Diffusion

Question 1

Define diffusion

Answer 1

The net movement of molecules/ions from a higher concentration to a lower concentration moving down the concentration gradient.

Question 2

When does diffusion end?

Answer 2

When equilibrium occurs and a concentration gradient no longer exists

Question 3

Is diffusion passive or active?

Answer 3

Passive

Question 4

Why does diffusions occur?

Answer 4

Because molecules move randomly using their own kinetic energy

Question 5

What direction is diffusion?

Answer 5

Occurs in both directions across a membrane

Question 6

Is equilibrium reached with oxygen?

Answer 6

No because respiration is always occuring

Question 7

What happens with simple diffusion? When does it occur?

Answer 7

Large lipid soluble molecules dissolve and pass through the bilayer easily and small non polar molecules pass between phospholipids easily

Question 8

What is ficks law?

Answer 8

The larger the surface area is, the bigger the difference in concentration and the thinner the exchange surface is which means the faster the rate of diffusion is. (Shorter diffusion distance)

Question 9

How do you calculate rate of diffusion?

Answer 9

Rate of diffusion is proportional to the area of diffusion x difference in concentration over the thickness of surface over which diffusion takes place

Question 10

What are the adaptations of the small intestine?

Answer 10

• large sa: volume ratio
• folded inner walls are lined with numerous minute finger like projections called villi

Question 11

Is the bi-layer fully permeable?

Answer 11

No it is partially permeable which is why large water soluble molecules and ions can’t get through

Question 12

How do carrier proteins transport glucose?

Answer 12

The carrier protein has a glucose binding site. Glucose binds to the protein which then changes the protein shape, releasing the glucose. The carrier protein returns to its original shape ready to bind to another glucose

Question 13

Why does facilitated diffusion plateau?

Answer 13

The proteins become saturated and they can only carry one molecule at a time. This means sometimes there are not enough proteins. With simpleSimple diffusion there is nothing to restrict their movement

Question 14

Compare and contrast simple and facilitated diffusion

Answer 14

Both are passive processes
Substances pass down a concentration gradient from high concentration to low in both
With both the rate increases with temperature/concentration gradient and surface area
Only facilitated involves carrier and channel proteins
Increasing concentration plateaus facilitated diffusion eventually