Elements of Life

Elements of Life

Introduction

• This lecture covers the elements of life, especially carbon, and how they contribute to the wide variety of biomolecules.

Composition of Living Things

• Living things are made of:
  • Atoms
  • Compounds
  • Molecules
• The variety of molecules enables life to function.
• All living things that have ever existed are made of the same elements.
• Living things constantly exchange matter with their environment.
  • Atoms from the environment (ground, air, grass) become part of living organisms.
• Exchange of waste and nutrients is essential for life.

Carbon-Based Chemistry

• The chemicals that make up living things are carbon-based.
• Carbon is the main atom in living things.
• Organic chemistry focuses on carbon-containing molecules, especially those in living things.
• Most of your body mass (besides water) is carbon.
• Carbon can form an enormous variety of complex organic compounds.
  • Organic matter is carbon-based.
  • Living things are carbon-based life forms.

Bonding Properties of Carbon

• Each carbon atom can form up to four covalent bonds.
• Carbon has four valence electrons.
• Carbon can form:
  • Four single covalent bonds
  • Two double bonds
  • A double bond and two single bonds
• This bonding versatility makes carbon an ideal building block for large molecules like proteins.

Hydrocarbons

• Hydrocarbons are molecules made of only carbon and hydrogen.
• Example: Methane (CH_4) is a simple hydrocarbon and a greenhouse gas.
• Carbon's ability to form four bonds allows for the creation of complex hydrocarbon structures.

Four Main Classes of Biomolecules

• Biomolecules can be grouped into four main categories:
  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic acids

Composition of Biomolecules

• Carbohydrates: Carbon, Hydrogen, and Oxygen
• Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, and Sulfur
• Lipids: Carbon, Hydrogen, and Oxygen
• Nucleic Acids: Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus

Isomers

• Isomers: Molecules with the same chemical formula but different structures and properties.
• The arrangement of atoms can result in different purposes within a living thing.
• Three types of isomers:
  • Structural isomers
  • Cis-trans isomers
  • Enantiomers

Structural Isomers

• Different arrangements of atoms.
• Example: Four carbons can be arranged in a line or a T-shape, resulting in different molecules despite having the same chemical formula.

Cis-Trans Isomers

• Different arrangements of atoms around a double bond.
• Single bonds are more flexible than double bonds.
• Double bonds are more rigid, limiting variation.
• Trans isomer: Two of the same groups are on different sides of the double bond.
• Cis isomer: Two of the same groups are on the same side of the double bond.

Enantiomers

• Isomers that are mirror images of one another due to carbon being bonded to four different things.
• A central carbon is bonded to four different groups (e.g., hydrogen, hydroxyl, methyl, carboxyl).
• The molecules have the same chemical formula but different shapes.
• Analogy: Your hands are mirror images of each other.