4.2 Diffusion

Question 1

What is simple diffusion?

Answer 1

The net movement of molecules or ions from a higher concentrated region to a lower concentrated region.

Question 2

Which factors affect simple diffusion?

Answer 2

•Temperature
•Surface area
•Diffusion pathway length
•Concentration gradient
•The amount of transmembrane channels and transport proteins .

Question 3

What is a limitation of simple diffusion?

Answer 3

Large polar molecules cannot diffuse across the membrane due to the phospholipid bilayer

Question 4

What is facilitated diffusion?

Answer 4

A passive process which uses transport proteins and carrier proteins in the cell surface membrane to transport substances ( that cannot diffuse across the membrane )
Across the membrane, they are specific to the substance and move down a concentration gradient

Question 5

What is a protein channel?

Answer 5

Proteins which form water filled hydrophilic channels across the membrane which allow water soluble substances like ions to pass through they are selective and only open in the presence of a specific ion otherwise remain closed.

Question 6

How does a protein channel work?

Answer 6

The specific ion binds with the specific protein causing it to change shape in a way that closes it to one side of the membrane and opens it to the other side.

Question 7

What is a carrier protein?

Answer 7

A protein which transports larger molecules such as glucose and amino acids across the plasma membrane

Question 8

How do carrier proteins work ?

Answer 8

The molecule binds with the specific protein causing it to change shape say that the molecule is released to the inside of the membrane.