Study Guide: Atoms, Functions of Life, and Biological Reactions

Atoms and Subatomic Particles

Overview of Atomic Structure

Atoms are the fundamental building blocks of all matter, characterized by their structure and constituent particles. The atomic number, determined by the number of protons in the nucleus of an atom, is a crucial identifier of elements.

Subatomic Particles

  1. Proton

    • Location: Found in the nucleus of the atom.
    • Charge: Positive (+1).
    • Function: Contributes to the atomic mass and establishes the identity of the element.

  2. Neutron

    • Location: Also located in the nucleus.
    • Charge: Neutral (0).
    • Function: Contributes to atomic mass; variations in the number of neutrons lead to the formation of isotopes.

  3. Electron

    • Location: Orbiting the nucleus in electron clouds.
    • Charge: Negative (-1).
    • Function: Involved in chemical bonding.
Atomic Mass and Stability
  • Atomic Mass is calculated as the sum of protons and neutrons. The electrons, while numerous, do not significantly contribute to the mass of the atom.
  • Stability: Atoms can be unstable due to a change in the number of neutrons, leading to the formation of radioactive isotopes.

Chemical Bonds

  • Elements are defined as pure substances consisting of only one type of atom.
  • A compound is formed when two or more elements chemically bond together.
Types of Bonds

  1. Ionic Bonds

    • Mechanism: Electrons are transferred from one atom to another, resulting in the formation of charged ions: cations (positive) and anions (negative).
    • Example: Formation of salts.

  2. Covalent Bonds

    • Mechanism: Electrons are shared between atoms, forming molecules.
    • Example: Water (H₂O).

  3. Hydrogen Bonds

    • Mechanism: Weak attractions between polar molecules.
    • Example: Interaction between water molecules.
Ions and Solubility
  • Ions:
    • Cation: A positively charged ion due to loss of electrons.
    • Anion: A negatively charged ion due to gain of electrons.
  • Solubility: Water's polar covalent bonds enable it to dissolve ionic and polar substances; thus, it is an effective solvent in biological systems.

Chemical Reactions

  • Series of processes that lead to the transformation of reactants into products.
    • Synthesis Reaction (A + B → AB): Two or more reactants combine to form one product.
    • Dehydration Synthesis: Water molecule is removed to form a new bond between subunits.
    • Decomposition Reaction (AB → A + B): A compound breaks down into simpler parts.
    • Hydrolysis: A compound is broken down by the addition of water.
    • Exchange Reaction (AB + CD → AD + CB): Atoms or groups of atoms in compounds swap places.

Functions of Life

There are five basic functions of life critical to organisms:

  1. Organization: All living things consist of cells, the fundamental unit of life.
  2. Metabolism: Refers to all chemical reactions in the body, including both anabolic and catabolic processes.
    • Anabolism: The buildup of complex molecules from simpler ones, requiring energy.
    • Catabolism: The breakdown of larger molecules into smaller ones, releasing energy.
  3. Responsiveness: The ability to detect and respond to changes in the environment, essential for survival.
  4. Growth and Development: Increase in size and maturation, which is indicative of the organism's life cycle.
  5. Reproduction: Creating new cells for growth or new organisms, essential for the continuation of the species.

Homeostasis and Feedback Mechanisms

  • Homeostasis: The process of maintaining a stable internal environment despite external fluctuations.
  • Negative Feedback: A response mechanism that reverses a change to return the system to its set point; critical for stabilizing conditions like body temperature (e.g., sweating when overheated).
  • Positive Feedback: A amplified response mechanism, usually occurring during specific events such as childbirth contractions.

Levels of Biological Organization

  1. Chemical Level: The simplest level consisting of atoms and molecules.
  2. Cellular Level: Cells are the smallest living units performing essential functions.
  3. Tissue Level: Groups of similar cells working together to perform a specific function.
  4. Organ Level: Structures composed of two or more different tissue types working together for a common function.
  5. Organ System Level: Groups of organs that contribute to a common function.
  6. Organism Level: The highest level of organization representing a living individual.

Anatomical Terminology

  • Anatomy vs. Physiology: Anatomy refers to the study of body structure, while physiology focuses on the functions of those structures.
  • Levels of Anatomy:
    • Microscopic Anatomy: Study of structures not visible to the naked eye, including cytology (cells) and histology (tissues).
    • Gross Anatomy: Study of structures that can be observed without the aid of a microscope.
    • Developmental Anatomy: Focuses on the growth and changes from fertilization to adulthood.
    • Regional Anatomy: Study of specific body regions.
    • Systemic Anatomy: Study of specific organ systems such as the cardiovascular or digestive systems.
  • Reactants and Products: Reactants are the starting materials in a chemical reaction, while products are the substances formed as a result of that reaction.

Types of Biological Reactions

  1. Synthesis Reaction: The formation of a larger molecule from smaller units (e.g., A + B → AB).
  2. Decomposition Reaction: The breakdown of compounds into simpler products (e.g., AB → A + B).
  3. Exchange Reaction: A reaction where parts of two molecules exchange to form new molecules (e.g., AB + CD → AC + BD).
  4. Hydrolysis: A chemical reaction that uses water to break down compounds, essential for digestion.
  5. Dehydration Synthesis: A process that builds larger molecules while releasing water as a by-product.