Biomolecules — Core Principles

Core Principles

Biomolecules are the organic compounds that form the basis of life, essential for all biological processes. They are primarily composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur. The four major classes are carbohydrates, proteins, nucleic acids, and lipids.

Carbohydrates serve as primary energy sources (e.g., glucose) and structural components (e.g., cellulose). They are classified into monosaccharides, disaccharides, and polysaccharides, linked by glycosidic bonds.

Proteins are the 'workhorses' of the cell, performing diverse functions like catalysis (enzymes), structural support, and transport. They are polymers of amino acids, linked by peptide bonds, and their function depends critically on their specific 3D structure (primary, secondary, tertiary, quaternary). Denaturation leads to loss of function.

Nucleic acids (DNA and RNA) store and transmit genetic information. They are polymers of nucleotides, each containing a sugar, a nitrogenous base, and a phosphate group. DNA forms a double helix with specific base pairing (A-T, G-C), while RNA is typically single-stranded and involved in protein synthesis.

Lipids are hydrophobic molecules important for energy storage, membrane structure (phospholipids), and signaling (steroids). Vitamins are essential micronutrients acting as cofactors, classified as fat-soluble (A, D, E, K) or water-soluble (B-complex, C), with deficiencies leading to specific diseases. Enzymes are protein catalysts that speed up biochemical reactions by lowering activation energy, exhibiting high specificity and sensitivity to temperature and pH.

Important Differences

vs DNA and RNA

Aspect	This Topic	DNA and RNA
Full Name	Deoxyribonucleic Acid	Ribonucleic Acid
Pentose Sugar	Deoxyribose	Ribose
Nitrogenous Bases	Adenine (A), Guanine (G), Cytosine (C), Thymine (T)	Adenine (A), Guanine (G), Cytosine (C), Uracil (U)
Typical Structure	Double-stranded helix	Single-stranded (can fold into complex 3D structures)
Primary Function	Storage and transmission of genetic information	Involved in gene expression (protein synthesis)
Location in Eukaryotic Cells	Mainly nucleus, also mitochondria and chloroplasts	Nucleus, cytoplasm, ribosomes
Stability	More stable due to deoxyribose and double helix	Less stable due to ribose (2'-OH group) and single strand

DNA and RNA are both nucleic acids, vital for life, but differ significantly in their chemical composition and structural roles. DNA, with its deoxyribose sugar and thymine base, primarily serves as the stable, long-term repository of genetic information, forming a double helix. RNA, containing ribose sugar and uracil, is typically single-stranded and plays diverse roles in expressing that genetic information, including messenger (mRNA), transfer (tRNA), and ribosomal (rRNA) functions. These distinctions are fundamental to the central dogma of molecular biology.