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Introduction to physiology with pharmacology > Cell membrane transport > Flashcards

Cell membrane transport Flashcards

Semester 1 Year 1

1
Q

What are 2 types of passive transport?

A

Simple + facilitated diffusion

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2
Q

What are 2 types of active transport?

A

Primary (direct) + secondary (indirect)

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3
Q

What is the purpose of an electrochemical gradient?

A

Drives passive transport

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4
Q

What is an electrochemical gradient dependent on?

A

Always dependent on conc. grad. of the solute. For charged molecules, also dependent on any difference in voltage between ICF and ECF

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5
Q

What is simple diffusion?

A

Movement of an uncharged solute through lipid bilayer

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6
Q

What does the speed of simple diffusion depend on?

A
  • permeability of membrane to solute
  • difference in con. between ECF and ICF
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7
Q

What type of solute does simple diffusion allow to move?

A

Hydrophobic solutes

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8
Q

What type of solutes do transmembrane proteins allow to move?

A

Hydrophilic solutes

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9
Q

What are transmembrane proteins composed of?

A

Membrane-spanning alpha-helical domains

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10
Q

What is a proteins membrane topology?

A

How the protein moves in + out of the membrane

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11
Q

What are the types of transmembrane protein?

A

Pore, channel, carrier, pump

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12
Q

How does a pore act as a transmembrane protein?

A

Form a channel but has not gate on it

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13
Q

How does a channel act as a transmembrane protein?

A

Is a gated pore - can open and close for substances to move through

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14
Q

How does a carrier act as a transmembrane protein?

A

It doesn’t have a clear opening, so substances bind to it

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15
Q

How does a pump act as a transmembrane protein?

A

Requires ATP to change shape for transport

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16
Q

How do transmembrane proteins allow substances to move across?

A

Create hydrophilic permeation pathways through the membrane

17
Q

What is special about the amino acid sequence of transmembrane proteins?

A

Amphipathic helices - alternating hydrophobic and hydrophilic amino acids as determined by their variable regions

18
Q

Which way do the hydrophobic + hydrophilic surfaces of the transmembrane protein face?

A

Hydrophobic-lipid membrane (outside)
Hydrophilic-creates central pore (inside)

19
Q

Describe pores

A

-allow for facilitated diffusion
-driving force for movement=electrochemical gradient
-always open
-made up of multiple subunits

20
Q

Describe channels

A

-allow for facilitated diffusion
-driving force for movement=electrochemical gradient
-gated ion channels
-made up of multiple subunits

21
Q

What does each channel have?

A

-a moveable gate
-a sensor
-a selectivity filter
-an open channel pore

21
Q

What are the types of sensors found in a channel?

A

-voltage
-ligand
-mechanical (membrane stretches so channel opens)

21
Q

Describe carriers

A

-allow facilitated diffusion
-driving force for movement=electrochemical gradient
-never has a continuous transmembrane path

22
Q

How do carriers work?

A

-the molecule enters the carrier through the outer gate + binds at the binding site
-outer gate closes + inner gate opens
-molecule exits + enters cell
-inner gate closes

22
Q

Is carrier mediated facilitated diffusion faster or slower?

A

Slower

23
Q

What limits carrier mediated facilitated diffusion?

A

-can become saturated
-limited by number of carriers in membrane
-limited by the speed by which carrier cycles through steps

24
Q

Describe active transport

A

-moves solutes against its electrochemical gradient
-requires metabolic energy
-uses ATP

25
Q

What are the 2 types of active transport?

A

Primary and secondary

26
Q

Describe primary active transport

A

-uses a pump
-driving force is a chemical reaction e.g ATP hydrolysis into ADP

26
Q

Describe secondary active transport

A

-uses cotransporters + exchanges
-uses electrochemical gradient from primary step
-driving force=coupling the uphill movement of 1 solute with the downhill movement of another

27
Q

What else can carriers mediate?

A

-pumps
-cotransporters
-exchangers

28
Q

Describe the sodium potassium ATPase pump

A

-pump moves sodium out of cell + potassium into it
-breakdown of ATP drives their movement in opposite directions
-pumps can become saturated

29
Q

Describe cotransporters (symporters)

A

-move solutes in the same direction
-secondary active transport
-requires a driving solute whose electrochemical gradient provides energy (usually inward Na+)

30
Q

Describe exchangers (antiporters)

A

-move solutes in opposite directions
-requires a driving solute whose electrochemical gradient provides energy (usually inward Na+)

31
Q

Which transmembrane protein has the slowest rate of transport?

A

Carrier

Introduction to physiology with pharmacology (22 decks)

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