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Week 7 - 12 > Molecular Movement > Flashcards

Molecular Movement Flashcards

1
Q

What happens in diffusion?

A

Down conc. gradient

Through lipid bilayer or protein channel / carrier

No energy required

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2
Q

What happens in active transport?

A

Against conc. gradient

Protein carrier

Requires energy (ATP)

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3
Q

What happens as extracellular concentration increases in passive transport?

A

Rate of influx increases in proportion

Linear relationship

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4
Q

How do you calculate rate of diffusion into cell?

A

Permeability coefficient multiplied by concentration gradient across membrane

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5
Q

Equation for rate of diffusion into cell:

A

Vinward = PΔS

Vinward = rate of diffusion into cell

P = permeability coefficient

ΔS = conc. gradient across membrane

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6
Q

How do you work out concentration gradient across membrane?

A

Outside concentration minus inside concentration

ΔS = [S]o - [S]i

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7
Q

What does rate of diffusion in passive transport depend on?

A

Thickness + viscosity of membrane

Size, shape, polarity + solubility in membrane of substrate

Concentration difference!!

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8
Q

What’s a partition coefficient?

A

Gives a measure of how well a substance dissolves in lipid or aqueous phase

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9
Q

How do you find partition coefficient?

A

Shake substance with oil and water mixture

Measure conc. of substance in oil and water after settling

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10
Q

Equation to find partition coefficient:

A

[X]oil
K = ————
[X]water

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11
Q

Why does water move more quickly than expected?

A

Intrinsic protein channels transport water (aquaporins)

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12
Q

What do aquaporins form in the membrane?

A

Tetramers - each monomer acts as a water channel

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13
Q

What happens in diffusion through aqueous membrane channels?

A

Substance stays in aqueous solution and passes through hydrophilic channels - allow rapid transport

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14
Q

How wide are aquaporins?

A

1x water molecule wide - too narrow to permit any hydrated ions to pass through

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15
Q

How many aquaporins have been found in the body?

A

13

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16
Q

What are protein channels like?

A

Highly specific

Transport ions

May be opened/closed by gate

17
Q

What are the types of gated protein channels?

A

Voltage gated

Ligand gated

18
Q

What happens in a voltage gated channel?

A

Potential difference inside/outside cell causes confirmation change

19
Q

What happens in a ligand gated channel?

A

Binding of chemical ligand causes conformational change

20
Q

What type of channel is a sodium channel?

A

Voltage channel

21
Q

What do sodium channels do?

A

Lined with negatively charged amino acids

Pull sodium ion away from water shell

Allow smaller sodium ion to diffuse through

22
Q

Why can’t potassium ions diffuse through sodium channels?

A

Unhydrated potassium ions too large

23
Q

What happens in a potassium channel?

A

Carbonyl oxygens strip water molecules from potassium molecule

24
Q

What is facilitated diffusion also known as?

A

Carrier mediated transport

25
Q

What can carrier mediated transport include?

A

Active transport - against conc. gradient

Facilitated diffusion - down conc. gradient

26
Q

What happens in facilitated diffusion?

A

Substance binds to specific carrier which causes conformational change -> substance transported

27
Q

What is rate of diffusion in facilitated diffusion limited by?

A

Vmax of carrier protein

Carrier proteins require time to open and close

28
Q

What can active transport be inhibited by?

A

Competitive inhibitors binding to active site

29
Q

Where can active transport get their energy from?

A

Directly from energy source - primary AT

Secondarily from energy stored as concentration difference resulting from secondary process - secondary AT

30
Q

Example of primary AT:

A

Sodium/potassium pump

Obtains energy directly from breakdown of ATP

31
Q

What does the sodium/potassium pump do?

A

Transports Na+ out of cells and K+ into cells

Establishes negative voltage inside cell

32
Q

Structure of sodium/potassium pump:

A

2 K+ binding sites on external side

3 Na+ binding sites on internal side

33
Q

Where does ATPase activity occur on sodium/potassium pump?

A

Internal side

34
Q

What is the sodium/potassium pump important for?

A

Controlling cell volume

Contribution to electrical potential across membrane

Used to drive secondary active transport

35
Q

What happens in secondary active transport?

A

Indirect use of energy source

Movement of 2 or 3 substances is linked

36
Q

What do symporters do?

A

Transport substances in same direction as ‘driver’ ion

Uses electrochemical gradient

37
Q

What do antiporters do?

A

Transport substance in opposite direction of driver ion

Week 7 - 12 (38 decks)

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