Energy Value of Foods. Main Sources of Energy for Cells Carbohydrates and lipids (fats) Proteins (in cases of illness or injury) Cellular respiration

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  • Energy Value of Foods

  • Main Sources of Energy for CellsCarbohydrates 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 organismExpressed in kilojoules (kJ)The calorie (Cal) is often used on packaging1 Cal= 4.184 kJ Energetic Value of Foods

    CarbohydratesLipids (fats)Proteins17kJ/g37kJ/g17kJ/g

  • Energy DemandsBasal metabolismPhysical activitiesDigestion 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

  • Basal MetabolismAmount 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)

  • Nutritional RequirementsTo 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 EnergyEffects on Mass

    Input=Output mass maintainedInputoutput gain of mass

    The quality of what we eat is important as well

  • HomeworkWhat 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 Lauries mass in the long term if her food gave her the following amount of energy each day. i) 15 700 kJii) 10 300 kJiii) 13 200kJ

  • Transformation of FoodMechanical and Chemical

  • Mechanical transformationlarge 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 moleculessmaller molecules can be absorbed and utilized by the cells

  • Absorption of Nutrients

  • Homework1. 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 themB) nutrients from the chemical digestion of proteinsC) contractions of the digestive tube allowing food to advanceD) chemical secretion coming from the pancreasE) secretion allowing mechanical digestion of lipidsF) contribute to chemical digestion of proteins in the stomachG) passage of nutrients from the digestive tube to the blood or lymphH) nutrients from the chemical digestion of carbohydrates

  • 3. Indicate in which digestive organ(s) each phenomenon takes place.A) peristalsisB) chewingC) action of gastric juicesD) action of bileE) churningF) action of saliva4. In which organ does chemical digestion of the following nutrients take place? In which organ does it finish?A) carbohydratesB) proteinsC) lipids (fats)5. What is the principal site of absorption of the following nutrients?A) waterB) glucoseC) mineralsD) glycerolE) vitamins

    Carbohydrates:The most important source of energy.Makes up the largest part of our diets.a. Source: Plantsb. Composition: Carbohydrates are made up of either a single sugar molecule or a chain of sugar molecules. Monosaccharide: One sugarExamples: Glucose (C6H12O6), Galactose, FructoseDisaccharide: Two sugarsExample: Sucrose = Glucose + FructosePolysaccharides: Many sugars Examples: Starch: stores energy in plantsCellulose component of the cell wall in plants, cannot be digested by humans = fiber. LipidsSupply energy to the body.Difficult for the body to break down so you stay full longer. Storage compound: one gram of lipid contains about twice the amount of energy as one gram of carbohydrate or protein. Three groups:Fats, oils, waxes (waterproof coating of plant leaves)Phospholipids (cell membrane)Steroids (make hormones)Most common type of lipid = one glycerol and three fatty acids. Lipids are insoluble in water.ProteinsProteins are used in cells to build cell structures and are used in chemical activities. Enzymes are proteins that aid in the reactions that occur during processes such as digestion and respiration.Proteins are composed of 20 amino acids arranged in different orders and of different lengths. There are 8 amino acids that are not made by the body. These essential amino acids must be obtained from the food we eat. Vitamins, minerals, water do not give the cell any energyBasal metabolic rate- amount of energy required to perform vital functions such as heartbeat, respiration, basic cellular activitiesTable of values represents requirements for adolescentsChanges due toChange in amount of physical activity Change in amount of food consumed

    Mechanical Digestion - Food is crushed and liquefied by the teeth, tongue, and peristaltic contractions (waves of involuntary muscle contraction) of the stomach and small intestine. This creates a greater surface area for the digestive enzymes to work upon. The complex molecules of carbohydrates, proteins, and fats are transformed by chemical digestion into smaller molecules that can be absorbed and utilized by the cells. Does not completely break down all moleculesChemical Digestion - Many glandular structures, dispersed throughout the body, are involved in breaking food into simple molecules that can be absorbed. In the mouth, the salivary glands produce saliva, which both lubricates food and begins the process of starch digestion. Saliva contains salivary amylase (ptyalin), an enzyme that digests starch to maltose (a disaccharide). As food leaves the mouth, the esophagus conducts it to the stomach via the cardiac sphincter by means of peristaltic waves of smooth muscle contraction.

    During mastication, salivary glands secrete saliva to soften the food into a bolus (semi-solid lump) Once food gets partially broken down in the stomach, it becomes a thin watery liquid called chyme. Glucose; Amino acids; Fatty acids;Glycerol- biggest part of absorptionWater;vitamins; minerals- start of absorptionIn large intestine- water; vitamins;minerals-biggest part of absorption


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