Matter, Atoms, and Biomolecules: Foundations of Biology

Posted on Sep 10, 2025 in Chemistry

Fundamentals of Matter and Atoms

Matter

Matter is defined as the amount of mass that occupies a space.

The Atom and Its Subatomic Particles

An atom is considered the indivisible part of matter and is composed of three primary subatomic particles:

  • Protons (H+): Subatomic particles with a positive charge.
  • Neutrons (n): Subatomic particles with a neutral charge.
  • Electrons (e-): Subatomic particles with a negative charge.

Isotopes and Atomic Properties

An isotope is an atom that contains a greater number of neutrons than the standard form of the element, which can lead to radioactivity.

The atomic number represents the number of protons an element possesses.

Atomic weight is the sum of an atom’s protons and neutrons.

Essential Bioelements for Life

Primary Bioelements (99.3% of Body Mass)

These elements are crucial for life and make up the majority of an organism’s mass:

  • Carbon (18%): Essential for forming vital macromolecules such as sugars, fats, proteins, and nucleic acids.
  • Oxygen (18%): Critical for all bodily functions. It is produced by plants through photosynthesis and is a key component of the water molecule.
  • Hydrogen (10%): Functional in food transport chains and various metabolic processes.
  • Nitrogen (3%): Very important for fixing atmospheric nitrogen, converting it into nitrites and nitrates, which are vital for plant growth and nutrient cycles.

Secondary Bioelements

These elements are also vital, though present in smaller quantities:

  • Sulfur: Aids the body in setting and metabolizing vitamins.
  • Calcium: Essential for the mineralization of bones and teeth.
  • Phosphorus: Often bound to fat molecules, allowing the capture and transport of other substances.
  • Magnesium: Gives plants their green coloration and is responsible for the process of photosynthesis.
  • Potassium: Helps in the process of nerve impulse transmission.
  • Sodium: Crucial for nerve impulse transmission and fluid balance.
  • Chlorine: Involved in the process of muscle contraction and relaxation.

Molecules: Building Blocks of Life

Inorganic Molecules

Molecules are defined as a set of two or more elements joined by chemical bonds. They are broadly classified into two groups:

Inorganic molecules are those found ubiquitously in nature.

Water: The Universal Solvent

Water is the universal solvent, capable of dissolving both inorganic substances (like salts and minerals) and many organic substances (like sugars).

Organic Molecules (Biomolecules)

Biomolecules are organic molecules whose primary function is to support life processes, including metabolism.

Carbohydrates

Carbohydrates are essential biomolecules, categorized by their sugar units:

  • Monosaccharides: Simple sugars consisting of a single carbohydrate unit.
  • Disaccharides: Sugars formed by two carbohydrate units joined by a glycosidic bond.
  • Polysaccharides: Complex carbohydrates formed by multiple (two or more) monosaccharide units. Examples include:
    • Starch: Sugars produced by plant cells for energy storage.
    • Glycogen: A sugar produced by animals, serving as an energy reserve.
    • Chitin: A type of sugar produced by insects, forming their exoskeletons.

Lipids

Lipids are a diverse group of organic molecules, including:

  1. Fatty Acids
  2. Triacylglycerols
  3. Phospholipids: A type of molecule containing a phosphorus group, primarily found in cell membranes.
  4. Steroids: Ring-shaped molecules that provide structural form to cells.
    • Cholesterol: Gives rigidity to the cell membrane.
    • Testosterone: The primary male sex hormone.

Proteins

Proteins are complex macromolecules vital for structure and function. For example:

  • Hemoglobin: Responsible for transporting oxygen in the blood.

Nucleic Acids

Nucleic acids are organic molecules composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus. They carry the genetic material of all organisms and are crucial for transforming genetic information into cellular proteins.

Cell Theory: Historical Milestones

The understanding of cells has evolved through the contributions of several key scientists:

  1. Marcello Malpighi: An Italian physiologist and doctor who discovered the function and form of red blood cells.
  2. Robert Hooke: Utilized a microscope to observe the cell wall, becoming the first to observe and coin the term “cell.”
  3. Robert Brown: Discovered the nucleus within plant cells.
  4. Johannes Purkinje: Described the cell’s watery, viscous substance, which he termed “protoplasm.”