Question

For the following questions answer with as much detail as possible. If a metabolic pathway is involved draw a name all molecular structures and name all enzymes. Indicate cell type and location within the cell as well as any transport mechanisms.

Since the fatty acid pathways are serpentine, show one pass through the sequence and then you may simply state how many times a sequence is repeated until a new reaction is needed. If asked to synthesize a fatty acid, synthesize oleic acid. If asked to break down a fatty acid use 15:2 Δ9,12.

While vacationing in the outer rim of the Milky Way, you stop for lunch at the big bang burger bar. Not trusting the local fare, you err on the side of caution and order a burger fries and a Coke. Little do you know that the triglycerides in this portion of the galaxy are composed entirely of a single fatty acid -15:2 Δ9,12. Fortunately, humans can metabolize this fatty acid just as they would any other.

Feeling guilty for your large lunch, later in the day you do some laps in the hotel swimming pool.

a. After a few laps, your glycogen stores are depleted, what hormone is in effect?

b. How does this hormone stimulate release of stored triglycerides? How are those released triglycerides transported?

c. Once in your muscles, using names and structures explain how the triglycerides are used to produce energy.

d. How many molecules of ATP can be generated from one molecule of your lunchtime triglyceride (all three fatty acids and the glycerol backbone)?

Answer 1

a.) The hormone that is in effect after glycogen stores are depleted is glucagon.

b.) When the glycogen stores of the body are depleted and the body is under stress,level of the hormones glucagon and epinephrine begins to rise in the blood.The surface of adipose cells have specific receptors for these hormones where these hormones bind and this results in activation of a reaction pathway in the cell that leads to activation of an enzyme called lipase. Lipase catalyzes the hydrolysis of triglycerides and free fatty acids and glycerol are produced, fatty acids are released.

Released triglycerides transported by lipoproteins.

c.) Once triglycerides are in the muscles,the free fatty acids are converted to CoA. Mitochondria is the site where the fatty acid-CoA thioesters are oxidized.Fatty acid-CoA thioesters are converted to CO2 and water in the mitochondrial matrix and ATP is produced.

d.) If we consider a triglyceride with three 16-C fatty acid chains,for one 16-C chain of fatty acid,ATP molecules produced= 129.
So for all the three fatty acid chains= 129 X 3=387 molecules of ATP.
ATP molecules produced from breakdown of glycerol= 15
So by adding,387+15= 402 molecules of ATP.
402 molecules of ATP can be generated from one molecule of your lunchtime triglyceride.