Lipids and Membranes

Question 1

Amphiphilic

Answer 1

Containing both polar and nonpolar regions

Question 2

4 major classes of lipids

Answer 2

Fatty acids
Phospholipids
Glycosphingolipids
Isoprenoids

Question 3

Simplest class of lipids

Answer 3

Fatty acids

Question 4

Fatty acid nomenclature

Answer 4

Carboxyl group is C-1
Main chain is named as usual
Unsaturations: delta^n (n= carbon where double bond is located)

Question 5

Effects of unsaturations in fatty acid chains

Answer 5

Increased flexibility: looser packing

Lowered melting point

Question 6

Triacylglycerols

Answer 6

3 fatty acids esterified with one molecule of glycerol
Hydrophobic storage form of fatty acids
Most abundant lipid form

Question 7

Metabolism of triacylglycerols

Answer 7

Broken down in small intestine by lipases

Question 8

Glycerophospholipids

Answer 8

Compose majority of membranes
Amphiphilic molecules (polar head, nonpolar tail)

Question 9

Phosphatidates

Answer 9

Form of glycerophospholipids
Have glycerol backbone, fatty acids at C-1 and C-2 and phosphate at C-3
Present in small amounts (rather rare)

Question 10

Phospholipases

Answer 10

Class of enzymes that catalyze cleavage of esters in phospholipids

Question 11

Plasmalogens

Answer 11

Form of glycerophospholipid with C-1 substituent linked by vinyl ether linkage
Found in CNS as well as peripheral nerve and muscle tissue

Question 12

Sphingolipids

Answer 12

Sphingosine backbone

Particularly abundant in CNS cells

Question 13

Ceramide

Answer 13

Precursor of all other sphingolipids

Question 14

Sphingomyelins

Answer 14

Class of sphingolipid
Phosphocholine at C-1
Major component of myelin sheath

Question 15

Cerebrosides

Answer 15

Class of sphingolipid
Monosaccharide attached through beta-glycosidic bond
Abundant in nerve tissue and myelin sheaths
Different subclasses, depending on ID of sugar

Question 16

Gangliosides

Answer 16

Class of sphingolipid
Linked to complex oligosaccharide containing N-acetylneuraminic acid
Used in cell-surface signaling

Question 17

Steroids

Answer 17

Classified as isoprenoids
Shared fused, four-ring structure
Derived from squalene
Hydrophobic
Precursor of steroid hormones and bile salts as well as component of certain membranes

Question 18

Waxes

Answer 18

Nonpolar esters of long-chain fatty acids and long-chain monohydroxylic alcohols

Question 19

Functions of biological membranes

Answer 19

Separation of cellular components
Generation and maintenance of ion and small molecule gradients
Assistance of biosynthesis and delivery of transmembrane proteins

Question 20

Formation of lipid bilayers

Answer 20

Spontaneous formation: hydrophobic interactions

Question 21

Lipid-to-protein ratio of biological membranes

Answer 21

25-50% lipid
50-75% protein
<10% carbohydrate

Question 22

Fluid-mosaic model

Answer 22

Membranes are dynamic structures in which lipids and proteins can rapidly rotate and diffuse

Question 23

Flippase and floppase

Answer 23

Enzymes which catalyze transverse diffusion of certain phospholipids

Question 24

Factors affecting membrane fluidity

Answer 24

Increased temp- increased fluidity
Unsaturated fatty acids- increased fluidity
Cholesterol: decreased fluidity at high temps, increased fluidity at low temps (fluidity buffer)

Question 25

Liposomes

Answer 25

Synthetic vesicles composed of lipid bilayers that enclose an aqueous compartment
Great method for solubilizing certain drugs and delivering them within the body

Question 26

Integral membrane proteins

Answer 26

Span the bilayer completely (hydrophobic middle)

Includes pores and channels used in passive and active transport

Question 27

Peripheral membrane proteins

Answer 27

Associated with one face of membrane through charge-charge interactions and/or H-bonding with integral membrane proteins or polar head groups

Question 28

Lipid-anchored membrane proteins

Answer 28

Tethered to membrane through covalent bond to lipid anchor

Question 29

Membrane transport depends on…

Answer 29

Concentration gradient

Charge gradient

Question 30

Passive transport

Answer 30

Movement of solute down its concentration gradient without expenditure of energy
Continues until concentration gradient is equalized

Question 31

Active transport

Answer 31

Requires energy to move molecule up its concentration gradient
Usually uses ATP as energy source

Question 32

2 types of active transport

Answer 32

Primary active transport: powered by direct source of energy

Secondary active transport: uses ion concentration gradient to power second transport process