Carbohydrates

Let's analyze each statement to identify the incorrect ones:

1. Glucose exists in two different crystalline forms, -D-glucose and -D-glucose.

This statement is correct. Glucose has two anomeric forms: and .

2. -D-glucose and -D-glucose are anomers.

This statement is correct. Anomers are isomers of monosaccharides that differ in configuration only at the hemiacetal/acetal carbon, also known as the anomeric carbon.

3. -D-glucose and -D-glucose are enantiomers.

This statement is incorrect. Enantiomers are mirror images of each other and cannot be turned into one another by rotation. and forms are not mirror images; they differ only in the configuration at the anomeric carbon.

4. Cellulose is a straight chain polysaccharide made of only -D-glucose units.

This statement is correct. Cellulose is composed of -D-glucose units linked by -1,4-glycosidic bonds.

5. Starch is a mixture of amylase and amylopectin, both contain unbranched chain of -D-glucose units.

This statement is incorrect. Starch contains both amylose and amylopectin, but amylopectin is branched, not unbranched. Only amylose is an unbranched chain of -D-glucose units.