Organic Compounds in Anatomy & Physiology

Overview of Organic Compounds

Organic compounds are essential molecules that form the basis of life. They are primarily composed of carbon, hydrogen, and oxygen, and are classified into four major groups: carbohydrates, lipids, proteins, and nucleic acids. Each group has distinct structures and functions that are vital for cellular processes and overall physiology.

Carbohydrates

Structure and Classification

• Monosaccharides: Simple sugars with a 1C:2H:1O ratio, often forming ring structures. Examples include glucose, galactose, fructose, ribose, and deoxyribose.

• Disaccharides: Composed of two monosaccharide subunits joined by a polar covalent bond. Examples: lactose, sucrose, maltose.

• Polysaccharides: Large, highly branched polymers with hundreds of monosaccharide subunits. Example: glycogen.

Functions

• Energy: Glucose is the main fuel for all cells; disaccharides and polysaccharides are broken down to release monosaccharides for energy.

• Structure: Ribose and deoxyribose are components of nucleic acids.

• Energy Storage: Glycogen is stored in the liver and skeletal muscle cells for later use.

Lipids

Structure and Types

• Triglycerides: Consist of three fatty acids bonded to a glycerol backbone. Can be made from various combinations of saturated and unsaturated fatty acids.

• Phospholipids: Composed of two fatty acids and a phosphate group attached to a glycerol backbone. Main component of cell membranes.

• Steroids: Characterized by a four-ringed hydrocarbon structure with various modifications. Includes hormones and cholesterol.

Functions

• Energy Storage: Triglycerides are stored in adipose (fat) cells and released as needed.

• Protection and Insulation: Lipids cushion and insulate organs.

• Structure: Phospholipids form the structural basis of all cell membranes.

• Regulation: Steroid hormones regulate physiological processes; cholesterol is a key component of cell membranes.

Proteins

Structure and Types

• Di- and Polypeptides: Chains of two or 10–50 amino acids, respectively, joined by peptide bonds. Examples: substance P, endorphins, glucagon, calcitonin, insulin.

• Proteins: Polymers of more than 50 amino acids that fold into specific three-dimensional shapes. Examples: collagen, keratin, amylase, albumin, hemoglobin.

Functions

• Structure: Proteins are the primary structural molecules in the body.

• Movement: Involved in cell and muscle movement.

• Catalysis: Many proteins function as enzymes to speed up biochemical reactions.

• Transport: Proteins transport substances throughout the body.

• Defense: Proteins play roles in immune defense mechanisms.

• Regulation: Many act as hormones or chemical messengers.

Nucleotides and Nucleic Acids

Structure and Types

• ATP (Adenosine Triphosphate): Consists of the nitrogenous base adenine, ribose sugar, and three phosphate groups.

• Nucleic Acids: Polymers of nucleotides arranged as a double helix (DNA) or a single strand (RNA).

Functions

• ATP: Main source of chemical energy for the body; drives cellular work.

• Nucleic Acids: DNA stores genetic information and instructions for protein synthesis; RNA carries out these instructions.

ATP Synthesis and Function

• ATP is synthesized from adenosine diphosphate (ADP) and an inorganic phosphate (), a process requiring significant energy, usually derived from glucose catabolism.

• Hydrolysis of ATP releases energy (), which is used by cells to perform work.

• Continuous ATP production is essential; oxygen is required for efficient ATP synthesis, explaining the necessity of breathing.

Summary Table: Organic Compounds

Example: ATP in Cellular Respiration

• During cellular respiration, glucose is broken down in the presence of oxygen to produce ATP, which powers muscle contraction, nerve impulse transmission, and biosynthesis.

Additional info: The hydrolysis of ATP is a key exergonic reaction in metabolism, and the continuous regeneration of ATP from ADP and phosphate is fundamental to sustaining life processes.