Human Digestion Biology

Digestion and Nutrients

• The purpose of digestion is to convert dietary components into molecules that the body's cells can use, providing energy and raw materials for growth, maintenance, and tissue repair.
• Nutrients are classified into four categories: carbohydrates, fats, proteins, and nucleic acids.
• Carbohydrates are macronutrients that provide energy, and include simple sugars (monosaccharides and disaccharides), complex carbohydrates (polysaccharides), and fiber.
• Fats are the most energy-dense nutrient, and include triglycerides, phospholipids, and cholesterol.
• Proteins are composed of amino acids and are essential for growth, maintenance, and repair.
• Nucleic acids are found in RNA and DNA.

Carbohydrates

• Simple sugars are the fastest energy source and include glucose, fructose, and galactose.
• Disaccharides are formed by dehydration synthesis and include maltose, sucrose, and lactose.
• Complex carbohydrates (polysaccharides) include starch, cellulose, and glycogen.
• Starch is an energy storage polysaccharide found in plants, while cellulose is a structural polysaccharide found in plant cell walls.
• Glycogen is a storage polysaccharide found in animals.

Fats

• Fats are insoluble in water and consist of one glycerol molecule bonded to three fatty acid molecules.
• Unsaturated fats are considered healthy, while saturated fats are considered unhealthy.
• Cholesterol is a waxy steroid found in cell membranes, and is essential for hormone production.
• High cholesterol levels can lead to atherosclerosis, heart disease, and gallstones.

Protein

• Proteins are composed of amino acids and are essential for growth, maintenance, and repair.
• Protein structure can be classified into primary, secondary, tertiary, and quaternary structures.
• Denaturation is a temporary change in protein shape, while coagulation is a permanent change.

Vitamins and Minerals

• Vitamins are essential nutrients required in small quantities for various bodily functions.
• Vitamins A, B, C, and D are essential for vision, energy metabolism, bone growth, and immune function.
• Minerals are essential nutrients required for various bodily functions, including bone growth, nerve function, and blood health.

Indicator Tests

• Benedict's test is used to detect simple sugars, with a positive result indicating the presence of glucose.
• Iodine test is used to detect starch, with a positive result indicating the presence of amylose.
• Biuret test is used to detect proteins, with a positive result indicating the presence of peptides.
• Translucence test is used to detect lipids, with a positive result indicating the presence of fatty acids.

Enzymes

• Enzymes are biological catalysts that speed up chemical reactions at low temperatures.
• Enzymes are specific to particular substrates and have an active site where the substrate binds.
• The enzyme-substrate complex forms a reaction product, which is then released.

Digestive System

• The digestive system consists of the alimentary canal and accessory organs.
• The alimentary canal includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.
• The accessory organs include the liver, pancreas, gallbladder, and salivary glands.

Processes of Digestion

• Ingestion is the process of taking in food.
• Digestion is the breakdown of food into smaller molecules.
• Absorption is the process of taking in nutrients through the bloodstream.
• Egestion is the process of eliminating waste products.

Organs of the Digestive System

• Liver: synthesizes, breaks down, stores, and detoxifies nutrients.
• Gallbladder: stores bile, which is used to break down fats.
• Pancreas: produces bicarbonate ions, carbohydrates, proteases, and lipases to break down nutrients.
• Small intestine: completes digestion and absorbs nutrients.
• Large intestine: absorbs water, electrolytes, and vitamins, and stores feces.
• Anus: a sphincter that relaxes to allow defecation.