Cell Membranes I

Question 1

What are the layers of the cell?

Answer 1

Apical = Top Part 
Lateral =  Middle Part
Basal = Bottom Part

Question 2

What is the structure of the plasma membrane like?

Answer 2

Lipid bilayer (phospholipids and others) combined with proteins (structural) and carbohydrates located in the outer monolayer.

Question 3

Name some single membrane examples.

Answer 3

Lysosome
Endoplasmic Reticulum
Golgi Apparatus
Vacuoles

Question 4

Name some double membrane examples.

Answer 4

Plasma Membrane
Mitochondria
Chloroplasts
Nuclear Envelopes.

Question 5

What is an example of a common lipid?

Answer 5

Phosphoglycerides = Phospholipids derived from glycerol.

Question 6

What are sphingolipids?

Answer 6

Phospholipids derived from sphingosine.

Amino alcohol which contains long unsaturated hydrocarbon chain

Question 7

What is the ratio of lipids?

Answer 7

Phospholipids = 75% 
Cholesterol = 20%

Question 8

What is the structure of lipids?

Answer 8

Hydrophilic head (negatively charged) 
Hydrophobic tail (uncharged)

Question 9

What is the positioning of the lipid molecule?

Answer 9

Tails meet in the inner region of the membrane = AWAY FROM THE WATER.
Heads meet in the outer region of the membrane = TOWARDS TO THE INTRACELLULAR / EXTRACELLULAR FLUID.

Question 10

What is the number of main phosphoglycerides?

Answer 10

3 main phosphoglycerides.

Question 11

What is the number of main sphingolipids?

Answer 11

1 main sphingolipid.

Question 12

What does phospholipids in water create?

Answer 12

Forms into micelles.

Question 13

What are liposomes?

Answer 13

Spherical vesicles of at least one lipid bilayer.

Question 14

What are lipids normally composed by?

Answer 14

Phosphatidylcholine.

Question 15

How can liposomes be formed artificially?

Answer 15

Disrupts cell membranes.

Question 16

What are liposomes used as?

How does it carry out this function?

Answer 16

Vehicle for administration of nutrients and pharmaceutical drugs.
Membrane of liposome will FUSE with membrane of cell to deliver the content into the cell.

Question 17

Where is cholesterol normally present ?

Answer 17

Present in animal cell membranes.

Question 18

What is the purpose of cholesterol?

Answer 18

• Regulates membrane fluidity.

- Allows presence of protein channels in the membrane.

Question 19

How does it regulate membrane fluidity?

Answer 19

Hydroxyl head of cholesterol will attach to the phospholipids and DISRUPT non - covalent bonds between fatty acids.

Question 20

What are glycolipids?

Answer 20

Lipids with carbohydrate attached by covalent - bond surface of the eukaryotic membrane.

Question 21

What is the function of glycolipids?

Answer 21

Maintains membrane stability and facilitates cellular recognition in immune response.

Question 22

What is glycocalyx?

Answer 22

Glycoprotein and glycolipid hybrid which surrounds cell membranes of some bacterial cells.

Question 23

How can lipid cell membrane fluidity vary?

Answer 23

• Temperature
• Fatty Acid Composition
• Chain Length
• Degree and Extent of saturation
• Cholesterol content

Question 24

What does a longer chain mean in terms of a lipid chain?

Answer 24

MORE interaction.

Question 25

Why does the structure of lipids become more rigid?

Answer 25

There is a very TIGHT packing.

Question 26

What is the structure of lipids like during low temperature?

Answer 26

Without the cholesterol there is NO rigidity. | When cholesterol is ADDED : FLUIDITY INCREASES.

Question 27

What is the structure of lipids like during high temperatures?

Answer 27

Without the cholesterol there is RIGIDITY. | When cholesterol is ADDED : FLUIDITY DECREASES.

Question 28

What is a sickness which can lead to decreased membrane fluidity?

Answer 28

Spur Cell Anaemia. This is very common in patients with liver cirrhosis. LEADS TO CELL DEATH.

Question 29

What is the solution to spur cell anaemia?

Answer 29

Liver Transplant.

Question 30

What is the 2 modes of transport for lipids?

Answer 30

Lateral Movement | Transverse Movement

Question 31

Explain lateral movement of lipids.

Answer 31

Free movement of molecules and therefore, the lateral movement is VERY RAPID.

Question 32

Explain transverse movement of lipids.

Answer 32

'Flip - flopping' movement and therefore, the transverse movement is VERY SLOW. *Requires action of three enzymes*

Question 33

What are the 3 enzymes required to adjust the cell membrane fluidity?

Answer 33

Flippase Floppase Scramblase

Question 34

What is the purpose of flippase?

Answer 34

Moves phospholipids from the outer to the inner leaflet. (REQUIRES ATP).

Question 35

What is the purpose of floppase?

Answer 35

Moves phospholipids from INNER to OUTER leaflet. | REQUIRES ATP

Question 36

What is the purpose of scramblase?

Answer 36

Bidirectional moment.

Question 37

Which membrane does scramblase work on?

Answer 37

ER membrane.

Question 38

Which membrane does flippase work on?

Answer 38

Golgi Membrane or Plasma Membrane.

Question 39

What is the process of phagocytosis?

Answer 39

1) Recruitment to find the 'eat - me' signals. 2) Recognition of 'eat - me' signals // Engulfment of corpse. 3) Process and Degrade the corpse. 4) Pos engulfment consequences. (Releases anti - inflammatory cytokines.)

Question 40

What molecules is released the MOST when cells are dying?

Answer 40

Phosphatidylserine.

Question 41

What are the 3 main integral membrane proteins?

Answer 41

Alpha - Helix = Recognition / Receptors. Helical Bundle = Enzymes / Transporters / Receptors. Beta - Barrel = Transporters (channel proteins).

Question 42

What is the main trans - membrane domain?

Answer 42

Alpha - Helix

Question 43

What bonds do integral membrane proteins have?

Answer 43

Strong non - covalent bonds.

Question 44

Where are peripheral membrane proteins located?

Answer 44

Located on either side of thee membrane.

Question 45

What bonds do peripheral membrane proteins have?

Answer 45

Associated by non - covalent bonds.

Question 46

How are carbohydrates attached?

Answer 46

Covalently linked to proteins or lipids of the external layer.

Question 47

What is the function of carbohydrates?

Answer 47

Involved in cell - cell interactions / cellular recognition and cell adhesion.

Question 48

What is the function of the nuclear pore complex?

Answer 48

Exchange of components and prevention of the transport of non - desired material.