Help with Saccharides and Carbohydrates
Help Questions
GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Saccharides and Carbohydrates
Sucrose is a polysaccharide made up of __________ and __________.
ribose . . . glucose
Explanation
Sucrose is one of the more common sugars, and is composed of glucose and fructose. Sucrose is also known as table sugar.
Galactose and glucose are the components of lactose. Maltose is made up of two glucose molecules.
Which of the following is the primary reason that starch can be digested by humans, but cellulose cannot?
Type of glycosidic linkage
Number of monomers in the chain
Aldose versus ketose monosaccharide structure
Presence of branching subunits
Explanation
Both starch and cellulose are polysaccharides composed of glucose monosaccharides, but only starch can be digested by humans. The reason for this lies in the type of glycosidic linkages between glucose monomers. Starch has alpha (1-4) linkages which can be broken down, but cellulose has beta (1-4) linkages. Humans do not have the necessary enzyme to digest this type of glycosidic linkage.
Which of the following sugars is a ketose?
Fructose
Glucose
Galactose
Ribose
Explanation
A ketose is defined as any monsaccharide that has a ketone functional group while in its linear form. Fructose is a ketose, while the other three options are all aldoses.