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Biochem Ca1 Cram > Lipids > Flashcards

Lipids Flashcards

1
Q

What are lipids ?

A

Complex organic compounds with greater structural variation, includes fats, oils, waxes and related compounds

– Relatively insoluble in water
– Soluble in nonpolar solvents (eg- ether, chloroform)

– Compartmentalized (membrane-associated lipids, triacylglycerol in adipocytes or in association with protein (lipoprotein particles) or on albumin.

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2
Q

14 importances of lipids

A

• Important dietary constituent. 20%-35% total energy intake for a healthy adult.
– Determine the taste and palatability of food
– Provide energy 9 kcal/g
– Storage - Energy storage – lipids deposited in adipose tissues

– Transport
• (gut)-Facilitate absorption of fat- soluble vitamins.
• Transport function in the blood

– Structural
• Contain essential fatty acids (EFA) important for normal growth and development
• Cell membrane

• Insulator
– Act as a thermal insulator
– Electric insulators in neurons

• Constitute important in signaling molecules

• Protects internal organs

• Plays a major role in obesity and atherosclerosis

• Function of lipoproteins – HDL, LDL

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3
Q

Acceptable macronutrient distribution (adults) of protein, fat , carb

A

Protein is 10 -35 %
Fat is 20-35%
Carb is 45-65 %

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4
Q

3 classifications of lipids

A

Simple Lipids

Complex Lipids

Derived Lipids

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5
Q

What are simple lipids ?

A

Fats - esters of fatty acids with glycerol.
e.g. Triglyceride Di and monoglyceride.
Waxes esters of FA with higher molecular weight alcohol

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6
Q

What ate complex lipids and 3 categories ?

A

Simple lipids + additional group or base

  1. Phospholipids = Sphingophospholipids
    e.g. Sphingomyelin it has sphingosine phosphoric acid 2 fatty acids and choline
    And
    Glycerophopholipids
    glycophosphate and nitrogen base or inositol
  2. Glycolipids. or Glycosphingolipids
  3. Other complex lipids ex. Sulfolipids, amino lipids
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7
Q

What are derived lipids

A

Derived from lipids
e.g. cholesterol prostaglandins, Retinal Cholecalciferol etc

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8
Q

Formula of fatty acids

A

• CH3(CH2)nCOOH

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9
Q

Function of FA?

A

Free fatty acids can be oxidized by many tissues to provide energY

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10
Q

What is nature of fatty acids

A

Amphipathic

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11
Q

What form do FA exist in

A

free (unesterified) or esters (eg. Triacylglycerols)

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12
Q

What affects physical properties of FA

A

length of the hydrocarbon chain and the degree of unsaturation

• melting point changes with the length and saturation.

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13
Q

According to length what is FA

A

• According to the length
– Short (2-4)- CH3COOH Acetic acid
– medium (6-12) – eg. coconut oil (lauric acid C12)
– long chain (14-22)- essential FA
– > 22 Very long chain

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14
Q

2 groups of FA

A

• Two groups – Saturated and Unsaturated
• Unsaturated- mono (MUFA) and poly unsaturated (PUSFA)
• Unsaturated – two types of configurations cis and trans
• Nomenclature – Delta and omega (ω)

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15
Q

Molecular formula of saturated acids Lauric, myristic, palmitic, stearic

A

C11 H23 COOH
C13 H27 COOH
C15 H31 COOH
C17 H35 COOH

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16
Q

Structure of MUFA oleic acid

A

Oleic C17 H33 COOH 18:1 cisD9

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17
Q

Structure of PUFA LA ,ALA ,ARA ,EPA ,DHA

A

Linoleic acid (LA) Omega 6
C17 H31 COOH
18:2 cisD9,12
α-linonenic acid (ALA) Omega 3
C17 H29 COOH
18:3 cisD9,12,15

arachidonic acid (ARA) Omega 6
C20 H32 O2
20:4 cisD5,8,11,14
eicosapentaenoic acid (EPA) Omega 3
C20 H30 O2
20: 5 cisD5,8,11,14,17

Docosahexaenoic acid (DHA) Omega 3
C 22 H32 O2
20: 6 cisD4,7,10,13,16,

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18
Q

What is essential FA and example

A

• Lenoleic Acid (LA), the precursor of omega 6
and α Lenolenic Acid (ALA), the precursor of omega 3 cannot be synthesized by mammals. Thus known as essential FA.

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19
Q

Role of LA & ALA and derivatives

A

play a significant role in the structure of biological membranes.

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20
Q

Function of ARA sand other C 20 PUFA

A

give rise to eicosanoids involved in variety of biological processes.

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21
Q

FUNCTION OF DHA and EPA

A

• DHA plays a major role in development of the brain and retina during foetal development and the first two years of life. Consumption of an adequate amount of DHA together with EPA is recommended even after 2 years due to the probable evidence of reduce risk of cardiovascular mortality and anti-inflammatory effects. But no evidence of mental or physical benefits during this age range.
• An intake of at least 300mg/day EPA+DHA, of which 200 mg/day are DHA is recommended for pregnant and lactating mothers.
• Brest milk provides adequate amount to infants.
• Conditionally essential amino acids in case of
dietary inadequacy

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22
Q

Explain 2 essential FA pathways and functions

A

1.Omega 6 fatty acids
LA (vege nd sunflower oil ) to GLA to DGLA to AA ( animal fats, liver, egg lipids, fish)

  1. Omega 3 fatty acids
    ALA (green leafy , flax,chia, canola, walnut, and soybean oils) to SDA (stearadonic acid )
    to ETA (eicosatetranoeic acid) to EPA ( oily fish, algae and krill oil) to DPA (docasopentanoeic acid ) to DHA ( oily fish, algae and krill oil)
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23
Q

4 Health benefits of omega 3 FAT

A

• Anti inflammatory effects of ALA, EPA and DHA
• For certain chronic diseases where the inflammation is a contributory cause, the diets rich in ω3 fatty acids are beneficial
• eg cardiovascular disease and for other chronic degenerative diseases such as cancer, rheumatoid arthritis, and Alzheimer disease.

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24
Q

What is most naturally occurring FA ?

A

Cis

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25
Q

Cis and Trans configuration and biomedical importance

A

• Hydrogenation of fats, commercial applications (different degree of harness, margarine and spreads by partial hydrogenation of oils)
• Biomedical importance of hydrogenated food
– Partial hydrogenation converts a part of cis-isomers
into trans-unsaturated fats
– Consumption of transfats(TFA) increases the risk of coronary heart disease, and other disease such as diabetes mellitus, cancer by raising the levels of LDL cholesterol and lowering levels of HDL cholesterol.
• Technological advancement to reduce generation of TF.

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26
Q

TFA during pregnancy and lactation

A

TFA (in partially hydrogenated vegetable oils) are transmitted from mother to foetus and from mother to infant in breast milk. Negative outcomes related to conception, foetal loss, and growth. Thus it is recommended that industrially-derived trans fatty acids should be as low as practical for pregnant and lactating women.

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27
Q

Did Fats and oils in heat

A

Long term exposure to heat and repeated frying of oils rich in PUFA generates harmful chemicals. Saturated fats and monounsaturated fats are relatively resistant to heating.

28
Q

Order of saturated fat from low to High(14 components )

A

Safflower
Canola
Sunflower
Corn
Peanut
Olive
Soybean
Cottonseed
Chicken fat
Lard
Beef fat
Palm oil
butter
Coconut oil

29
Q

PUFA of 14 in order low to high

A

Coconut
Butter and beef fat
Olive oil
Palm
Lard
Chicken fat
Canola
Peanut
Cottonseed
Soybean
Corn
Sunflower
Safflower

30
Q

MUFA in order low to high of 14

A

Coconut
Safflower
Cottonseed
Subnfower
Soybean
Corn
Butter
Palm
Beef fat
Lard and chicken fat
Peanut
Canola
Olive oil

31
Q

Unsaturated vs saturated FA and examples

A

US FA. VS. S FA
1. 1/more double bonds. 1. No double bonds
2. More soluble
3. Liquid at rtp. Solid at rtp
4.more volatile
5. Can be hydrogenated Can’t
6. Exhibits cis, trans. Doesn’t
Ex. Plied acid, palmitleic acid. Stearin acid, palmitic acid

32
Q

What is TAG

A

• 3 FAs linked to a single glycerol with ester linkages.
• Simplest lipids.
• Non polar, hydrophobic, essentially insoluble in water

33
Q

2 functions of TAG

A

• TAG provides stored energy (adipose) serving as metabolic fuel & insulator.
• The main storage form of fatty acids.

34
Q

2 risks of TAG and how to counteract

A

• high levels of triglycerides in the bloodstream have been
linked to atherosclerosis
• Diets that are rich CHO with a high glycemic load elevates TAG in blood
• Moderate exercises may reduce TAG levels in blood

35
Q

What are PL

A

• Compound Lipid (Simple lipids + other groups)
• Amphipathic in nature
• The predominant lipids of plasma
membranes
• Two groups ;
glycerophospholipids and sphingophospholipids

36
Q

What is glycerophospholipids ? And 5 examples

A

Phosphatidic acid (PA)
DAG with a phosphate group and the precursor for other glycerophospholipds

Alcohol +PA → Glycerophospholipids

Serine + PA → phosphatidylserine (PS)
Ethanolamine + PA → phosphatidylethanolamine (PE) (cephalin) Choline + PA → phosphatidylcholine (PC) (lecithin)
Inositol + PA → phosphatidylinositol (PI)
Glycerol + PA → phosphatidylglycerol (PG)

37
Q

What is Sphingophospholipids (sphingomyelin) and how is it formed

A

• The backbone of sphingomyelin is the amino alcohol sphingosine
• A long-chain fatty acid is attached to the amino group of
sphingosine producing a ceramide
• Sphingosine in combination with phosphorylcholine produces
sphingomyelin
• Sphingomyelin is an important constituent of the myelin sheath of
nerve fibers
phosphorylcholine

38
Q

Comparison of glycerophospholipid and sphingophospholipid structures.

A

• In glycerophospholipids,
Glycerol backbone
linked to
An alcohol ( GLYCEROL,INOSITOL,CHOLINE, SERINE,ETHANOL-AMINE) , phosphate , 2FA

• in sphingolipids,
Sphingosine backone
Linked to
Alcohol ( CHOLINE) , phosphate , 1 FA

• In glycerophospholipids, two (2) hydrophobic tails
and both are fatty acid chains
• in sphingolipids,
Two (2) hydrophobic tails but only one is a fatty acid chain and the other is part of the sphingosine moiety.
• Both have polar head groups.

39
Q

Functions of selected phospholipids
1.Phosphatidylcholines (Lecithins) as a surfactant.

A

• Choline + PA → phosphatidylcholine (PC) (lecithin) produced by type II cells.
• form a stiff layer between air and water interphase
• Reduces surface tension
• Reduces the pressure needed to re inflate
• Prevent alveoli collapse
• Respiratory distress syndrome (RDS) in preterm infants is associated with insufficient surfactant production and/or secretion

Act as choline reservoir

40
Q

4 other functions of phospholipids

A

• The predominant lipids of plasma membranes
• blood coagulation- required for the conversion of Prothrombin to thrombin by active factor X
(Cephalin)
• lipid absorption-lowers the surface tension of water & aids in the emulsification of lipids
• Plays a role in the enzymatic action:- Some mitochondrial enzymes require tightly bound PL for their action eg- cardiolipin, a phospholipid found in mitochondria, is essential for mitochondrial function. (mitochondrial dysfunction in aging and in pathologic conditions including heart failure)

41
Q

What are Glycolipids (glycosphingolipids)

A

• Lipids + carbohydrates
• are derivatives of ceramides
• Ceramide is sphingosine plus FA

42
Q

Name 2 neutral glycosphingolipids, thru structure, where found

A

1.Cerebrosides- simplest form. Contains galactose or glucose.
Predominantly in the brain and peripheral nervous tissue, with high concentrations in the myelin sheath
2. Globosides- ceramide oligosaccharides (addition of monosaccharides or other substituted sugars such as N- acetylgalactosamine.

43
Q

Name one acidic glycolipid , its structure and functions

A

Gangliosides- derivatives of ceramide oligosaccharides with the addition of one or more sialic acids (eg Neuraminic acid).
They function in cell–cell recognition and communication.
as receptors for hormones and bacterial toxins such as cholera toxin.

44
Q

Explain lysosomal lipid storage disease

A

• Enzymes required for the degradation of sphingolipids are present in lysosomes.
• Any defect in enzymes causes accumulation of sphingolipid (Lysosomal lipid storage diseases)
• Early death due to neurologic deterioration
• Most of them are autosomal-recessive diseases,

45
Q

What are eicosanoids

A

• 20 carbon units
• Derive from ARA or other C 20 PUFA.
• Physiologically and pharmacologically active compounds
• produced in very small amounts in almost all tissues
• Eicosanoids are not stored, and they have an extremely short half-life, being rapidly metabolized to inactive products.

46
Q

3 examples of Eicosanoids

A

Prostaglandins (PG),
thromboxanes (TX)
and leukotrienes (LT)

47
Q

3 functions of eicosanoids

A

• Physiologically, they are considered to act as local hormones
• Family of very potent biological signaling molecules.
• Mainly acts as a short-range messenger affecting tissues near the cells that produces them.

48
Q

2 important biosynthesis pathways to make important eicosanoids from arachidonic acid

A

• Synthesis of prostaglandins and thromboxanes
• Synthesis of leukotrienes

49
Q

Explain pathway of synthesis of prostaglandins and thromboxanes
From AA

A
  1. AA converted to prostaglandins and thromboxanes in presence of a PGH synthase enzyme
50
Q

What is PGH Synthase

A

• prostaglandin endoperoxide synthase (PGH synthase).

• This enzyme has two catalytic activities:
– fatty acid cyclooxygenase (COX) activity, which requires two molecules of O2, ( convert AA to PGG2)
– peroxidase activity,which is dependent on reduced glutathione

• PGH2 is converted to a variety of prostaglandins and thromboxanes.

51
Q

2 Isozymes of prostaglandin endoperoxide synthase (PGH) synthase

A

• Two isozymes of PGH synthase ( COX-1 and COX-2)
• COX-1 in most tissues and is required for maintenance of healthy gastric tissue, renal homeostasis, and platelet aggregation. (In platelets)
• COX-2 is inducible in a limited number of tissues mediates the pain, heat, redness, and swelling of inflammation and the fever of infection. (In epithelium)

52
Q

What are thrombocytes and prostaglandins formed ?

A

Thromboxane A2 synthase makes TxA2
Prostaglandin E2, D2, F2a synthase makes PGE2, PGD2, PGF2a
Prostacyclin Synthase makes PGI2

53
Q

Explain leukotrine synthase

A

Membrane lipids converted to AA catalysed by Phospholipase A2
Or
Diet to AA.

AA converted to leukotrine by lipooxygenases

54
Q

Applications- Leukotriene

A

• Leukotrienes are mediators of allergic response and inflammation.
• Their synthesis is not inhibited by NSAIDs.
• Use of
– Inhibitors of 5-lipoxygenase
– leukotriene receptor antagonists
in the treatment of asthma.

55
Q

TXA2 function

A

Produced by COX 1 primarily in platelets
Promotes platelet aggregation
Vasoconstriction
Mobilizes intracellular calcium
Contraction of smooth muscles
Relaxation of smooth muscles

56
Q

PGI2 function

A

Produced by COX-2 primarily in endothelium of vessels
Vasodilation
Inhibit platelet aggregation

57
Q

PGE2 function

A

Produced by most tissues , especially kidney
Vasodilation
Relaxes smooth muscle
Used to induce labour
Stimulate uterine contractions
Required for fever response

58
Q

PGF2 function

A

Produced by most tissues
Vasoconstriction \ontraction of smooth muscles
Stimulate uterine contraction
Used to induce labor

59
Q

Priduction of LTA4

A

Produced in leukocytes, platelets, mast cells,heart and lung vascular tissue

60
Q

LTA4 to LTC4 and others and functions

A

Add glu-cys-gly to make LTC4 and by removal glu TO LTD4 to LTE4 by removal of GLY

Contraction of smooth muscle
Bronchoconstriction
Vasoconstriction
Inc vascular permeability
Cysteinyl LTs make slow reacting substances of anaphylaxis
Involved in patio-hydrology of asthma

61
Q

LTB4 function

A

Inc chemotaxis of polymorphonuclear leukocytes
Release of lysosomal enzy,es
Adhesion of wbc

62
Q

Inhibitor of conversion of membrane PL to AA

A

Cortisol

63
Q

Inhibitor of conversion of membrane of AA to PGG2 by COX 1

A

Aspirin
Indomethacin
Phenylbutazone
Other NSAID

64
Q

Inhibitor of conversion of membrane of AA to PGG2 by COX 2

A

Selective COX 2 inhibitors ( ex. Celecoxib )

            But opp. Effect by cytokines, endotoxin, growth factors, tumour promoters
65
Q

Applications- Anti-inflammatory drugs

A

• a steroidal anti-inflammatory agent (cortisol) inhibits s phospholipase A2 activity
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). Aspirin, indomethacin, and phenylbutazone inhibit both COX-1 and COX-2.
• COX-2 inhibitors eg-coxibs (celecoxib) reduce pathologic inflammatory processes mediated by COX-2 while maintaining the physiologic functions of COX-1. But they increased risk of heart attacks.

66
Q

Explain the biochemical basis of Aspirin-induced asthma

A
67
Q

Biochemical basis of low-dose aspirin therapy used to lower the risk of stroke and heart attacks

A

• Aspirin inhibits both COX-1 and COX-2
– COX-1 in platelets responsible for production of TXA2 that promotes
platelet aggregation.
– COX-2 in endothelial responsible for production of PGI2 that inhibits platelet aggregation.
• Platelets- no nuclei thus cannot regenerate COX 1
• Endothelial cells contains nuclei and can regenerate COX 2
synthesis then continue to produce PGI2
• Thus [PGI2] > [TXA2]
• Then the over all balance favored inhibition of platelet aggregation

Biochem Ca1 Cram (13 decks)

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