Section 28: Carbohydrates: Functions of Carbohydrates
Polymers that contain sugars .
(a) may store hereditary information.
(b) may store energy.
(c) may protect cells.
Both (b) and (c).
(a), (b), and (c).
Good choice! Polymers that contain sugars do all the named functions and more. For example,
they also lubricate the path of roots through soil and they glue plant cells together.
Section 32: Lipids: Functions of Lipids
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).
Correct! Low water solubility is the trait that defines lipids.
Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of
phospholipids." What would a good student say?
Yes. Nonpolar molecules aren't compatible with water.
Not so. Fats are small enough to travel easily without help.
Right. Fats are too polar to travel alone in water.
You have it backwards. Fats help phospholipids to travel.
Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids.
Good choice! Water rejects nonpolar molecules such as fats, so fats travel inside particles that
are coated with polar parts of phospholipids and proteins.
Section 36: Proteins: Functions of Proteins
Which biological activity does NOT directly involve proteins?
Defending cells against viruses.
Changing the shape of a cell.
Breaking food polymers into smaller molecules.
None of the above; proteins are involved in all of them.
Right! Proteins have all the listed functions and many more.
Proteins: Secondary Structure
The helical foldings of proteins are stabilized mainly by bonds between .
S and S.
CO and NH.
Right! Hydrogen bonds between these groups keep the helix coiled.
Which of the following is true of pleated sheet foldings within a polypeptide?
The side chains are parallel to the plane of the sheet.
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