CELL TRANSPORT MECHANISMS

Question 1

What are cell membranes made up of? (5)

Answer 1

-phospholipids
-glycoproteins
-glycolipids
-cholesterol
-intrinsic and extrinsic proteins

Question 2

What is a surface membrane?(1)

Answer 2

Selectively permeable….

Question 3

What are the roles of the cell membrane (surface)? (4)

Answer 3

-separates cell components from the outside of the cell
-controls what gets in and out of cells
-cell signalling via glycoproteins/glycolipids
-cell to cell communication

Question 4

What are the roles of the cell membrane (within cells)? (3)

Answer 4

-separates contents of cell organelles from cytoplasm
-surface for metabolic reactions (mitochondria)
-allow transport of RNA and ribosomes in and out of the nucleus (nuclear membranes)

Question 5

What factors affect fluidity of the cell membrane? (3)

Answer 5

-temperature
-cholesterol
-saturated lipids

Question 6

How does temperature affect fluidity of a cell membrane? (2)

Answer 6

Low temperature- lipids are closely packed/less fluid.
High temperature- lipids get more kinetic energy and therefore more fluid

Question 7

How does cholesterol affect the fluidity of a cell membrane? (2)

Answer 7

Cholesterol is attached to the fatty acid chains, so keeps molecules together and stops them moving apart-prevents too much fluidity or solidity.

Question 8

How does saturated lipids affect the fluidity of a cell membrane? (2)

Answer 8

Lipids with long and saturated tails have a high melting point which decreases fluidity.
The straight unkinked fatty acid chains mean the lipid molecules can pack together more closely

Question 9

what is the equation for water potential? (1)

Answer 9

Turgor pressure + osmotic potential

Question 10

What is the value for osmotic potential? (1)

Answer 10

Always negative

Question 11

What is the value for turgor pressure? (1)

Answer 11

Usually positive

Question 12

What is the value for water potential? (1)

Answer 12

Usually negative

Question 13

What is turgor pressure? (1)

Answer 13

The inward pressure of the cell wall on the cytoplasm.

Question 14

What is hydrostatic pressure? (1)

Answer 14

When the cytoplasm swells and presses against the cell walls.

Question 15

When is a plant cell considered rigid? (1)

Answer 15

When the osmotic force moving water into the plant cell is balanced by the turgor pressure forcing it out, the plant cell is rigid.

Question 16

What is the osmotic potential? (1)

Answer 16

The potential of water to move out of a solution across a partially permeable membrane as a result of dissolved solutes.

Question 17

What is the osmotic potential of pure water? (1)

Answer 17

Exactly zero.