Basic Principles of Chemistry as They Apply to Body Processes

Introduction

Chemistry is fundamental to understanding all physiological reactions in the human body, including movement, digestion, heart function, and nervous system activity. The study of chemistry in anatomy and physiology can be divided into basic chemistry and biochemistry.

Key Terms Related to Basic Chemistry

Elements and Atoms

• Element: A substance that cannot be broken down into simpler substances by ordinary chemical methods. Examples include carbon, oxygen, hydrogen, and nitrogen.

• Atoms: The smallest particles of an element that retain the properties of that element. Atoms are the unique building blocks for each element.

• Major elements (C, O, H, N) make up about 96% of the human body. Nine additional elements make up 3.9%, and 11 trace elements make up less than 0.01%.

Molecules and Compounds

• Molecule: A general term for two or more atoms bonded together (e.g., O2).

• Compound: A specific molecule that contains two or more different kinds of atoms bonded together (e.g., C6H12O6).

• Molecules with only one type of atom are simply called molecules, while those with different atoms are compounds.

Mixtures

• Mixture: Two or more components physically intermixed. Mixtures do not involve chemical bonding between components.

• Three basic types of mixtures:

  • Solutions: Homogeneous mixtures with very small solute particles evenly distributed in a solvent (e.g., mineral water).

  • Colloids (Emulsions): Heterogeneous mixtures with larger solute particles that do not settle out (e.g., Jell-O). Colloids often appear cloudy or milky and can undergo sol-gel transformations.

  • Suspensions: Heterogeneous mixtures with large, visible solute particles that settle out over time (e.g., a mixture of water and sand, or blood cells in plasma).

• Comparison between mixtures and compounds:

  • Mixtures can be separated by physical means; compounds can only be separated by breaking chemical bonds.

  • Mixtures can be either homogeneous or heterogeneous; compounds are always homogeneous.

Properties of Solutions, Colloids, and Suspensions

Key Points

• Elements are the fundamental substances of matter; atoms are their smallest units.

• Molecules and compounds are formed by chemical bonding between atoms.

• Mixtures involve physical combinations of substances without chemical bonding.

• Understanding the differences between solutions, colloids, and suspensions is important for interpreting physiological fluids.

Example

• Blood: Blood is a suspension because blood cells will settle out if left undisturbed. Plasma, the liquid component, is a solution containing dissolved nutrients, gases, and proteins.

Additional info: These foundational chemistry concepts are essential for understanding more advanced topics in anatomy and physiology, such as cellular metabolism, enzyme function, and the chemical basis of physiological processes.