L16 Dietary Lipids Flashcards
What are common properties of lipids and examples of lipids?
-insoluble in water
-soluble in non-polar substances like ether and chloroform
oils, steroids, waxes, fata
what are 5 functions of lipids
- energy storage
- structural components of biomembranes
- thermal insulators for tissues and organs
- signaling molecules
- hormone precursor
Where are the 5 places you can find lipids in the cell and their role there
- plasma membrane
phospholipid remodelling - mitochondrion
beta-oxidation - endoplasmic reticulum (ER)
phospholipid and neutral lipid biosynthesis - Lipid storage droplets
lipolysis - cytosol
FA biosynthesis (transient)
What is dyslipidemia and what are its consequences
metabolic disorder where lipids or lipoproteins are out of balance (abnormally high or low levels)
accumulation of lipid in blood, joints, eyes
heart problems
What is atherosclerosis and some of its consequences
Lipid accumulation in a blood vessel e.g. artery causing the narrowing of the vessel
impaired blood flow and oxygen transport to tissues = tissue damage
heart attacks or strokes
What are the properties of neutral lipids
no polar head
hydrophobic
Categorize the following as neutral lipids or amphipatic:
glycolipids
cholesterol
triacylglycerol
cholesteryl esters
phospholipids
sphingolipids
neutral: triacylglycerol, cholesteryl esters
amphipatic: phospholipids, sphingolipids, glycolipids, cholesterol
describe lipoprotein structure
phospholipid and cholesterol monolayer
inside transporting cholesteryl ester and triacylglycerol
describe a dietary lipid’s journey through the body
ingested and absorbed in SI mostly
chylomicron (lipoprotein) travels through lymphatic system into blood where it binds to LPL (lipoprotein lipase receptors) of different muscle and adipose tissues to distribute mostly triacylglycerol (TAG)
chylomicron remnants return to liver to make bile salts
What stimulates VLDL (lipoprotein) release by liver
reduced insulin action
fasting conditions
describe the 3 steps of dietary lipid absorption at the enterocyte
- gallbladder releases bile salts to emulsify dietary fat into micelles
- pancreas releases pancreatic lipase which breaks down each TAG into one monoglyceride and two free FAs - this aids in absorption by making the lipids more hydrophilic
- i-FABP (intestinal fatty acid binding protein) carries FA inside the enterocyte
What are the three kinds of lipids absorbed by the gastric mucosa
FA, MA, sterols
where are chylomicrons assembled
endoplasmic reticulum ER
Where can you find free FAs in the cell? What is their function there?
mitochondrion: beta-oxidation
cytosol: FA biosynthesis
What are the 2 characteristic structures of FAs
carboxylic acid COOH
long hydrocarbon (C,H) tail
What happens to the melting point of saturated FAs if the number of carbons go up?
the melting point increase
What happens to the melting point of unsaturated FAs if the number of carbons go up
the melting point decrease
TF: The more double bonds a FA has, the low the melting point
True
What are the two way to name unsaturated FAs? (in terms of numbering the carbons)
start counting from the COOH group
start counting from the last (omega) carbon
TF: branched FAs are common in humans
False
they are present in bacteria and some ruminants
What are the two branched FAs that humans possess and what makes them different from normal unbranched FAs?
pristanic and phytanic acid
they undergo alpha-oxidation (peroxisome) instead of beta-oxidation (mitochondria)
What are isoprenoids
molecules similar to FAs that have some branching
TF: TAG’s are 100% hydrophobic
True
What are two ways triglycerides are transported through the body
Chylomicrons (exogenous triglycerides from diet)
VLDL (endogenous triglycerides from liver)
Where can you find triacylglycerols in the cell? (cellular location)
lipid storage droplets (chylomicrons or VLDLs)
TF: phospholipids are 100% hydrophobic
False,
they have polar heads
Where can you find phospholipids in the cell?
plasma membrane, endoplasmic reticulum (ER)
TF: dietary lipids can be used to generate phsopholipids
True
Why are cis fats considered healthier than trans fats?
Trans fats increase the risk of cardiovascular disease due to their straight structure which increases packing ability
Cis fats are bent so they do not pack as well, decreasing their impact on cardiovascular disease
