Cells: Exchange across cell membranes - diffusion

Question 1

What is diffusion

Answer 1

The net movement of particles (molecules or ions) from an area of high concentration from an area of lower concentration

Question 2

What is simple diffusion

Answer 2

It is a form of diffusion that does not require the assistance of membrane proteins

Question 3

Diffusion is a passive process what does this mean

Answer 3

It moves down the concentration gradient so, no energy is required for diffusion to happen

Question 4

What is facilitated diffusion

Answer 4

The transport of polar molecules and ions into and out of a cell through carrier or channel proteins

Question 5

What are the two types of proteins that enable facilitated diffusion

Answer 5

• Channel proteins
• Carrier proteins

Question 6

Channel and carrier proteins ate highly specific what does this mean

Answer 6

They only allow one type of molecule or ion to pass through

Question 7

How do channel proteins enable facilitated diffusion

Answer 7

They allow polar compounds to avoid the non-polar central layer of the plasm membrane as they have hydrophilic (water-filled) interiors

Question 8

How do carrier proteins enable facilitated diffusion

Answer 8

The carrier protein changes shape of when a substance binds to it, allowing the substance from outside of the cell to move to the inside

Question 9

Name the factors that affect diffusion

Answer 9

• Concentration gradient
• Temperature
• Membrane surface area
• Thickness of membrane
• Number of channel or carrier proteins

Question 10

How does the concentration gradient affect diffusion

Answer 10

The bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion

Question 11

How does the temperature affect diffusion

Answer 11

The higher the temperature, the faster the rate of diffusion

Question 12

How does the membrane surface area affect diffusion

Answer 12

The larger the surface area of the membrane that a substance is diffusing through (e.g. the membrane around a cell), the faster the rate of diffusion

Question 13

How does the thickness of membrane affect diffusion

Answer 13

The thicker the exchange surface, the slower the rate of diffusion

Question 14

How does the number of carrier or channel in a cell membrane affect facilitated diffusion

Answer 14

• The number of channel or carrier proteins affects the rate of facilitated diffusion
• The more proteins, the faster the rate