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Are lipids: wax, steroids, cholesterol, phospholipids
Fatty acids supply the carboxyl groups; the hydroxyls come from glycerol.
Tail lengths of 16 to 22 are common. There may be from 0 to 6 double bonds.
Every double bond is a place where hydrogen could be added.
Water rejects nonpolar molecules such as fats, so fats travel inside particles that are coated with polar parts of phospholipids and proteins.
Every cell depends on phospholipid bilayers to limit leakage of molecules through membranes.
The hydrogen bonds in water exclude the nonpolar tails of phospholipids, forcing the molecules into a bilayer.
Water on both sides of the membrane excludes the tails, forcing them into the interior where they face one another.
Polar molecules have trouble escaping from the water to enter a membrane, and nonpolar molecules have trouble moving from the membrane into water. Thus, neither kind of molecule moves easily through membranes.
A phospholipid has a strongly polar (charged) head and two nonpolar tails.
Phospholipids are close relatives of fats, but the difference makes them amphipathic and allows them to form the basis of membranes. Important stuff!
If LDL exceeds HDL, your body is probably storing excess cholesterol, which may clog the arteries and cause heart disease.
This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.
-polar interactions among the phospholipid head groups on the same surface of the membrane
-hydrophobic interactions among the fatty acid tails of phospholipids on opposite sides of the membrane
-hydrophobic interactions between the phospholipid tails and the surface of integral membrane proteins buried in the membrane
-hydrophobic interactions among the fatty acid tails of phospholipids on the same side of the membrane
What do fats, steroids, and waxes have in common?
(a) Moderate polarity.
(b) Low solubility in water.
(c) They occur in membranes.
Both (a) and (c).
Both (b) and (c).
Dr. Haxton told one of his students, “To move in the bloodstream, fats need the help of phospholipids.” What would a good student say?
-You have it backwards. Fats help phospholipids to travel.
-Not so. Fats are small enough to travel easily without help.
-Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids.
-Yes. Nonpolar molecules aren’t compatible with water.
-Right. Fats are too polar to travel alone in water.
The presence of many C-C and C-H bonds causes fats to be …
(a) rich in energy.
(b) insoluble in water.
(c) low in energy.
Both (a) and (b).
Both (b) and (c).
In fat synthesis,________and fatty acids combine to make fats plus________.
In the reaction that builds a fat,________ groups react with ________ groups.
Triglycerides vary with respect to the number of …
(a) hydrocarbon tails.
(b) C atoms in the tails.
(c) double bonds in the tails.
Both (b) and (c).
All of the above.
A food company hydrogenated a barrel of fat. The treatment …
(a) made the fat less fluid.
(b) made the fat less saturated.
(c) lengthened the fat tails.
(d) put more bends (kinks) in the fat tails.
Both (a) and (d).
The most unsaturated fats have …
-the longest hydrocarbon tails.
-the fewest double bonds.
-the most double bonds.
-the highest ratio of H to C.
-the shortest hydrocarbon tails.
What do DNA, proteins, and fats have in common?
-They are polymers.
-They are polar.
-They contain carbonyl groups.
-They contain nitrogen.
-They contain phosphorus.
Which of these is NOT a lipid?
Which of these is rich in unsaturated fats?
-a fat that is solid at room temperature
A function of cholesterol that does not harm health is its role _____.
-as a component of animal cell membranes
-in calcium and phosphate metabolism
-All of cholesterol’s effects cause the body harm.
-the most abundant male sex hormone
-as the primary female sex hormone
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