Fat disposal Flashcards
Properties of Fat
- hydrophobic
- fats need to be carried around bloodstream within capsules (lipoproteins)
- need to emulisfy for digestion
Formation of Emulsions
using molecules that have both hydrophobic/philic properties
e.g. phospholipids
purpose of amphiphilic molecules
- acts as a detergent
- emulsify fat into tiny particles
- micelles
Where are bile salts made and what from
- liver and from cholesterol
where are bile salts secreted?
- in small intestines
- stored in gall bladder
after digestion what happens to bile salts
reabsorbed and taken back into the liver via hepatic portal vein.
purpose of bile salts
to surround fat and emulsify
pancreatic lipase
hydrolyses fat into FA and glycerol
what happens if bile duct is blocked
no bile secreted –> less fat digestion –> lower calorie intake
Orlistat
side effects:
- oily spotting in stool
- gas with oil discharge
- need to go to bathroom often
- fat in faecal species
This indirectly causes people to stop eating fatty foods as if they do they will suffer the consequences
why do we need Lipoproteins
- fats need to be packaged for transport
structure of lipoprotein
inside a phospholipid shell - a lipoprotein (shell around the fat which is a monolayer)
coat studded with proteins (apoproteins - enzyme and docking)
different types of lipoproteins (size, internal composition and apoproteins)
Lipoproteins from gut
- lipoproteins made by -intestinal cells
- chylomicrons (contains fat and dietary cholesterol)
- they do not enter bloodstream instead go through lymphatics
packaging cholesterol
- esterify
- just to make it completely hydrophobic
chylomicrons
interact lipoprotein lipase
what stimulates LPL (lipoprotein lipase)
insulin
remnants of chylomicron
- remove of fat from chylomicrons (still contains fat)
- endocytose by liver
- any fats in the remnants will be in the liver and engulfed by hepatocytes and enter liver
What does VLDL stand for
Very low density lipoproteins
- they assemble from fat
- excreted into bloodstream
LDL
low density lipoproteins –> strip fat
how is cholesterol delivered
tissues take LDL through LDL receptor
- cell will indicate through expressing LDL receptors if they want cholesterol. If cells have enough cholesterol they stop expressing LDL receptors
What regulates cholesterol
- insulin, cholesterol levels
- gene expression, enzyme degradation
- can be inhibited by statins
LDL is bad
- LDL become oxidised with time
- macrophages take up LDL without control (become foam cells)
- creates inflammatory env –> formation of plagues
Reverse Cholesterol transport - HDL
- High density lipoprotein
- produced by liver ( thins disc of phospholipids)
- goes back to liver with rest –> bile salts
- get rid of cholesterol
CETP
cholesterol ester transfer protein
- catalyses exchange of cholesterol ester for triglyceride
consequence of CETP
HDL takes back more fat and less cholesterol
Cholesterol remains in circulation
- VLDVL enriched with cholesterol
ways to reduce blood cholesterol
- reduce consumption of cholesterol
- inhibit absorption of choelsterol from gut via competitive inhibitors
- decrease reabsorption of bile salts using resins that bind bile salts (liver has to make more bile salts from cholesterol)
ways to reduce blood cholesterol
- reduce consumption of cholesterol
- inhibit absorption of choelsterol from gut via competitive inhibitors
- decrease reabsorption of bile salts using resins that bind bile salts (liver has to make more bile salts from cholesterol)
importance of cholersterol
- steroid hormone synthesis
- regulating membrane fluidity
Membrane with saturated FA
- no double bonds
- membrane is crystalline
Membrane with Unsaturated FA - structure
- unsaturated FA –> kinks
- membrane is less crystalline, more fluid and permeable
Trans fats
- catalytic hydrogenation of polyunsaturated fatty acids ( add hydrogen to naturally occuring fat acids, incomplete and random formation of new TRANS double bonds)
