1. Topic: Photosynthesis-Ch 6 Cellular Respiration-Ch 7 American biochemist and Nobel laureate Albert Szent-Gyorgyi, “What drives life is thus a little electric current, set up by the sunshine.”

2. Light Absorption Occurs in chloroplasts VISIBLE LIGHT (roygbiv).
Each color = a specific wavelength
Pigments: compound that absorbs light (specific pigments absorb specific wavelengths in nanometers)

3. Chloroplast Structure
Surrounded by a double membrane
Inside a chloroplast:
Flattened membranes = thylakoid
Stacks of thylakoids = grana
Stroma = liquid
in the space
surrounding
the grana

4. Pigments Found in thylakoids
Chlorophyll a = Most important pigment, absorbs the most light (absorbs red, blue; reflects green)
Chlorophyll b = absorbs slightly different wavelength
Carotenoids, Xanthophylls = red, orange, and yellow absorb additional wavelengths

5. Structure of Chlorophyll

6. Photosynthesis
Converts inorganic compounds into organic ones using the energy from sunlight & biochemical pathways
2 Stages
1. Light Dependent (capturing light energy or “Light”) stage
releases oxygen for us to breathe
makes ATP and NADPH to run Calvin Cycle
2. Calvin cycle (Light Independent or “Dark") stage
Makes organic cmpds (sugar for plant)

7. Autotrophs: Make their own organic compounds (food) ex. plants, algae
Heterotroph: cannot make their own food

8. Photosystems Cluster of pigment molecules w/ a specific job
Photosystem I
Photosystem II

9. Photosynthesis Equation
6CO2 + 6H2O + light C6H12O6 + 6O2

10. Light Reactions - a 5 step process
Occurs in the thylakoid membrane
Step 1
Light energy (from sun) excites electrons in chlorophyll a molecules, these excited electrons leave the chlorophyll a molecule (photosystem II)
This is oxidation reaction…..PS II lost an electron

11. Light Reactions - a 5 step process
Excited electrons leave the chlorophyll a & go to the Primary Electron Acceptor (2)
This is reduction reaction…it gained electron
Step 3
Primary electron acceptor gives the electrons to the electron transport chain
Protons move INTO thylakoid from low to high

12. Light Reactions - a 5 step process
In photosystem I electrons gets excited again by light energy (more sunlight)
Oxidation reaction…lost electrons
These electrons go to another primary electron acceptor (1)
These lost electrons are replaced by the electrons that came from photosystem II

13. Light Reactions - a 5 step process
Primary electron acceptor (I) gives the electrons to another ETC (I).
This ETC (I) moves electrons to the stroma side of the memb.
Electrons combine w/ a proton (H+) & NADP+ this becomes NADPH
Reduction…gains electrons
NADPH is nicotinamide adenine dinucleotide phosphate…..HOLDS ENERGY

14. Replacing Electrons in PS II
Where do the electrons come from?
An enzyme splits 2 molecules of water into 4 protons, 4 electrons and 1 molecule of oxygen (O2)- this is where oxygen is given off in photosynthesis

15. Chemiosmosis The process by which ATP is made in the light reaction
Happens in between PSII and PSI
More protons accumulate inside the thylakoid than stroma = conc. Gradient is high to low
Some protons came from water splitting, others were pumped in using energy generated by ETC

16. Chemiosmosis
Protons flow out to stroma through ATP synthase enzyme in membrane, this releases energy
ATP synthase uses released energy to convert ADP to ATP
ATP synthase = multifunction protein!

17. Chemiosmosis

18. Chemiosmosis

19. Components of the light reaction
Oxygen (given off)
ATP made (used in calvin cycle/dark rxn)
NADPH made (used in calvin cycle/dark rxn)
Water is consumed

23. Calvin Cycle Where CO2 is incorporated Occurs in stroma of chloroplast
Makes 3C sugars (carbohydrate)

24. Calvin Cycle

25. Calvin Cycle
Step 1
3CO2 diffuses into stroma from cytosol, CO2 gets added to
RuBP (ribulose biphosphate) by enzyme Rubisco which is a 5 carbon carbohydrate to equal a 6-Carbon molecule that immediately splits into 2 3-carbon molecules (PGA)
phosphoglycerate

26. Calvin Cycle
Step 2
PGA converted into G3P (glyceraldehyde 3-phosphate) by adding P (from ATP) & H (from NADPH) to the 3-carbon molecules.
Then the ADP, NADP and P are used again in light reactions to make more ATP and NADPH
In other words…..Binds H carried by NADPH to Carbon from CO2, with the help of ATP….all this was produced in light reactions…

27. Calvin Cycle
Step 3
Most G3P is converted back into RuBP (keeps cycle going), but some G3P leaves cycle & is used to make organic compounds
Plants using Calvin cycle are C3 plants (for the 3 Carbon compound produced)

28. Calvin Cycle Requires
ATP
NADPH
CO2

29. Stomata Pores on leaves through which CO2 enters & O2 exits
Low CO2 & High O2 stop calvin cycle

30. Alternative Pathways, C4
Hot dry climate
Partially close stomata during day
Make a 4 C compound first even though CO2 is low and O2 is high
Lots of grasses do this + corn, sugar cane
They lose about half as much water as C3 plants when producing same amount of carbs

31. Alternative Pathways, CAM
Open night and incorporate C into a bunch of other compounds they then use for photosynthesis during the day…grow slowly; lose less water
Ex: cactus, pineapple
CAM stands for crassulacean acid metabolism

32. REVIEW Light Dependent Reactions In thylakoid Collect light
Produce ATP, NADPH
Release Oxygen
Consume water
Calvin Cycle/Dark Rxn/Light independent
In stroma
Take in Carbon dioxide
Produce carbohydrate (G3P)

33. REVIEW

34. Factors affecting photosynthesis rate
Varies based on:
amount of light (increase  level off)
amount of carbon dioxide (increase  level off)
Temperature (increase  decrease)

35. How do you get the energy out of the organic compounds
How do you get the energy out of the organic compounds? Cellular Respiration =
CH 7!

36. Cellular Respiration
Energy is generated by a series of reactions ultimately used to form ATP from ADP
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

37. 2 steps are: 1. Glycolysis 2. Aerobic Respiration

38. Glycolysis First Step in Respiration Occurs in the cytosol
Splits ONE glucose into TWO pyruvate molecules
Does not require oxygen= anaerobic
Uses 2 ATP process and 2 NAD+
Makes 4 ATP
Net yield = 2 ATP

39. After Glycolysis: If O2 present = aerobic resp. If no O2 = fermentation

40. Fermentation Glycolysis + an anaerobic pathway = fermentation
Produces NAD+ which keeps glycolysis going..w/out NAD+ then glycolysis
would stop and no ATP
would be made
Anaerobic process
Does not produce ATP
Lactic acid pathway
Ethyl alcohol pathway

42. Lactic Acid fermentation
Pyruvic acid is converted into lactic acid, forming NAD+
Yogurt, cheese, muscle cells
Produced when strenuous exercise exceeds immediate demands of muscle tissues

43. Alcoholic fermentation
Pyruvic acid  ethyl alcohol
Creates NAD +
Yeast, wine, bread

44. Efficiency of anaerobic pathways
Not very efficient
Cannot sustain large multicellular organisms
OK for bacteria & early life on Earth

45. Aerobic Respiration
If oxygen is present, the pyruvic acid from glycolysis undergoes cellular respiration
Pyruvic acid still has a lot of energy in it

46. Aerobic Respiration - 2 steps
Step 1: Krebs cycle
Step 2: Electron transport chain & chemiosmosis
In Eukaryotes these occur in mitochondria
In Prokaryotes these occur in the cytosol

47. Krebs Cycle
Pyruvic acid diffuses into mitochondria MATRIX & forms acetyl CoA

48. Krebs Cycle
4 carbon beginning product is regenerated at the end of the cycle

49. Krebs Cycle
If what you start with is the same as what you end with, what is the point of the Krebs cycle?
It generates other “stuff” while going through the cycle

50. Krebs Cycle
Acetyl CoA does a bunch of stuff and generates: (1 glucose = 2 turns of Krebs cycle)
4 molecules of CARBON DIOXIDE (is given off as waste),
6 molecules of NADH,
2 molecules of FADH2
2 molecules of ATP
Krebs still only makes
2 ATP like glycolysis…
So rest of products go into
Mitochondrial inner membrane to make more!

51. Electron Transport Chain

52. Electron Transport Chain
Series of electron carriers accept electrons from NADH and FADH2

53. Electron Transport Chain
Chemiosmosis creates ATP from ADP - just like in photosynthesis!

54. The Role of Oxygen What does the end of the ETC do with its electrons?
Oxygen is “final electron acceptor”
Oxygen combines with protons & electrons that were part of NADH and FADH2 to create water!!!!!!!!

55. Aerobic Respiration Much more efficient than anaerobic
Produces 38 ATP (glycolysis + krebs + ETC)
C6H12O6 + 6O2 6CO2 + 6H2O + ATP

56. Summary of Cellular Respiration

57. Cellular Respiration Summary

58. ETC and Chemiosmosis!