Energy Value of Foods Main Sources of Energy

Energy Value of Foods

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

Energy Value • The amount of energy a food can provide to an organism • Expressed in kilojoules (k. J) • The calorie (Cal) is often used on packaging • 1 Cal= 4. 184 k. J Energetic Value of Foods Carbohydrates Lipids (fats) Proteins 17 k. J/g 37 k. J/g 17 k. J/g

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

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 k. J vs. 5500 k. J)

Nutritional Requirements • To meet energy needs, a certain proportion of carbohydrates, lipids, and proteins is needed (vary with age, sex, size, physical activity) Energy values Carbohydrates in … Lipids Proteins % of Kilojoules (k. J) 55% of k. J ingested 30% of k. J ingested 15% of k. J ingested Grams (g) 340 g 85 g 93 g

Input and Output of Energy Effects 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

In class work 1. 2. 3. 4. What is the average amount of energy (in k. J) 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 k. J. 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 k. J ii) 10 300 k. J iii) 13 200 k. J

Transformation of Food Mechanical and Chemical

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

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

Organs of digestive system Mechanical transformation Glands Secretion from glands Foods transformed Results of transformation 1. Mouth Chewing Salivary Saliva carbohydrates Carbohydrates partially broken down 2. Pharynx Swallowing - - 3. Esophagus peristalsis - - 4. Stomach • Churning • Peristalsis Gastric juices proteins Proteins partially digested 5. small intestine • Emulsion of lipids by bile(secreted by the liver) • churning • Peristalsis pancreas Intestinal Pancreatic juices Intestinal juices Carbohydrates partially digested Proteins partially digested Lipids(fats) Glucose Amino acids Fatty acids Glycerol 6. large intestine • churning • Peristalsis - -

Absorption of Nutrients Site of Absorption Nutrients Absorbed Small intestine Glucose Amino acids Fatty acids Glycerol Water Vitamins minerals Large intestine Water Vitamins minerals

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 lucu. pbworks. com

• 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