Here is the description of the Watson and Crick model of DNA and the differentiation between cellulose and glycogen: i) Watson and Crick model of DNA: The Watson and Crick model describes DNA as a double helix structure. It consists of two polynucleotide strands coiled around a central axis. The two strands run in antiparallel directions, meaning one strand runs $5' \to 3'$ and the other runs $3' \to 5'$. The backbone of each strand is made of alternating deoxyribose sugar and phosphate groups, while the nitrogenous bases (adenine, guanine, cytosine, and thymine) project inwards. Adenine (A) always pairs with thymine (T) via two hydrogen bonds, and guanine (G) always pairs with cytosine (C) via three hydrogen bonds. This specific base pairing ensures the constant diameter of the helix and allows for accurate DNA replication. ii) Differentiation between cellulose and glycogen: | Feature | Cellulose