Photosynthesis and Cellular Respiration

1. Photosynthesis and Cellular Respiration Honors Biology

2. Photosynthesis and respiration form a continuous cycle because the products of one process are the reactants for the other.

3. Photosynthesis • Reactants: CO2, H2O, light • Products: Carbohydrate, O2 • Write the equation…

4. Where do the reactants come from? How do they get into the plant? • Water from rain – through roots – remember CAPILLARY ACTION • CO2 into leaves through stomata – openings in the leaf • Light is trapped by chlorophyll in leaf cells

5. Stomata allow CO2 to enter and O2 and H2O to exit. Guard cells control the opening and closing of the stomata.

6. Cellular Respiration • Reactants: carbohydrates, O2 • Products: CO2, H2O, and ATP for cell processes • Write the equation…

7. Energy is stored in organic molecules made by linking carbon atoms together. Excess carbohydrates produced by plants provide food for animals.

8. Before we start… • An electron carrier is an energy carrier. • NADPH • NADH • FADH2

9. Photosynthesis is the process that transforms light energy to chemical bond energy.

10. It takes place in the Chloroplast. • Thylakoid membrane: internal membranes that trap energy • Grana: stack of membranes • Stroma: liquid portion of chloroplast

11. Photosynthesis consists of two reactions: light reactions and Calvin Cycle.

13. LIGHT REACTIONS: the “photo” in photosynthesis

15. Electrons in chlorophyll absorb Energy: when enough is absorbed, electrons leave and release Energy along electron transport chains.

16. Chlorophyll F A new kind of chlorophyll that catches sunlight from just beyond the red end of the visible light spectrum has been discovered. The new pigment extends the known range of light that is usable by most photosynthetic organisms. Harnessing this pigment’s power could lead to biofuel-generating algae that are super-efficient, using a greater spread of sunlight than thought possible.

17. Chlorophyll picks up replacement electrons when water is split. Hydrogen’s electrons are taken, leaving H+. Oxygen is released.

19. Energy from one ETC is stored as ATP. H+ are pumped into the thylakoid until the pressure increases and forces the H+ out through ATP synthetase channels into the stroma.

20. Energy from the other ETC is stored as NADPH Excited electrons combine with H+ and NADP (an electron acceptor)

22. NADPH and ATP are used in the Calvin Cycle.

23. REVIEW OF LIGHT REACTION • Light is absorbed • Water is split • NADPH and ATP are produced • Oxygen is released

24. CALVIN CYCLE: the “synthesis” in photosynthesis

25. Carbon Dioxide Fixation: • Carbon (in CO2) is added to a FIVE- Carbon organic compound (already in the cycle) • Produces SIX-Carbon molecule (unstable)

26. IMMEDIATELY • SIX-Carbon Unstable Molecule is split • Produces 2 THREE-Carbon PGA molecules

27. 2 THREE-Carbon PGA • Added to NADPH and ATP (from light reaction) • Produces 2 THREE-Carbon PGAL sugar

28. The 2 THREE-Carbon PGAL may combine to form glucose or another carbohydrate. Most are used to regenerate the original FIVE-Carbon compound to restart the cycle.

29. PGA Original 5-C compound PGAL C6H12O6

30. Review of Calvin Cycle • CO2 used • NADPH and ATP from light reaction used • Glucose produced

31. CELLULAR RESPIRATION

32. Two Stages • Breakdown of Glucose • Production of ATP

33. STAGE 1 • GLYCOLYSIS: “to break up glucose” • Anaerobic: does not require oxygen • Occurs in the cytoplasm

34. STAGE 1 continued • Requires 2 ATP • Glucose is broken down into 2 THREE-Carbon molecules of pyruvate • Produces 2 NADH and 4 ATP • NET gain of 2 ATP

35. After glycolysis, the remainder of the process is aerobic (requires oxygen).

36. STAGE 2 • Pyruvate enters mitochondria • Converted to a TWO Carbon Acetyl group • CO2 is released • NADH is produced • Acetyl group combines with coenzyme A to make Acetyl coA

37. STAGE 2 continued • Acetyl coA enters the Krebs cycle (Citric Acid Cycle) • Acetyl coA combines with a FOUR-Carbon molecule already in the cycle to make a SIX-Carbon molecule (citric acid) • coA is released • CO2 is released from the SIX-Carbon molecule, leaving a FIVE-Carbon molecule (NADH made) • CO2 is released again from the FIVE-Carbon molecule, leaving a FOUR-Carbon molecule (NADH and ATP made)

38. STAGE 2 continued • FOUR-Carbon compound is converted to a new FOUR-Carbon compound, making FADH2 • New FOUR-Carbon compound is converted to the compound that started the cycle • NADH and FADH2 are used in the electron transport chain

39. The short version: • It produces ATP , NADH, and FADH2, and releases CO2

41. STAGE 2 continued • Electron Transport Chain • NADH and FADH2 (from Krebs cycle) pass through the ETC in the inner membranes of mitochondria • Large amounts of ATP produced as H+ are pumped through the membrane • At the end of the ETC, H+ and electrons combine with O2 to form H2O

42. The short version: • It requires oxygen, uses NADH and FADH2, and it produces ATP for cell processes

44. When oxygen is not available • Fermentation occurs in animals: e- from glycolysis are added to organic molecules to form Lactic Acid. • Not very efficient…only 2 ATP • Alcoholic fermentation occurs in fungi and plants: Bacteria and yeast can convert pyruvic acid into alcohol and carbon dioxide.