lipids Flashcards
(45 cards)
what are lipids?
- soluble in organic solvents
- wide variety of structures and functions
- source of energy
- cell and organelle membranes
what are saturated vs unsaturated fatty acids?
- saturated have the max # of H atoms and only have single bonds
- unsaturated are missing H atoms and have double bonds with cis or trans config
what is the delta system vs omega system?
- delta: numbering starts from carboxyl end
- omega: numbering starts from methyl end
what is the delta system nomenclature?
carbons:double bonds △^position of double bonds
what is the omega system nomenclature?
carbons:double bonds ⍵/n-location of first double bond
what are the essential fatty acids and why are they essential?
- linoleic acid (n-6) and alpha linolenic acid (n-3)
- humans lack enzymes that insert double bonds beyond the delta 9 position
what are signs of linoleic and alpha linolenic acid deficiency?
- n-6: dermatitis, reduced growth, reduced reproductive maturity
- n-3: low IQ, low visual acuity
what are the enzymes used in EFA desaturation and elongation?
- desaturase: insert double bonds
- elongase: adds more carbons
what does linoleic acid convert to and how?
- arachidonic acid
- desaturation then elongation then desaturation
what does alpha linolenic acid convert to and how?
- eicosapentaenoic acid
- desaturation, elongation, desaturation
which part of EFA desat and elong is not efficient?
conversion of alpha linolenic acid to eicosanoid (less than 8%)
what are eicosanoids?
- derived from FAs
- hormone like, function locally
- promote inflammation
what are triglycerides?
- dietary and storage lipids
- glycerol that has been esterified with 3 fatty acids
what are phospholipids?
- more polar than TAGs
- in membrane, intracellular signalling
- hydrophilic head
what are sterols?
- free or esterified with FA
- in membranes
- precursor for hormones
what is significant about cholesterol structure?
- most common sterol
- two different forms
where are lipids digested and by what?
- mouth, stomach, liver, gallbladder, small intestine
- lipase and bile acids
what are mixed micelles?
- spherical complexes containing lipid digestion products and bile acids
- access spaces between microvilli in intestine
what is enterohepatic circulation?
- cholesterol makes bile salts
- bile salts stored in the gallbladder
- released into small intestine to help emulsify dietary lipids
a. creates mixed micelles - bile acids are reabsorbed back into the liver
5% lost in feces
how do soluble fibres affect enterohepatic circulation?
- reduce efficiency
- hold onto bile acids which are lost in feces
what are the brush border enzymes involved in lipid absorption?
- pancreatic lipase
- cholesterol esterase
- phospholipase
how does lipid absorption work?
lipids are partially broken down by brush border enzymes and enter across the membrane via lipid transporters, then are remade inside the cell as chylomicrons that enter the lymphatic system via lacteal to bypass the liver and target different tissues
what are chylomicrons/chylomicron remnants?
- high lipid and low protein
- contain apob-48, apoc, apoe
- increase in circulation after a meal
what are VLDLs?
- very low density lipoproteins
- high lipid, low protein
- apob-100, apoc, apoe
