Biomolecules II

Nucleotides and Nucleic Acids

• Nucleotides are the building blocks of nucleic acids, composed of three parts: a 5-carbon sugar, a phosphate group, and a nitrogenous base group.
• There are two types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
• DNA is a double-stranded nucleic acid that carries inheritance information, provides directions for its own replication, and programs a cell's activities by directing protein synthesis.
• RNA is usually single-stranded, but sometimes double-stranded, and plays a crucial role in protein synthesis, carrying information from DNA for protein production.

Polymerization of Nucleotides

• Nucleotides are linked together through condensation or dehydration reactions, forming a polynucleotide chain.
• The sugar-phosphate backbone of nucleic acids is formed through phosphodiester linkages, with protruding nitrogenous bases.

Components of Nucleic Acids

• Nitrogenous bases are categorized into two families: pyrimidines (cytosine, thymine, and uracil) and purines (adenine and guanine).
• Adenine pairs with thymine (in DNA) or uracil (in RNA), while guanine pairs with cytosine, forming complementary base pairs.

Structure of Nucleic Acids

• Nucleic acids have a helical structure, with DNA being double-stranded and RNA being usually single-stranded.
• The double-stranded structure of DNA is formed through hydrogen bonding between complementary base pairs.

Functions of Nucleic Acids

• DNA carries inheritance information, while RNA plays a crucial role in protein synthesis, carrying information from DNA for protein production.
• Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA) are different types of RNA, each with specific functions.

Nucleotides and Energy

• Nucleotides are not only the building blocks of nucleic acids but also serve as energy molecules (e.g., ATP, GTP) and coenzyme molecules (e.g., NAD+, FAD).

Vitamins

• Vitamins are organic compounds present in trace amounts, essential for normal physiological function, and deficiencies cause specific syndromes.
• Vitamins are classified into two categories: fat-soluble (A, D, E, and K) and water-soluble (B, C, and folic acid).

Water

• Water is characterized by two important parameters: water content (moisture content) and water activity (aw), which measures the amount of unbound water present in food.
• Water activity increases as temperature increases.

DNA vs RNA

• DNA is a double helix with two polynucleotide strands wrapped around each other, while RNA is usually a single polynucleotide strand.
• The base sequence along a DNA/mRNA polymer is unique for each gene, and DNA stores hereditary information, transmitting it from one generation to another.

Amino Acids and Proteins

• Amino acids have a specific structure, consisting of an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group).
• There are 20 amino acids used to make proteins, classified into essential and conditional amino acids.
• Polypeptides are chains of amino acids linked together through peptide bonds, and their unique linear sequence determines their specific properties.

Proteins

• A protein's functional shape results from four levels of structure: primary, secondary, tertiary, and quaternary structure.
• Primary structure is the unique linear sequence of amino acids, determined by inherited genetic information.