4. Lipids Flashcards
Explain the structure of a fatty acid.
Fatty acids are long hydrocarbon tails (14-18 usually) with a carboxylic acid functionality at the end. Most fatty acids are an even number of carbons because they are synthesized two carbons at a time.
saturated = no double bonds unsaturated = double bonds present
Explain the structure of triglyceride.
glycerol is a 3 carbon triol. 3 fatty acids become esterfied to each alcohol group to form triglyceride which is the compound known as fat.
What is amphipathic?
something that is both hydrophobic and hydrophilic
amphoteric - something that is an acid and a base.
What is saponification?
base-catalyzed hydrolysis of esters (e.g. triglyceride) to form carboxylic acid.
Fats are more efficient energy storage molecules than carbs because they package more tightly together (due to their hydrophobicity) and they have more energy per bond (since fats are more reduced). Why are they not our main energy source?
Because carbs are much easier to mobilize. Fats are slower and harder to deal with.
How do we increase the fluidity of the phospholipid membrane?
- unsaturated fatty acid tails. Kinks prevent tails from packing closely together
- shorter tails = less London dispersion forces, increases fluidity
- cholesterol (which depends on temperature)
t or f, waxes are long chain fatty acids esterfied to long chain alcohols.
true
What are the fat soluble vitamins?
DEAK
D - regulates blood calcium and phosphate
E - protects skin, anti-oxidant
A - used for eye sight (retinal)
K - used for blood clotting
Fats are absorbed from the intestine and travel as chylomicrons to the liver and other areas through the lymphatic system. Once they enter the cells, the triglyceride molecules are hydrolyzed into glycerol and free fatty acids. What occurs before the fatty acids are transported into the mitochondria?
fatty acid activation. Fatty acid gets converted into Acyl-coA by acyl-coA synthetase. This compound is then transported into the mitochondria.
This activation costs 2 ATP.
What is beta oxidation of fatty acids? What are the products?
Once activated, the acyl-coA compound is transported into the mitochondria.
It then goes through a 4 step process that cleaves off one acetyl-coA (2 carbon) unit. This generates 1 NADH and 1 FADH2.
beta oxidation continues to cleave 2C off the FA until the final round, in which case it cleaves 4C.
the acetyl-coA can then enter the Krebs cycle.
How many molecules of acetyl coA, NADH, and FAD2 does a 12 carbon fatty acid produce?
12 carbon FA = 6 acetyl-coA molecules
only 5 rounds of beta oxidation
5 NADH and 5 FADH2
remember though, acetyl-coA can now enter the Krebs cycle where it will generate another 3NADH, 1FADH2, and 1 GTP
t or f, for a fatty acid with x number of carbons, there will be x/2 - 1 rounds of beta oxidation.
true
What is ketogenesis? Why does it occur?
ketogenesis is the conversion of acetyl-coA into different kinds of ketone bodies that are capable of crossing the blood brain barrier (e.g. acetone, B-hydroxy-butyrate). Ketogenesis occurs during times of starvation, where glucose levels and glycogen stores are very low.
essentially, the body breaks down fat to form acetyl-coA which is then converted into ketones for the CNS.
In type 1 diabetes, patients cannot produce insulin and thus cannot reduce glucose levels. If a patient has not received an insulin injection in a while, they cannot uptake the free glucose. Thus their bodies rely on beta oxidation of fatty acids. What is a consequence of this?
A lot of beta oxidation leads to some acetyl-coA being converted to ketones. Enough of this can lead to diabetic keto-acidosis.
insulin injection allows your cells to uptake the free glucose which prevents beta oxidation.
What is a key difference between fatty acid oxidation and fatty acid synthesis?
FA oxidation - mitochondrial matrix (after the fatty acid activated by acyl-coA synthetase)
FA synthesis - cytoplasm
