Chapter 23, Problem 1STP

Interpretation Introduction

Interpretation:

The statement which is not true for carbohydrates needs to be determined.

Concept introduction:

Carbohydrates are classified as monosaccharides, disaccharides, oligosaccharides and polysaccharides. Carbohydrate is present in foods like milk, popcorn, potatoes, corn etc.

Answer to Problem 1STP

Option D is the correct option, i.e., Option D is not true of carbohydrates.

Explanation of Solution

Cellulose contains glucose subunits. The bonding in the glucose subunits is different from the bonding present in glycogen or starch. So, the starch or glycogen can be easily digested by human body but the cellulose cannot be digested by the human body. Cellulose contains beta linkage which cannot be digested by human body due to absence of necessary enzymes.

Therefore, the statement D “Cellulose, made only by plants, is easily digestible by humans” is not true of carbohydrates

Conclusion

Carbohydrates are classified as monosaccharides, disaccharides, oligosaccharides and polysaccharides. Monosaccharides are simple carbohydrates. The exists in two forms- cyclic form and open-chain form. In equilibrium, in aqueous solution, these two forms of monosaccharides exist. Hence, the given statement A “Monosaccharides in the aqueous solution continuously interconvert between an open-chain structure and a cyclic structure” is true.

Lactose is a disaccharide which is formed from glucose and galactose. Lactose and galactose are stereoisomers. Starch is generated from a glucose monomer unit. Therefore, bonding in both the starch and lactose is same. So, the statement B “The monosaccharide in starch are linked together by the same kind of bond that links the monosaccharides in lactose” is true.

Carbohydrate has the general chemical formula is ${\text{C}}_{\text{n}}{\left({\text{H}}_{\text{2}}\text{O}\right)}_{\text{n}}$. Therefore, the statement C “All carbohydrates have the general chemical formula ${\text{C}}_{\text{n}}{\left({\text{H}}_{\text{2}}\text{O}\right)}_{\text{n}}$ ” is true.