Cell membrane and transport

Question 1

What is the usual thickness of the cell membrane under an electron microscope?

Answer 1

7-8nm

Question 2

What biological molecules make up the cell membrane?

Answer 2

PROTEINS
glycoproteins
lipoproteins
simple proteins
lipids
phospholipids
glycolipids
cholesterol

Question 3

What is the difference between extrinsic and intrinsic proteins?

Answer 3

Intrinsic proteins span the whole phospholipid bilayer, extrinsic proteins do not

Question 4

What is the fluid mosaic model?

Answer 4

The individual phospholipid molecules can move around within a layer
Proteins embedded in the bilayer vary in shape and size and are distributed randomly

Question 5

What are the major functions of the cell membrane?

Answer 5

Taking up nutrients
Secreting chemicals
Cell recognition

Question 6

Describe the permeability of the cell membrane

Answer 6

Selectively permeable to water and some solutes

Question 7

How do lipid soluble substances move through the cell membrane compared to water soluble substances?

Answer 7

Lipid soluble substances diffuse across the membrane dissolved in a phospholipid
water soluble substances have to use temporary intrinsic protein channels

Question 8

What factors affect the rate of diffusion across the plasma membrane?

Answer 8

surface area
the concentration gradient
temperature
size of molecule
lipid solubility
availability of specific ion channels
thickness of the membrane

Question 9

How does water move through the cell membrane?

Answer 9

via aquaporins, protein channels that are specialised for water transport

Question 10

What 2 factors sum to make the water potential in plants?

Answer 10

the solute potential
the opposite pressure potential from the cell wall

Question 11

What does plasmolysed mean?

Answer 11

the cell has lost water and shrunk, the cytoplasm of the cell has pulled away from the cell wall

Question 12

What happens when a cell is placed in a hypotonic solution?

Answer 12

animal cell will burst
plant cell will take in water until prevented by the pressure potential and then is fully turgid

Question 13

What is cotransport?

Answer 13

A type of facilitated diffusion where 2 substances are simultaneously transported across a membrane by one protein without ATP

Question 14

What is phagocytosis?

Answer 14

Where a large particle enters the cell, becomes enclosed in membrane and forms a vesicle and is transported through the cytoplasm

Question 15

What is secretion/endocytosis?

Answer 15

substances leaving the cell after being transported through the cytoplasm through a vesicle

Question 16

How does the cell membrane change?

Answer 16

It is constantly having portions removed or added to it through phagocytosis and secretion

Question 17

What is pinocytosis?

Answer 17

The entry of liquids through being enclosed in the membrane to form a vesicle and then transported through the cytoplasm

Question 18

When does active transport not take place?

Answer 18

In the presence of a respiratory inhibitor such as cyanide

Question 19

How are solutes transported across the membrane?

Answer 19

Through a special carrier protein

Question 20

What is exocytosis?

Answer 20

The active process of a vesicle fusing with the cell membrane and releasing the molecules it contains