Life , water and chemistry

Elements and Living Organisms

  • Key Elements in Organisms: Approximately 25 elements are vital for life, with only 11 of the 92 naturally occurring elements primarily found in living organisms.

    • Major Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) comprise 96.5% of an organism's weight.

    • Minor Elements: Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg) make up the remaining 3.5%.

  • Trace Elements: Essential but required in minute quantities (less than 0.01%), including Iodine (I), Iron (Fe), etc.

  • Example of Iodine: Only 0.0004% of human weight is iodine, critical for thyroid function—deficiency can lead to goiter.

Structure of Atoms

  • Atoms Composition: The smallest units of elements that retain chemical properties; each element consists of one type of atom.

  • Chemical Symbols: Elements are identified by symbols (e.g., C for carbon, Na for sodium).

  • Compounds: Formed from fixed ratios of different elements (e.g., Water: H₂O, Sodium Chloride: NaCl).

Atomic Structure**

  • Components: Each atom has a nucleus containing protons and neutrons, surrounded by electrons in orbitals.

    • Protons: Positively charged, determines the element's atomic number.

    • Neutrons: Neutral particles found in the nucleus.

  • Electrons: Negatively charged, occupy orbitals around the nucleus.

Isotopes and Atomic Mass

  • Isotopes: Atoms with the same number of protons but different numbers of neutrons (e.g., Carbon-12, Carbon-14).

  • Mass Number: Total number of protons and neutrons in the nucleus, influencing atomic mass but not charge.

Radioactive Isotopes in Medicine

  • Applications: Used for imaging and treatment; e.g., radioactive iodine for thyroid disease, thallium for heart disease.

  • Mechanism: Radioisotopes can destroy cancer cells via radiation therapy.

Electron Configuration

  • Energy Levels: Electrons are distributed in energy levels or shells around the nucleus, defining an atom's chemical reactivity.

  • Valence Electrons: Electrons in the outermost shell involved in chemical bonding; determine the atom's reactivity.

  • Chemical Bonds: Atoms may bond via ionic, covalent, or hydrogen bonds, influenced by valence electrons.

Types of Chemical Bonds**

  1. Ionic Bonds: Formed via transfer of electrons; results in charged ions (e.g., Na+ and Cl-).

  2. Covalent Bonds: Formed by sharing electron pairs; bond characteristics shape molecules (e.g., CH₄ shapes and properties).

  3. Hydrogen Bonds: Weak attractions between polar molecules; important for water’s properties and biological structures.

  4. Van der Waals Forces: Weak attractions affecting molecular shapes, significant in larger biological molecules.

Properties of Water**

  • Polarity: Water is polar, creating a positively charged hydrogen end and a negatively charged oxygen end. This affects how water interacts with other molecules.

  • Hydrogen Bonding: Leads to unique properties: high boiling point, high specific heat, cohesion, adhesion, and surface tension.

  • Importance in Life: Water’s ability to act as a solvent facilitates biochemical reactions; crucial for maintaining cellular structure and function.

Water's Role in Biological Reactions

  • Dissociation: Water can ionize into H+ and OH-; maintaining pH in biological systems.

  • Acids and Bases: Affect pH balance in solutions; acids increase H+ concentration while bases decrease it.

  • Buffers: Maintain pH by absorbing excess H+ or OH- in biological systems (e.g., blood buffering system).

Conclusion**

  • Understanding atoms, molecules, and their interactions is crucial for grasping biochemical processes necessary for life.