Food and Digestion - Summary Notes

Learning Objectives

Understand the components of a balanced diet: carbohydrates, protein, lipid, vitamins, minerals, water, and dietary fiber.
Identify sources and functions of carbohydrates, protein, lipid, vitamins A, C, and D, calcium and iron, water, and dietary fiber.
Understand how energy needs change with activity, age, and pregnancy.
Identify elements in carbohydrates, proteins, and lipids.
Describe carbohydrates, proteins, and lipids as large molecules from smaller units.
Describe the alimentary canal: mouth, oesophagus, stomach, small intestine, large intestine, and pancreas.
Understand peristalsis.
Understand digestive enzymes: amylase/maltase (starch to glucose), proteases (proteins to amino acids), lipases (lipids to fatty acids and glycerol).
Understand bile production (liver), storage (gall bladder), and its roles in neutralizing stomach acid and emulsifying lipids.
Understand small intestine adaptations for absorption, including villi.
Investigate the energy content in a food sample.

A balanced diet includes carbohydrates, lipids, proteins, minerals, and vitamins, along with dietary fiber and water, in the right amounts for health.

Main fuel for energy, cells release energy by oxidizing glucose during cell respiration.
Sources: fruits, vegetables, starch (potatoes, rice, wheat).
Starch: A polymer of glucose, storage carbohydrate in plants.
Glycogen: Similar to starch, found in animal tissues (liver, muscle) for energy storage.
Cellulose: A polymer of glucose, forms plant cell walls, indigestible by humans but functions as dietary fiber.

Contain carbon, hydrogen, and oxygen; lower proportion of oxygen than in carbohydrates.
Function: Energy storage, insulation, protection of organs, essential part of cell structure.
Made of glycerol and fatty acids.
Too much saturated fat and cholesterol can lead to heart disease.

Make up about 18% of body mass, needed for growth and repair.
Sources: meat, fish, cheese, eggs, beans, peas, and nuts.
Polymers made from 20 different amino acids, contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
Proteins function as structural components (collagen, keratin) and enzymes (haemoglobin).

Elements from food needed for various functions.
Examples: calcium (teeth, bones), iron (haemoglobin).
Deficiency can cause diseases like rickets (calcium deficiency) or anaemia (iron deficiency).

Starch test: Iodine solution turns blue-black.
Glucose test: Benedict's solution and heat form a brick-red precipitate.
Protein test (Biuret test): Potassium hydroxide and copper sulfate turn the solution purple.
Lipid test: Ethanol dissolves lipids, creating a cloudy emulsion in water

Measured in kilojoules (kJ).
Carbohydrates: 17 kJ/g
Lipids: 39 kJ/g
Proteins: 18 kJ/g
Energy needs depend on age, size, and activity level.
Calorimeter measures energy content by burning food and measuring heat released.

Digestion: Breakdown of large insoluble molecules into small soluble ones for absorption.
Mechanical Digestion: Physical breakdown of food (e.g., chewing).
Chemical Digestion: Enzymes break down food.

Villi: Increase surface area for absorption.
Microvilli: Further increase surface area on villi cells.
Lacteals: Absorb products of fat digestion.
Epithelium: Single layer of cells for easy diffusion.
Hepatic Portal Vein: Transports absorbed food to the liver.
Assimilation: The process of soluble food molecules being absorbed from the blood into cells of the body's tissues, and used to build new parts of cells.