Chapter 7-Energy from Food

1. Chapter 7-Energy from Food Life on Earth is solar-powered. Photosynthetic organisms convert the energy of sunlight into chemical energy in foods.

2. Classification of Organisms • Autotrophs (self-feeders)=Producers. • Start with inorganic molecules and make organic molecules. • Process of Photosynthesis: reactants products. 6CO2 + 6H2O+ energy C6H12O6 + 6O2. • Plants, algae,seaweed, and photosynthetic bacteria. • Heterotrophs (other eaters)=Consumers. • Obtain food by eating producers or other consumers.

3. Cellular Respiratation • Producers and consumers-plants and animals. • Chemical process- oxygen converts chemical energy in food into chemical energy of ATP Reactants Products C6H12O6 + 6O2 6CO2 + 6H2O + energy (38 ATP) • ATP main energy source for work.

4. Chemical Recycling • Water, carbon dioxide (CO2), oxygen, and glucose are continually recycled.

5. Concept 7.2- Energy • Definition of energy- • 2 basic forms- • Kinetic energy- energy in motion • Potential energy- stored energy • Example- climbing stairs. • Class examples- • Energy is not created or destroyed. • Energy is converted from one form to another.

6. Water slide analogy-. • What happens to the energy as we come to a stop? • What is thermal energy? • A type of kinetic energy in which there is random movement of molecules. • Heat is thermal energy that is transferred from a warmer object to a cooler one. • The thermal energy that occurs when we exercise cannot be retrieved. To do more work we need more energy provided by the foods we eat.

7. Chemical Energy -a form of potential energy found stored in foods.

8. Putting Chemical Energy to Work • Organic molecules in food are high in chemical energy • Glucose reacts with oxygen in cellular respiration. • The “exhaust” is water and carbon dioxide. • Cells are more efficient than autos. 40% of energy from food is used for work. • The other 60% is lost as heat (thermal energy) • Calorie= amount of energy to raise the temperature of 1 gram of water by 10 C. • A calorie is too small- We use kcal=1,000 cal.

9. ATP provides energy for the cell • Key- Chemical energy in food has to be converted to energy stored in ATP. • ATP Adenosine triphosphate. • Adenosine= 5 carbon sugar ribose + nitrogen containing compound adenine. • Triphosphate= tail of 3 phosphate groups.

11. How ATP Packs Energy • The phosphate groups are the source of energy. • Each phosphate group is negatively charged and since like charges repel, this contributes to the potential energy stored in ATP. • Spring comparison. • A chemical reaction breaks one of the phosphate bonds and potential energy is released. • The result is ADP= Adenosine diphosphate.

12. Types of Cellular Work • The Phosphate group is transferred to another molecule by specific enzymes. • The molecule that accepts the phosphate group changes, driving the work. • 3 types of work- • Chemical work- building molecules • Transport Work- moving solutes across membranes • Mechanical Work- muscle contractions.

13. ATP Cycle is Continuous • Work consumes ATP. • ADP and phosphate regenerate ATP. • The source of this energy is the organic molecules in the food we eat. • Very fast reaction.

14. Cellular Respiration • An aerobic process- Oxygen is needed • Cellular respiration’s main function to generate ATPs • Cellular respiration transfers hydrogen and carbon atoms from glucose to oxygen forming CO2 and H2O. • “Falling electrons”-released from C-H bonds fall towards oxygen ( an electron grabber), releasing energy. • Electron Transport Chains- a series of transfers in which electrons are passed from one electron carrier to the next releasing energy to make ATP.

15. 3 stages of Cellular Respiration • Stage 1- Glycolysis- “splitting of sugar.” • occurs in the cytoplasm of the cell. • Oxygen is not used in this step- Anaerobic. • 6 C glucose molecule is broken down into two 3C pyruvic acid molecules. • Results in 2 ATPs being produced. • Glycolysis transparency- figure 7-17 pg. 149.

16. Glycolysis:

17. Stage 2- Krebs Cycle. • Occurs in the cell’s mitochondria. • Each Pyruvic acid (from glycolysis) is broken down into a 2C molecule called Acetyl CoA. • Each AcetylCoA enters the Krebs cycle and produces 1 ATP. • Since there are two Pyruvic acid molecules this results in 2 ATPs per glucose molecule. • Krebs Cycle transparency- figure 7-18 pg.150.

18. Krebs Cycle

19. Stage 3- Electron Transport Chain. • Occurs in inner membrane of mitochondria. • 2 parts. • Electron transport chain. • Electrons are pulled to oxygen at the end of the chain. • ATP production. • Energy released during each transfer provides for ATP to be formed from ADP and Phosphate. • Results in 34 ATPs per glucose molecule.

20. Electron Transport Chain. • A staircase, releasing energy at each step.

21. Electron Transport Chain

23. Result of Cellular Respiration • To generate ATP for cellular work. • One glucose molecule yields 38 ATP. • Glycolysis= 2 ATP. • Krebs Cycle= 2 ATP. • Electron Transport Chain= 34 ATP. • Most ATP production requires oxygen. • We cannot survive long without oxygen!!!

24. Fermentation- Anaerobic • Makes ATP when oxygen is not available. • Makes ATP from glycolysis. • Yield of 2 ATP. • Fermentation regenerates enough ATP for short bursts of activity. • Ex. A sprint (not a marathon). • Fermentation in muscle cells produces lactic acid – a waste product resulting in fatigue. • Since oxygen is consumed to convert lactic acid back to pyruvic acid, we have increased breathing after exercise.

25. Fermentation in Microorganisms • Yeast ferment sugar producing alcohol. • This is alcoholic fermentation. • Beer, wine, champagne. • Baker’s yeast- CO2- makes bread rise. • Fungi and bacteria produce lactic acid in fermentation. • Milk is transformed into yogurt and cheese. • Cabbage is transformed into sauerkraut.