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6 types of nutrients – Why we eat Which provide energy? Water Energy (calories) “Building blocks” Essential nutrients Vitamins Minerals Primarily vitamins and minerals Carbohydrates Protein Fats Water is critical for body functions The body is about 70% water Found both inside and outside the cells Functions Helps regulate body temperature Transports nutrients Excretes waste products Food as Fuel Water Nutrients supply energy Protein Carbohydrates These nutrients supply energy (calories) to power muscle contraction, maintain body temp and other cell functions Fats What is a calorie? Cells Break down high energy molecules in food in cellular respiration. Generate many molecules of ATP. Way we measure the energy stored in food Definition: A calorie is the amount of energy required to raise the temperature of one gram of water by 1ºC. Energy (Calories) from Nutrients Nutrient Carbohydrates Energy Carbohydrate 4 Cal/g Protein 4 Cal/g Fat 9 Cal/g Primary source of energy for living organisms Simple sugars Polysaccharides Table sugar, soft drinks Long starch molecules Fat is the most energy-rich nutrient Alcohol contributes 7 Cal/g, but is not a nutrient. Triglycerides: the most common type of fat Why do we need Fats? Dietary fats provide Energy for the body Fat-soluble vitamins Essential fatty acids Long-term energy storage in adipose tissue Kinds of Fatty Acids Saturated Fatty Acids (All Single Bonds C-C) Stored energy for later use Body structure Reduce Heart Disease Risk Trans-Fatty Acids (Hydrogenated) Heighten Heart Disease Risk Not Found Naturally! 3 fatty acids attached to a backbone of glycerol How the body uses fat Heighten Heart Disease Risk Unsaturated Fatty Acids (Some Double Bonds C=C) Triglycerides Make up body fat 95% of fat in food Structure: Cell membranes The brain is 60% lipid Every neuron is insulated by the lipids in its myelin sheath Why do we need Protein? Body structures Helps build muscle, bone, skin and hair Regulates body functions Some hormones are proteins Protects you from illness Antibodies are protein Can be metabolized for energy Sources: Getting the right nutrients Alcohol provides energy (7 Cal/g) But it has no necessary function in the body Toxic when consumed in large amounts meat, eggs, beans, nuts What is a “good diet”? Is alcohol a nutrient? Foods that provide energy Vitamins, minerals and other essential nutrients that the body can’t make Basic advice for good nutrition Eat a variety of foods Eat less Getting the correct amount of food energy (cal) A new look for the Food Pyramid USDA unveiled “MyPlate” this year Simpler than the Food Pyramid Fruit & vegetables take up half the plate Fruits, vegetables and whole grains don’t overeat Avoid too much junk food Exercise more What happens to food after you swallow? Macromolecules in food are broken down → Molecules small enough for cells to absorb Foods are digested by enzymes H2 O Protein Enzymes: proteins that speed up chemical reactions Amino acid OH H Enzyme (pepsin) Carbohydrate H2 O Sugar OH H Enzyme (amylase) Fat Fatty acid Glycerol H2 O H2 O H H O OH H OH H H2 O Enzyme (lipase) Figure 22.3 Food is broken down into its monomers that are recombined into new molecules Cheese protein (a polymer of amino acids in a specific sequence) Summary: Digestion of foods Amino acid monomer Breakdown of protein by human digestive system Amino acids Absorption of amino acids by cells lining the small intestine; transport via bloodstream to other cells Human protein Cells use amino acids from the cheese and other foods to produce new human proteins Figure 22.2-3 Harvesting energy from food Where is the energy in ATP? ATP Or how food gets from to and body structures ADP Why is ATP a good source of energy for cells? Some ways cells use energy It is versatile–can be used in many types of reactions Its breakdown is easily coupled with energy-requiring reactions To build macromolecules To transport molecules across the membrane It provides just the right amount of energy for cellular reactions To power muscle contraction Energy systems: Metabolism how our bodies harvest energy from food 3 ways our body makes ATP Immediate energy system (ATP-CP system) Anaerobic Creatine phosphate ATP CP is stored in muscles in small amounts. Broken down to replenish ATP stores Produces instant energy for sudden movement e.g. a punch or a kick Primary system during low- to moderate-intensity exercise Produces most ATP O2 required All energy systems are used continuously! Carbs are the main energy source for glycolysis The immediate energy system glycolysis system Primary energy system during high intensity exercise Produces a small amount of ATP uses no O2 Aerobic system fastest supply of ATP uses no O2 ATP is generated from the anaerobic metabolism of glucose and glycogen Powers short, maximal bursts of energy Muscle action for lift and hold Glycolysis! Carbs are the main energy source for glycolysis Glycolysis energy system Blood glucose Blood glucose Stored glycogen Stored glycogen Doesn’t require O2 (anaerobic) Aerobic respiration Provides ATP quickly (~100 times faster than aerobic respiration) Inefficient Provides energy for intense activity lasting 1/2 - 2 minutes If oxygen is limiting, ATP is made by glycolysis Does lactic acid buildup cause muscle burn? Blood glucose Stored glycogen Lactic acid (by-product) X Aerobic respiration Endurance events For longer periods of activity the body switches to the Energy is obtained from the breakdown of fat (and carbohydrate) in the presence of oxygen Lactic acid isn’t the culprit Muscle soreness is caused by actual muscle cell damage and inflammation Aerobic exercise aerobic system Once thought that lactic acid causes muscle fatigue and “muscle burn” It takes about 10 million ATP molecules per second to power an active muscle cell Requires fatty acids as fuel ATP production is dependent on oxygen availability Metabolism of fuel molecules Glucose, simple sugars Glycolysis and aerobic respiration work together Glycolysis generates a small amount of ATP Glycolysis and Aerobic energy production Fatty acids Aerobic respiration only O2 Athletic Performance Aerobic respiration Requires O2 Generates the most ATP 34 Is protein used for energy? Small amounts used as Fuel Digested to Strength-and- Endurance power events events Main fuel Glucose Fatty acids ATP production Anaerobic Aerobic Bursts of ATP More ATP, slower No Yes Is oxygen used? Where Is the Energy in Food? Built Into Amino Acids Proteins Enzymes Body Parts Getting energy from food… Stored in chemical bonds between the C, H and O atoms Glucose Enzymes + Mitochondria = Highly Controlled Metabolism is the process of harvesting this energy and converting it to ATP Cellular metabolism releases the energy in chemical bonds so slowly that the energy can be harvested efficiently