Energy Value of Foods

1. Energy Value of Foods

2. Main Sources of Energy for Cells • Carbohydrates and lipids (fats) • Proteins (in cases of illness or injury) • Cellular respiration is the process which releases chemical energy from foods Glucose + Oxygen gas energy + carbon dioxide + water

3. Energy Value • The amount of energy a food can provide to an organism • Expressed in kilojoules (kJ) • The calorie (Cal) is often used on packaging • 1 Cal= 4.184 kJ Energetic Value of Foods

4. Energy Demands • Basal metabolism • Physical activities • Digestion and absorption of what people eat (10% of daily energy or 1050 kJ) • Teenagers 13-15 years old need on average 10 500 kJ of energy per day

5. Basal Metabolism • Amount of energy required to maintain vital functions- heart beat, respiration, stable body temperature, cellular activities • In general, more elevated in males than females (7000 kJ vs. 5500 kJ)

6. Nutritional Requirements • To meet energy needs, a certain proportion of carbohydrates, lipids, and proteins is needed (vary with age, sex, size, physical activity)

7. Input and Output of EnergyEffects on Mass • Input=Output mass maintained • Input<output loss of mass • Input>output gain of mass The quality of what we eat is important as well

8. Homework • What is the average amount of energy (in kJ) that adolescents needs for their daily activities? • a) What is the name of the energy required to maintain vital functions? b) How much energy is required to maintain vital functions? • Laurie is a very active teenager. She trains several times per week with the swim team. The amount of energy she uses on a daily basis is 13200 kJ. State what would happen to Laurie’s mass in the long term if her food gave her the following amount of energy each day. i) 15 700 kJ ii) 10 300 kJ iii) 13 200kJ

9. Transformation of Food Mechanical and Chemical

10. Mechanical transformation • large pieces of food that are ingested have to be broken into smaller particles that can be acted upon by various enzymes

11. Chemical Transformation • uses water and digestive enzymes to break down molecules • smaller molecules can be absorbed and utilized by the cells

13. Absorption of Nutrients

14. Homework • 1. What are the two types of food transformation in digestion?Explain what happens during each of these transformations • 2. What are the names of the structures or processes described below? A) main facilitators of chemical digestion; digestive juices contain them B) nutrients from the chemical digestion of proteins C) contractions of the digestive tube allowing food to advance D) chemical secretion coming from the pancreas E) secretion allowing mechanical digestion of lipids F) contribute to chemical digestion of proteins in the stomach G) passage of nutrients from the digestive tube to the blood or lymph H) nutrients from the chemical digestion of carbohydrates

15. 3. Indicate in which digestive organ(s) each phenomenon takes place. A) peristalsis B) chewing C) action of gastric juices D) action of bile E) churning F) action of saliva • 4. In which organ does chemical digestion of the following nutrients take place? In which organ does it finish? A) carbohydrates B) proteins C) lipids (fats) • 5. What is the principal site of absorption of the following nutrients? A) water B) glucose C) minerals D) glycerol E) vitamins