Introduction to Chemistry in Anatomy & Physiology

Chemistry forms the basis for understanding the structure and function of the human body. Key concepts include matter, atoms, elements, chemical bonds, water, and pH, all of which are essential for physiological processes.

Matter and Atoms

Definitions and Properties

• Matter: Anything that takes up space (liquid, solid, or gas); can be living or non-living.

• Mass: Quantity of material in matter.

• Atom: The smallest stable unit of matter, composed of:

  • Proton (P+): Positive charge

  • Neutron (N): Neutral charge

  • Electron (E-): Negative charge

• Nucleus: Determines the mass of the atom.

Elements and Compounds

Definitions and Differences

• Element: A pure substance made up of only one kind of atom.

• Compound: A substance consisting of two or more different elements bonded together.

• Properties: Elements have uniform properties; compounds have properties that can differ from their constituent elements.

Major Elements in the Human Body

The following table summarizes key elements and their functions in the body:

Chemical Bonds

Types of Chemical Bonding

• Ionic Bond: Attraction of positive and negative ions.

  • Ion: An atom with a positive or negative charge.

  • Cation: Positively charged ion (e.g., Na+).

  • Anion: Negatively charged ion (e.g., Cl-).

  • Example:

  • Examples of ionic compounds: KCl, Ca3(PO4)2

• Covalent Bond: Atoms share electrons.

  • Nonpolar Covalent Bonds: Atoms share electrons equally (e.g., H2, N2, O2).

  • Polar Covalent Bonds: Atoms share electrons unequally (e.g., H2O).

Classifying Compounds as Polar or Nonpolar

• NH3 (Ammonia): Polar – Atoms share electrons unequally.

• O2 (Oxygen): Nonpolar – Atoms share electrons equally.

• C4H10 (Butane): Nonpolar – Atoms share electrons equally.

• H2O (Water): Polar – Atoms share electrons unequally.

Compounds may contain both polar and nonpolar bonds, but for classification:

• Proteins: Polar (amino acids can be polar or nonpolar)

• Sugars: Polar

• Fats: Nonpolar

• Carbon dioxide: Nonpolar

Importance of Polarity

• Polarity determines how substances interact, dissolve, and react in the body.

• Polar/nonpolar nature affects membrane interaction, signal transmission, and cellular processes.

Solubility and Interactions in Water

Solubility Principles

• Like dissolves like: Polar compounds dissolve in polar solvents (e.g., water); nonpolar compounds dissolve in nonpolar solvents (e.g., fat).

• Salt (ionic compound): Dissolves in water due to attraction between ions and water's partial charges.

• Proteins: Most are polar and dissolve in water.

• Sugar: Polar; does not dissolve in fat.

• Salt: Nonpolar; does not dissolve in fat.

• Proteins: Most do not dissolve in fat.

Hydrogen Bonds

• Water molecules (and other polar covalent compounds with hydrogen) can form hydrogen bonds.

• Hydrogen bonds give water unique properties essential for life, such as high specific heat and heat of vaporization.

Metabolism and Chemical Reactions

Definitions

• Metabolism: Sum of all chemical reactions in the body.

• Catabolism: Breakdown of organic molecules into simpler components, releasing energy.

• Anabolism: Building larger molecules from smaller ones, requiring energy.

Types of Reactions

• Exergonic: Releases energy (e.g., catabolism).

• Endergonic: Requires energy (e.g., anabolism).

Inorganic Chemistry: Water

Functions of Water in the Body

• Major component of blood plasma and cytoplasm.

• Most sugars and proteins dissolve in water; fats do not.

• Lipoproteins transport fats in blood by making them water-soluble.

Reactions Involving Water

• Hydrolysis: Adding water to break bonds apart.

• Dehydration: Removing water to build bonds.

General reaction for hydrolysis of a disaccharide:

General reaction for dehydration synthesis of a disaccharide:

• Hydrolysis is catabolic (releases energy).

• Dehydration is anabolic (requires energy).

Properties of Water

• High specific heat: Water resists changes in temperature, helping maintain stable internal conditions.

• High heat of vaporization: Significant energy is required to convert water from liquid to gas, aiding in cooling (e.g., sweating).

• Lubrication: Water is a component of many body fluids that lubricate membranes and joints.

pH and Acid-Base Balance

Definition and Measurement

• pH: Measure of acidity or alkalinity of a solution, on a scale of 0-14.

• Calculated as the negative logarithm of the concentration of hydrogen ions (H+) in moles per liter:

• Normal pH range of human blood: 7.25 to 7.45

pH Scale

Acids and Examples

• Acids release hydrogen ions (H+) when dissolved in water, lowering pH.

• Examples: Hydrochloric acid, carbonic acid, vinegar.

Calculating Hydrogen Ion Concentration

• pH 8: M

• pH 2: M

• pH 4: M

• A solution with pH 2 has 100 times more hydrogen ions than a solution with pH 4.

Summary Table: Key Concepts

Additional info: Academic context and explanations have been expanded for clarity and completeness.