Lipids (Lecture 16) Flashcards
Why are fatty acids important sources of energy? Name this process.
Through the process of beta-oxidation fatty acids are able to produce both FADH2 and NADH.
What does the break down of fatty acids produce and what is this compound used for?
the break down of fatty acids via beta oxidation produces acetyl CoA, which feeds into the CAC. (note that it also produces FADH2 and NADH in the process)
Is the process of fatty acid synthesis reversible?
Yes, acetyl CoA can be converted into FAs with the investment of ATP and NADPH (energy). This is FA synthesis.
What are lipids?
Lipids are a heterogeneous group of biological compounds, including fats, oils, steroids, waxes, etc, that are insoluble in water.
What are common properties of lipids? (2)
- insoluble in water
- soluble in non-polar solvents (ether and chloroform)
What are some functions of lipids? (6)
- energy storage
-important dietary component due to their high energy
-structural components of
biomembranes
-thermal insulators in subcutaneous tissues and around organs
-signaling molecules (PI, leukotrienes, DAG, PIP2, IP3)
-hormones precursors
What does their solubility in water depend on?
Depends on the Carbon chain. (longer the chain= more insoluble in water)
Why do lipids form micelles?
In order to avoid water, the hydrophobic tails will interact with one another, while the polar/ hydrophilic head groups will interact with the aqueous medium. Also, the delta G of the association of lipids with water is NOT favourable, when compared to with other lipids.
Relationship between dilution factor and micelles.
If the dilution factor of lipids is too high, then micelles will not form. This is because they must meet together in order to form these structures. Micelles are only formed at the lipid’s critical concentration.
3 lipid interaction structures
- micelles
- bilayers
- vesicles
Describe the process of atherosclerosis
Too much LDL accumulate under the intima of the arteries. macrophages will enter the site to try to solve the issue of increased levels of LDL, but will be overwhelmed by the excessive amount of lipids. This will cause the macrophages to die and a necrotic core will build. This can lead to heart attacks or strokes, since the heart and brain are not provided with enough oxygen (respectively)
Two types of lipids are…
PURIFIED LIPIDS: Fatty acids organized in the form of triglycerides. This category includes oils and butter. The triglycerides are totally neutral lipids (hydrophobic).
CELLULAR LIPIDS: contain membrane lipids and can either be neutral lipids or amphipathic lipids. the neutral cellular lions are triglycerol and cholesteryl ester and the amphipathic cellular lipids are phospholipids, sphingolipids, glycolipids and cholesterol.
Describe the lipid’s journey from consumption to clearance from the bloodstream
- absorbed in the intestine
- resecreted in the form of chylomicrons
- the chylomicrons are lipoproteins composed of a mono layer of phospholipids and cholesterol. The middle of the chylomicron contains neutral lipids.
- the chylomicrons travel in the bloodstream and associate to certain enzymes to mature.
- the released FAs from the mature chylomicrons are taken up by muscle and adipose tissue
- the chylomicron remnants are cleared via the liver form the circulation
Explain the absorption of dietary lipids.
- the dietary fats will enter the stomach and will be solubilized by bile salts that are stored in the gallbladder.
- bile salts from micelles due to their amphipathic nature.
- the amphipathic bile acids will coat the fat infested and create a hydrophobic core.
- the lipids meet the pancreatic lipase in the small intestine, which will digest the triglycerides found in the bile salt micelles into monoglycerides and free fatty acids
- the brush border of the intestinal endothelial cells will take up the fatty acids
- the fatty acids are then transported in the brush border via the i-FABP (fatty acid binding protein prevents the interaction with water)
- in the brush border, the fatty acids will be reassembled into triglycerides to be incorporated into chylomicrons
- the chylomicrons will be secreted into the lymph and will eventually reach the blood.
NPC1L1
transporter protein located in the mucosa that allows for the uptake of sterols
