lipid metabolism Flashcards
what are the 8 functions of lipids
- concentrated source of energy (9kcal/g)
- palatability of foods & increase satiety
- source of essential fatty acids
- carrier of fat-soluble vitamins
- necessary for growth and development
- imports precursors for the production of hormones
- affect inflammation and blood clotting
- key roles in disease development
what does saturated mean
-theres a maximum number fo H atoms within the molecule (only single bonds)
what does unsaturated mean
- there are “missing” H atoms
- presence of double bonds
- can be cis or trans
what is the most stable form of unsaturated fatty acids
trans
for FA nomenclature, what side does the delta system start at
numbering starts from the carboxyl end of fatty acid (C=O OH)
for FA nomenclature, what side foes the omega system start at?
numbering starts from the methyl end
diets with ,0.1% linoleum acid result in what?
poor skin growth and thickened dry skin
what are two essential fatty acids? why are they essential?
- linoleic acid and alpha linolenic acid
- humans lack the enzymes necessary to insert double bonds beyond the delta-9 position of a fatty acid
what does a n-6 deficiency result in?
skin: dermatitis
growth: decreases
reproduction: decreases
CNS: is fine
retinal: is fine
what does a n-3 deficiency result in?
skin: is fine
growth: is ok
reproduction: is fine
CNS: reduced IQ
Retinal: decreased visual acuity
how do diseases arise from fatty acids?
diseases have been linked to the w-6 and w-3 ratios
what are some examples of eicosanoids?
prostaglandins
thromboxjnes
leukotreines
what are eicosanoids
- metabolites of 20-carbon fatty acids (primarily AA and EPA)
- hormone-like (function locally)
- plays a role in inflammation, platelet aggregation. blood pressure
describe inflammation, correlating it to W6 and W3
W6: pro-inflammatory
W3: anti- inflammatory
where are eicosanoids stored?
they’re stored as phospholipids in cell membranes
- never free in the cell
what are triglycerides?
- neutral lipids
- main dietary lipid
- major storage form of lipids
what are the functions of TAGS
- lipogenisis (production of fatty acids)
- lipolysis (releases fatty acids in times of need)
- transport of lipoproteins
what are the principle functions of phospholipids
- components of membranes
- source of physiologically active fatty acids for eicosanoid synthesis
- anchors membrane proteins
- intracellular signalling
what are the principle functions of sterols
- essential components of membranes
- major precursor (for bile acid production, steroid sex hormone production, and vitamin D synthesis)
describe lipid digestion within the mouth
- lingual lipase (continuously released)
describe lipid digestion within the stomach
- gastric lipase (continually secreted, stable at low pH)
describe how the liver helps lipid digestion
the liver makes bile acids- which help digest them
describe how the gallbladder helps lipid digestion
- storage of bile acids
the release of bile is triggered by hormones
describe lipid digestion within the small intestine
- pancreatic enzymes (includes pancreatic lipase, cholesterol, and esterase’s
what are mixed micelles
small, spherical complexes containing lipid digestion products (and bile acids)
describe how mixed micelles work
- accesses the space between microvilli in the intestine
- excreted bile acids are then reabsorbed in the digestive tract
describe the efficiency of enterohepatic circulation
- soluble fibres reduce the efficiency of enterohepatic circulation by holding on to bile acids, which are then secreted in feces
how much bile acid is lost within feces?
about 5% of bile acids are lost in feces
how much bile acid is reabsorbed in the small intestine?
about 95% of bile acids are reabsorbed and recycles back to the liver
what are the three brush border enzymes?
- pancreatic lipase
- cholesterol esterase
- phospholipase
how are lipoproteins classified?
- ratio of lipid:proteins (affect density)
2. specific apolipoprotein (affects receptor interactions
what is considered good cholesterol
low lipid, high protein (high density lipoprotein)
what is the primary transport of dietary lipids
chylomicron and remnants
when do chylomicron concentrations increase
they increase in circulation after a meal
peak between 30min-3hr after eating
when/where do chylomicrons enter the system
chylomicrons enter the lymphatic system before entering the blood (therefore, dietary lipids are available to adipose and muscle before arriving at the liver)
where is lipoprotein lipase located
LPL is located on the surface of endothelial cells lining small blood vessels and capillaries
what activated LPL
lipoprotein lipase is activated by ApoC in chylomicrons
what is the function of LPL
lipoprotein lipase hydrolyzes the TAG in chylomicrons
what are chylomicron remnants
they are simply when chylomicrons become TAG-depleted
how are chylomicron remnants removed from circulation
chylomicron remnants (CR) are removed from circulation through ApoE- mediated interactions with a receptor in the liver
what is the main transporter of newly synthesized hepatic TAG
VLDL (very low density lipoprotein)
where/how is LDL taken up?
LDL is taken up by the liver via LOL-receptors (mediated endocytosis)
describe the esterification of cholesterol
-cholesterol obtained from plasma membranes is esterfied directly on high-density lipoproteins
what is reverse cholesterol transport
when high-density lipoproteins pick up cholesterol around the body and divert it back to the liver
function of lecithin-cholesterol-acyltransferase?
LCAT esterfies fatty acids to cholesterol
what is SRBI
a scavenger receptor class B1 (an HDL receptor in the liver)
what is CETP
cholesterol ester transfer protein
transfers cholesterol from HDL to VLDL and/or LDL
what are the three fates of cholesterol within the liver?
- converted into bile acids to replenish the bile acid pool
- secreted “as is” directly with bile (to be excreted in feces)- only if body doesn’t need more bile acids
- packaged into VLDL and sent around the body (if in fasted state)
function of LDL
LDL delivers cholesterol for essential functions but can also deposit cholesterol in unwanted places
high HDL levels=?
higher HDL levels means more cholesterol returning to the liver
where do lipids fit into gluconeogenesis?
- the glycerol backbone is glycogenic (and us used to make glucose in faster states)
where do lipids fit into the Krebs cycle
fat oxidation via acetyl coA
describe lipolysis in correlation to gluconeogenesis
- lipases hydrolyze ester linkages (aka lipolysis)
- fatty acids can undergo B-oxidation and can be used to generate energy
describe lipolysis in adipose tissue
hormone-sensitive lipase (HSL) cleaves a fatty acid from the glycerol backbone)
the complete breakdown of a TAG molecule releases what?
- the complete breakdown of a TAG molecule releases 1 glycerol and 3 fatty acids
what are the four steps within b-oxidation
- dehydrogenation
- hydration
- oxidation
- thiolysis
each round of b-oxygen removes how many carbons? and produces how many NADH, FADH
each round of beta oxidation removes 2 carbons, and produced 1 NADH and 1 FADH2
does limiting dietary cholesterol change blood cholesterol levels?
for healthy people, limiting dietary cholesterol does not change blood cholesterol much, but for people with high blood cholesterol, a decrease in dietary cholesterol with decrease LDL
what are trans fats
unsaturated fatty acids with at least one double blond in the trans configuration (both industrial and natural)
what does high intake of industrial trans fatty acids result in?
- increased LDL (cholesterol)
- increased total cholesterol
- increased inflammation
- decreased HDL
- linked to CVD
