Lipids, Plasma Membrane- Lecture 4

Question 1

The structure of the cell membrane is called a _____ composed of _____ that do not allow free passage of water and ____ with diverse functions.

Answer 1

bilayer
lipids
proteins

Question 2

What are the three most abundant lipids in the plasma membrane?

Answer 2

phospholipids, sphingomyelin, glycolipids, and cholesterol

Question 3

What kind(s) of lipids are commonly found on the extracellular side of the bilayer?

Answer 3

phosphatidycholine, sphingomyelin, and glycolipids

Question 4

What kind(s) of lipids are commony found on the cytosolic side of the bilater?

Answer 4

negatively charged phospholipids (phosphatidylserine [PS] and phosphatidylinositol [PI])
neutral phospholipid (phosphatidyl-ethanolamine)

Question 5

What kind(s) of lipids are found on both monolayers?

Answer 5

cholesterol

Question 6

The presence of _____ in the ____ leaflet is an indication that a cell is undergoing programmed cell death.

Answer 6

PS

outer

Question 7

What is passive transport?

Answer 7

the movement from high concentration to low concentrations through simple diffusion of molecules to which the membrane is permeable

Question 8

What is active transport?

Answer 8

the movement from low to high concentration requiring energy and mediated by pumps

Question 9

_____ fatty acids contain all single bonds between carbons whereas _____ fatty acids contain some double bonds.

Answer 9

Saturated

unsaturated

Question 10

What are glycerolipids?

Answer 10

esters of glycerol and fatty acids

Question 11

What is the composition of a glycerophospholipid?

Answer 11

two hydroxyl groups in the glycerol are in ester linkages to fatty acids and the third is attached to a polar head group through a phosphate group

Question 12

What is the composition of a TYPICAL sphingolipid?

Answer 12

sphingosine backbone (two long hydrocarbon chains and NO phosphate [unless you are sphingomylin whose X group is phosphocholine]) attached to a fatty acid and an X group

Question 13

What is the composition of cholesterol?

Answer 13

multi-ring structure, a hydrocarbon tail, and a hydroxyl group

Question 14

The presence of cholesterol in the bilayer _____ the impermeability.

Answer 14

increases

Question 15

What factors influence membrane fluidity?

Answer 15

temperature (higher temp increases fluidity)
phospholipid structure (length and saturation of phospholipids with shorter tails and unsaturated fatty acids increase fluidity)
Cholesterol (decreases fluidity)

Question 16

What are the two types of transmembrane proteins?

Answer 16

beta barrels (only found in mitochondria in eukaryotes)
alpha helical

Question 17

What are the key molecular characteristics of transmembrane helical proteins?

Answer 17

contain predominantly hydrophobic side chains that interact with the lipid bilayer
transmembrane residues face that face a polar channel have polar side chains
residues in the extracellular space adn cytosol often have polar sidechains (because they interact with aqueous environments)
intracellular regions close to the membrane tend to be abundant with positively charged residues