Lecture 2 - Structures Of Membrane Lipids

Question 1

What are phosphatidylcholine?

Answer 1

Class of phospholipids that incorporate choline as a head group

Question 2

What is a major component of phosphatidylcholine?

Answer 2

Biological membrane

Question 3

What are most phospholipids ?

Answer 3

Phosphoglycerides

Question 4

What are most membrane Lipids?

Answer 4

Phospholipids

Question 5

Phosphoglycerides

Answer 5

Two fatty acids, phosphoric acid and glycerol

Question 6

Why is glycerol a convenient component to stick things too ?

Answer 6

Hydroxyl groups are easy to make connections too - condensation reaction with a fatty acid

Question 7

Which bit of the molecule can vary?

Answer 7

Modify head group Fatty acid chains —> influences the thickness of bilayer Introduce double bones (desaturate it)- makes it less flexible but makes the membrane more fluid

Question 8

What remains the same in phosphoglycerides?

Answer 8

Phosphate and glycerol

Question 9

What does phosphatidylinostil do?

Answer 9

Linking proteins to membrane Role in cell signalling

Question 10

Cardiolipin

Answer 10

Lipid with properties found in the membranes generating electrochemical potential 4 acyl chains and tends to form nonlamellar structures Unusual —> double phosphoglycerides Creates a Lipid with 4 tails Special Role in inner mitochondrial membrane - help the association of specific proteins

Question 11

Sphingolipids

Answer 11

Fatty acid derivatives of sphingosine Occur chiefly in the cell membrane of the brain and nervous tissue Range of different head groups

Question 12

Sphingomyelin

Answer 12

Derivative of sphingosine and choline

Question 13

What is a way to classify Lipids?

Answer 13

Glycolipids

Question 14

What are sugars ?

Answer 14

Not charged - but very Polar and water soluble

Question 15

Cholesterol

Answer 15

Influenced the mechanical property of the membrane - makes it more stretchy, flexible and fluid over a wide range of temperatures Nearly all hydrophobic Largely absent from plant cells

Question 16

What are problems associated with cholesterol?

Answer 16

Complicated structures with rings - cannot pack as well Only hydrophilic and polar group: OH group

Question 17

What is cholesterol very closely related in structure and biosynthesis pathway with?

Answer 17

Testosterone and Oestrogen

Question 18

Mammalian plasma membrane (human erythrocytes)

Answer 18

Phosphoglycerides (PC, PE, PS) Sphingomyelin Glycolipid. Cholesterol (25%) No cardiolipin No PG

Question 19

Mitochondrial inner membrane (beef heart)

Answer 19

Phosphoglyxeride (PC, PE) Cardiolipin Not much cholesterol No glycolipids No sphingomyelin

Question 20

Bacterial plasma membrane (E.coli)

Answer 20

Phospgoglyceride (PE, PG) Cardiolipin (12%) No cholesterol No sphingomyelin No glycolipids

Question 21

Lipid anchored proteins

Answer 21

Located outside the lipid bilayer, on either the extracellular or cytoplasmic surface, but are convaently linked to a lipid molecule that is situated within layer

Question 22

Peripheral membrane proteins

Answer 22

Attachment to membrane surface - non covalent associations Do not penetrate he hydrophobic tails

Question 23

What does lipid bilayer give to the membrane?

Answer 23

Fluidity and elasticity

Question 24

How does Singer and Nicholson deserve the cell membrane?

Answer 24

2D liquid that restricts the lateral diffusion of membrane components

Question 25

What are the stable confirmation of the polypeptide backbone?

Answer 25

Alpha helix and beta sheets

Question 26

Alpha helical structure

Answer 26

The backbone of the polypeptide chain is all hidden in the rod-like structure

Question 27

Integral membrane proteins

Answer 27

Faced on hydrophobic alpha helices Hydrophilic domain stick out on the surface of membrane Have one membrane-spanning segment whereas others are multi-spanning

Question 28

What does genome sequencing studies suggest?

Answer 28

Integral proteins constitute 20-30% of all encoded proteins

Question 29

Transmembrane protein

Answer 29

They pass entirely through the lipid bilayer and thus have domains that protrude from both the extracellular and cytoplasmic side of membrane