion?

A

The movement of molecules from an area of high concentration to low concentration i.e. down a concentration gradient

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10
Q

What is osmosis?

A

The movement of water across a semi-permeable membrane from an area of low-solute concentration to high-solute concentration

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11
Q

What are the mechanisms of movement of molecules across the cell membrane?

A

Simple diffusion
Facilitated diffusion
Active transport
Exo/endocytosis

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12
Q

Explain facilitated diffusion.

A

Requires a transporter (carrier molecule or channel) to facilitate transport but no extra energy is needed as this is passive - molecules move down a concentration gradient

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13
Q

What molecules move via facilitated diffusion?

A

Larger molecules e.g. glucose + charged molecules

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14
Q

Explain active transport.

A

Uses ATP to move molecules against their concentration gradients

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15
Q

What is secondary active transport?

A

Where a molecule e.g. Na+ is actively pumped out of a cell then allowed back in via transporter that also takes in another substance e.g. sugars, AAs

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16
Q

What type of transport is endocytosis and exocytosis?

A

Bulk i.e. large molecules or other substances can be transported in bulk

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17
Q

How can the knowledge of this lecture be applied to physiological processes?

A

Absorption of food molecules in the gut as glucose is absorbed via co-transport with Na+

Secretion of acid into stomach - active process of pushing more acid into an already acidic environment

Excretion of substances from kidney

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18
Q

What are transporters?

A

Integral membrane proteins which are channels or carriers that are selective + regulated

Can be passive or active

19
Q

What is the difference between channels and carriers?

A

Channels are faster + less specific than carriers

20
Q

How are voltage-gated transporters regulated?

A

Respond to changes in membrane potential

21
Q

How are ligand-gated transporters regulated?

A

Binding of ligands e.g. EC (neurotransmitters) or IC (2nd messengers)

22
Q

How are mechanically-gated transporters regulated?

A

Respond to sound, touch + stretch etc.

23
Q

What is the difference between passive and active transporters?

A

Passive transporters do not use metabolic energy + transport is by facilitated diffusion from [high] to [low] whereas active transporters used metabolic energy derived from hydrolysis of ATP to move molecules against a concentration gradient

24
Q

What are the different names for co-transport systems?

A

Secondary

Coupled transport system

25
Q

What is the difference between symport and antiport?

A

Symport is where compounds go in the same direction whereas antiport is where the compounds are transported in the opposite direction to eachother - 1 compound will go down concentration gradient whilst the other goes against

26
Q

What are the different types of co-transport?

A

Symport

Antiport

27
Q

Why do molecules move into and out of cells?

A

Take in nourishment
Get rid of waste
Communicate with ‘outside world’

28
Q

What is an ion?

A

Charged particle

29
Q

What is an anion?

A

-tively charged particle

30
Q

What is a cation?

A

+vely charged particle

31
Q

Do ions need aid moving in and out of cells?

A

Yes because they are charged

32
Q

What is an electrochemical potential?

A

Combines chemical and electrical potential:

  • Chemical potential is concentration difference
  • Electrical potential is the charge difference
33
Q

Where is there an electrochemical potential?

A

Across plasma membrane

34
Q

What is membrane potential?

A

Charge difference across the membrane

35
Q

What is the resting membrane potential?

A

Inside membrane is more negative than outside so typical value in a resting cell is ~70mV

36
Q

What ions contribute to the membrane potential?

A

Ions close (<1nm) from membrane

37
Q

What are the main intracellular and extracellular ions?

A

IC: K+
EC: Na+ but also Cl- & Ca2+

38
Q

How is a resting membrane potential established?

A

Cell membrane more permeable to K+ than other ions as it contains K+ leak channels that are constantly open

More K+ inside the cell so it moves out but outside of cell is +vely charged which makes K+ want to move in - system reaches equilibrium where there is no net K+ movement

39
Q

Why is the cell membrane potential more negative on the inside?

A

Inside of cell contains large negatively charged molecules like DNA + RNA

40
Q

What ion movement occurs in hyperpolarisation?

A

K+ moves out of cells whilst Cl- moves in = making the cell more -ve

41
Q

What ion movement occurs in depolarisation?

A

Na+ & Ca2+ move into cell = making cell more +ve

42
Q

What are action potentials?

A

Cycles of depolarisation, hyperpolarisation + return to resting state due to opening + closing of voltage gated Na+ & K+ channels

43
Q

What is the function of action potentials?

A

Powerful way of signalling to a cell e.g. getting a muscle to contract

44
Q

What ion movement occurs during an action potential?

A

Na+ influx into cell

K+ efflux out of cell

Block 1 (54 decks)

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