Composition of Matter

Elements and Atoms

Understanding the basic composition of matter is essential for studying Anatomy & Physiology, as all biological processes are rooted in chemical interactions.

• Element: A pure substance consisting of only one type of atom. Examples include oxygen (O), carbon (C), and hydrogen (H).

• Atom: The smallest unit of an element that retains its chemical properties.

• Relationship: Elements are made up of atoms; atoms combine to form molecules and compounds.

Atomic Structure

Subatomic Particles

Atoms are composed of three main subatomic particles, each with distinct properties.

• Proton: Positively charged particle found in the nucleus.

• Neutron: Neutral particle found in the nucleus.

• Electron: Negatively charged particle orbiting the nucleus.

Relative Masses:

• Proton: 1 atomic mass unit (amu)

• Neutron: 1 amu

• Electron: ~0 amu (very small compared to protons and neutrons)

Identifying Elements

Atomic Number, Mass Number, and Radioisotopes

Each element is defined by its atomic number and mass number, which are crucial for understanding chemical behavior.

• Atomic Number (Z): Number of protons in the nucleus; determines the element's identity.

• Mass Number (A): Total number of protons and neutrons in the nucleus.

• Radioisotopes: Isotopes with unstable nuclei that emit radiation; used in medical imaging and treatments.

Formula:

• where is mass number, is atomic number, and is number of neutrons.

Molecules and Compounds

Definitions and Relationships

Molecules and compounds are formed when atoms bond together, playing vital roles in biological systems.

• Molecule: Two or more atoms chemically bonded together (e.g., ).

• Compound: A molecule containing atoms of different elements (e.g., ).

Chemical Bonds and Chemical Reactions

Bond Formation and Types

Chemical bonds hold atoms together in molecules and compounds, and their formation is fundamental to biological processes.

• Role of Electrons: Electrons in the outer shell (valence electrons) participate in bond formation.

• Valence Shell: The outermost electron shell; determines chemical reactivity.

• Types of Chemical Bonds:

  • Ionic Bond: Transfer of electrons from one atom to another, forming charged ions (e.g., NaCl).

  • Covalent Bond: Sharing of electron pairs between atoms (e.g., ).

  • Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., between water molecules).

Patterns of Chemical Reactions

Synthesis and Decomposition Reactions

Chemical reactions in the body are classified by how molecules are formed or broken down.

• Synthesis Reaction: Two or more reactants combine to form a larger product. General Equation:

• Decomposition Reaction: A compound breaks down into two or more simpler substances. General Equation:

Biochemistry

Organic vs. Inorganic Compounds

Biochemistry distinguishes between organic and inorganic compounds, both essential for life.

• Organic Compounds: Contain carbon and hydrogen; include carbohydrates, lipids, proteins, and nucleic acids.

• Inorganic Compounds: Do not contain both carbon and hydrogen; include water, salts, acids, and bases.

Water and Its Properties

Water is vital for homeostasis due to its unique properties.

• High Heat Capacity: Absorbs and releases heat slowly, helping regulate body temperature.

• Cohesion: Water molecules stick together due to hydrogen bonding.

• Polarity: Water is a polar molecule, allowing it to dissolve many substances.

Salts

Salts are important for maintaining electrolyte balance and are associated with water polarity.

• Function: Regulate nerve impulses, muscle contraction, and fluid balance.

Organic Compounds

Dehydration Synthesis and Hydrolysis

Organic molecules are built and broken down through specific chemical reactions.

• Dehydration Synthesis: Removal of water to join two molecules.

• Hydrolysis: Addition of water to break a molecule into smaller units.

Carbohydrates and Lipids

Carbohydrates and lipids are major classes of organic molecules with distinct structures and functions.

Proteins

Amino Acids and Protein Structure

Proteins are polymers of amino acids and have four levels of structural organization.

• Monomer: Amino acid

• Primary Structure: Sequence of amino acids

• Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding

• Tertiary Structure: 3D folding due to interactions among R groups

• Quaternary Structure: Association of multiple polypeptide chains

Nucleic Acids

DNA and RNA Structure and Comparison

Nucleic acids store and transmit genetic information. DNA and RNA differ in structure and function.