Biomolecules - Lipids Flashcards
Functional features of lipids?
– Relatively insoluble in water
– Soluble in nonpolar solvents (eg- ether, chloroform)
Presence of lipids in the human body?
Humanbody
– Compartmentalized (membrane-associated lipids, triacylglycerol in adipocytes or in association with protein (lipoprotein particles) or on albumin.
Lipids in the diet?
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
Biomedical importance of lipids?
- 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:
- Thermal Insulator
- Electric Insulator in neurones - Signalling molecule proteins
- Protects internal organs
- Lipoproteins
- Obesity
Classification of Lipids?
- Simple Lipids
- Complex Lipids
- Phospholipids: Sphingophospholipids and Glycerophophospholipids.
- Glycolipids
- Sulfolipids and Amino lipids - Derived Lipids
Where do we find fatty acids?
Importance of fatty acids?
- Exist in free (unesterified) or esters (eg. Triacylglycerols).
- Free fatty acids can be oxidized by many tissues to provide energy
Factors affecting physical properties of fatty acids?
- Length of the Hydrocarbon chain
- Degree of unsaturation
Classification of Fatty acids?
Two groups – Saturated and Unsaturated
* Unsaturated- mono (MUFA) and poly unsaturated (PUSFA)
* Unsaturated – two types of configurations cis and trans
What are essential fatty acids?
Examples?
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.
Explain DHA regarding pregnancy and infancy.
DHA plays a major role in development of the brain and retina during foetal development and the first two years of life
* 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.
LA, ALA and their derivatives play a significant role in the …
structure of biological membranes.
Health benefits of omega 3 FAT?
- 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.
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 diseases such as diabetes mellitus, and cancer by raising the levels of LDL cholesterol and lowering levels of HDL cholesterol.
Relationship between TFAs and Negative pregnancy outcomes.
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.
Structure of Triacylglycerols.
What is their nature and how soluble are they?
3 FAs linked to a single glycerol with ester linkages.
* Simplest lipids.
* Non polar, hydrophobic, essentially insoluble in water
function of TAGs
TAG provides stored energy (adipose) serving as metabolic fuel & insulator.
* The main storage form of fatty acids.
biomedical significance of TAGs
- 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
structure of phospholipids
- Compound Lipid (Simple lipids + other groups)
- Amphipathic in nature
- The predominant lipids of plasma
membranes - Two groups ;
glycerophospholipids and sphingophospholipids
What are glycerophospholipids?
Alcohol +PA → Glycerophospholipids
What are Sphingophospholipids (sphingomyelin)?
- 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
Comparison of glycerophospholipid and sphingophospholipid structures?
- 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.
Phosphatidylcholines (Lecithins) as a surfactant?
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
Functions of selected phospholipid?
1.Phosphatidylcholines (Lecithins) as a surfactant.
2. Acts as a choline reservoir
- 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).
Neutral glycosphingolipids?
Cerebrosides- simplest form. Contains galactose or glucose.
Predominantly in the brain and peripheral nervous tissue, with high concentrations in the myelin sheath
Globosides- ceramide oligosaccharides (addition of monosaccharides or other substituted sugars such as N- acetylgalactosamine.
Acidic glycosphingolipids?
*
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.
Lysosomal lipid storage diseases?
- 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,
Importance of DHA in the first two years of life.
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.
What are Eicosanoids?
- 20 carbon units
- Derive from ARA or other C 20 PUFA.
- Prostaglandins (PG), thromboxanes (TX) and leukotrienes (LT)
Function of Eicosanoids?
- Physiologically and pharmacologically active compounds
- 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.
Production and metabolism of eicosanoids?
- 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.
Biosynthesis of some important eicosanoids from Arachidonic acid?
- Synthesis of prostaglandins and thromboxanes
- Synthesis of leukotrienes
Synthesis of prostaglandins and thromboxanes?
- prostaglandin endoperoxide synthase (PGH synthase).
- This enzyme has two catalytic activities:
– fatty acid cyclooxygenase (COX), which requires two molecules of O2,
– peroxidase,whichisdependent on reduced glutathione - PGH2 is converted to a variety of prostaglandins and thromboxanes.
Isozymes of prostaglandin endoperoxide synthase (PGH) synthase?
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.
* COX-2 is inducible in a limited number of tissues mediates the pain, heat, redness, and swelling of inflammation and the fever of infection.
Functions of different prostaglandins?
Prostaglandins:
1. Vasoconstriction
2. Contraction of smooth muscles
3. Stimulates uterine contractions
4. Used to induce labor
Functions of different thromboxjnes?
- Platelet aggregation
- Vasoconstriction
- Contraction of smooth muscle
Functions of different leukotrines?
- Contraction of smooth muscle
- Bronchoconstriction
- Pathophysiology of asthma
Applications of Eicosanoids- Anti-inflammatory drugs?
- 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.
- Explain the biochemical basis of Aspirin-induced asthma
Biochemical basis of low-dose aspirin therapy used to lower the risk of stroke and heart attacks?
- 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.
Applications- Leukotriene?
- 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.
What are the characteristics of muscle cells?
- Excitability
- Conductivity
- Contractility
- Extensibility
- Elasticity
