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USING ENERGY

USING ENERGY. Energy is Conserved. But some of it is “lost” Only some Energy is “useful”. We started with 100J of Energy in form of Heat Energy We ended up with only 35 J of useful (electric) Energy. 65 J ended up back as heat. Only 35% Heat Useful E

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USING ENERGY

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  1. USING ENERGY Energy is Conserved. But some of it is “lost” Only some Energy is “useful”

  2. We started with 100J of Energy in form of Heat Energy We ended up with only 35 J of useful (electric) Energy. 65 J ended up back as heat. Only 35% Heat Useful E Efficiency = (useful Energy)/(input Energy)= e In this case e = 35%

  3. Example Problem Light bulbs are rated by the power that they consume, not the light that they emit. A 100 W incandescent bulb emits approximately 4 W of visible light. What is the efficiency of the bulb? Slide 11-12

  4. ENERGY AND US

  5. Checking Understanding When you walk at a constant speed on level ground, what energy transformation is taking place? A. Echem Ug B. UgEth C. Echem K D. Echem Eth E. KEth Slide 11-15

  6. Answer When you walk at a constant speed on level ground, what energy transformation is taking place? A. Echem Ug B. UgEth C. Echem K D. Echem Eth E. KEth Slide 11-16

  7. Example Problem A person lifts a 20 kg box from the ground to a height of 1.0 m. A metabolic measurement shows that in doing this work her body uses 780 J of energy. What is her efficiency? Slide 11-14

  8. Problem How far could a 68 kg person cycle at 15 km/hr on the energy in one slice of pizza? Slide 11-17

  9. 1 cal = 4.2 x 103 J = 4.2 kJ

  10. Problem How far could a 68 kg person cycle at 15 km/hr on the energy in one slice of pizza? Slide 11-17

  11. The work of life What do living things do with chemical energy? 1. Mechanical work muscular contraction motion of parts within cells 2. Maintaining Chemical Balance maintain appropriate concentrations of chemicals within cells 3. Biosynthesis build large biomolecules assemble larger parts of themselves Human Bioenergetics

  12. Basal metabolic rate It takes energy just to stay alive. Basal metabolic rate, or BMR For warm-blooded animals, most energy used to maintain body temperature. Human BMR: 1.0 Cal/kg-h Example: m = 70 kg, 24 hour day Basal metabolism = 1.0 Cal/kg-h * 70 kg * 24 h/day =1680 Cal/day =7 million J/day This doesn’t account for any activity. Human Bioenergetics

  13. Energy needed for activity Calorimetry gives energy needed for various levels of activity. Energy expenditures above basal: Eating, reading 0.4 Cal/kg-h Doing laundry 1.3 Cello playing 1.3 Walking slowly 2.0 Walking 4 mph 3.4 Swimming 2 mph 7.9 Crew race 16.0 Human Bioenergetics

  14. Figuring total caloric needs:One 75 kg person’s day Basal metabolism 1.0 Cal/kg-h * 24 h * 75 kg 1800 Cal Reading, writing, talking, eating, 12.5 h 0.4 Cal/kg-h * 12.5 h * 75 kg 375 Cal Walking slowly, 1 h 2.0 Cal/kg-h * 1 h * 75 kg 150 Cal Playing cello, 1.25 h 1.3 Cal/kg-h * 1.25 h * 75 kg 120 Cal Energy needed for digestion 2500 Cal consumed * 8% 200 Cal Total needs 2645 Cal

  15. Fate of food energy What happens to food energy you ingest? Non-digestible and lost in waste 1 to 9 % Released as heat ~50% Energy required for digestion 6 to 10% Net energy captured chemically 30 to 40% Overall, we only “waste” around 5% of food energy. Cattle waste 30 to 40% of the energy in grass. Cow dung is OK fuel.

  16. Physicist’s guide to weight loss Less Energy in/ more Energy out

  17. Weight gain, weight loss Principle of energy balance should apply to body weight. Our bodies are our stores of chemical energy. If ingested energy matches energy needs, weight is stable. Substantial imbalance causes weight change. Most excess chemical energy stored as adipose tissue (i.e. “fat”.) Exchange rate: 7700 Cal/kg (or 3500 Cal/pound)

  18. How to lose weight Deficit of 3500 Cal ==> Loss of 1 lb of fat. Can you give up 500 Cal/day? 25% of 2000 Cal/day diet, 20% of 2500 Cal/day. Can you exercise to use 3500 Cal/week extra? 7 days/week at 500 Cal/session 50 minutes/day at 600 Cal/hour pace Either gives 3500 Cal deficit in 1 week, so expect to lose 1 pound/week.

  19. Why is it hard to lose weight? Either reducing plan is demanding. 20-25% reduction in intake, or serious pace of exercise. Progress is slow. Have to stick with it. Have to control all variables. If you exercise, don’t eat a lot more. If you diet, don’t reduce your activity. Body may adjust itself. Change in basal metabolic rate? Human Bioenergetics

  20. Metabolic pathways Huge books needed to organize information on set of metabolic reactions needed to build proteins, nucleic acids, polysaccharides, and lipids, and to break them down into simple molecules plus energy. • To a physicist, it seems a miracle that this works. • More miraculous that it works “on its own.” Human Bioenergetics

  21. Biochemistry and energy Energy for cells is provided by ATP

  22. Introducing ATP ATP (adenosine triphosphate) is the cellular currency for energy – it provides the fuel for most cellular activities. ATP has high potential energy and allows cells to do work. ATP works by phosphorylating (transferring a phosphate group) target molecules.

  23. We have to get energy, store it and use it.

  24. ENERGY LEVELS FOR LIFE GLUCOSE PHOTOSYNTHESIS Releases energy - ATPs ATP PROTEINS ETC

  25. As you read this millions of ATP molecules give up their energy in your cells. They provide the energy to keep cells working, make muscles move, synthesize new molecules etc. All the ATP now in your cells will be used up in a few minutes or less. If they are not replaced you will die. They are replaced by the breakdown of sugars and fat in your body.

  26. The Nature of Chemical Energy In cells, electrons are the most important source of chemical potential energy. The amount of potential energy in an electron is based on its position relative to positive and negative charges. Electrons closer to negative charges (from other electrons) and farther from positive charges (in nuclei of nearby atoms), have higher potential energy. In general, a molecule’s potential energy is a function of its electrons’ configuration and position.

  27. Structure and Function of ATP The electrons in ATP have high potential energy because the four negative charges in its three phosphate groups repel each other. Hydrolysis of the bond between the two outermost phosphate groups results in formation of ADP and Pi (inorganic phosphate, H2PO4−) in a highly energy releasing (exergonic) reaction. The released phosphate group is transferred to a protein.

  28. ATP Hydrolysis and Protein Phosphorylation Hydrolysis of ATP is exergonic (gives up energy) Energy released during ATP hydrolysis is transferred to a protein during phosphorylation. This phosphorylation usually causes a change in the protein’s shape.

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