M&R 2 - Permeability Barriers Flashcards

0
Q

What is the relationship between the rate of passive transport and increasing concentration gradient.

A

The rate of passive transport increases linearly with increasing conc gradient.

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1
Q

How do non polar molecules travel across bilayers?

A

They diffuse across the hydrophobic domain

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2
Q

How does water travel across the membrane?

A

Water diffuses passively down the osmotic gradient

In some cells the moment of water is also facilities by aquaporins

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3
Q

Why is the movement of ions and hydrophilic molecules important?

A

Maintains intracellular pH
Maintains ionic composition
Regulates cell volume

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4
Q

What are the two thermodynamically viable mechanisms of facilitated diffusion?

A
Carrier molecules (ping pong)
Protein channels (pores)
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5
Q

What is the difference between active and passive transport?

A

Active needs energy passive is spontaneous.

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6
Q

What are the three ‘currencies’ of free energy used for active transport?

A

ATP
electron transport
Light

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7
Q

What is a co-transporter?

A

This is when the transport of one substance is linked to concentration of another.

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8
Q

What is a uni port?

A

One solute molecule from one side -> the other side

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9
Q

What is co transport in the same direction called? And what is different?

A

Same - symport

Different - anti port

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10
Q

What are the features of a Na+/K+ ATPase pump?

A

Plasma membrane pump that uses ATP to pump 3 sodium out and 2 potassium in.
Necessary for electrical excitability
Drives secondary active transport that leads to -
The control of pH, regulation of cell volume etc

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11
Q

Why do calcium levels need to be controlled in cells?

A

Ca2+ is toxic to cells. (See MoD)

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12
Q

What are the features of the PMCA pump?

A

Expels Ca2+ from the cell in exchange for H+ (anti port)
Uses ATP.
It has a high affinity for calcium but a low capacity

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13
Q

What are the features of the SERCA pump?

A

Accumulates Ca2+ in the ER in exchange for H+ (antiport)

Uses ATP, also has a high affinity low capacity

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14
Q

What are the features of the NCX pump?

A

Uses the Na+ gradient set il by the sodium potassium pump
(Secondary active transport)
Removes most Ca2+
Electrogenic - as current flows in direction of sodium gradient

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15
Q

What are the features of the Na+ glucose co transport

A

In the SI and the kidney the entry of sodium privies energy for the entry of glucose. (Symport)

16
Q

When are ions used in pH regulation?

A

When buffering capacity is exceeded.

17
Q

What are the features of the NHE pump?

A

Sodium in H+ out.

One to one exchange that raises cell pH and regulates cell volume.

18
Q

What are the features of the NBC transporter?

A

This is the sodium bicarbonate transporter
Pumps sodium and bicarbonate in
And H+ and Cl- out.
Acid out - base in

19
Q

What is the band 3 anion exchange?

A

This acidifies the cell by moving chloride ions inwards and pumping bicarbonate out.

20
Q

How to cells respond to swelling?

A

They then extrude the osmotic ally active ions (sodium, potassium and chloride) via transporters.

21
Q

How do cells respond to shrinkage?

A

This causes an influx of osmotically active ions

22
Q

What is the normal bicarbonate reabsorption mechanism by the proximal tube?

A

The sodium potassium pump drives other channels by keeping intracellular Na+ concentrations low.
NHE can pump H+ ions into the lumen
H+ goes to ‘pick up’ bicarbonate and bring it back into the cell.

23
Q

What is renal hypertensive therapy?

A

These are drugs which in it sodium transporters which in turn reduces the reuptake of Na+ so less water is reabsorbed.
Less water = less BV = less BP

24
Q

What do loop diuretics do?

A

These act on the thick ascending limb

They block the NKCC2 transporter preventing sodium reuptake into the proximal cells

25
Q

What do the thiazides do?

A

These act on the distal convoluted tube

They block NCCT transporters.

26
Q

What do amilorides do?

A

These block ENaC transporters to prevent sodium uptake.

In the cortical collecting duct.

27
Q

What do spironolactones do?

A

These are glucocorticoid receptor antagonists used to reduce the effect of raised aldosterone. Also in the cortical collecting duct .
Decreases blood pressure.