Membranes

Question 1

What is the structure of a phospholipid?

Answer 1

Glycerol, two fatty acids and a phosphate group

Question 2

What is the width of the cell membrane?

Answer 2

7nm

Question 3

What’s the difference between intrinsic and extrinsic proteins?

Answer 3

Intrinsic proteins pass right through the membrane such as carrier and channel proteins, extrinsic do not pass the entire way through, or are peripheral (only on the outside)

Question 4

What is the glycocalyx?

Answer 4

The layer above the membrane consisting of carbohydrate chains from glycoproteins

Question 5

What does ?fluid mosaic? model mean?

Answer 5

The model is called fluid because the phospholipid and protein molecules move around each other. The model is called a mosaic because proteins embedded between the phospholipids vary in shape, size and patter

Question 6

What is the function of glycoproteins and glycolipids in the cell membrane?

Answer 6

Cell to cell communication and recognition

Question 7

What is the function of cholesterol in the cell membrane?

Answer 7

To maintain fluidity

Question 8

How do lipid soluble substances pass through the cell membrane?

Answer 8

They can dissolve in the fatty acid tails and move through the membrane by simple diffusion

Question 9

How do ions pass throught the cell membrane?

Answer 9

They must pass through a channel protein by facilitated diffusion

Question 10

What is active transport?

Answer 10

Movement from an area of low to high concentration, against a concentration gradient. This is done through a carrier protein and requires ATP

Question 11

Which transport protein is used for active transport?

Answer 11

A carrier protein

Question 12

What is a channel protein for water called?

Answer 12

An aquaporin

Question 13

What is the specific term for bulk transport of a solid into a cell?

Answer 13

Phagocytosis

Question 14

What is the term for bulk transport of a liquid into a cell?

Answer 14

Pinocytosis

Question 15

What is the term for bulk transport out of a cell?

Answer 15

Exocytosis

Question 16

Why do endocytosis and exocytosis require ATP?

Answer 16

ATP is required to provide energy to move the cell membrane

Question 17

What is osmosis?

Answer 17

Water molecules move down a water potential gradient through a selectively permeable membrane.

Question 18

What is the water potential of pure water?

Answer 18

0 Kpa, the highest water potential can be

Question 19

In a plant cell the water potential=

Answer 19

The solute potential (?s) which is the effect of solutes lowering the water potential of the cell sap (negative value) and ?p which is the opposite pressure provided by the cell wall and is usually positive (?cell = ?s+ ?p).

Question 20

Hypotonic means

Answer 20

A solution with a higher water potential than a cell

Question 21

Hypertonic means

Answer 21

A solution with a lower water potential than a cell

Question 22

Isotonic means

Answer 22

A solution with the same water potential as a cell

Question 23

When in hypertonic solution, what will happen to a plant and animal cell and why?

Answer 23

Water will move out of the cell, down a water potential gradient by osmosis. The plant cell is plasmolysed or flaccid, the animal cell is crenated

Question 24

When in hypotonic solution, what will happen to a plant and animal cell and why?

Answer 24

Water will move into the cell, down a water potential gradient by osmosis. The plant cell is turgid, the animal cell will swell and lyse (burst)

Question 25

When a plant cell is in incipient plasmolysis, what is happening to water movement?

Answer 25

There is no net water movement into or out of the cell

Question 26

How would you recognise a plant tissue in incipient plasmolysis?

Answer 26

50% of cells are plasmolysed, 50% are turgid

Question 27

How would you recognise a plant cell in incipient plasmolysis?

Answer 27

The cell membrane is just beginning to move away from the cell wall

Question 28

Why would cyanide stop active transport?

Answer 28

Because it is a non competitive respiratory inhibitor, which would prevent production of ATP. ATP is required to provide energy for active transport

Question 29

What does increasing temperature do to the cell membrane?

Answer 29

As temperature increases the membrane becomes more fluid, and slightly more permeable. When the temperature increases too much proteins will denature and lost their shape, creating pores that make the membrane even more permeable.