Cell Membranes I Flashcards

1
Q

What are the layers of the cell?

A
Apical = Top Part 
Lateral =  Middle Part
Basal = Bottom Part
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2
Q

What is the structure of the plasma membrane like?

A

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

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3
Q

Name some single membrane examples.

A

Lysosome
Endoplasmic Reticulum
Golgi Apparatus
Vacuoles

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4
Q

Name some double membrane examples.

A

Plasma Membrane
Mitochondria
Chloroplasts
Nuclear Envelopes.

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5
Q

What is an example of a common lipid?

A

Phosphoglycerides = Phospholipids derived from glycerol.

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6
Q

What are sphingolipids?

A

Phospholipids derived from sphingosine.

Amino alcohol which contains long unsaturated hydrocarbon chain

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7
Q

What is the ratio of lipids?

A
Phospholipids = 75% 
Cholesterol = 20%
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8
Q

What is the structure of lipids?

A
Hydrophilic head (negatively charged) 
Hydrophobic tail (uncharged)
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9
Q

What is the positioning of the lipid molecule?

A

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.

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10
Q

What is the number of main phosphoglycerides?

A

3 main phosphoglycerides.

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11
Q

What is the number of main sphingolipids?

A

1 main sphingolipid.

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12
Q

What does phospholipids in water create?

A

Forms into micelles.

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13
Q

What are liposomes?

A

Spherical vesicles of at least one lipid bilayer.

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14
Q

What are lipids normally composed by?

A

Phosphatidylcholine.

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15
Q

How can liposomes be formed artificially?

A

Disrupts cell membranes.

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16
Q

What are liposomes used as?

How does it carry out this function?

A

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

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17
Q

Where is cholesterol normally present ?

A

Present in animal cell membranes.

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18
Q

What is the purpose of cholesterol?

A
  • Regulates membrane fluidity.

- Allows presence of protein channels in the membrane.

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19
Q

How does it regulate membrane fluidity?

A

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

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20
Q

What are glycolipids?

A

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

21
Q

What is the function of glycolipids?

A

Maintains membrane stability and facilitates cellular recognition in immune response.

22
Q

What is glycocalyx?

A

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

23
Q

How can lipid cell membrane fluidity vary?

A
  • Temperature
  • Fatty Acid Composition
  • Chain Length
  • Degree and Extent of saturation
  • Cholesterol content
24
Q

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

A

MORE interaction.

25
Why does the structure of lipids become more rigid?
There is a very TIGHT packing.
26
What is the structure of lipids like during low temperature?
Without the cholesterol there is NO rigidity. | When cholesterol is ADDED : FLUIDITY INCREASES.
27
What is the structure of lipids like during high temperatures?
Without the cholesterol there is RIGIDITY. | When cholesterol is ADDED : FLUIDITY DECREASES.
28
What is a sickness which can lead to decreased membrane fluidity?
Spur Cell Anaemia. This is very common in patients with liver cirrhosis. LEADS TO CELL DEATH.
29
What is the solution to spur cell anaemia?
Liver Transplant.
30
What is the 2 modes of transport for lipids?
Lateral Movement | Transverse Movement
31
Explain lateral movement of lipids.
Free movement of molecules and therefore, the lateral movement is VERY RAPID.
32
Explain transverse movement of lipids.
'Flip - flopping' movement and therefore, the transverse movement is VERY SLOW. *Requires action of three enzymes*
33
What are the 3 enzymes required to adjust the cell membrane fluidity?
Flippase Floppase Scramblase
34
What is the purpose of flippase?
Moves phospholipids from the outer to the inner leaflet. (REQUIRES ATP).
35
What is the purpose of floppase?
Moves phospholipids from INNER to OUTER leaflet. | REQUIRES ATP
36
What is the purpose of scramblase?
Bidirectional moment.
37
Which membrane does scramblase work on?
ER membrane.
38
Which membrane does flippase work on?
Golgi Membrane or Plasma Membrane.
39
What is the process of phagocytosis?
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.)
40
What molecules is released the MOST when cells are dying?
Phosphatidylserine.
41
What are the 3 main integral membrane proteins?
Alpha - Helix = Recognition / Receptors. Helical Bundle = Enzymes / Transporters / Receptors. Beta - Barrel = Transporters (channel proteins).
42
What is the main trans - membrane domain?
Alpha - Helix
43
What bonds do integral membrane proteins have?
Strong non - covalent bonds.
44
Where are peripheral membrane proteins located?
Located on either side of thee membrane.
45
What bonds do peripheral membrane proteins have?
Associated by non - covalent bonds.
46
How are carbohydrates attached?
Covalently linked to proteins or lipids of the external layer.
47
What is the function of carbohydrates?
Involved in cell - cell interactions / cellular recognition and cell adhesion.
48
What is the function of the nuclear pore complex?
Exchange of components and prevention of the transport of non - desired material.