Biochemistry

Sucrose is a non-reducing disaccharide formed by α-1,2-glycosidic linkage between C1 of glucose and C2 of fructose, blocking both anomeric carbons. It cannot mutarotate or act as a reducing sugar. Other options are reducing sugars with free anomeric carbons.

Maltose consists of two glucose units linked by an α-1,4-glycosidic bond. Sucrose contains glucose and fructose, lactose contains glucose and galactose, and trehalose has an α-1,1-glycosidic linkage.

Fructose is a ketohexose (6-carbon ketone sugar) with the molecular formula C₆H₁₂O₆, making it a structural isomer of glucose. Galactose and mannose are aldohexoses (epimers of glucose), while ribose is a pentose.

Mannose differs from glucose only at the C2 position (the configuration of the -OH group and -H). Therefore, mannose is the C2 epimer of glucose.

Glycogen synthase catalyzes the transfer of glucose from UDP-glucose to the C4-OH group of the terminal glucose in glycogen, forming α-1,4-glycosidic bonds.

Sedoheptulose is a seven-carbon ketose (heptose) that participates in the non-oxidative phase of the pentose phosphate pathway.

Fructokinase phosphorylates fructose to fructose-1-phosphate in the liver. This bypasses the rate-limiting phosphofructokinase step, making fructose metabolism less regulated.

Sucrose (α-glucose + β-fructose) is a non-reducing sugar because both anomeric carbons are involved in the 1,2-glycosidic linkage, making it unable to reduce Benedict's reagent.

Complete oxidation of glucose yields approximately 30-32 ATP molecules when accounting for the cost of transporting NADH across the mitochondrial membrane (P/O ratio of 2.5 for NADH and 1.5 for FADH2).

Phosphoglucose isomerase catalyzes the reversible isomerization of glucose-6-phosphate to fructose-6-phosphate, the second step of glycolysis.