Examples of Keto Sugar:

a) Fructose:
Fructose is a monosaccharide and is commonly known as fruit sugar. It is a keto sugar because it contains a ketone functional group. The ketone group is located on the second carbon atom of the sugar molecule. Fructose is naturally found in fruits, honey, and some vegetables. It is sweeter than glucose and is commonly used as a sweetener in various food and beverage products.

b) Ribulose:
Ribulose is a ketopentose sugar that contains a ketone group. It is an important molecule in the process of photosynthesis as it plays a key role in the carbon fixation pathway known as the Calvin cycle. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is an enzyme that catalyzes the addition of carbon dioxide to ribulose during photosynthesis.

c) Ribose Sugar:
Ribose is a pentose sugar that is an important component of nucleotides, the building blocks of RNA and DNA. It does not contain a ketone group and is therefore not a keto sugar. Ribose plays a crucial role in genetic information storage and transfer.

d) Dihydroxy Acetose:
Dihydroxy acetose, also known as dihydroxyacetone, is a ketotriose sugar. It contains a ketone group and is commonly used in the cosmetic industry as a self-tanning agent. Dihydroxy acetose reacts with amino acids in the skin, resulting in the formation of brown pigments called melanoidins, which give a tan appearance.

Correct Answer: A, B, D

Fructose, ribulose, and dihydroxy acetose are examples of keto sugars because they contain a ketone functional group. Ribose sugar, on the other hand, is not a keto sugar as it does not contain a ketone group.