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AP Biology chapter 5.3
Terms in this set (13)
Lipids include fats, waxes, oils, phospholipids, and steroids. What characteristic do all lipids share?
All lipids mix poorly, if at all, with water.
What are the building blocks of fats? Label
The building blocks of fats are glycerol and fatty acids. In the figure below, the glycerol molecule is in
gray, and the three fatty acids are in yellow.
If a fat is composed of 3 fatty acids and 1 glycerol molecule, how many water molecules will be removed to form it? Again, what is this process called?
One water molecule is removed for each fatty acid joined to the glycerol, equaling three water molecules for every triacylglycerol formed. This process is called dehydration synthesis.
Draw a fatty acid chain that is 8 carbons long and is unsaturated. Circle the element in your chain that makes it unsaturated, and explain what this means.
Unsaturated fatty acids have one or more double bond, with one fewer hydrogen atom on each double- bonded carbon. Nearly all double bonds in naturally occurring fatty acids are cis bonds, which cause a kink in the hydrocarbon chain whenever they occur.
Name two saturated fats.
lard, butter, or most animal fats
28. Name two unsaturated fats.
olive oil, cod liver oil or most plant or fish fats.
Why are many unsaturated fats liquid at room temperature?
The kinks where the cis bonds are located prevent the molecules from packing together closely enough to solidify at room temperature.
28. What is a trans-fat? Why should you limit them in your diet?
A trans fat is an unsaturated fat with a trans double bond; the result of the process of hydrogenating vegetable oils to prevent lipids from separating out in liquid (oil) form. Trans fats should be limited in your diet because they have been found to contribute to atherosclerosis, a cardiovascular disease caused by plaque buildup within the walls of blood vessels.
29. List four important functions of fats.
Energy storage, long-term food reserve in mammals, adipose tissue cushions vital organs, body insulation.
31. Why is the "tail" hydrophobic? Answer in terms of the phospholipid bilayer as a whole.
The "tails" are hydrophic (avoid water) because they are hydrcarbon. As previously discussed in chapter 4, hydrocarbons are hydrophobic compounds because the great majority of their bonds are relatively nonpolar carbon-to-hydrogen.
32. Which of the two fatty acid chains in the figure with question 30 is unsaturated? Label it. How do you know it is unsaturated?
The fatty acid chain on the right is unsaturated. We know this because of the kink in the chain, indicating a double bond.
Some people refer to the cholesterol molecule to the right has three hexagons and a doghouse. Where can cholesterol be found within an animal cell? Why is cholesterol such an important molecule in animals?
Cholesterol, a steroid
What are other examples of steroids?
Possible examples include vertebrate sex hormones.