1. Lesson Overview Lesson Overview Energy and Life Energy & Life Submitted by Joe McCoy (April 2013)

2. Lesson Overview Lesson Overview Energy and Life Chemical Energy and ATP One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP). ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.

3. Lesson Overview Lesson Overview Energy and Life Storing Energy Adenosine diphosphate (ADP) looks almost like ATP, except that it has two phosphate groups instead of three. ADP contains some energy, but not as much as ATP. When a cell has energy available, it can store small amounts of it by adding phosphate groups to ADP, producing ATP. ADP is like a rechargeable battery that powers the machinery of the cell.

4. Lesson Overview Lesson Overview Energy and Life Using Biochemical Energy One way cells use the energy provided by ATP is to carry out active transport. Many cell membranes contain sodium-potassium pumps. ATP provides the energy that keeps these pumps working, maintaining a balance of ions on both sides of the cell membrane.

5. Lesson Overview Lesson Overview Energy and Life Using Biochemical Energy ATP powers movement, providing the energy for motor proteins that contract muscle and power the movement of cilia and flagella.

6. Lesson Overview Lesson Overview Energy and Life Heterotrophs and Autotrophs What happens during the process of photosynthesis? In the process of photosynthesis, plants convert the energy of sunlight into chemical energy stored in the bonds of carbohydrates.

7. Lesson Overview Lesson Overview Energy and Life Heterotrophs and Autotrophs Organisms that obtain food by consuming other living things are known as heterotrophs. Some heterotrophs get their food by eating plants. Other heterotrophs, such as this cheetah, obtain food from plants indirectly by feeding on plant-eating animals. Still other heterotrophs, such as mushrooms, obtain food by decomposing other organisms.

8. Lesson Overview Lesson Overview Energy and Life Heterotrophs and Autotrophs Organisms that make their own food are called autotrophs. Plants, algae, and some bacteria are able to use light energy from the sun to produce food. The process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates that can be used for food is known as photosynthesis.

9. Lesson Overview Lesson Overview Energy and Life Pigments Plants gather the sun’s energy with light-absorbing molecules called pigments. The plants’ principal pigment is chlorophyll.

10. Lesson Overview Lesson Overview Energy and Life Pigments The two types of chlorophyll found in plants, chlorophyll a and chlorophyll b, absorb light very well in the blue-violet and red regions of the visible spectrum, but not in the green region, as shown in the graph. Leaves reflect green light, which is why plants look green.

11. Lesson Overview Lesson Overview Energy and Life Pigments Plants also contain red and orange pigments such as carotene that absorb light in other regions of the spectrum.

12. Lesson Overview Lesson Overview Energy and Life Pigments Most of the time, the green color of the chlorophyll overwhelms the other pigments, but as temperatures drop and chlorophyll molecules break down, the red and orange pigments may be seen.

13. Lesson Overview Lesson Overview Energy and Life Chloroplasts Photosynthesis takes place inside organelles called chloroplasts. Chloroplasts contain saclike photosynthetic membranes called thylakoids, which are interconnected and arranged in stacks known as grana.

14. Lesson Overview Lesson Overview Energy and Life Chloroplasts Pigments are located in the thylakoid membranes. The fluid portion outside of the thylakoids is known as the stroma.

15. Lesson Overview Lesson Overview Energy and Life Energy Collection Because light is a form of energy, any compound that absorbs light absorbs energy. Chlorophyll absorbs visible light especially well. When chlorophyll absorbs light, a large fraction of the light energy is transferred to electrons. These high-energy electrons make photosynthesis work.

16. Lesson Overview Lesson Overview Energy and Life High-Energy Electrons What are electron carrier molecules? An electron carrier is a compound that can accept a pair of high-energy electrons and transfer them, along with most of their energy, to another molecule.

17. Lesson Overview Lesson Overview Energy and Life High-Energy Electrons NADP + (nicotinamide adenine dinucleotide phosphate) is a carrier molecule. NADP + accepts and holds two high-energy electrons, along with a hydrogen ion (H + ). In this way, it is converted into NADPH. The NADPH can then carry the high-energy electrons to chemical reactions elsewhere in the cell.

18. Lesson Overview Lesson Overview Energy and Life An Overview of Photosynthesis What are the reactants and products of photosynthesis? Photosynthesis uses the energy of sunlight to convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products).

19. Lesson Overview Lesson Overview Energy and Life An Overview of Photosynthesis Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen. In symbols: 6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 In words: Carbon dioxide + Water  Sugars + Oxygen

20. Lesson Overview Lesson Overview Energy and Life An Overview of Photosynthesis Plants use the sugars generated by photosynthesis to produce complex carbohydrates such as starches, and to provide energy for the synthesis of other compounds, including proteins and lipids.

21. Lesson Overview Lesson Overview Energy and Life Light-Dependent Reactions Photosynthesis involves two sets of reactions. The first set of reactions is known as the light-dependent reactions because they require the direct involvement of light and light-absorbing pigments.

22. Lesson Overview Lesson Overview Energy and Life Light-Dependent Reactions The light-dependent reactions use energy from sunlight to produce ATP and NADPH. These reactions take place within the thylakoid membranes of the chloroplast.

23. Lesson Overview Lesson Overview Energy and Life Light-Dependent Reactions Water is required as a source of electrons and hydrogen ions. Oxygen is released as a byproduct.

24. Lesson Overview Lesson Overview Energy and Life Light-Independent Reactions Plants absorb carbon dioxide from the atmosphere and complete the process of photosynthesis by producing sugars and other carbohydrates. During light-independent reactions, ATP and NADPH molecules produced in the light-dependent reactions are used to produce high- energy sugars from carbon dioxide.

25. Lesson Overview Lesson Overview Energy and Life Light-Independent Reactions No light is required to power the light-independent reactions. The light-independent reactions take place outside the thylakoids, in the stroma.

26. Lesson Overview Lesson Overview Energy and Life Chemical Energy and Food Energy stored in food is expressed in units of calories. A Calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. 1000 calories = 1 kilocalorie, or Calorie. Cells use all sorts of molecules for food, including fats, proteins, and carbohydrates. The energy stored in each of these molecules varies because their chemical structures, and therefore their energy-storing bonds, differ. Cells break down food molecules gradually and use the energy stored in the chemical bonds to produce compounds such as ATP that power the activities of the cell.

27. Lesson Overview Lesson Overview Energy and Life Overview of Cellular Respiration What is cellular respiration? Cellular respiration is the process that releases energy from food in the presence of oxygen.

28. Lesson Overview Lesson Overview Energy and Life Overview of Cellular Respiration If oxygen is available, organisms can obtain energy from food by a process called cellular respiration. The summary of cellular respiration is presented below. In symbols: 6 O 2 + C 6 H 12 O 6  6 CO 2 + 6 H 2 O + Energy In words: Oxygen + Glucose  Carbon dioxide + Water + Energy The cell has to release the chemical energy in food molecules (like glucose) gradually, otherwise most of the energy would be lost in the form of heat and light.

29. Lesson Overview Lesson Overview Energy and Life Stages of Cellular Respiration The three main stages of cellular respiration are glycolysis, the Krebs cycle, and the electron transport chain.

30. Lesson Overview Lesson Overview Energy and Life Stages of Cellular Respiration Glycolysis produces only a small amount of energy. Most of glucose’s energy (90%) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis.

31. Lesson Overview Lesson Overview Energy and Life Stages of Cellular Respiration During the Krebs cycle, a little more energy is generated from pyruvic acid.

32. Lesson Overview Lesson Overview Energy and Life Stages of Cellular Respiration The electron transport chain produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

33. Lesson Overview Lesson Overview Energy and Life Oxygen and Energy Pathways of cellular respiration that require oxygen are called aerobic. The Krebs cycle and electron transport chain are both aerobic processes. Both processes take place inside the mitochondria.

34. Lesson Overview Lesson Overview Energy and Life Oxygen and Energy Gylcolysis is an anaerobic process. It does not directly require oxygen, nor does it rely on an oxygen-requiring process to run. However, it is still considered part of cellular respiration. Glycolysis takes place in the cytoplasm of a cell.

35. Lesson Overview Lesson Overview Energy and Life Comparing Photosynthesis and Cellular Respiration What is the relationship between photosynthesis and cellular respiration? Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food.

36. Lesson Overview Lesson Overview Energy and Life Comparing Photosynthesis and Cellular Respiration Photosynthesis and cellular respiration are opposite processes. The energy flows in opposite directions. Photosynthesis “deposits” energy, and cellular respiration “withdraws” energy. The reactants of cellular respiration are the products of photosynthesis and vice versa.

37. Lesson Overview Lesson Overview Energy and Life Comparing Photosynthesis and Cellular Respiration The release of energy by cellular respiration takes place in plants, animals, fungi, protists, and most bacteria. Energy capture by photosynthesis occurs only in plants, algae, and some bacteria.

38. Lesson Overview Lesson Overview Energy and Life Fermenation How do organisms generate energy when oxygen is not available? In the absence of oxygen, fermentation releases energy from food molecules by producing ATP.

39. Lesson Overview Lesson Overview Energy and Life Fermentation Fermentation is a process by which energy can be released from food molecules in the absence of oxygen. Fermentation occurs in the cytoplasm of cells.

40. Lesson Overview Lesson Overview Energy and Life Fermentation Under anaerobic conditions, fermentation follows glycolysis. During fermentation, cells convert NADH produced by glycolysis back into the electron carrier NAD +, which allows glycolysis to continue producing ATP.

41. Lesson Overview Lesson Overview Energy and Life Alcoholic Fermentation Yeast and a few other microorganisms use alcoholic fermentation that produces ethyl alcohol and carbon dioxide. This process is used to produce alcoholic beverages and causes bread dough to rise.

42. Lesson Overview Lesson Overview Energy and Life Alcoholic Fermentation Chemical equation: Pyruvic acid + NADH  Alcohol + CO 2 + NAD +

43. Lesson Overview Lesson Overview Energy and Life Lactic Acid Fermentation Most organisms, including humans, carry out fermentation using a chemical reaction that converts pyruvic acid to lactic acid. Chemical equation: Pyruvic acid + NADH  Lactic acid + NAD +

44. Lesson Overview Lesson Overview Energy and Life Energy and Exercise How does the body produce ATP during different stages of exercise? For short, quick bursts of energy, the body uses ATP already in muscles as well as ATP made by lactic acid fermentation. For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP.

45. Lesson Overview Lesson Overview Energy and Life Quick Energy Cells normally contain small amounts of ATP produced during cellular respiration, enough for a few seconds of intense activity. Lactic acid fermentation can supply enough ATP to last about 90 seconds. However, extra oxygen is required to get rid of the lactic acid produced. Following intense exercise, a person will huff and puff for several minutes in order to pay back the built-up “oxygen debt” and clear the lactic acid from the body.

46. Lesson Overview Lesson Overview Energy and Life Long-Term Energy For intense exercise lasting longer than 90 seconds, cellular respiration is required to continue production of ATP. Cellular respiration releases energy more slowly than fermentation does. The body stores energy in the form of the carbohydrate glycogen. These glycogen stores are enough to last for 15 to 20 minutes of activity. After that, the body begins to break down other stored molecules, including fats, for energy.