Question 1

Which of the following best describes the relationship between D-glyceraldehyde and dihydroxyacetone as shown in the first image?

Accepted Answer

They are tautomers.

Question 2

In the context of carbohydrate stereochemistry, what distinguishes D-glyceraldehyde from L-glyceraldehyde as shown in the second and third images?

Accepted Answer

The configuration of the hydroxyl group on the chiral carbon.

Question 3

Which statement about the C-2 endo and C-3 endo conformations of β-D-ribofuranose (fourth image) is correct?

Accepted Answer

The C-2 endo conformation has the C-2 atom above the plane of the ring.

Question 4

Which of the following statements about the furanose and pyranose forms of D-ribose (fifth image) is correct?

Accepted Answer

Both furanose and pyranose forms can exist as α or β anomers.

Question 5

In the context of the sixth image, which conformation of a pyranose ring is generally more stable and why?

Accepted Answer

Chair, because it allows for maximal separation of bulky groups.

Question 6

Which of the following best describes the relationship between D-glucose and D-mannose as shown in the seventh image?

Accepted Answer

They are epimers.

Question 7

Which of the following is true regarding the formation of a glycosidic bond in disaccharides (see image 12)?

Accepted Answer

It involves the elimination of water between two monosaccharides.

Question 8

Which disaccharide is composed of β-D-galactose and β-D-glucose, as shown in image 14?

Accepted Answer

Lactose

Question 9

Which modification of monosaccharides increases their biochemical versatility and allows them to serve as signal molecules or become more reactive, as described in the study materials?

Accepted Answer

Reaction with alcohols, amines, or phosphates

Question 10

Which of the following statements about glycoproteins is correct, based on the images and study materials?

Accepted Answer

N-linked glycans are attached through N-acetylglucosamine to asparagine residues.

Question 11

Which of the following best describes the difference between an epimer and an anomer, as illustrated in the seventh image?

Accepted Answer

Epimers differ at only one chiral carbon (not the anomeric carbon), while anomers differ at the anomeric carbon.

Question 12

Which of the following statements about the α and β anomers of glucose is correct?

Accepted Answer

The β anomer has the C-1 hydroxyl group above the plane of the ring.

Question 13

Which of the following is a correct statement about the stability of glycosidic bonds in disaccharides and polysaccharides?

Accepted Answer

They are metastable and require enzymatic or acidic catalysis for hydrolysis.

Question 14

Which of the following is a distinguishing feature of storage polysaccharides such as amylose and glycogen?

Accepted Answer

They are composed of only one type of monosaccharide.

Question 15

Which of the following best explains why unsaturated fatty acids have lower melting points than saturated fatty acids?

Accepted Answer

The kinks from double bonds prevent tight packing and reduce van der Waals interactions.

Question 16

Which of the following is true about the amphipathic nature of membrane lipids, as shown in the images?

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 17

Which of the following is a correct statement about the difference between facilitated diffusion and active transport across membranes?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient without energy input.

Question 18

Which of the following best describes the role of glycosyltransferases in carbohydrate metabolism?

Accepted Answer

They catalyze the formation of glycosidic bonds between monosaccharides.

Biochem Midterm study guide slightly messed up.

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