2.1 Elements and Atoms: The Building Blocks of Matter

The Fundamental Components of the Human Body

• Basic Chemical Elements

  • The smallest and most fundamental material components of the human body are basic chemical elements.

  • Chemicals called nucleotide bases form the foundation of the genetic code, providing the instructions for building and maintaining the human body from conception through old age.

  • Approximately three billion nucleotide base pairs exist in human DNA.

• Components of Human Chemistry

  • Includes organic molecules (carbon-based) and biochemicals (produced by the body).

  • Involves elements essential for life, which cannot exist without many of the earth's elements.

  • Elements involved in chemical reactions, energy transformation, electrical activity, and muscle contraction include phosphorus, carbon, sodium, and calcium.

• Origin of Life Elements

  • Most elements found in the human body originated in stars.

  • These elements can form inorganic and organic compounds vital for life, such as water, glucose, and proteins.

2.1 Elements and Atoms: The Building Blocks of Matter

• Learning Objectives

  • Discuss relationships among matter, mass, elements, compounds, atoms, and subatomic particles.

  • Distinguish between atomic number and mass number.

  • Identify the distinction between isotopes of the same element.

  • Explain the occupation of electron shells by electrons and their contribution to atomic stability.

• Definition of Matter

  • Mater: The substance of the universe; defined as anything occupying space and possessing mass.

  • Mass vs. Weight:

  • Mass: Amount of matter in an object, unchanged regardless of location (e.g., remains the same in outer space).

  • Weight: The mass of an object affected by gravity; varies depending on the gravitational pull (e.g., a pound of cheese on Earth weighs less on the moon due to weaker gravity).

• Elements and Compounds

  • All matter is composed of one or more of the 92 fundamental substances known as elements.

  • Definition of an Element: A pure substance that cannot be created or broken down by ordinary chemical methods.

  • Elements must be acquired from the environment by the body as it cannot synthesize them.

  • Example: Calcium (Ca++): Essential for several body processes, including bone strengthening. It must be ingested through food.

  • In dietary products, the human digestive system breaks down food into constituent elements, including calcium, which cannot be further broken down.

• Common Elements in the Human Body

  • The elements prevalent in the human body from most to least abundant include:

  • Oxygen (O)

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

  • Each element is represented by a one- or two-letter symbol.

  • These elements in the body are derived from the food consumed and the air breathed.

• Nature of Compounds

  • Elements rarely occur independently; they typically combine to form compounds.

  • Definition of a Compound: A substance composed of two or more elements bonded chemically.

  • Example: Glucose: A crucial body fuel composed consistently of three elements: carbon, hydrogen, and oxygen.

  • The specific elemental composition of glucose is fixed: six carbon and six oxygen units for every twelve hydrogen units.