Eukaryotes - Membrane Lipids

Question 1

Cell Membrane

Answer 1

A lipid bilayer with embedded proteins, acting as a permeabiltiy barrier and defining cell/organelle structure.

Question 2

Amphiphatic

Answer 2

Both hydrophobic and hydrophilic.

Question 3

What are the most abundant phospholipids?

Answer 3

Phosphoglycerides

Question 4

What is membrane spontaneous formation dependent on?

Answer 4

Acyl chain degree of saturation
Length of acyl chains
Temperature

Question 5

What organelles have double membrane layer?

Answer 5

Chloroplast, nucleus and mitochondria.

Question 6

What are the three classes of membrane lipids?

Answer 6

Phosphoglycerides
Sphingolipids
Sterols

Question 7

What is the general structure of phosphoglycerides?

Answer 7

Two acyl chains esterfied to OH groups in glycerol phosphate, with polar head grojup bound to phosphate

Question 8

How are phosphoglycerides classifed?

Answer 8

Molecular identity of their head group.

Question 9

Phosphatidylcholine

Answer 9

The most abundant phospholipid with a positively charged choline esterfied to phosphate group.

Question 10

Phosphoinositides

Answer 10

Modified with additonal phosphate, important in signal transduction mechanisms

Question 11

What are three examples of phosphoglycerides?

Answer 11

Phosphatidylcholine
Phosphoinositides
Lysophospholipids

Question 12

What is the general structure of sphingolipids?

Answer 12

Single hydrophobic acyl chain, and a phosphate head group esterfied to a sphingoid base backbone.

Question 13

Sphingomyeline

Answer 13

The most abundant sphingolipids, containing a phosphocholine bound to sphingosine

Question 14

What is the function of sphingomyeline?

Answer 14

Toxin receptors, tissue development and adhesion.

Question 15

General structure of cholesterol?

Answer 15

Four fused rings, a OH group, and branched hydrophobic tail.

Question 16

How is cholesterol integrated into the membrane?

Answer 16

Interacalation between phospholipids

Question 17

Function of cholesterol in the membrane?

Answer 17

Fluidity maintenance by preventing close association of acyl chains.

Question 18

Phospholipid

Answer 18

Amphiphatic lipids with phosphate head groups and two acyl chains.

Question 19

What does lipid movement around their axis result in?

Answer 19

Rates of exchange between neighbouring lipids thus lateral diffusion

Question 20

How do lipids switch between leaflets?

Answer 20

Proteins like flippases

Question 21

What is membrane composition of the GA and ER?

Answer 21

GA has more sphingolipids whilst ER more phosphoglycerides, as they are each where they’re synthesised.

Question 22

How does lipid structure determine fluidity?

Answer 22

Longer acyl chains have more charge to aggregate by VDV forces, whilst shoter more fluid.

Question 23

How do unsaturated acyl chains increase fluidity?

Answer 23

More kinks so less aggregate capabiltiies.

Question 24

What is an example of lipid concentration differing in either leaflet?

Answer 24

Madin Darby Canine Kidney Cells has more sphingomyelin and phosphatidylcholine exoplasmically, with more fluid lipids in cytoplasmic leaflet.

Question 25

Function of phosphatidylserine?

Answer 25

A cytoplasmic leaflet protein switching by flippase to ecoplasmic in platlet stimulation interacting with enzymes for blood clotting.

Question 26

What are the major lipids in membranes?

Answer 26

Phosphatidylcholine
Phosphatidylethanolamine
Phosphatidylserine
Phosphatidylionsitol
Phosphatidic Acid

Question 27

Lipid Rafts

Answer 27

Asymmetric distribution/localisation of lipids to certain parts of membranes.

Question 28

What is the function of lipid rafts?

Answer 28

Membrane stability, dense cell receptor concentration in endocytosis, exocytosis etc.