Cell membrane transportation systems

Question 1

What is the cell membrane?

Answer 1

• The cell membrane is a biological entity;
• It separates the inside of a cell from the outside environment;
• Is selectively permeable to ions and molecules; and
• Serves as the attachment surface for the cell wall and the intracellular cytoskeleton

Question 2

What is diffusion?

Answer 2

• Substances move from high concentration to low concentration
• It is a passive process and no extra energy or ATP is required

Question 3

What are the two types of diffusion?

Answer 3

Simple and facilitated

Question 4

What is simple diffusion?

Answer 4

Simple diffusion is the unassisted passage of small, hydrophobic, nonpolar molecules from a higher concentration to a lower concentration.

Question 5

What are non polar molecules?

Answer 5

Nonpolar molecules are water fearing and do not easily dissolve in water.

Question 6

What is facilitated diffusion?

Answer 6

Uses protein channels: exmaples, glucose, some ions)

Question 7

What is Osmosis?

Answer 7

The special type of diffusion that in particular moves water across membranes

Water will move from one side to the other in order to establish an equilibrium (equal amounts of water on both sides)

Question 8

What is active transport?

Answer 8

• When substances need to be moved AGAINST a gradient
• Energy is required
• Molecules are moved across via proteins called transports or pumps

Question 9

What is exocytosis?

Answer 9

Exocytosis is the reverse of endocytosis and involves the release of material from vesicles or vacuoles that have fused with the plasma membrane. Exocytosis is typical of cells that export material (secretory cells).

Question 10

What is endocytosis?

Answer 10

Endocytosis is the engulfment of material. It typically occurs in certain white blood cells of the human defence system.

Question 11

What are the two types of endocytosis?

Answer 11

Phagocytosis: “cell eating”
- Involves the engulfment of solid material and results in the formation and vacuoles.

Pinocytosis: “cell drinking”
- Involves the uptake of liquids or fine suspensions and results in the formation of pinocytic vesicles.

Question 12

What is cytosis?

Answer 12

A form of active transport involving infolding or outfolding of the plasma membrane. Cells are able to do this because of the flexibility of the plasma membrane