The Chemical Level of Organization

Introduction to Elements in Biology

The study of anatomy and physiology begins at the chemical level, where the properties and interactions of atoms and elements form the foundation for all biological processes. Understanding the chemical composition of the human body is essential for grasping how physiological systems function.

• Major Elements: The majority of biological matter is composed of four elements: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

• Mineral Elements: Elements such as Sodium (Na), Potassium (K), Magnesium (Mg), Calcium (Ca), and Phosphorous (P) are present in smaller but physiologically significant quantities.

• Trace Elements: Other elements are present in minute amounts but are still essential for health.

Example: The periodic table highlights the elements most relevant to human biology, with major, mineral, and trace elements color-coded for clarity.

The Relevance of Chemistry to Anatomy & Physiology

Chemistry underpins many physiological processes. Understanding chemical principles is crucial for explaining:

• Electrical Excitability: Neurons and muscle cells function by moving ions across their membranes.

• Digestion: Enzymes, which are proteins, catalyze the breakdown of food.

• Hormone Specificity: Chemical structure determines how hormones interact with specific target cells.

Atomic Structure and Properties

Atoms and Subatomic Particles

An atom is the smallest stable unit of matter. Atoms are composed of three types of subatomic particles:

• Protons (p+): Positively charged; located in the nucleus.

• Neutrons (n0): Neutral (no charge); located in the nucleus.

• Electrons (e-): Negatively charged; travel around the nucleus in electron shells.

Example: A carbon atom is identified by its unique number of protons.

Atomic Number and Atomic Mass

Atoms of different elements are distinguished by their numbers of subatomic particles:

• Atomic Number: The number of protons in the nucleus; unique to each element.

• Atomic Mass (Mass Number): The sum of protons and neutrons in the nucleus.

• In a neutral atom, the number of protons equals the number of electrons.

Formula:

• Atomic Number ():

• Mass Number ():

Example: Calcium (Ca) has an atomic number of 20 and an atomic mass of 40. Therefore, a neutral calcium atom has 20 protons, 20 electrons, and 20 neutrons ( neutrons).

Table: Major, Mineral, and Trace Elements in the Human Body

Additional info: Trace elements include iron (Fe), zinc (Zn), copper (Cu), and iodine (I), which are essential for enzyme function, oxygen transport, and hormone synthesis.

Got it ✅ I pulled everything from your Amerman BIO 109 Ch 2 PDF and matched it to the learning objectives you listed. Here’s a breakdown with simple explanations, examples, and details directly tied to your text:

Chapter 2 Learning Objectives – Study Notes

Atomic Structure & Subatomic Particles

• Atoms = smallest unit of matter.

• Protons (p⁺) = positive charge, in nucleus.

• Neutrons (n⁰) = neutral, in nucleus.

• Electrons (e⁻) = negative charge, orbit nucleus.

• Atomic number = # of protons (and # of electrons if neutral).

• Mass number = protons + neutrons.

Ions (Cations vs Anions)

• Ion = atom that gains/loses electrons.

  • Cation = lost e⁻ → positive charge (ex: Na⁺).

  • Anion = gained e⁻ → negative charge (ex: Cl⁻).

Chemical Bonds

1. Ionic bond = transfer of electrons (ex: NaCl).

2. Covalent bond = sharing electrons.

   • Nonpolar = equal sharing (ex: H₂).

   • Polar = unequal sharing (ex: H₂O).

3. Hydrogen bonds = weak attraction between partially charged regions (ex: water, DNA).

Sodium & Potassium

• Na⁺ and K⁺ are key ions for nerve and muscle cell function (movement across membranes = electrical signals).

Energy in Reactions

• Exergonic = releases energy (ex: digestion).

• Endergonic = requires energy (ex: building proteins).

Catabolic vs Anabolic Reactions

• Catabolic = break down, release energy (hydrolysis, digestion).

• Anabolic = build up, require energy (dehydration synthesis, protein building).

Water Properties

• >50% of body is water.

• Functions: high heat capacity (temp regulation), protection (cushions brain), lubrication (reduces friction), solubility (universal solvent).

Solutions

• Solvent = dissolving agent (ex: water).

• Solute = dissolved substance (ex: salt).

• Solution = mixture of solvent + solute.

• Hydrophilic = dissolves in water (polar/ionic).

• Hydrophobic = does not dissolve (nonpolar, ex: oils).

Acids, Bases, pH

• Acid = donates H⁺ (ex: HCl).

• Base = accepts H⁺ (ex: NaOH).

• pH scale = 0–14, logarithmic:

  • <7 = acidic

  • 7 = neutral

  • 7 = basic

• [H⁺] increases → lower pH.

• Buffers stabilize pH (prevent protein denaturation).

Enzymes

• Proteins that act as catalysts.

• Lower activation energy → speed up reactions.

• Specific (fit to one substrate).

• Reusable, not consumed in reaction.

• Regulated (can be turned on/off).

Organic Molecules

1. Carbohydrates: energy + structure.

   • Monosaccharides (glucose), disaccharides (sucrose), polysaccharides (glycogen).

2. Lipids: hydrophobic, energy storage, insulation, cell membranes.

   • Fatty acids, triglycerides, phospholipids, steroids (cholesterol, hormones).

3. Proteins: made of amino acids, shape = function.

   • Functions: support, movement, enzymes, and defense.

   • Denaturation = loss of shape → loss of function.

4. Nucleic Acids: DNA & RNA.

   • Store genetic info, direct protein synthesis.

ATP (Adenosine Triphosphate)

• Cell’s energy currency.

• Made by adding P to ADP (requires food energy).

• Hydrolysis of ATP → releases energy for nearly all cellular activities.

✅ Key Takeaway

This chapter is basically the foundation of chemistry in biology: atoms → bonds → water → reactions → macromolecules → ATP.