Energy Flow Through Living Things: Photosynthesis & Cellular Respiration

1. Energy Flow Through Living Things: Photosynthesis & Cellular Respiration Chapter 8&9

2. 8-1 Energy and Life • Living things need energy to survive • comes from food • energy in most food comes from the sun • Plants use light energy from the sun to produce food • autotrophs organisms that make their own food • Ex - plants • heterotrophs organisms that must obtain energy from the foods they consume • animals

3. Chemical Energy and ATP • Energy – the ability to do work • Forms: light, heat, electricity, chemical compounds • chemical compound that cells use to store and release energy is adenosine triphosphate (ATP) • ATP - basic energy source for all cells

4. Chemical Energy and ATP The three phosphate groups are the key to ATP's ability to store and release energy. • ATP consists of: • adenine • ribose (a 5-carbon sugar) • 3 phosphate groups Adenine Ribose 3 Phosphate groups ATP

5. Chemical Energy and ATP • Storing Energy • ADP has two phosphate groups instead of three. • A cell can store small amounts of energy by adding a phosphate group to ADP. ATP ADP Energy + Energy Adenosine Triphosphate (ATP) Adenosine Diphosphate (ADP) + Phosphate Fullycharged battery Partiallycharged battery

6. Chemical Energy and ATP • Releasing Energy • Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. 2 Phosphate groups P ADP

7. Chemical Energy and ATP ATP energy uses: • cellular activities: active transport, protein synthesis • muscle contraction • Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy. • Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.

8. 8-2 Photosynthesis • Photosynthesis - the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen

9. The Photosynthesis Equation • The Photosynthesis Equation • The equation for photosynthesis is: • 6CO2 + 6H2O C6H12O6 + 6O2 • carbon dioxide + water sugars + oxygen Light Light

10. The Photosynthesis Equation Light energy O2 Light-Dependent Reactions (thylakoids) H2O ADPNADP+ ATPNADPH CO2+H20 Sugar Calvin Cycle (stroma)

11. Light and Pigments • photosynthesis requires chlorophyll • pigments - light-absorbing molecules that gather the sun's energy • The main pigment in plants is chlorophyll. • There are two main types of chlorophyll: • chlorophyll a • chlorophyll b

12. Light and Pigments • Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. 100 80 60 40 20 0 Chlorophyll b Chlorophyll a Estimated Absorption (%) Wavelength (nm) 400 450 500 550 600 650 700 750 Wavelength (nm)

13. Light and Pigments • Chlorophyll does not absorb light will in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. 100 80 60 40 20 0 Chlorophyll b Chlorophyll a Estimated Absorption (%) 400 450 500 550 600 650 700 750 Wavelength (nm)

14. Light Energy • Light is a form of energy • compound that absorbs light also absorbs energy from that light • chlorophyll absorbs light  the energy is transferred directly to electrons in the chlorophyll molecule  raising the energy levels of these electrons • high-energy electrons are what make photosynthesis work

15. Pop Quiz Word Bank ADP Ribose Phosphate groups Bonds ATP Adenine Adenosine • This molecule is called _____. • Energy in this molecule is stored in the _____. 3. 5. 4.

16. 8-3 Inside a Chloroplast • Inside a Chloroplast • In plants, photosynthesis takes place inside chloroplasts. Plant Chloroplast Plant cells

17. Inside a Chloroplast • Chloroplasts contain thylakoids—saclike photosynthetic membranes. Single thylakoid Chloroplast

18. Inside a Chloroplast • Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. • Stroma – space outside of the thylakoids Granum Stroma Chloroplast

19. Inside a Chloroplast • Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Photosystems Chloroplast

20. Photosynthesis Reactions • reactions of photosystems include: • light-dependent reactions (requires light) • take place within the thylakoid membranes • uses water, ADP, and NADP+ • produces oxygen, ATP, and NADPH • light-independent reactions (Calvin cycle) • takes place in the stroma • ATP and NADPH not stable enough to store the energy they carry for more than a few minutes • uses ATP and NADPH energy to build high-energy sugars for long term storage

21. Photosynthesis Reactions • The two sets of photosynthetic reactions work together. • The light-dependent reactions trap sunlight energy in chemical form. • The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water.

22. Inside a Chloroplast H2O CO2 Light NADP+ ADP + P Light- dependent reactions Calvin cycle Calvin Cycle Chloroplast Sugars O2

23. Electron Carriers • electrons in chlorophyll absorb sunlight  electrons gain energy • Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules • One carrier molecule is NADP+. • transport electrons • NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+) - NADP+ NADPH • energy of sunlight can be trapped in chemical form • NADPH carries high-energy electrons to chemical reactions elsewhere in the cell to make carbohydrates

24. Factors Affecting Photosynthesis • Many factors affect the rate of photosynthesis, including: • Water • Temperature • Intensity of light

25. 9-1 Chemical Pathways • Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Cells Animal Mitochondrion Plant Plant Cells

26. Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria. Intermembrane space Outer membrane Mitochondrion Animal Cells Inner membrane Plant Cells Matrix

27. Chemical Energy and Food • Chemical Energy and Food • One gram of the sugar glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy • calorie - the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius • Cells gradually release the energy from glucose and other food compounds beginning with glycolysis - releases a small amount of energy.

28. Overview of Cellular Respiration • If oxygen is present: • cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen • glycolysis  Krebs cycle  electron transport chain • equation: • 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy • oxygen + glucose → carbon dioxide + water + Energy

29. Overview of Cellular Respiration Electrons carried in NADH Electrons carried in NADH and FADH2 Pyruvicacid Glucose Glycolysis Cytoplasm Mitochondrion

30. Overview of Cellular Respiration • Glycolysis – cytoplasm • Krebs cycle and electron transport - mitochondria Glycolysis Cytoplasm Mitochondrion

31. Stretch break You have 2 minutes to talk, stretch, stand up…

32. Glycolysis • the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound • ATP Production • cell uses up 2 molecules of ATP to start the reaction • When glycolysis is complete, 4 ATP molecules have been produced  a net gain of 2 ATP molecules • NADH Production • removes 4 high-energy electrons  electron carrier called NAD+  becomes an NADH molecule. • The NADH molecule holds the electrons until they can be transferred to other molecules.

33. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2 Pyruvic acid

34. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2 Pyruvic acid

35. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2 Pyruvic acid

36. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid

37. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid 2

38. Glycolysis 4 ADP 2 ATP 2 ADP 4 ATP 2NAD+ 2 Pyruvic acid 2 To the electrontransport chain

39. Glycolysis • The Advantages of Glycolysis • very fast - cells can produce thousands of ATP molecules in a few milliseconds • does not require oxygen

40. Fermentation • oxygen is not present  glycolysis is followed by a different pathway - fermentation • Fermentation – release of energy (ATP) from food in the absence of oxygen • cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid • Anaerobic – does not require oxygen

41. Fermentation • Alcoholic Fermentation • Yeasts and a few other microorganisms use alcoholic fermentation • Forms ethyl alcohol and carbon dioxide as wastes • equation: • pyruvic acid + NADH → alcohol + CO2 + NAD+

42. Fermentation • Lactic Acid Fermentation • pyruvic acid that accumulates from glycolysis  converted to lactic acid • regenerates NAD+ so that glycolysis can continue • converts glucose into lactic acid • equation: • pyruvic acid + NADH → lactic acid + NAD+

43. Fermentation • The first part of the equation is glycolysis.

44. Fermentation • The second part shows the conversion of pyruvic acid to lactic acid.

45. The Totals

46. Comparing Photosynthesis and Cellular Respiration • The energy flows in photosynthesis and cellular respiration take place in opposite directions.

47. Comparing Photosynthesis and Cellular Respiration • On a global level, photosynthesis and cellular respiration are also opposites. • 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.