Lipids Flashcards

1
Q

features of lipids

A

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

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2
Q

Functions of lipids

A

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

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3
Q

The main classes of lipids

A

Fatty acids
Triacylglycerols
Phospholipids
Glycolipids
Steroids
Terpenes

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4
Q

Saturated fatty acids

A

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

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5
Q

Unsaturated fatty acids

A

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

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6
Q

head and tail of fatty acids

A

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

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7
Q

Polyunsaturated fatty acids

A

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

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8
Q

Triacylglycerols

A

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

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9
Q

The main function of triacylglycerols

A

energy storage

insulation against low temperatures

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10
Q

the most abundant lipids in the membrane?

A

Phospholipids

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11
Q

What do Phospholipids include?

A

phosphoglycerides or sphingolipids, depending on their chemistry

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12
Q

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

A

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

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13
Q

basic component of phosphoglycerids

A

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

Phosphate is charged under physiological pH

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14
Q

What are sphingolipids based on?

A

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

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15
Q

How a molecule ceramide is formed?

A

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

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16
Q

diversity of sphingolipids

A

sphingomyelins

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

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17
Q

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

A

fatty acid

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18
Q

function of phospholipids

A

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

19
Q

Where sphingolipids can be found?

A

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)

20
Q

roles of lipid rafts

A

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

21
Q

how glycolipids are formed?

A

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

22
Q

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

A

cerebrosides
gangliosides

23
Q

what are cerebrosides?

A

neutral glycolipids
each molecule has a sugar as its head group

24
Q

what are gangliosides?

A

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

25
what are steroids? what is their polarity?
derivatives of a 4-ringed hydeocarbon skeleton, which distinguishes them from other lipids relatively nonpolar->hydrophobic
26
how do steroids differ from one another?
in the positions of double bonds and functional groups
27
Cholesterol - most common steroid structure?
contains a rigid ring structure + single polar hydroxyl group + short nonpolar hydrocarbon chain
28
How does cholesterol orient itself?
in the bilayer, it orients with hydroxyl grouo close to the polar head group of adjacent phospholipid molecule
29
2 kinds of steroid hormones
glucocorticoids mineralocorticoids
30
What are the glucocorticoids?
e.g. cortisol family of hormones promoting synthesis of glucose and suppress inflammation
31
What are mineralocorticoids?
e.g. aldosterone regulate ion balance by promoting reabsorption os Na, Cl, bicarbonate ions by kidney
32
From what terpenes are synthesized?
5-carbon compound isoprene (isoprenoids)
33
Isoprene and its derivatives are joined to
produce substances such as vitamin A and cartenoid pigments
34
What are isoprene-based compounds, dolichols, involved in?
activating sugar compounds (during assembly of bacterial cell wall, addition of polysaccharide units to certain proteins and lipids)
35
What are other isoprene-based compounds?
electron carriers such as coenzyme Q (ubiquinone) and plastoquinone polyisoprenoids (polymers of isoprene) are found in cell walls of the Archae
36
What is osmosis?
movement of water: low solute C -> high solute C through water diffusion
37
What facilitate water flow?
aquaporins (water channels)
38
What is tonicity?
relative concentrations of solutes in 2 solutions determines movement of water into ot out of cells
39
Hypotonic solution
low solute C/high water C red blood cells exposed to it will swell and burst
40
Hypertonic solution
high solute C/low water C red blood cells exposed to it will shrink
41
Isotonic solution
the same osmotic pressure as referenced solution for human blood=0.9% NaCl
42
2 driving forces for passive transport
concentration gradient electrical gradient (for ions)
43
What is passive membrane transport?
passage of hydrophobic and small polar molecules via diffusion (osmosis)