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Microbiology MD2001 > Molecule Movement > Flashcards

Flashcards in Molecule Movement Deck (14)
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1
Q

Define uniport and contrasport

A

Uniport - moving one molecule

Contrasport - moving more than one different molecules

2
Q

Define symport and antiport

A

Symport - moving in the same direction

Antiport- moving in the opposite direction

3
Q

Define DeltaS and P in the equation for Vinwards

A

Delts S = conc gradient across membrane

P = permeability coefficient

4
Q

What is the partition coefficient?

A

The measure of how well a substance dissolves in lipid or aqueous.

5
Q

What does the rate of transport through lipids depend on?

A

The polarity of a substance, less polar substance will pass through the membrane faster than polar.

6
Q

What allows for the rapid diffusion of water across a membrane?

A

Aquaporin molecules. However these molecules only allow for the passage of one water molecule at a time and are too narrow to allow for the passage of hydrated ions

7
Q

What effects the passive passage of molecules through aqeuous membranes

A

The size of the molecule. The rate of influx decreases as size increases.

8
Q

Describe two gated channels

A

Voltage Gated - The potential difference in or out of the cell causes a conformational change
Ligand Gated - Binding of a chemical ligand causes a confromational change.

9
Q

Give an example of a voltage gated channel

A

Sodium channels are voltage gates. These are very selective and only allow for the passage of unhydrated sodium and potassium ions.

10
Q

Describe some of the features of facilitated diffusion (carrier mediated transport)

A

It requires a specific substance to bind to a carrier which causes a confromational change allowing for the substance to pass through the molecule.
However this type of transport can saturate as time is required for the carrier protein to open.

11
Q

Describe some of the features of active transport

A

It requires energy to transport molecule against a conc gradient and is key where specific ion concs must be maintained. Can be primary or secondary

12
Q

Describe Primary active transport and give some examples.

A

It uses energy sources directly. Ca (ion) ATPase - present on cell membrane and the sarcoplasmic reticulum of muscle fibres. Maintains low Ca concs
H (ion) ATPase - found in parietal cells of gastric glands and intercalated cells of renal tubules. It concentrates H+ ions.

13
Q

Describe some of the features of Secondary active transport and give an example

A

It uses an indirect source of energy. Example -
Sodium creates a high electrochemical energy due to pressure to diffuse through the membrane. Sodium and a second molecule bind to the symporter and are both transported into the cell using sodium electochemical energy.

14
Q

Describe the role of the sodium/potassium pump in maintaing cell volume

A

Cell membrane isn’t permeable to Na but small amount do leak into cells. This must be removed or the cell would burst.
Phosphorylation of an ATP molecule causes a conformational change that causes 3 x Na ions to extrude across the membrane and 2 x K ions to be introduced into the cell.