Nucleic Acids: Sugars & Bases - AP Biology

Each nucleotide consists of three parts:

• Phosphate group
• Five-carbon sugar (either ribose in RNA or deoxyribose in DNA)
• Nitrogenous base

DNA (deoxyribonucleic acid): Sugar: deoxyribose Bases: adenine (A), guanine (G), cytosine (C), thymine (T) RNA (ribonucleic acid): Sugar: ribose Bases: adenine (A), guanine (G), cytosine (C), uracil (U) RNA is usually single-stranded. 3. Purines and Pyrimidines Purines: double-ring structures — adenine (A) and guanine (G) Pyrimidines: single-ring structures — cytosine (C), thymine (T), uracil (U) 4. Base Pairing Rules In DNA: A pairs with T (via 2 hydrogen bonds) G pairs with C (via 3 hydrogen bonds) In RNA, uracil replaces thymine: A pairs with U 5. Chargaff’s Rule In double-stranded DNA: %A = %T %G = %C 6. Biological Relevance Hydrogen bonding between bases maintains DNA’s double-helix structure. A higher proportion of G–C pairs increases DNA stability due to stronger bonding. DNA and RNA play central roles in storing and expressing genetic information. Nucleic Acids: Sugars & Bases - AP Biology - Question 1 Nucleic Acids: Sugars & Bases - AP Biology - Question 2 Nucleic Acids: Sugars & Bases - AP Biology - Question 3