Ch 7: Biologically Important Molecules (Princeton Review)

Question 1

Carbohydrates are chains of hydrated carbon atoms with the molecular formula ______. The chain usually begins with an aldehyde or ketone and continues as a ________ in which each carbon has a hydroxyl substituent.

Answer 1

C_nH_2nO_n

polyalcohol

p. 226

Question 2

Carbohydrates can be broken down to ___ in a process called oxidation, aka burning or combustion.

Answer 2

CO₂

p. 226

Question 3

Glucose in the form of the polymer ________ is also the building block of wood and cotton.

Answer 3

cellulose

p. 226

Question 4

Disaccharides and polysaccharides are broken down into their component monosaccharides by enzymatic ________.

Answer 4

hydrolysis

p. 233

Question 5

The triglyceride is composed of 3 fatty acids __________ to a glycerol molecule.

Answer 5

esterified

p. 237

Question 6

Why is it necessary to store fatty acids in the relatively inert form of fat?

Answer 6

Because free fatty acids are reactive chemicals.

p. 237

Question 7

The triacylglycerol undergoes reactions typical of esters, such as base-catalyzed hydrolysis. Soap is economically produced by base-catalyzed hydrolysis of triglycerides from animal fat into fatty acid salts (_____). This reaction is called __________.

Answer 7

soaps

saponification

p. 238

Question 8

Lipases are enzymes that _________ ____.

Answer 8

hydrolyze fats

p. 238

Question 9

Eicosanoids are a class of molecules derived from __-carbon (“eicosa” is Greek for 20) polyunsaturated fatty acids, most frequently arachidonic acid. The eicosanoids include the ________, thromboxanes, leukotrienes, and lipoxins. These molecules almost always act on the cells that produce them or on neighboring cells, that is, over short distances and time periods, and, therefore, can be classified as autocrine/ paracrine hormones.

Answer 9

20

prostaglandins

[The term eicosanoids was introduced in the “Lipids as cofactors and signaling molecules” Khan Academy video]

Question 10

Steroids are actually a __________ lipid, which means they have 4 cyclic rings.

Answer 10

tetracyclic

[From “Lipids as cofactors and signaling molecules” Khan Academy video]

Question 11

Which lipids are considered hydrolyzable?

Answer 11

triglycerides/ triacylglycerol

phospholipids

sphingolipids

Question 12

Which lipids are considered non-hydrolyzable lipids?

Answer 12

prostaglandins

steroid hormones

cholesterol

fat-soluble vitamins

Question 13

When the C5 in glucose nucleophilically attacks the carbonyl carbon (C1), it forms a __________.

Answer 13

hemiacetal

p. 229

Question 14

In monosaccharide rings, the anomeric carbon is always the carbonyl carbon, so in aldoses it is C1, but in ketoses it is . The interconversion between the two anomers is called _________.

Answer 14

C2

mutarotation

p. 230

Question 15

Why is β-D-glucopyranose the most prevalent sugar in nature?

Answer 15

First of all, it can store a lot of energy, and bc all of the OH groups are equatorial, making it a very stable molecule.

Bottom line, high energy, high stability.

p. 230

Question 16

The carbons in monosaccharides are numbered beginning with carbon #1 at the most ________ end of the carbon chain, which is the end with the aldehyde or ______.

Answer 16

oxidized

ketone

p. 226

Question 17

Like amino acids, carbohydrates are assigned 1 of 2 configurations, either D or L, based on the configuration of the last chiral carbon in the chain (farthest from the aldehyde or ketone). By convention, this configuration is determined by comparison with glyceraldehyde.

Answer 17

p. 227

Question 18

What is the molecular formula for glyceraldehyde and what does its structure look like?

Answer 18

C₃H₆O₃

Question 19

How can you remember the structure of D-glucose?

Answer 19

draw general structure of a hexose sugar and remember that carbons 2, 4, and 5 have the -OH on the right

Question 20

A sugar monomer which forms a five-membered ring is known as a…

Answer 20

….furanose.

Question 21

A sugar monomer which forms a five-membered ring is known as a…

Answer 21

….pyranose.

Question 22

What is maltose?

Answer 22

a disaccharide formed from two units of glucose joined by an α-1,4 bond

Question 23

What functional group makes certain lipids hydrolyzable?

Answer 23

an ester group

(there might be others, not sure?)

Question 24

Waxes are not ___________, despite being esters. The ester group is not enough to make the whole molecule polar. This is why waxes are so resistant to mixing with water. Soap on the other hand, does have a polar and nonpolar section.

Answer 24

amphipathic

Question 25

Describe the difference between an acetal and a hemiacetal.

Answer 25

Acetals are a single carbon bonded to two ethers.

Hemiacetals are a single carbon bonded to one ether and one alcohol.

Question 26

Fructose forms a 5-membered ring, but it still has 6 carbons, which makes it a…

Answer 26

…ketohexose.