Carbohydrate Chemistry and Metabolism Flashcards

Which monosaccharide is the primary fuel for the brain under normal conditions?

Answer: Glucose

Glucose is the brain's primary energy substrate under normal fed conditions, as the blood-brain barrier limits the transport of most other fuels.

The anomeric carbon of glucose is carbon number:

Answer: C-1

C-1 of glucose is the anomeric carbon, the former carbonyl carbon that becomes the new chiral center when the open-chain form cyclizes to form alpha or beta glucopyranose.

Which disaccharide is composed of glucose and fructose joined by an alpha(1→2) glycosidic bond?

Answer: Sucrose

Sucrose (table sugar) consists of glucose and fructose linked by an unusual alpha(1→2) glycosidic bond involving both anomeric carbons, making it a non-reducing sugar.

Glycogen is the storage polysaccharide in animals. Its branching involves which type of linkage?

Answer: Alpha(1→4) in chains with alpha(1→6) at branch points

Glycogen has linear alpha(1→4)-linked glucose chains with alpha(1→6) branch points approximately every 8–12 residues, allowing rapid glucose release from multiple ends simultaneously.

The enzyme lactase cleaves lactose into which two monosaccharides?

Answer: Glucose + galactose

Lactase (beta-galactosidase) hydrolyzes the beta(1→4) glycosidic bond of lactose to release glucose and galactose, which are absorbed in the small intestine.

Which reaction does hexokinase catalyze in the first step of glycolysis?

Answer: Glucose → glucose-6-phosphate (using ATP)

Hexokinase catalyzes the phosphorylation of glucose to glucose-6-phosphate using ATP, trapping glucose in the cell and committing it to metabolism.