Chapter 5.1

You can tell this molecule is NOT a phospholipid because it contains ... (a) a glycerol backbone. (b) nitrogen. (c) ester linkages. Both (a) and (c). None of the above. It looks like a phospholipid to me!

None of the above. It looks like a phospholipid to me! A courageous (and correct) choice! It is a phospholipid.

A function of cholesterol that does not harm health is its role _____.

as a component of animal cell membranes Cholesterol is an important component of animal cell membranes.

Which of these is a polysaccharide?

cellulose Cellulose is a carbohydrate composed of many monomers.

Sucrose is formed when glucose is joined to fructose by a(n) _____.

glycosidic linkage Glycosidic linkages join simple sugars to form polysaccharides.

Which of these is a source of lactose?

milk Lactose is the sugar found in milk.

_____ is the most abundant organic compound on Earth.

Cellulose Cellulose, a component of plant cell walls, is the most abundant organic compound found on earth.

Which of the following complex carbohydrates is listed with its correct function?

Cellulose: structural component of plant cell walls Cellulose is indeed the main structural component of plant cells walls.

Which of these is NOT a lipid? wax phospholipid RNA cholesterol steroids

RNA RNA is a nucleic acid

The presence of many C-C and C-H bonds causes fats to be ...

(a) rich in energy. (b) insoluble in water. Excellent! The many C-C and C-H bonds make fats nonpolar and insoluble in water. They can also be oxidized, releasing much energy.

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).

(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.

Which statement is true of sucrose? (a) It's a disaccharide. (b) It contains glucose. (c) It's table sugar. Both (a) and (c). (a), (b), and (c).

(a), (b), and (c). Good work! We use sucrose as our table sugar because plants make plenty of it. They use it as their main circulating fuel, and sugar beets and sugar cane store a lot of it. It's a disaccharide made of glucose and fructose.

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).

(b) Low solubility in water. Correct! Low water solubility is the trait that defines lipids.

In a membrane, the________of the phospholipids in one monolayer face the________of the phospholipids in the other monolayer.

(c) tails; tails Jackpot! Water on both sides of the membrane excludes the tails, forcing them into the interior where they face one another.

Which statement is true of phospholipids? (a) Their synthesis uses fatty acids. (b) Some of their tails have double bonds. (c) They all ionize. All the above. Both (a) and (b).

All the above. Nice work! Every phospholipid has all these traits.

Which complex carbohydrate contains only a-1,4-glycosidic linkages?

Amylose Amylose is formed from a-1,4-glycosidic linkages of glucose.

Triglycerides vary with respect to the number of ...

Both (b) and (c). Very good! Tail lengths of 16 to 22 are common. There may be from 0 to 6 double bonds.

What do phosphoglycerides and fats have in common?

Ester linkages. Great choice! Like fats, phosphoglycerides are made by coupling fatty acids to glycerol by means of ester linkages.

What does cholesterol have in common with sex hormones?

Four linked rings Good choice! All steroids have four linked rings.

Which statement is true of the molecule shown here? It's called maltose. It's a polysaccharide. Inability to digest it causes some adults to be unable to tolerate milk. It differs from sucrose in that an O atom links the sugars. It's made by breaking down starch, during beer production.

Inability to digest it causes some adults to be unable to tolerate milk. Right! It's lactose, or milk sugar. Nearly all children can digest it, but many adults lose the enzyme needed to separate the sugars.

For good health, you don't want your body to run the LDL part of this diagram faster than the HDL part because ...

LDL cholesterol is stored; HDL cholesterol is destroyed. Right! If LDL exceeds HDL, your body is probably storing excess cholesterol, which may clog the arteries and cause heart disease.

Which molecule is not a carbohydrate? Hints

Lipid A lipid is a hydrophobic polymer, not a carbohydrate.

Which of the following statements about monosaccharide structure is true?

Monosaccharides can be classified according to the spatial arrangement of their atoms.

Which polysaccharide contains a modified monosaccharide?

Peptidoglycan The N-acetylglucosamine and N-acetylmuramic acid units that make up peptidoglycan are composed of modified glucose monomers.

Which lipid is most amphipathic?

Phospholipid Excellent! A phospholipid has a strongly polar (charged) head and two nonpolar tails.

Which of these is a phospholipid?

Phospholipids are composed of a phosphate group, a glycerol, and fatty acids

saturated fat

The fatty acid tails lack double bonds.

True or false? Peptidoglycan is a polysaccharide found only in bacteria.

True

Which fact is most important in causing phospholipids to behave as they do in water?

Water molecules make hydrogen bonds. Good thinking! The hydrogen bonds in water exclude the nonpolar tails of phospholipids, forcing the molecules into a bilayer.

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. Good choice! Water rejects nonpolar molecules such as fats, so fats travel inside particles that are coated with polar parts of phospholipids and proteins.

Glycogen is _____.

a polysaccharide found in animals Animals store energy in the form of glycogen.

Palm oil and coconut oil are more like animal fats than are other plant oils. Because they _____ than other plant oils, they may contribute to cardiovascular disease.

contain fewer double bonds Evidence suggests that a diet high in saturated fats may contribute to human cardiovascular disease.

In fat synthesis,________and fatty acids combine to make fats plus________.

glycerol; water Good choice! Water is a by-product of the reaction that makes ester links between glycerol and fatty acids.

In the reaction that builds a fat,________ groups react with ________ groups.

hydroxyl; carboxyl Correct! Fatty acids supply the carboxyl groups; the hydroxyls come from glycerol.

glucose + glucose —> _____ by _____.

maltose + water ... dehydration synthesis Maltose is the disaccharide formed when two glucose molecules are linked by dehydration synthesis.

To find the best source of phospholipids, look at ...

membranes. A fine choice. The great majority of a cell's phospholipids occur in membranes.

Which of these is rich in unsaturated fats?

olive oil Olive oil is a plant oil, and most plant oils are rich in unsaturated fats.

It is difficult for molecules to pass through the phospholipid bilayer because ...

polar molecules attract one another. Great! 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.

Phospholipids are most important for ...

preventing leakage from cells. Right! Every cell depends on phospholipid bilayers to limit leakage of molecules through membranes.