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Pre-Vet 3 > 8. Lipids > Flashcards

8. Lipids Flashcards

1
Q

functions of lipids (8)

A

-energy storage
-membrane components
-coenzymes
-electron carriers
-light-absorbing pigments
-hormones
-intracellular messengers
-detergents

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2
Q

are lipids soluble?

A

insoluble in water but soluble in organic solvents (hydrophobic)

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3
Q

Fatty acids

A

carboxylic acids with 4-36 carbons (COOH followed by a carbon chain)
-have a hydrophobic and hydrophilic segment (amphipathic)

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4
Q

name some fatty acids (5)

A

-stearic acid
-palmitic acid
-oleic acid
-linoleic acid
-linolenic acid

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5
Q

stearic acid

A

saturated fatty acid (18:0; 18 carbons, 0 double bonds)
-also called octadecanoic acid
-makes up 5% of human body fat
-waxy solid with a high melting point (70 degrees C)

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6
Q

what does it mean to be saturated vs unsaturated

A

saturated: no double bonds (saturated with hydrogens)
-no bends from double bonds, therefore can pack closer together; solid at room temp

unsaturated: at least one double bond
-not as close of packing; therefore liquid at room temp

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7
Q

palmitic acid

A

16:0 (saturated)
-makes up 25% of human fat

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8
Q

oleic acid (6)

A

mono-unsaturated fatty acid (one double bond)
-18:1 (Δ9)
-carbon 9 is the site of unsaturation
-oil at room temp
-double bond puts a bend in the hydrocarbon tail; has a lower melting point (13 degrees C)
-makes up about 46% of human fat
-also called cis-9-octadecenoic aicd

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9
Q

linoleic acid

A

18:2 (Δ9,12); di-unsaturated
-melting point is -5 degrees C
-essential fatty acid in the diet of mammals
-called an ω-6 FA because the last double bond is 6 atoms from the end of the chain

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10
Q

linolenic acid

A

18:3 (Δ9,12,15)
-has a melting point of -17 degrees C
-an ω-3 polyunsaturated FA

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11
Q

characteristics of fatty acids (7)

A
  1. all have an even number of carbons (except for some marine organisms)
  2. none have conjugated double bonds (every second bond is double; ex aromatic rings)
  3. double bonds are always in the cis configuration (trans fats are NOT made in the body)
  4. long chain saturated fatty acids are the least solule in water
    5.the carboxyl pka is 2.5-5.0 (deproponated in the body)
  5. melting points increase with chain length
  6. amphipathic fatty acids form micelles in water
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12
Q

how are fatty acids made soluble in serum?

A

by binding to a protein called albumin (chaperone for fatty acids throughout the blood)

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13
Q

explain fatty acids and micelles

A

water entropy effects drive the hydrocarbon chain to associate in a way such that their polar heads interact with water
-lipids can also place their hydrocarbon chains in the air and their head groups at the surface of water to form a monolayer

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14
Q

CMC

A

critical micelle concentration
-the point at which there is enough fatty acid present to form a micelle

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15
Q

triacyl glycerols (5)

A

-also called triglycerides
-natural fats
-formed through a condensation reaction between a glycerol and three fatty acids
-carboxylic group of the fatty acids no longer available (attached to the glycerol)
-the fatty acids can be saturated OR unsaturated, may be identical or different

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16
Q

functions of triglycerides

A
  1. energy storage, fat cells (adipocytes), seeds
  2. insulation (found under the skin in seals, walruses, etc)
  3. echo location or buoyancy in sperm whales
  4. water repellent (ex: water fowl and plants secreting wax layers)
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17
Q

how many times more energy does fat have compared to carbs? why?

A

about 2x more
-because the carbon is more reduced (lots of hydrogens)

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18
Q

soap

A

a detergent used to pull oil molecules off of the skin (does not kill bacteria); saponification
-triglyceride

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19
Q

saponification

A

the process soap uses to clean
-hydrophobic tails of the soap form micelles around non-polar oil molecules
-this allows the oil molecules to be suspended in water, which then gets washed away

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20
Q

wax

A

a very hydrophobic fatty acid storage form (lots of CH2)
-bees wax: triacontanyl palmitate

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21
Q

glycerophosopholipids

A

main components of cell membranes
-one oxygen on the phosphate bonds to a “head” group

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22
Q

basic structure of glycerophospholipids , using phosphatidic acid

A

phosphatidic acid = diacyl glycerol phosphate

-two tails (humans: one is saturated, one is unsaturated)
-head group is always polar
-number of carbons: usually 16 or 18

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23
Q

what are some types of phospholipid head groups?

A
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24
Q

what do glycerophospholipids form and why?

A

form bilayers due to the hydrophobic effect (water entropy)

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25
Q

vesicles

A

formed by curved bilayers
-also called liposomes
-ex: golgi apparatus in the cell (composed of stacked lipid bilayers)

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26
Q

phospholipases

A

located in lysosomes, degrade phosphate lipids
-will cut at different places (ex: head and phosphate, just the head, etc)
-will be used at different times
-involved in inflammation, fever, pain, reproduction, etc. (signalling)

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27
Q

lysophospholipid

A

a phospholipid which has had one of its fatty acid chains removed
(the structure left behind after using a phospholipase)

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28
Q

C vs D vs A1 vs A1 phospholipases

A

C: cuts the head and phosphate
D: cuts just the head
A2: cuts a tail, from the inside
A1: cuts a tail, from the outside

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29
Q

what causes toxic shock syndrome?

A

the platlet-activating factor is an ether linked phospholipid hormone
-major cause of TSS
(cuts off blood pressure and causes rapid organ failure)

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30
Q

sphingolipids , types

A

DO NOT have glycerol
-derivatives of sphingosine which is derived from the amino acid serine (glycerol substitute)

-types: ceramides, phosphocholine, sphingolyelin, gangliosides, etc

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31
Q

ceramide

A

type of sphingolipid (does not have glycerol)
-the fatty acid is in a amide linkage

32
Q

sphingomyelin

A

type of sphingolipid

-head group is phosphocholine
-size and shape is similar to glycerophospholipids
-found in the plasma membrane and in the myelin sheath of axons

33
Q

gangliosides

A

glycophingolipids that have complex oligosaccharides as head groups
-abnormal metabolism of ganglioside results in genetic diseases (ex: Tau-Sachs, Sandhoff, etc)

34
Q

which blood group is the universal receiver and why? universal donor?

A

universal receiver: type AB (have both antigens, meaning they can receive any type)

universal donor: type O (A and B both have the parts that type O has, therefore receiving it does not cause a reaction)

35
Q

terpenes and steroids

A

non-saponifiable lipids (cannot act as soaps/detergents)
-includes sterols
-synthesized from Δ3-isopentenyl pyrophosphate (activated isoprene)
-head to tail condensation yields the monoterpene geranyl pyrophosphate

36
Q

what are two unit terpenes/steroids called? 3? 4? 6? 8?

A

two units: monoterpene (10 carbons)
three units: sesquiterpene (15 carbons)
four units: diterpine (20 carbons)
six units: triterpene (30 carbons)
eight units: teteaterpene (40 carbons)

37
Q

vitamin D3

A

also called cholecalciferol
-formed in the skin by a UV-light photochemical reaction on 7-dehydrocholesterol
-cleaved to form vitamin D

38
Q

vitamin E

A

also called A Tocopherol
-double ring structure with a tail
-redox reactions on the aromatic rings prevent oxidative damage to the lipid
-“antioxidant”
-a sesquiterpene

39
Q

vitamin D

A

-active form of vitamin D3
important in Ca2+ and PO4(3-) metabolism

40
Q

vitamin K

A

used as a blood clotting co-factor and sesquiterpene
-non-polar, therefore can move through the membrane into the blood

41
Q

plastoquinone

A

a chloroplast electron carrier
-mobile, due to having a non-polar tail

42
Q

dolichol

A

a sugar carrier
-used to carry sugars through non-polar environments

43
Q

cholesterol

A

there is a “good” form (HDL) and a “bad” (LDL) form of cholesterol
-diet can raise/lower levels of good and bad cholesterol
-diets rich in saturated fatty acids and trans fatty acids are a risk factor for cornory artery disease

44
Q

LDL

A

low density lipoprotein
-bad cholesterol
-a large protein called Apolipoprotein B-100 carries fats and cholesterol into the bloodstream

45
Q

HDL

A

high density lipoprotein
-“good” cholesterol
-apolopoprotein A1 and A2 carry triglycerides and cholesterol
-trans fats lower levels of HDL

46
Q

how does hydrogenation impact fats?

A

-removes a double bond to make it more solid
-raises the melting point and produced semi-solid fats (for margarine or other foods)
-semi-solid fats are preferred for baking because of the way they mix with flour and alter the texture of food

47
Q

lipid purification

A

used to separate a mixture of lipids

48
Q

how to do lipid purification?

A
  1. extract tissue with an organic solvent (non-aqueous, therefore non polar substances dissolve)
    -lipids are soluble, polar molecules are not

2.separate lipids by THIN LAYER CHROMATOGRAPHY, or by adsorption chromatography using silica gel
-polar and charged lipids bind to silica but neutral lipids to not

  1. elude different types of lipids with the appropriate solvent
49
Q

what are polar lipids eluded with in lipid purification? charged lipids?

A

polar lipids: eluted with acetone
charged lipids: eluted with methanol

50
Q

what are membranes composed of?

A

lipids, proteins, steroids, carbs

51
Q

characteristics of membranes (5)

A
  1. lipid bilayers are 5-8 nm thick
  2. lipids can diffuse laterally
  3. transbilayer diffusion (flip flop) is rare; but enzymes are present to assist in it if it does happen
  4. tough but flexible (semi-fluid)
  5. able to seal temporary leaks
52
Q

flipases

A

enzymes which assist in transbilayer diffusion
-from the outer to the inner leaflet

53
Q

what happens to membranes when the temperature is changed

A

bilayers undergo a phase transition from gel (solid) to liquid crystal (melting)

at low temperature, the fatty acid tails are rigid and packed; it is in an ordered gel phase

at high temperature, the fatty acid tails are mobile; it is in a disordered liquid-crystalline phase

-the phase transition of membranes in living cells is broad; may be between 10-40 degrees C

54
Q

what does the fluidity of a membrane depend on

A

depends on the amount of saturated and unsaturated lipids and the amount of sterol present

55
Q

what are the two types of membrane proteins?

A
  1. peripheral membrane proteins
  2. integral membrane proteins
56
Q

peripheral membrane proteins, example (4)

A

associate with the SURFACE of the bilayer
-held in place by weak interactions (H-bonds, van der waals, electrostatic interactions) or covalent attachment to the lipid
-high salt concentrations may release them from the membrane

-example: cytochrome C

57
Q

integral membran proteins

A

span the bilayer (go through)
-their external surface is hydrophilic, internal is hydrophobic (to allow polar substances through)
-removal from the membrane is usually by detergent extraction
-three classes

58
Q

what are the three classes of integral membrane proteins?

A
  1. transverse membrane as a single alpha helix
  2. transverse membrane as 4-16 alpha helices
  3. transverse membrane as 8-16 beta-strands forming a giant beta barrel (called a PORIN)
59
Q

which molecules do not cross membranes freely?

A

-CH4
-O2
-N2
-H2O
-NO
-CO
-any bulky or polar substances
-must use transport proteins

60
Q

second messengers

A

small molecules that relay signals received by cell-surface receptors to effector proteins
-able to enter the cell via diffusion because of their small size
-ex: NO (vasodilator) CO (binds to hemoglobin stronger than oxygen)

61
Q

aquaporins

A

type of integral membrane protein used to increase rapid transport of water across membranes
-used in cells in kidneys, lungs, etc
-form a pore that permits rapid diffusion of water (called facilitated diffusion)

62
Q

facilitated diffusion

A

movement of a molecule into/out of a cell using a transport protein
-many large, polar molecules are transported this way (including carbs and amino acids)
-the transport proteins used are called permeases

63
Q

example of a permease?

A

red blood cell glucose permease
-made of 12 alpha-helices that from a pore to transport glucose 50,000 times faster than simple diffusion

64
Q

active transporters

A

can pump solute against a concentration gradient

65
Q

example of an active transporter

A

the Na+/K+ ATPase uses energy from the hydrolysis of ATP to pump 2K+ into the cell and 3Na+ out of the cell
-one ATP is required per 2K/3Na
-most animal cells have higher concentrations of NA+ out than in and larger concentrations of K+ going in than out; therefore there is a net movement of positive charge going OUT of the cell
-up to 25% of resting metabolic energy of a cell is used to maintain this gradient

66
Q

signal transduction

A

the transmission of information across membranes

67
Q

how does signal transduction work?

A
  1. hormones are secreted by cells into the extracellular fluid and bind to membrane receptors on target cells
  2. a conformational change in the receptor transmits a signal across the membrane activating a second messenger system
    -causes the necessary reaction
    -hormones cannot get into the cell themselves, which is why a receptor is needed
68
Q

example of a signal transduction: adrenaline

A

epinephrine (adrenaline) binds to adrenergic receptors, activating phospholipase C (an integral membrane protein enzyme)
-it acts on phosphatoidyl insitol 4-5 biphosphate, releasing diacylglyerol and inositol 1,4,5 triphosphate

69
Q

example of signal transduction: insulin

A

insulin binds to the insulin receptor and activated an enzyme cascade that leads to changes in sugar and lipid metabolism
-diabetes: causes the insulin receptor to stop working
-can overwhelm the system (by increasing [insulin] to get the system to work

70
Q

are membrane proteins free to move?

A

depends
-some are able to diffuse laterally in the plane of the bilayer
-others are anchored to the cytoskeleton

71
Q

where on membranes are carbs found?

A

abundant on plasma membrane
-rare on intracellular membranes (found outside)

72
Q

trans fats

A

-lower levels of good cholesterol (HDL)
they are found in small amounts naturally in meats and diary products
-large amounts found in foods produced by partial hydrogenation of plant oils and animal fats

73
Q

coenzyme Q

A

also called ubiquinone
-a mitochondrial electron carrier

74
Q

example of a tetraterpene

A

beta-carotene
-used for vision, found in carrots
-fat soluble vitamin
-animals can cleave it in the centre to produce two retinols (vitamin A)

75
Q

blood group antigens

A

O, A, B blood group antiens are glycosphinolipids with different complex carbohydrate head groups
-important in cell surface recognition events
-same structure until the top

76
Q

ether-linked fatty acids

A

the ester bond which links the fatty acid to the glycerol is replaced with an ether bond

Pre-Vet 3 (11 decks)

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