Lecture Notes: DNA, RNA, and Lipids

DNA and RNA

• Nucleotides:

  • Prokaryotes can synthesize their own nucleotides.
  • Two types of nucleotides:
    • Purines:
      • Adenine (A) and Guanine (G).
      • Mnemonic: "Angels are pure and have two wings" -> A and G are purines and have two rings.
    • Pyrimidines:
      • Thymine (T), Cytosine (C), and Uracil (U).
      • They have one ring.

• Sources of Nucleotide Components:

  • Purines:
    • Amino group from aspartate provides nitrogen.
    • Formyl group from folic acid provides carbons.
    • Amide nitrogen from glutamine.
  • Pyrimidines:
    • Derived from various sources.

Lipids

• Function:

  • Form cell membranes.

• Fatty Acid Synthesis:

  • Involves adding two carbons to a skeleton derived from a three-carbon molecule called malonate.
  • Process:
    • Malonate: Consists of three carbons.
    • Two carbons from malonate are added, resulting in a four-carbon molecule after releasing one carbon dioxide.
    • Repeated addition leads to longer carbon chains, with a carbon dioxide molecule released each time.

• Effects of Temperature:

  • Short fatty acid chains are preferred at low temperatures to maintain membrane fluidity.
  • Long fatty acid chains are favored at high temperatures to stabilize the membrane.

• Final Step:

  • Fatty acids attach to glycerol to form lipids.

Summary

• Discussed biosynthesis of nucleotides and lipids, focusing on critical pathways and their biological relevance.
• Highlighted importance of temperature in determining fatty acid chain length and membrane stability.