Lipids

Question 1

features of lipids

Answer 1

macromolecules - high molecular weight
important in cellular structures (membranes)
Hydrophobic (soluble in nonpolar solvents such as chloroform or other)
have relatively few polar groups, but some are amphipathic, having polar and nonpolar regions
Diverse functions

Question 2

Functions of lipids

Answer 2

energy storage
membrane structure
signaling (steroid hormones)
electron transport (coenzyme Q)
pigments
antioxidants (vitamin E)

Question 3

The main classes of lipids

Answer 3

Fatty acids
Triacylglycerols
Phospholipids
Glycolipids
Steroids
Terpenes

Question 4

Saturated fatty acids

Answer 4

each carbon atom in the chain is bonded to the maximum number of hydrogens, have long straight chains that pack together well CnH2nO2

Fatty acids without double bonds

Question 5

Unsaturated fatty acids

Answer 5

have one or more double bonds, so they have bends (angle) in the chains and are less tightly packed

Question 6

head and tail of fatty acids

Answer 6

polar carboxyl group - head
non-polar hydrocarbon chain - tail

Question 7

Polyunsaturated fatty acids

Answer 7

have more than one double bond
linoleate - 18-carbon unsaturated fatty acids

Question 8

Triacylglycerols

Answer 8

glycerol (3-carbon alcohol with a hydroxyl group on each carbon) + 3 fatty acids (by ester bonds formed by the removal of water)

Question 9

The main function of triacylglycerols

Answer 9

energy storage

insulation against low temperatures

Question 10

the most abundant lipids in the membrane?

Answer 10

Phospholipids

Question 11

What do Phospholipids include?

Answer 11

phosphoglycerides or sphingolipids, depending on their chemistry

Question 12

common alcohol groups (small hydrophilic alcohol linked to P by ester bond) of phosphoglycerides?

Answer 12

serine, ethanolamine, choline, or inositol, which contribute to the polar nature of the phospholipid head group

Question 13

basic component of phosphoglycerids

Answer 13

phosphatic acid (two fatty acids and a phosphate group attached to glycerol)

Phosphate is charged under physiological pH

Question 14

What are sphingolipids based on?

Answer 14

sphingosine - has a long hydrocarbon chain with a single site of unsaturation near the polar end

Question 15

How a molecule ceramide is formed?

Answer 15

Sphingosine can form an amide bond to a long-chain fatty acid (up to 34 carbons), resulting in a molecule called a ceramide

different polar groups attached to the hydroxyl group of the ceramide -> whole family of sphingolipids

Question 16

diversity of sphingolipids

Answer 16

sphingomyelins

accumulation of sphingomyelin leads to Niemann-Pick disease – mental retardation, early death (due to lack of sphingomyelinase)

Question 17

a long, unbranched hydrocarbon chain with a carboxyl group at one end -> amphipatic

Answer 17

fatty acid

Question 18

function of phospholipids

Answer 18

due to amphipatic nature -> key component of bilayer structure in membrane

Question 19

Where sphingolipids can be found?

Answer 19

in the outer leaflet of the plasma membrane bilayer, often in lipid rafts (in the outer monolayer of animall cells have elevated levels of cholesterol an sphingolipids; less fluid than the rest of the membrane)

Question 20

roles of lipid rafts

Answer 20

transporting nutrients and ions across membranes
binding activated immune system cells to their mirobial targets
transporting cholera toxin into intestinal cells

Question 21

how glycolipids are formed?

Answer 21

by the addition of carbohydrates to lipids
derivatives of sphingosine or glycerol

Question 22

the most common glycolipids that are prominent in brain and nerve cells

Answer 22

cerebrosides
gangliosides

Question 23

what are cerebrosides?

Answer 23

neutral glycolipids
each molecule has a sugar as its head group

Question 24

what are gangliosides?

Answer 24

has an oligosaccharide head group with 1 or more negatively charged sialic acid residues

Question 25

what are steroids?
what is their polarity?

Answer 25

derivatives of a 4-ringed hydeocarbon skeleton, which distinguishes them from other lipids
relatively nonpolar->hydrophobic

Question 26

how do steroids differ from one another?

Answer 26

in the positions of double bonds and functional groups

Question 27

Cholesterol - most common steroid
structure?

Answer 27

contains a rigid ring structure + single polar hydroxyl group + short nonpolar hydrocarbon chain

Question 28

How does cholesterol orient itself?

Answer 28

in the bilayer, it orients with hydroxyl grouo close to the polar head group of adjacent phospholipid molecule

Question 29

2 kinds of steroid hormones

Answer 29

glucocorticoids
mineralocorticoids

Question 30

What are the glucocorticoids?

Answer 30

e.g. cortisol
family of hormones promoting synthesis of glucose and suppress inflammation

Question 31

What are mineralocorticoids?

Answer 31

e.g. aldosterone
regulate ion balance by promoting reabsorption os Na, Cl, bicarbonate ions by kidney

Question 32

From what terpenes are synthesized?

Answer 32

5-carbon compound isoprene (isoprenoids)

Question 33

Isoprene and its derivatives are joined to

Answer 33

produce substances such as vitamin A and cartenoid pigments

Question 34

What are isoprene-based compounds, dolichols, involved in?

Answer 34

activating sugar compounds (during assembly of bacterial cell wall, addition of polysaccharide units to certain proteins and lipids)

Question 35

What are other isoprene-based compounds?

Answer 35

electron carriers such as coenzyme Q (ubiquinone) and plastoquinone

polyisoprenoids (polymers of isoprene) are found in cell walls of the Archae

Question 36

What is osmosis?

Answer 36

movement of water: low solute C -> high solute C through water diffusion

Question 37

What facilitate water flow?

Answer 37

aquaporins (water channels)

Question 38

What is tonicity?

Answer 38

relative concentrations of solutes in 2 solutions
determines movement of water into ot out of cells

Question 39

Hypotonic solution

Answer 39

low solute C/high water C
red blood cells exposed to it will swell and burst

Question 40

Hypertonic solution

Answer 40

high solute C/low water C
red blood cells exposed to it will shrink

Question 41

Isotonic solution

Answer 41

the same osmotic pressure as referenced solution
for human blood=0.9% NaCl

Question 42

2 driving forces for passive transport

Answer 42

concentration gradient
electrical gradient (for ions)

Question 43

What is passive membrane transport?

Answer 43

passage of hydrophobic and small polar molecules via diffusion (osmosis)