Unit 2: Topic 7 - Facilitated Diffusion

Question 1

How do cells maintain their internal and external environments?

Answer 1

The cell membrance plays a big part in a cel maintaining homeostasis. Homeostasis is a balanced state in the cell meaning that external and internal environments stive to remain balanced and there are complications when cells are out of homeostasis.

Question 2

Why are small molecules able to diffuse more easily than large molecules?

Answer 2

Small molecules are able to fit between the gaps in the cell membranes, so they can easily diffuse through the cell membrane. Large molecules, however, can not fit between the gaps in the cell membrane, so they can not easily diffuse through the cell membrane.

Question 3

Can charged ions diffuse across the cell membrane, and if not, what do they need to go through the membrane?

Answer 3

Charged ions cannot diffuse across the membrane on their own (they are repelled by the nonpolar region of the phospholipid bilayer). They must use transport proteins to move through facilitated diffusion.

Question 4

Can charged large polar molecules diffuse across the cell membrane and if not what do they need to go through the membrane?

Answer 4

Large polar molecules cannot diffuse across the membrane on their own (they are too large to pass through and are repelled by the nonpolar region of the phospholipid bilayer). Large polar molecules require a channel protein to pass through the cell membrane.

Question 5

What happens when a large number of ions move across the cell membrane?

Answer 5

The membrane becomes polarized, meaning that the charge inside the membrane is opposite to the charge outside of the membrane (one side will be positive and the other negative).

Question 6

What are aquaporins, and what is their function?

Answer 6

They are membrane proteins that allow water specifically to pass through the membrane in large amounts easily.

Question 7

What is active transport and what does it require?

Answer 7

Active transport is the movement of substances against their concentration gradient across the cell membrane. Substances naturally want to move with the concentration gradient, so it requires energy (usually from ATP) to move substances across their concentration gradient. Additionally, active transport requires membrane proteins to transport the substances.

Question 8

Is active transport used to maintain concentration gradients?

Answer 8

Yes, active transport is used to maintain concentration gradients

Question 9

Why is Na+/K+ ATPase important?

Answer 9

Na+/K+ ATPase uses energy from ATP to pump sodium and/or potassium across the cell membrane to help maintain membrane potential.