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 (kJ) The calorie (Cal) is often used on packaging 1 Cal= kJ Energetic Value of Foods CarbohydratesLipids (fats)Proteins 17kJ/g37kJ/g17kJ/g

Energy Demands Basal metabolism Physical activities Digestion and absorption of what people eat (10% of daily energy or 1050 kJ) Teenagers years old need on average kJ 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 kJ vs kJ)

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 in … CarbohydratesLipidsProteins % of Kilojoules (kJ) 55% of kJ ingested 30% of kJ ingested 15% of kJ ingested Grams (g)340g85 g93 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

Homework 1.What is the average amount of energy (in kJ) that adolescents needs for their daily activities? 2.a) What is the name of the energy required to maintain vital functions? b) How much energy is required to maintain vital functions? 3.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 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) kJ ii) kJ iii) kJ

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 GlandsSecretion from glands Foods transformed Results of transformation 1.MouthChewingSalivarySalivacarbohydratesCarbohydrates partially broken down 2.PharynxSwallowing Esophagusperistalsis StomachChurning Peristalsis GastricGastric juicesproteinsProteins 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 AbsorptionNutrients Absorbed Small intestineGlucose Amino acids Fatty acids Glycerol Water Vitamins minerals Large intestineWater 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

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