Carbohydrates-I

These flashcards cover the fundamental concepts of Carbohydrates-I, including definitions, biological roles, classifications, isomerism, and chemical reactions.

What were carbohydrates originally believed to be and what was the associated chemical formula?

They were believed to be hydrates of carbon with the formula $C(H_2O)$.

What is the current chemical definition of carbohydrates?

Polyhydroxy aldehydes or ketones, or substances that yield these compounds on hydrolysis.

What is the general molecular formula for carbohydrates?

$$C_n(H_2O)_n$$

How is glucose synthesized and stored in plants?

Glucose is synthesized from $CO_2$ and $H_2O$ by photosynthesis and stored as starch or converted to the cellulose of the plant framework.

Which coenzymes contain carbohydrates as part of their structure?

$NAD^+$, $NADP^+$, $FAD$, and $CoA$.

According to functional groups, what are the two types of sugar?

Aldehyde sugar (Aldo-sugar) and Ketone sugar (Keto-sugar).

How are carbohydrates classified according to the number of basic sugar units?

Monosaccharides (single sugar unit), Disaccharides (two sugar units), Oligosaccharides (3-10 sugar units), and Polysaccharides (more than 10 sugar units).

What are the sub-classifications of polysaccharides?

Homo polysaccharides and Heteropolysacchrides.

Provide examples for Triose, Tetrose, and Pentose sugars.

Triose ($3$ carbons): Glyceraldehyde, Dihydroxyacetone; Tetrose ($4$ carbons): Erythrose; Pentose ($5$ carbons): Ribose, Ribulose, Xylulose.

Provide examples for Hexose and Heptose sugars.

Hexose ($6$ carbons): Glucose, Galactose, Mannose, Fructose; Heptose ($7$ carbons): Sedoheptulose.

What is defined as compounds with the same molecular formula but different structures?

Isomerism

Give an example of functional group isomers provided in the text.

Glyceraldehyde and dihydroxyacetone.

What are enantiomers?

Mirror images of molecules, such as D-Glucose and L-Glucose.

What is mutarotation?

The spontaneous conversion of one anomer (such as $\alpha$-anomer) to the other (such as $\beta$-anomer).

Contrast Pyranose and Furanose ring structures.

Pyranose refers to a six-membered ring structure (e.g., Glucopyranose), and Furanose refers to a five-membered ring structure.

What are epimers?

Structures that differ in the position of the $-OH$ group at only one carbon atom.

Which sugar is the C2 epimer of D-glucose?

D-mannose

Which sugar is the C4 epimer of D-glucose?

D-galactose

In optical activity, what are the characteristics of dextrorotatory and levorotatory substances?

Dextrorotatory ($+$, usually D isomers) rotate light to the right; levorotatory ($---$, usually L isomers) rotate light to the left.

What is the difference between an O-glycosidic bond and an N-glycosidic bond?

An O-glycosidic bond is formed with a hydroxyl oxygen atom of an alcohol, while an N-glycosidic bond is formed with the nitrogen of an amine.

Why are maltose and lactose considered reducing sugars while sucrose is non-reducing?

Maltose and lactose contain free keto or aldo groups, whereas sucrose does not contain free keto or aldo groups.

What is the clinical use for the reducing properties of sugars?

Detection of glucose in the urine.

What acid is produced by the oxidation of glucose and what is its function?

Glucuronic acid; it is used by the liver for conjugation reactions in the detoxification of foreign compounds.

What alcohol is produced by the reduction of glucose, and what is its clinical significance?

Sorbitol; it is responsible for many complications of diabetes mellitus.

Which sugars yield sorbitol upon reduction?

Glucose and fructose.

What alcohol is produced by the reduction of galactose?

Galactitol