Carbon is the backbone of life, forming diverse molecules essential for biological processes. Its unique bonding properties allow it to create complex structures like carbohydrates, lipids, proteins, and nucleic acids, each with specific roles in living organisms.

These biomolecules are the building blocks of life. Carbohydrates store energy, lipids form cell membranes, proteins catalyze reactions and provide structure, while nucleic acids store and transmit genetic information. Understanding their functions is key to grasping how life works.

The Importance of Carbon and Biological Molecules

Carbon's essentiality for life

• Carbon's four valence electrons enable formation of four covalent bonds creating complex, stable molecules essential for life (methane, glucose)
• Carbon atoms form single, double, or triple bonds with each other producing diverse molecular structures (ethane, ethene, ethyne)
• Carbon-based molecules construct long chains, branched structures, and rings fundamental to life's complexity and diversity (fatty acids, amino acids, nucleotides)
• Carbon readily bonds with hydrogen, oxygen, nitrogen, and sulfur which are crucial elements in biological molecules (carbohydrates, proteins, nucleic acids)

Types of biological molecules

• Carbohydrates contain carbon, hydrogen, and oxygen typically in a 1:2:1 ratio
  • Store energy (glucose, starch) and provide structural support (cellulose, chitin)
• Lipids are mostly carbon and hydrogen with some oxygen
  • Store energy, insulate, and form cell membranes (fats, oils, steroids, phospholipids)
• Proteins are amino acid chains linked by peptide bonds
  • Catalyze reactions (enzymes), provide structural support, transport molecules, and facilitate signaling (collagen, hemoglobin, insulin)
• Nucleic acids are nucleotide polymers containing a sugar, phosphate group, and nitrogenous base
  • DNA and RNA store and transmit genetic information (genes, mRNA, tRNA)

Macromolecules and their building blocks

• Macromolecules are large, complex molecules made up of smaller subunits
• Monomers are the basic building blocks that can be joined to form larger molecules
• Polymers are long chains of repeating monomers linked by covalent bonds
• Dehydration synthesis joins monomers by removing a water molecule, forming a covalent bond
• Hydrolysis breaks bonds between monomers by adding water, reversing dehydration synthesis
• Functional groups are specific arrangements of atoms within molecules that give them characteristic chemical properties

Amino Acids, Proteins, and the Roles of Biological Molecules

Amino acid structure and protein function

• Amino acids have a central carbon bonded to an amino group, carboxyl group, hydrogen, and variable R group which determines amino acid properties (glycine, cysteine)
• Amino acids link via peptide bonds forming polypeptides with sequences determined by the genetic code (insulin, collagen)
• Protein primary structure is the linear amino acid sequence
• Protein secondary structure is local polypeptide chain folding stabilized by hydrogen bonds
  • Alpha helices and beta sheets are common secondary structures
• Protein tertiary structure is the 3D shape of a single polypeptide chain determined by R group interactions (hydrogen bonds, ionic bonds, disulfide bridges)
• Protein quaternary structure is the arrangement of multiple polypeptide subunits, not present in all proteins (hemoglobin, DNA polymerase)
• Protein structure dictates function and alterations can modify or eliminate function (sickle cell anemia, cystic fibrosis)

Roles of major biomolecules

• Carbohydrates
  1. Store energy: glucose and simple sugars are readily broken down for cellular energy
  2. Provide structural support: cellulose in plant cell walls and chitin in arthropod exoskeletons
• Lipids
  1. Store energy: triglycerides (fats) are efficient long-term energy storage molecules
  2. Insulate: subcutaneous fat regulates body temperature in animals
  3. Form cell membranes: phospholipids are the main component, providing a barrier and regulating transport
• Proteins
  1. Catalyze reactions: enzymes catalyze biochemical reactions enabling life processes
  2. Provide structural support: collagen and keratin provide strength in skin, bones, and hair
  3. Transport molecules: hemoglobin carries oxygen throughout the body
  4. Facilitate signaling: hormones and receptors are often proteins that enable cell communication
• Nucleic acids
  1. Store genetic information: DNA contains genes, the genetic blueprint for an organism
  2. Transmit genetic information: DNA is replicated and passed to daughter cells during cell division
  3. Enable gene expression: RNA (mRNA) transfers genetic information from DNA to ribosomes for protein synthesis
  4. Catalyze reactions: some RNA molecules (ribozymes) catalyze biochemical reactions like protein enzymes