3.1 Carbon Atoms and Molecular Diversity

CHNOPS: Essential Elements in Living Things

Living organisms are primarily composed of six major elements, often remembered by the mnemonic CHNOPS: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur. These elements form the basis for most biological molecules.

• Carbon is unique in its ability to form four covalent bonds, allowing for a wide variety of stable compounds.

• Hydrogen and Oxygen are key components of water and organic molecules.

• Nitrogen is found in amino acids and nucleic acids.

• Phosphorus is essential for nucleic acids and energy transfer (ATP).

• Sulfur is present in some amino acids and vitamins.

Example: The PBS video "CHNOPS: Ingredients for Life" explores the role of these elements in biology.

Definition of "Organic" in Science

Organic compounds are defined by the presence of carbon and at least one carbon-hydrogen bond, and they are typically made by cells.

• Organic compounds must contain carbon and at least one carbon-hydrogen bond (e.g., methane, CH4).

• Inorganic compounds may contain carbon but lack carbon-hydrogen bonds or are not made by cells (e.g., CO2, CO).

Example: Organic foods and cleaning products are labeled based on their carbon content and biological origin.

Structure and Properties of Carbon Compounds

Bonding and Versatility of Carbon

Carbon atoms are important because they form four covalent bonds, allowing for the creation of many different, stable compounds. The tetrahedral geometry of carbon's bonds (bond angle of 109.5°) enables complex molecular structures.

• Carbon has four valence electrons and can form single, double, or triple covalent bonds.

• Carbon skeletons can vary in length, branching, position of double bonds, and presence of rings.

Example: Ethane, propane, butane, and isobutane demonstrate variations in carbon chain length and branching. Cyclohexane and benzene are examples of ring structures.

Isomerism in Organic Molecules

Isomers are compounds with the same molecular formula but different structures and properties. There are three main types:

• Structural isomers: Differ in covalent arrangement of atoms (e.g., pentane vs. 2-methylbutane).

• Cis-trans isomers (geometric isomers): Differ in spatial arrangement around a double bond. "Cis" means atoms are on the same side; "trans" means on opposite sides.

• Enantiomers: Isomers that are mirror images of each other, differing in spatial arrangement around an asymmetric carbon.

Example: The difference between cis-2-butene and trans-2-butene affects their chemical properties.

ATP: The Energy Currency of the Cell

Structure and Function of ATP

Adenosine triphosphate (ATP) is the immediate energy source for cells. It is used for making large molecules, active transport, and movement within the cell.

• ATP contains three covalently bonded phosphate groups, storing potential energy.

• When ATP is hydrolyzed (a phosphate group is removed), energy is released for cellular work:

• ATP is unstable and not stored long-term; energy is stored as starch, glycogen, or fats.

Example: ATP hydrolysis powers muscle contraction and active transport.

Biological Macromolecules

Overview of Macromolecules

Macromolecules are large, complex molecules essential for life. They include carbohydrates, proteins, nucleic acids, and lipids.

Macromolecules: Polymers Built from Monomers

Most macromolecules are polymers, formed by joining monomers through covalent bonds.

• Polymerization: The process of bonding monomers to form larger polymers.

• Monomer: The smallest repeating subunit of a macromolecule.

Examples of Monomer-Polymer Relationships:

• Proteins: Amino acids are joined by peptide bonds to form polypeptides.

• Carbohydrates: Monosaccharides are joined by glycosidic bonds to form disaccharides or polysaccharides.

Summary Table: Macromolecule Functions and Examples

Additional info:

• Macromolecules are essential for cell structure and function.

• ATP is a nucleotide derivative and is crucial for energy transfer in cells.

• Isomerism increases the diversity of organic molecules, impacting biological function.

• e simplest is methane (see below CH4)