Group 12 Saccharides Chemistry & Function

Identify which are the D configuration.

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Answer explanation

D configuration if the hydroxyl group is to the right of the last stereocenter carbon in a Fischer projection.

L configuration if the hydroxyl group is to the left of the last stereocenter carbon in a Fischer projection.

The _____ cyclic form of a monosaccharide is known as a _____.

• five-member, pyranose

• six-member, pyranose

• six-member, furanose

• five-member, furanose

Answer explanation

Six-member cyclic form known as pyranose because it resembles the six-membered pyran ring structure.

Five-member cyclic form known as furanose because it resembles the five-membered furan ring structure.

Any molecule that readily interconvert with each other through movement of a H atom.

• Stereoisomers

• Tautomer

• Enantiomer

• Anomers

Answer explanation

Stereoisomers are two compounds with identical molecular formulas whose atoms are linked in the same order but in different spatial arrangements.

Enantiomer molecules are mirror images of one another but non-superimposable.

Anomers are isomers differing at C1 atom of an aldose or the C2 atom of a ketose.

Which of the following statements about oligosaccharides is correct?

• They consist of 3 to 10 monosaccharides.

• They are connected by peptide bonds.

• Examples include maltose and sucrose.

• They are composed exclusively of glucose units.

Answer explanation

• b: Oligosaccharides are connected by O-glycosidic bonds, not peptide bonds, which are found in proteins.
  

• c: Maltose and sucrose are disaccharides, not oligosaccharides.
  

• d: Oligosaccharides can consist of various types of monosaccharides, not just glucose.

Which statement about the glycosidic bond in disaccharides is correct?

• It forms through a hydrolysis reaction.

• It links two monosaccharides by removing a water molecule.

• It involves the bonding of two aldehyde groups.

• It is always a β-1,4 bond.

Answer explanation

• Correct: The glycosidic bond in disaccharides forms through a condensation reaction, where a water molecule is removed during the bonding process​.
  

• Incorrect:

  • a: The bond forms through a condensation reaction, not hydrolysis, which breaks the bond.

  • c: Glycosidic bonds involve the reaction of a hydroxyl group with a carbon atom, not two aldehyde groups.

  • d: Glycosidic bonds can vary; they may be α-1,4, β-1,4, or other types depending on the sugars involved.

Why are some adults unable to digest lactose effectively?

• They lack the enzyme sucrase needed to break down lactose.

• Their levels of lactase enzyme decrease with age.

• They cannot produce glucose or galactose.

• Their intestinal walls are impermeable to all disaccharides.

Answer explanation

• Correct: Lactase is the enzyme responsible for hydrolyzing lactose into glucose and galactose. Many adults experience a natural decline in lactase production as they age, leading to lactose intolerance​.
  

• Incorrect:

  • a: Sucrase hydrolyzes sucrose, not lactose.

  • c: The inability to produce glucose or galactose is not the issue; rather, it is the inability to break lactose into these monosaccharides.

  • d: Intestinal walls are impermeable to disaccharides, but this is not the cause of lactose intolerance; the issue is insufficient enzyme activity to hydrolyze lactose into absorbable monosaccharides.

Which type of polysaccharide is made up of one type of monosaccharide only?

• Cellulose

• Hyaluronic acid

• chondroitin sulphate

Answer explanation

Cellulose under category of homopolysaccharides which composed of one sugar monomer only

Which type of glycosidic bond can be digested by human digestive system?

• alpha 1-4 bond

• beta 1-4 bond

Answer explanation

Beta bond found in cellulose which cannot be digested by human as human do not have enzyme cellulase

What does the process glycogenesis meant?

• process of synthesizing glycogen from glucose, primarily occurring in the liver and muscle tissues.

• process by which glycogen, the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into glucose

Answer explanation

process of glycogen convert to glucose is glycogenolysis