What is a cell membrane

Question 1

Why are membranes important?

Answer 1

• Forms an outer boundary of every cell
• Selectively permeable- controls entry of nutrients and exit of waste
• Maintains an ion concentration gradient between inside and outside of cell
• Participates in joining of cells to form tissues/organs
• Enables cells to respond to changes in environment
• Membrane functions are crucial for cell survival

Question 2

Two main constituents of a cell wall?

Answer 2

Protein and lipid

Question 3

What are many functional differences between cell types due to?

Answer 3

Variations in the composition of their plasma membranes

Question 4

Phospholipid molecule description?

Answer 4

Hydrophillic head
Glycerol backbone
Hydrophobic fatty acid chains (Tails)

Question 5

How is cell membrane arranged in water?

Answer 5

With the hydrophilic head groups oriented towards the water and the hydrophobic tail groups oriented away from the water

Question 6

Name for structure of cell membrane?

Answer 6

Phospholipid Bilayer

Question 7

What gives the cell membrane it’s Fluidity?

Answer 7

Phospholipids rotate, move laterally, flex, twirl, vibrate in their own half of the membrane millions of times per second. (They however do not flip)

Question 8

What stiffens the cell membrane?

Answer 8

Cholesterol molecules

Question 9

Phospholipid bilayer membranes are impermeable to@

Answer 9

Charged ions (Almost any water soluble substance)

Question 10

What molecules can cross lipid bilayer?

Answer 10

Water, oxygen, CO2, NH3, (Small uncharged polar molecules)

Question 11

Why can water get through the membrane?

Answer 11

Can fit through the gaps made by phospholipid molecules when they move

Question 12

3 basic functions of lipid bilayer?

Answer 12

Forms Basic structure of membrane
Hydrophobic barrier interior serves as a barrier
Responsible for membrane fluidity- change cell shape

Question 13

2 types of membrane proteins?

Answer 13

Peripheral or Integral (Or docking- marker acceptors)

Question 14

Peripherally associated membrane proteins?

Answer 14

Not embedded within the membrane

Adhere tightly to the cytoplasmic/ extracellular surfaces of the Plasma membrane

Question 15

Integral Membrane Proteins?

Answer 15

Associated with lipid bilayer in 3 ways

1) Proteins that span the lipid bilayer once or several times (Transmembrane Proteins)
2) Proteins that are embedded but do not cross the bilayer
3) Proteins that are linked to a lipid component of the membrane of a fatty acid derivative that intercalates into the membrane

Question 16

What are peripheral proteins bonded to?

Answer 16

Non-covalently bonded with integral proteins

Question 17

5 main functions of integral proteins?

Answer 17

1) Ligand Binding Receptors
2) Adhesion molecules
3) Can carry out trans-membrane movement of water molecules
4) Can be enzymes
5) Can participate in intracellular signalling

Question 18

Docking- marker acceptor proteins?

Answer 18

Located on inner membrane surface

Interact with secretory vesicles leading to exocytosis of vesicle contents.

Question 19

Glycocalyx formed by?

Answer 19

Glycoproteins and glycolipids

Question 20

What serves as self-identity markers on cells?

Answer 20

Short carbohydrate chains on the outer membrane surface

These enable cells to interact with and identify one another

Question 21

Carbohydrates Role?

Answer 21

Self-identity Markers- enable cells to interact with and identify each other
Role in tissue growth- cells don’t overgrow territory

Question 22

3 types of specialized cell junction?

Answer 22

Tight Junctions
Desmosomes
Gap junctions

Question 23

Tight Junctions

Answer 23

Join the lateral edges of epithelial cells near their lumenal (apical) membranes (can be tight or leaky junctions)

Question 24

Desmosomes

Answer 24

Adhering junctions that anchor cells together, especially in tissues subject to stretching eg skin, heart, uterus

Question 25

Gap junctions

Answer 25

‘Communicating junctions that allow the movement of charge carrying ions and small molecules between two adjacent cells.

Question 26

Basolateral membrane faces the?

Answer 26

Blood

Question 27

Example of muscles that Gap junctions help?

Answer 27

Heart muscles to contract and relax in coordination-

Allows rapid spread of electric activity