1.DNA is a molecule composed of two chains in form a compose by, and pentose. And the structure and function of genes.

DNA is a molecule composed of two chains in form of a DOUBLE HELIX compose by ORGANIC NITROGEN CONTAINING BASE, PHOSPHATE GROUPS and PENTOSE.

Explanation:

Nucleic acids are found in all living cells. They are composed of strands made up of repeating units called nucleotides. Each nucleotide consists of

--> a five carbon sugar( PENTOSE)

--> a phosphate group

--> an organic nitrogen containing base: adenine, guanine, cytosine or thymine.

The two types of nucleic acids include:

--> Deoxyribonucleic acid ( DNA) and

--> Ribonucleic acid ( RNA)

Deoxyribonucleic acid ( DNA) is found in chromosomes located in the nucleus of cells.

STRUCTURE OF DNA

The DNA molecule consists of two strands that curve spirally to form a double helix structure. The strands are held together by hydrogen bonds between the base side arms. Each base on one strand will only pair with a specific base on the other strand: hence guanine will only pair with cytosine and adenine with thymine.

FUNCTIONS OF DNA

It stores the organism's hereditary traits and directs the day to day metabolic activities of each cell in the organism.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.