Fundamental Concepts in General Biology: Atomic Structure, Chemical Bonds, and Water Properties

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Atomic Structure and Subatomic Particles

Subatomic Particles: Protons, Neutrons, and Electrons

Atoms are the basic units of matter, composed of three main subatomic particles: protons, neutrons, and electrons. Each particle has distinct properties that determine the atom's behavior and identity.

Protons: Positively charged particles located in the nucleus. The number of protons defines the atomic number and the element.
Neutrons: Neutral particles also found in the nucleus. Neutrons contribute to the atomic mass and can vary in number, resulting in isotopes.
Electrons: Negatively charged particles that orbit the nucleus in electron shells. Electrons are involved in chemical bonding and reactions.

Example: A carbon atom has 6 protons, 6 neutrons, and 6 electrons.

Isotopes and Their Biological Uses

Definition and Application of Isotopes

Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses. Some isotopes are stable, while others are radioactive and decay over time.

Radioisotope: An isotope that emits radiation as it decays. Used in biological research for tracing molecules and imaging.
Example: Carbon-14 is used in radiocarbon dating and as a tracer in metabolic studies.

Valence Electrons and Chemical Bonding

Role of Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom. They determine the atom's chemical reactivity and bonding behavior.

Elements in the same group of the periodic table have the same number of valence electrons and similar chemical properties.
Valence electrons participate in forming chemical bonds, such as ionic and covalent bonds.

Example: All Group 1 elements (alkali metals) have one valence electron and react similarly.

Molecules vs. Compounds

Definitions and Examples

A molecule is two or more atoms bonded together. A compound is a molecule that contains atoms of different elements.

Molecule Example: O2 (oxygen gas)
Compound Example: H2O (water)

Ionic and Covalent Bonds

Comparison and Biological Significance

Ionic bonds form when electrons are transferred from one atom to another, creating charged ions. Covalent bonds form when atoms share electrons. Both types of bonds are essential for the structure and function of biological molecules.

Ionic Bond Example: NaCl (sodium chloride)
Covalent Bond Example: H2O (water)

Ionic bonds often result in crystalline solids, while covalent bonds create stable molecules with specific shapes.

Unique Properties of Water

Water's Biological Importance

Water exhibits several unique properties due to its molecular structure and hydrogen bonding:

Cohesion: Water molecules stick to each other, enabling surface tension.
High Heat Capacity: Water absorbs and retains heat, stabilizing temperatures in organisms and environments.
Solvent Abilities: Water dissolves many substances, facilitating chemical reactions in cells.
Additional info: Adhesion: Water molecules stick to other surfaces, aiding transport in plants.

Each property supports life by maintaining homeostasis, enabling transport, and facilitating biochemical reactions.

Hydrogen Bonds and Water's Polarity

Formation and Biological Importance

Hydrogen bonds arise from water's polarity, where the oxygen atom is slightly negative and the hydrogen atoms are slightly positive. This allows water molecules to attract each other.

Hydrogen bonds are crucial for the structure of proteins and DNA.
They contribute to water's unique properties, such as high boiling point and surface tension.

Biological Importance: Hydrogen bonds stabilize macromolecules and facilitate molecular interactions.

Molecular Polarity and Solubility

Influence on Water Solubility

Molecular polarity refers to the distribution of electrical charge across a molecule. Polar molecules dissolve well in water, while nonpolar molecules do not.

Water is a polar solvent, so it dissolves ionic and polar substances (e.g., salts, sugars).
Nonpolar molecules (e.g., oils) are insoluble in water.

pH, Buffers, and Biological Systems

Importance of pH and Buffers

pH measures the concentration of hydrogen ions () in a solution. Biological systems require stable pH for proper function.

Acids: Substances that increase in solution.
Bases: Substances that decrease in solution.
Buffers: Solutions that resist changes in pH by neutralizing acids and bases.

Example: The bicarbonate buffer system helps maintain blood pH in humans.

Capillary Action

Mechanism and Examples

Capillary action is the movement of liquid through narrow spaces due to cohesion and adhesion. It is essential for transporting water in plants and other biological systems.

Occurs when adhesive forces between water and a surface are stronger than cohesive forces between water molecules.
Examples from nature: Water movement in plant xylem; absorption of water in paper towels.