Photosynthesis and Cellular Respiration

1. Photosynthesis and Cellular Respiration

2. Outline I. Photosynthesis A. Introduction B. Reactions II. Cellular Respiration A. Introduction B. Reactions

3. Review: What is ATP?

4. Review: What is ATP? • Adenosine Triphospate • Adenine + Ribose + 3 Phosphate groups • One of the principle chemical compounds that cells use to STORE and RELEASE energy.

5. Storing Energy • ADP (Adenine diphospate) • Only 2 phosphates (hence the “di”) • Key to how living things STORE energy! • (When energy is available, the cell stores it by adding phosphate to make ATP=stored battery ready to power cell).

6. Releasing Energy • “Shooting off” 1 phosphate  ENERGY!! • ATP provides energy for a variety of cellular activities! • Ex: active transport across cell membranes, protein synthesis, and muscle contraction

7. ADP ATP • Cells regenerate ATP from ADP as needed by using energy in FOOD, aka …

8. ADP ATP • Cells regenerate ATP from ADP as needed by using energy in FOOD, aka … GLUCOSE!

9. Photosynthesis • Photo = light • Synthesis = putting together

10. Photosynthesis • Converting sun energy into chemical energy usable by cells (glucose) • Autotrophs: self feeders, organisms capable of making their own food • Photoautotrophs: use sun energy e.g. plants photosynthesis-makes glucose from light • Chemoautotrophs: use chemical energy, NOT sunlight • e.g. bacteria that use sulfide or methane

11. Photosynthesis • Photosynthesis takes place in specialized structures inside plant cells called chloroplasts • Light absorbing pigment molecules e.g. chlorophyll

12. Why are leaves green? • Chlorophyll absorbs all of the light waves except green. Because the green is not absorbed, it is reflected, so that is the only color wavelength our eye can pick up. • Accessory pigments – help to fill in this gap • Carotenoids – orange (like carrots) • Xanothphyl – yellow

14. Inside the chloroplast • Thylakoids: Sac-like photosynthetic membranes arranged in stacks. • Organize chlorophyll/other pigments into photosystems (clusters that collect light).

15. What does a plant need to survive?

16. Overall Reaction • 6CO2 + 6H2O + light energy → C6H12O6 + 6O2 • Carbon dioxide + water + light  glucose + oxygen KNOW BOTH OF THESE EQUATIONS. YOU WILL SEE THEM AGAIN!

17. 2 types of reactions in photosynthesis • Light dependent • Light independent (CALVIN CYCLE)

18. Electron Carriers • Overview: • Sun excites electrons = gain energy • Need special carrier! (Think red-hot coal!) • Electron acceptor molecules (ex: NADP+) • NADP+ uses hydrogen ions (H+) to trap some of the sunlight in chemical form = converts to NADPH. • Carries e- to other chemical reactions in the cell

19. Light Dependent Reactions • Occur in the thylakoid! • Produce oxygen gas • Converts ADP and NADP+ into energy carriers ATP + NADPH

20. Light Dependent Reactions • Overview: Pigments in Photosystems absorb light = electrons gain energy • Electrons are passed on to the Electron Transport Chain • Does the chorophyll run out of electrons?

21. Light Dependent Reactions • In Thylakoid: • System that provides new e- to chlorophyll to replace ones lost • Electrons come from water! H2O • Enzymes on inner surface membrane of thylakoid break up each H2O into: • 2 e- (replace e- lost to the ETC) • 2H+ions (released inside thylakoid membrane) • 1 oxygen atom (released into the air!)

22. Light-dependent Reactions 5. H+ ions cant cross membrane directly • ATP synthase! • Allows H+ ions to pass through it! • As it turns, binds ADP and phosphate group …. • Producing ATP!

23. Energy Shuttling • Recall ATP: cellular energy-nucleotide based molecule with 3 phosphate groups bonded to it, when removing the third phosphate group, lots of energy liberated= superb molecule for shuttling energy around within cells. • Other energy shuttles-coenzymes (nucleotide based molecules): move electrons and protons around within the cell NADP+, NADPH NAD+, NADP FAD, FADH2

24. This light dependent reaction is the source of nearly ALL of the oxygen in Earth’s atmosphere! Thanks photosynthesis!

25. Light-dependent Reactions • Photosystem: light capturing unit, contains chlorophyll, the light capturing pigment • Electron transport system: sequence of electron carrier molecules that shuttle electrons, energy released to make ATP • Electrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactions • Light reactions yield ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent or dark reactions)

26. Uses: H2O, ADP, and NADP+Makes: Oxygen, ATP, and NADPH

28. Calvin Cycle (light independent or “dark” reactions) • ATP and NADPH generated in light reactions used to fuel the reactions which take CO2 and H+ to make glucose. • Simplified version of how carbon and energy enter the food chain

30. Harvesting Chemical Energy • Plants and animals both use products of photosynthesis (glucose) for metabolic fuel • Heterotrophs: must take in energy from outside sources, cannot make their own e.g. animals • When we take in glucose (or other carbs), proteins, and fats-these foods don’t come to us the way our cells can use them

31. Photosynthesis vs. Cellular Respiration

32. Photosynthesis vs. Cellular Respiration

33. Photosynthesis vs. Cellular Respiration

34. Photosynthesis vs. Cellular Respiration

35. Photosynthesis vs. Cellular Respiration

36. Photosynthesis vs. Cellular Respiration

37. Photosynthesis vs. Cellular Respiration

38. Cellular Respiration Overview • Transformation of chemical energy in food into chemical energy cells can use: ATP • These reactions proceed the same way in plants and animals. Process is called cellular respiration • Overall Reaction: • C6H12O6 + 6O2→ 6CO2 + 6H2O

39. Cellular Respiration Overview • Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell • At this point life diverges into two forms and two pathways • Anaerobic cellular respiration (aka fermentation) • Aerobic cellular respiration

40. C.R. Reactions • Glycolysis • Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate • Process is an ancient one-all organisms from simple bacteria to humans perform it the same way • Yields 2 ATP molecules for every one glucose molecule broken down • Yields 2 NADH per glucose molecule

42. Anaerobic Cellular Respiration • Some organisms thrive in environments with little or no oxygen • Marshes, bogs, gut of animals, sewage treatment ponds • No oxygen used= ‘an’aerobic • Results in no more ATP, final steps in these pathways serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis. • End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

44. Aerobic Cellular Respiration • Oxygen required=aerobic • 2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria • 1. Kreb’s Cycle • 2. Electron Transport Chain

45. Kreb’s Cycle • Completes the breakdown of glucose • Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO2 and H2O • Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2 • Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3rd stage

47. Electron Transport Chain • Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase). • As electrons drop down stairs, energy released to form a total of 32-34 ATP • Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

49. Energy Tally • 34-36 ATP for aerobic vs. 2 ATP for anaerobic • Glycolysis 2 ATP • Kreb’s 2 ATP • Electron Transport 32-34 ATP 36-38 ATP • Anaerobic organisms can’t be too energetic but are important for global recycling of carbon