Human Digestion Biology

Study Notes

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.

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 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.

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 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.

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 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.

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.

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.