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Biology OCR (5, plasma membranes) > Diffusion > Flashcards

Flashcards in Diffusion Deck (17)
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1
Q

What is the definition of diffusion?

A

the net passive movement of particles (atoms, ions or molecules) from a region of high concentration to a region of low concentration. It continues until the concentration reaches equilibrium between the two areas.

2
Q

What are the two factors which affect the rate of diffusion?

A

Temperature and concentration

3
Q

How does an increase in temperature affect the rate of diffusion?

A

The particles would have more kinetic energy and so would move at higher speeds

4
Q

How does concentration affect the rate of diffusion?

A

The greater the difference in concentration between the two areas the faster the rate of diffusion because the overall movement from the higher concentration o the lower concentration would be greater

5
Q

What is meant by simple diffusion?

A

Diffusion in the absence of a barrier or membraneq

6
Q

How can you calculate the rate of diffusion?

A

Distance/time

7
Q

Why are membranes described as partially permeable?

A

Because they will only allow particular substances to enter the cell

8
Q

What substances move through the membrane the easiest?

A

Small non-polar molecules

9
Q

What substances have the hardest time of trying to move through the membrane?

A

Large polar molecules

10
Q

Why are polar molecules or ions move through the membrane slowly or not at all?

A

They are repelled by the hydrophobic core of the membrane (non-polar lipid tails)

11
Q

What are the two factors that affect the rate at which molecules and ions move through the membrane?

A

Surface area and thickness of membrane

12
Q

How does increasing the surface area affect the rate of diffusion of molecules and ions across the membrane?

A

The larger the surface area the higher the rate of diffusion

13
Q

How does decreasing the thickness of the membrane affect the rate of diffusion of molecules and ions across the membrane?

A

The thinner the exchange surface, the higher the rate of diffusion

14
Q

What is the name given to the movement of a polar molecule or ion via a channel protein or carrier protein?

A

Facilitated diffusion

15
Q

Why are membranes with channel proteins selectively permeable/

A

Because most channel proteins are specific to one molecule or ion

16
Q

Does facilitated diffusion require energy?

A

No. because the movement of molecules is still down a concentration gradient

17
Q

The more protein channels…..

A

The higher the rate of diffusion overall