Chemistry in Anatomy & Physiology

Introduction

Chemistry is fundamental to understanding the structure and function of the human body. This section covers essential chemical principles relevant to Anatomy & Physiology, including mixtures, chemical reactions, and the role of organic and inorganic compounds in homeostasis.

Mixtures

Types of Mixtures

A mixture is any substance containing two or more components physically intermixed. Mixtures are classified based on the uniformity and particle size of their components.

• Solutions: Homogeneous mixtures with very small particles that do not settle out. - Solvent: The dissolving medium (e.g., water is the body's primary solvent). - Solute: The substance dissolved in the solvent (e.g., NaCl in saline solution).

• Colloids: Heterogeneous mixtures with larger particles that do not settle out. - Can undergo sol-gel transformation, changing from fluid to solid state and vice versa. - Example: Cytosol of cells changes consistency during cellular activities.

• Suspensions: Heterogeneous mixtures with large particles that do settle out. - Example: Blood, where cells are suspended in plasma.

Concentration of Solutions

The concentration of a solution describes how much solute is present in a given amount of solvent.

• Percent Solution: Amount of solute expressed as a percentage of the total solution volume.

• Molarity (mol/L): Number of moles of solute per liter of solution. Formula: Reminder: A mole of any element or compound equals its molecular weight in grams.

Chemical Reactions

Types of Chemical Reactions

Chemical reactions involve the formation, breaking, or rearrangement of chemical bonds. They are essential for all physiological processes.

• Synthesis Reaction: Bonds are formed between atoms to create larger, more complex structures. - Example: Anabolic reactions in the body, such as protein synthesis. - General equation:

• Decomposition Reaction: Bonds are broken to create smaller molecules or individual atoms. - Example: Catabolic reactions in the body, such as digestion. - General equation:

Inorganic Compounds & Their Role in Homeostasis

Water

Water is the most abundant inorganic compound in the body and is vital for cellular function and homeostasis.

• Universal Solvent: Water dissolves and transports nutrients, gases, and waste products. - Surrounds charged structures, facilitating interactions.

• High Heat Capacity: Water absorbs and releases large amounts of heat with minimal temperature change. - Helps maintain stable body temperature.

• Cushioning: Water-based fluids protect internal organs from physical trauma.

• High Heat of Vaporization: Large amounts of heat are required to convert water from liquid to gas. - Important for cooling the body via sweating.

• Reactivity: Water participates in chemical reactions, such as hydrolysis and dehydration synthesis. - Hydrolysis: Water is used to break bonds. - Dehydration synthesis: Water is removed to form bonds.

Electrolytes, Acids, and Bases

Electrolytes are substances that dissociate in solution to form ions, which are essential for physiological functions.

• Electrolytes: Na+, K+, Fe2+ are crucial for muscle contraction, nerve impulse transmission, and oxygen transport.

• Acids: Release H+ ions in solution, lowering pH.

• Bases: Release OH- ions in solution, raising pH.

• Blood pH: Maintained between 7.35 and 7.45 for optimal cellular function.

Buffers

Buffers are systems that prevent drastic changes in pH, protecting the body from damage due to acid-base imbalance.

• Weak acids: Release some (but not all) H+ ions, moderating pH changes.

• Weak bases: Bind excess H+ ions when pH becomes too acidic.

• Result: Buffers maintain pH stability, preventing cellular damage.

Organic Compounds & Homeostasis

Carbon and Macromolecules

Organic molecules in the body contain carbon, which is electroneutral and forms diverse molecular structures.

• Macromolecules: Large polymers made up of smaller units called monomers.

Carbohydrates

Carbohydrates are sugars and starches that serve as a primary energy source and play roles in cell communication.

• Monomer: Monosaccharide (e.g., glucose, fructose, galactose).

• Monosaccharides can combine to form disaccharides and polysaccharides.

• Functions:

  • Provide easily accessible energy.

  • Facilitate cell interactions and communication (e.g., carbohydrates on cell surfaces).

Lipids

Lipids are hydrophobic molecules that include triglycerides, phospholipids, and steroids, each with distinct functions.

• Triglycerides: Composed of fatty acids and glycerol.

  • Saturated: Only single covalent bonds; solid at room temperature (e.g., animal fats).

  • Unsaturated: One or more double bonds; liquid at room temperature (e.g., plant oils).

  • Trans fats: Artificially hydrogenated oils (e.g., processed foods).

  • Omega-3 fatty acids: Found in cold-water fish; beneficial for health.

• Phospholipids: Triglycerides with two fatty acid chains and a phosphate group; form cell membranes.

• Steroids: Include cholesterol, which is a precursor for steroid hormones.

• Functions: Protection, insulation, energy storage, and membrane structure.

Proteins

Proteins are polymers of amino acids with diverse structures and functions.

• Monomer: Amino acid.

• Specific amino acid sequences determine protein structure and function.

• Types:

  • Fibrous proteins: Long strands; provide support and strength (e.g., collagen, muscle).

  • Globular proteins: Compact, spherical; chemically active (e.g., enzymes, antibodies).

• Enzymes: Biological catalysts that lower activation energy and increase reaction rates. - Formula for activation energy: - Enzymes are highly specific; some catalyze only one reaction, others multiple.

ATP: The Energy Molecule

Adenosine triphosphate (ATP) is the primary energy carrier in cells, essential for all physiological processes.

• ATP contains three phosphate groups with high-energy bonds.

• Energy is released when a phosphate group is transferred to another molecule. Formula:

• ATP is required for chemical reactions, cell transport, and muscle contraction.

• Without ATP, cellular processes cease, leading to cell death.

Summary Table: Types of Mixtures

Summary Table: Macromolecules

Additional info: Nucleic acids are also important macromolecules in the body, though not detailed in the provided notes.