1.1 The Chemistry of Life
Atoms and Molecules:
• Atoms: The smallest particle of an element. Each atom consists of protons,
neutrons, and electrons.
• Molecules: Formed when two or more atoms bond together. For example:
o Oxygen molecule (O₂) = two oxygen atoms.
o Water molecule (H₂O) = two hydrogen atoms + one oxygen atom.
Compounds: Molecules formed by atoms of different elements.
• Example: Water (H₂O) is a compound formed by two hydrogen atoms and one oxygen
atom.
Important Elements in Living Organisms:
• Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sodium
(Na), Potassium (K), Calcium (Ca), Sulfur (S), Iodine (I), Iron (Fe), Magnesium
(Mg).
Carbon is a key element in organic molecules.
Oxygen and hydrogen are essential for water and energy production.
Nitrogen is crucial for amino acids and DNA.
Key Compounds in Cells:
1. Carbohydrates: Source of energy.
2. Lipids (Fats): Energy storage, cell membrane structure.
3. Proteins: Enzymes, structural components, and hormones.
4. Nucleic Acids (DNA and RNA): Genetic material.
5. Water (H₂O): Medium for chemical reactions, temperature regulation.
Types of Chemical Compounds:
1. Inorganic Compounds: Do not contain carbon (e.g., water and mineral salts).
o Carbon Dioxide (CO₂): An exception (contains carbon but is inorganic).
2. Organic Compounds: Contain carbon (e.g., carbohydrates, proteins, lipids, nucleic
acids).
, 1.1.1 Water
Properties of Water:
• Temperature Regulation: Water regulates body temperature through sweating.
Evaporation removes heat, cooling the body.
• Body Composition: 65% of the human body is water. Water is a crucial part of all
biological processes.
• Transport Medium: Transports food through the alimentary canal, and nutrients and
corpuscles (blood cells) in the bloodstream.
• Lubricating Agent: Provides lubrication in bodily fluids like saliva, tears, and vaginal
fluids.
• Solvent for Biological Chemicals: Many substances dissolve in water, making it
essential for biochemical reactions.
• Chemical Reaction Medium: In the cytoplasm of cells, water facilitates chemical
reactions necessary for life.
• Hydrolysis Reactions: Water is required to break down large molecules into smaller
ones (e.g., during digestion).
Water Molecule Structure:
• Polar Molecule: Water has partial positive charges on the hydrogen atoms and a
partial negative charge on the oxygen atom, allowing it to interact with other polar
molecules and ions.
Minerals
Importance of Minerals:
❖ Minerals are inorganic substances required for various biological functions.
❖ Plants absorb minerals from the soil, and animals obtain them from food.
❖ Essential for metabolic reactions and maintaining bodily functions.
Types of Minerals:
❖ Macroelements: Needed in large amounts (e.g., calcium, potassium, phosphorus).
❖ Microelements: Needed in trace amounts (e.g., iron, zinc, iodine).
