Biology Chapter on Living Things and Elements

Shared Properties of Living Things

• Living things move, respire, respond to stimuli, obtain and use energy, excrete waste products, reproduce, and grow.
• These characteristics differentiate living things from non-living things.

Chemical Basis of Life

• Life can be viewed as matter.
• Atoms are the smallest units of matter.
• Elements are pure substances that cannot be broken down into simpler substances.
• Over 100 elements exist, with 92 occurring naturally.
• Biogenic elements are found in living matter.

Biogenic Elements

• Macrobiogenic Elements: C, O, H, N, S, P, Na, K, Ca, Mg, Cl, and Fe.
  • These elements make up about 95% of living matter.
  • They have a building function.
• Microbiogenic Elements: Cu, I, Mo, Mn, Zn, and Co.
  • These elements are present in living organisms at less than 0.1%.
  • They have a catalytic function, acting as components of enzymes.
• Trace Elements: Al, As, B, Br, F, Li, Ni, Se, Si, Ti, and V.
  • These elements are present in organisms at less than 0.001%.
  • Like microbiogenic elements, they are involved in enzymes and have catalytic functions.

Elements in Living and Non-living Matter

• Carbon is significantly more abundant in living matter (18.5%) compared to non-living matter (0.18%).
• Oxygen is more abundant in living matter (65%) than non-living matter (49.40%).

Carbon, Oxygen, Hydrogen, and Nitrogen

• Carbon is the foundation of all living matter.
• Carbon's ability to bond with itself and other elements forms the basis of molecules and macromolecules.
• Oxygen and Hydrogen are present in both organic and inorganic compounds and are integral to water (H2O).
• Nitrogen is a component of proteins, nucleic acids, nitrates, and ammonium carbonates – essential for plant nutrition and protein synthesis.

Covalent and Ionic Bonding

• Covalent Bonds: Formed when atoms share electrons to achieve stability, satisfying the octet rule.
  • Carbon forms stable covalent bonds with H, O, and OH.
• Ionic Bonds: Formed by the electrostatic attraction between oppositely charged ions.

The Octet Rule

• The octet rule states that atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight electrons in their outermost electron shell.
• This rule is crucial for understanding the bonding behavior of atoms and the formation of molecules.

Bonding in Carbon

• Carbon has an atomic number of 6, meaning it has 6 protons and 6 electrons.
• To achieve stability, carbon shares its electrons with other atoms through covalent bonding.

Essential and Harmful Elements

• Useful Elements: Iron (Fe), Aluminum (Al), Gold (Au), Silver (Ag), Copper (Cu), Nickel (Ni), Manganese (Mn), and Titanium (Ti).
• Harmful Elements: Arsenic (As), Lead (Pb), and Mercury (Hg).

The Building Blocks of Matter

• All matter is composed of atoms.
• Atoms are made up of protons, neutrons, and electrons.
• Protons, neutrons, and electrons are found in elements.
• Elements form molecules, which can be small (micro) or large (macro), when bonded together.