Biology, Eighth Edition, by Campbell & Reece, et al.
My notes and thoughts from Biology 111, for Monday, September 15, 2008. The entire series can be found here.
The class started with a reminder that the next class period (Wednesday the 17th) would be our first exam.
Then there was a short review of Hydrocarbons generally, and carbohydrates specifically, just to get us back to the place where we had left off.
We picked up this lecture with our discussion of Lipids.
Triglycerides —> Fats & Oils
Saturated Fat: glycerol on the left with three fatty acids
Glycerol + 3 Fatty Acids
When a glycerol molecule, C3H5(OH)3 (the vertical part on the left of the image), picks up three fatty acids (the long strings of C and H on the right), they combine to form a triglyceride.
Triglycerides are fats and oils. If the long fatty acid chains all remain straight, each carbon bonding with two Hydrogen atoms and its two neighbor Carbon atoms, the triglyceride can pack densely, and thus becomes a solid at room temperature. This is a saturated fat.
Unsaturated Oil: Glycerol on the left with three fatty acids. Note the kink in one fatty acid.
If one or more of the long fatty acids develops a “kink”, ie two Carbons double bond and dump a Hydrogen, the stack can not pack as densely, and thus becomes a liquid at room temperature. This is an unsaturated oil. If there is one kink, it’s a monounsaturated oil, and if more than one, it’s a polyunsaturated oil.
Ta-da. It was kind of cool to suddenly understand the difference between them after having heard the terms for so long in reference to food labels.
We can measure energy in units called calories.
Because of fat’s high percentage of hydrocarbons (all along those fatty acid chains), it has a high caloric content. For comparison, a gram of fat contains 9 calories, while a gram of carbohydrates contains 4 calories. Remember that those Hydrogen – Carbon bonds are high energy content because of the non-polar covalent bond.
(Lecture continues below the fold)
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