2: Cell membranes

Question 1

The cell membrane is ___ permeable.

Answer 1

selectively

Question 2

Functional differences between cell types are due to variations in the composition of the ___ ___.

Answer 2

cell membranes

Question 3

What are the two main components of cell membranes?

Answer 3

Lipids

Proteins

Question 4

Phospholipid heads are (hydrophilic / hydrophobic).

Answer 4

Heads are hydrophilic

Question 5

Phospholipid tails are (hydrophilic / hydrophobic).

Answer 5

hydrophobic

Question 6

Due to the hydrophilic/phobic nature of the phospholipid heads and tails respectively, the lipids arrange themselves into a ___.

Answer 6

bilayer

Question 7

The cell membrane consists of embedded ___ and a phospholipid ___.

Answer 7

proteins , bilayer

Question 8

Is the phospholipid bilayer fluid or rigid?

Answer 8

Fluid

Question 9

All phospholipids are constantly ___.

Answer 9

moving

Question 10

What molecule helps to stabilise the fluid phospholipid bilayer?

Answer 10

Cholesterol

Question 11

What kind of molecule can pass through the phospholipid bilayer?

Answer 11

Small, uncharged polar molecules

Question 12

Water soluble substances (can / cannot) pass through the phospholipid bilayer.

Answer 12

cannot

Question 13

Name some substances which can pass through the phospholipid bilayer.

Answer 13

O₂

H₂O

CO₂

Question 14

What are the two classes of membrane protein?

Answer 14

Integral

Peripheral

Question 15

What is another name for integral protein?

Answer 15

Transmembrane protein

Question 16

What is peripheral protein?

Answer 16

Protein which is not embedded in the membrane - adheres to cytoplasm instead

Question 17

What is integral protein?

Answer 17

Protein which spans the membrane one or more times

Question 18

Give some examples of types of integral protein.

Answer 18

Ligand-binding receptors

Adhesion molecules

Pores and channels

Carriers

Pumps

Enzymes

Question 19

Which cellular process do docking-marker acceptors help with?

Answer 19

Exocytosis of vesicles

Question 20

Apart from lipids and protein, what other molecule can be found on cell membranes in small amounts?

Answer 20

Carbohydrate

Question 21

When carbohydrate is bound to a) protein and b) lipid, what are those molecules called?

Answer 21

a) glycoproteins

b) glycolipids

Question 22

What layer is formed by glycoproteins and glycolipids on the surface of the cell membrane?

Answer 22

Glycocalyx

Question 23

What do membrane carbohydrates serve as on the cell membrane?

Answer 23

Self-identity markers

Question 24

What kind of molecule makes up self-identity markers on the cell membrane?

Answer 24

Carbohydrate

Question 25

Self-identity markers have an important role in cell-to-cell ___ and cell ___.

Answer 25

interactions , growth

Question 26

What are tight junctions?

Answer 26

Structures which join the lateral ends of epithelial cells together

Question 27

What are desmosomes?

Answer 27

Structures which anchor cells which stretch (e.g cardiac muscle, skin)

Question 28

What are gap junctions?

Answer 28

Communication junctions which allow the passage of ions between cells

Question 29

a) Structures which anchor stretchy cells
b) Structures which join the lateral ends of epithelial cells
c) Communication structures which allow for the passage of ions between cells

Match these definitions to tight junctions, desmosomes and gap junctions.

Answer 29

a) Desmosomes
b) Tight junctions
c) Gap junctions

Question 30

Overall, what are the three main molecules involved in the structure and function of the cell membrane?

Answer 30

Phospholipids (forming a bilayer)

Proteins

Carbohydrates