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Food as Fuel
• Cells need energy to function.
• Nutrients from food are digested and circulated throughout the body.
• A nutrient is any substance that has a useful function in the body.
• Calorie: heat required to raise temperature of 1g of H2O by 1°C
Organic vs. Inorganic
• Organic: Produced by living organisms.– Carbohydrates, protein, fats and vitamins.
• Inorganic: From rocks, soil and seas.– Water and minerals.
Macronutrients vs. Micronutrients
• Macronutrients - Needed in large amounts.– Carbohydrates, proteins and fats.
• Micronutrients - Needed in small amounts.– Vitamins and minerals.
Carbohydrates
• Composed of carbon, hydrogen & oxygen.
• Major source of energy.– Starches, etc.
• Made up of sugars– Ready source of glucose
• Excess stored as glycogen or as fat.
• Cellulose (fibre) indigestible but important.
Fats
• Concentrated source of energy– 2x the energy of carbs
• Also made of C, H and
O but in different ratio• Also used for insulation, forms
cell membranes, protects vital organs & increases nerve transmission.
Fats
• Unsaturated fats: Liquid at room temperature.– Easier for body to digest– e.g., olive oil, canola oil
• Saturated fats: Solid at room temperature.– Harder for the body to digest– e.g., butter, lard
Proteins
• Most abundant compound in body• Used throughout the body
– Structure for skin, organs, bones, etc. – Also enzymes and hormones
• Made of 20 amino acids– 8 are essential - get from diet
• Meat, eggs, milk, fish, etc.
Micronutrients
• Not an energy source• Consumed in small
amounts• Vitamins – Growth &
muscle function.- Often act as coenzymes.
• Minerals – e.g., iron (blood), calcium (bones), etc.
Water
• Most abundant substance in body.
• 90% of blood plasma.
• Transports all nutrients.
• Forms extracellular fluid between cells.
• Regulates body temperature