Organic and Inorganic Molecules: Chemical Composition and Biological Importance

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Organic and Inorganic Molecules in Living Organisms

Introduction

Organic and inorganic molecules are fundamental to the structure and function of living organisms. Understanding their properties and roles is essential for studying Anatomy & Physiology.

Organic molecules are carbon-based compounds, typically large and complex, such as carbohydrates, lipids, proteins, and nucleic acids.
Inorganic molecules are generally small, simple compounds that do not contain carbon as their primary element. Examples include water, salts, and many acids and bases.

Chemistry: The Chemical Composition of the Body

Organic vs. Inorganic Compounds

Organic Compounds: Always contain carbon, usually large and covalently bonded. Examples: carbohydrates, lipids, proteins, nucleic acids.
Inorganic Compounds: Usually lack carbon, often small and simple. Examples: water, salts, acids, bases.

Functions of Inorganic Compounds in the Body

Key Roles

Regulate fluid balance and nerve impulses
Support bone structure
Maintain pH balance
Drive chemical reactions

Water (H2O)

Importance and Properties

Water is the most abundant inorganic compound in the body, making up about two-thirds of body weight. Its unique chemical and physical properties are essential for human survival and support nearly every physiological function.

Acts as a universal solvent
Regulates body temperature
Lubricates joints and organs
Essential for chemical reactions

Functions Supported by Water

Regulates body temperature
Supports chemical reactions
Transports nutrients and wastes
Lubricates and cushions joints and organs
Maintains fluid and electrolyte balance
Aids digestion and absorption

Key Properties of Water

High heat capacity: Absorbs and releases large amounts of heat with minimal temperature change, helping to stabilize body temperature.
Polarity/solvent properties: Water is a polar molecule, making it an excellent solvent for ionic and polar substances.
Chemical reactivity: Participates in hydrolysis and other chemical reactions.
Cushioning: Provides protection and lubrication for organs and joints.

High Heat Capacity

Water absorbs and releases a large amount of heat before its temperature changes.
This property helps prevent sudden changes in body temperature.

Polarity and Solvent Properties

Water's polarity allows it to dissolve more substances than any other liquid, earning it the title "universal solvent."
Facilitates transport of nutrients, gases, and wastes in the body.

Chemical Reactivity

Water is involved in hydrolysis reactions, which break down complex molecules during digestion.
Enables metabolic reactions essential for life.

Cushioning and Lubrication

Water acts as a lubricant in joints (synovial fluid), eyes (tears), mouth (saliva), and around organs (serous fluids).
Absorbs shock and reduces friction, protecting tissues and organs.

Electrolytes and Their Importance

Definition and Types

Electrolytes are ions that conduct electrical currents in the body. They dissociate into ions in water and are essential for nerve signaling, muscle contraction, hydration, and pH balance.

Salts: Ionic compounds made of positive and negative ions. Example: NaCl (sodium chloride).
Acids: Release hydrogen ions (H+) in solution. Example: HCl (hydrochloric acid).
Bases: Release hydroxide ions (OH-) or accept H+. Example: NaOH (sodium hydroxide).

Major Electrolytes in the Human Body

Electrolyte	Main Function	Normal Range
Sodium (Na+)	Regulates fluid volume, pH balance	135-145 mEq/L
Potassium (K+)	Maintains heart rhythm, muscle function	3.5-5.0 mEq/L
Chloride (Cl-)	Works with sodium, acid-base balance	98-106 mEq/L
Calcium (Ca2+)	Bone/teeth formation, muscle contraction	8.5-10.5 mg/dL
Magnesium (Mg2+)	Enzyme function, DNA synthesisghthñ	1.7-2.2 mg/dL
Phosphate (PO43-)	Energy production (ATP)	2.5-4.5 mg/dL
Bicarbonate (HCO3-)	pH buffer	22-28 mEq/L
Sulphate (SO42-)	Detoxification, enzyme function	Variable

Acids, Bases, and the pH Scale

Definitions

Acids: Substances that release H+ ions in solution. Strong acids ionize completely; weak acids ionize partially.
Bases: Substances that release OH- ions or accept H+ ions. Strong bases ionize completely; weak bases ionize partially.

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution, ranging from 0 (most acidic) to 14 (most basic). A change of 1 pH unit represents a tenfold change in H+ concentration.

Neutral: pH 7 (equal H+ and OH- concentrations)
Acidic: pH < 7 (higher H+ concentration)
Basic: pH > 7 (lower H+ concentration)

pH Ranges of Human Body Fluids

Fluid	pH Range
Blood	7.35 - 7.45
Urine	6.2 - 7.6
Gastric Juice	1.5 - 3.5
Saliva	6.0 - 7.5
Vaginal Fluid	3.8 - 4.5
Skin	4.5 - 5.5
Cerebrospinal Fluid	7.3 - 7.4

Buffer Systems

Buffers help maintain pH stability in the body by neutralizing excess acids or bases.
Key buffer: Bicarbonate system in blood.

Organic Molecules: Composition and Function

Key Elements and Structure

Organic molecules are primarily composed of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). Some also contain phosphorus (P) and sulfur (S).
Monomers are the basic units; polymers are large molecules made of repeating monomers.

Types of Organic Molecules

Molecule	Monomer	Main Elements	Key Function
Carbohydrates	Monosaccharides	C, H, O	Energy, structure
Proteins	Amino acids	C, H, O, N (S)	Structure, enzymes, signaling
Lipids	Fatty acids, glycerol	C, H (O)	Energy storage, membranes
Nucleic acids	Nucleotides	C, H, O, N, P	Genetic information

Polymerization and Hydrolysis

Dehydration synthesis: Monomers join to form polymers by removing water.
Hydrolysis: Polymers are broken down into monomers by adding water.

Carbohydrates

Classification

Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose)
Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose, maltose)
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen)

Lipids

Types and Functions

Triglycerides: Energy storage, insulation
Phospholipids: Major component of cell membranes
Steroids: Hormones, cholesterol

Saturated vs. Unsaturated Fats

Saturated fats: No double bonds, solid at room temperature
Unsaturated fats: One or more double bonds, liquid at room temperature

Proteins

Structure and Function

Composed of amino acids linked by peptide bonds
Functions: structural support, enzymes, hormones, antibodies

Levels of Protein Structure

Primary: Sequence of amino acids
Secondary: Alpha helix or beta-pleated sheet (hydrogen bonds)
Tertiary: 3D folding (R-group interactions)
Quaternary: Multiple polypeptide chains

Nucleic Acids

Types and Functions

DNA (deoxyribonucleic acid): Genetic material, double helix structure
RNA (ribonucleic acid): Protein synthesis, single-stranded

Nucleotide Structure

Each nucleotide contains a pentose sugar, a phosphate group, and a nitrogenous base.

ATP (Adenosine Triphosphate)

Role in the Body

ATP is the primary energy carrier in cells.
Energy is released by breaking high-energy phosphate bonds:

ATP is replenished by oxidation of food fuels.

Summary Table: Organic Molecules

Molecule	Monomer	Main Elements	Key Function
Carbohydrates	Monosaccharides	C, H, O	Energy, structure
Proteins	Amino acids	C, H, O, N, (S)	Structure, enzymes, signaling
Lipids	Fatty acids, glycerol	C, H, (O)	Energy storage, membranes
Nucleic acids	Nucleotides	C, H, O, N, P	Genetic information

Additional info: These notes expand on the provided slides and text, adding definitions, examples, and tables for clarity and completeness.