1. Unit 4 Cellular Energetics
Photosynthesis (10) and Cellular Respiration (9)

2. Basic Key Terms
Heterotroph
Autotroph
Photoautotroph
Consumer
Producer

3. Structure of a Chloroplast

4. Parts of a Leaf Mesophyll- interior tissue
Stoma/stomata- pores that let gases in/out
Random FYI- about choroplasts in a typical mesophyll cell
Calculate- if you crushed 100 mesophyll cells in spinach leaves, approximately how many chloroplasts did you open up?

5. **plants don’t actually make glucose, but a 3 carbon sugar!
light
6CO2 + 6H2O  C6H12O6 + 6O2
**plants don’t actually make glucose, but a 3 carbon sugar!
Why do you think earlier biology classes tell you that glucose is made during photosynthesis?

6. Intro to Photosynthesis WS
Study off of the big ideas on that paper!

7. How does light work?

8. Pigments in photoautotrophs
Bottom picture, bacteria grow near largest amounts of oxygen
If a plant only gets a single wavelength you can see which the plant uses.

9. IMPORTANT BIG IDEA!!!

10. How do we know…
That the oxygen comes from the water and not the carbon dioxide???
1930’s researchers at Stanford Univ. found bacteria that use hydrogen sulfide instead of water for photosynthesis
They create a visible yellow waste product- and sulfur is yellow!

11. Purple sulfur bacteria

12. Further evidence
Interesting and important, but unlikely to be asked to recall this exact experiment on the AP exam.
Set up photosynthesis experiments using water containing a 18O
Heavy oxygen formed only when water was split.
When carbon dioxide was split, normal O formed
THEREFORE
Chloroplasts split water, then add Carbon dioxide

13. P.S. overview Light reaction Calvin cycle Batteries of P.S.
Important summary! New AP exam will not ask you to recite each step of the Calvin cycle or eTC.
Light reaction
In thylakoids
Water + light in
Oxygen out
Calvin cycle
In stroma
Carbon dioxide in
Sugar out
Batteries of P.S.
e- from H in water given to NADP+ making NADPH
Photophosphorylation- changing ADP ATP with light energy

17. Calvin Cycle
Named for Melvin Calvin who worked to figure out the mechanism in the 1940’s
Uses process called carbon fixation
Aka dark reactions or light independent reactions

18. Chlorophyll gets excited by light!
SCIENCE- an e- moves to a higher energy orbital when a photon of light hits it
Each pigment gets excited by a different wavelength of light
Fluorescence- after glow of e- falling back to ground state, releasing heat

19. Photosystems

20. 2 Photosystems in thylakoids
Photosystem II
Reaction center called P680 because it absorbs 680nm light best (red spectrum)
Chlorophyll a in reaction center
Happens 1st!!!
Photosystem I
Reaction center called P700 because it absorbs 700nm light best ( far red spectrum)
Happens 2nd!!!
Important! The PS labs are measuring the rate of the light reaction, so you do need to understand how it works.

21. Noncyclic electron flow mechanism for PS- main method

26. Translation from molecules to people

27. Cyclic electron flow- 2nd method
Purpose- to make ATP alone
Why?- calvin cycle uses up ATP faster than NADPH
When?- when the calvin cycle is running low
Trigger?- extra NADPH forms as calvin cycle slows down

28. Cyclic electron flow mechanism for PS- no photosystem II

30. Chemiosmosis- making ATP

31. Calvin Cycle broken down
Phase 1- carbon fixation Carbon dioxide + ribulose biphosphate using RuBP carboxylase (aka rubisco)
1C + 5C  6C   two 3C (3 phosphoglycerate)
Phase 2- reduction
3C + ATP  1,3 biphosphoglycerate
2e- from NADPH reduce 1,3 biphospho. To G3P (3C sugar for energy storage)
Reviewing this as an exercise because you DO need to know how to read these diagrams for the AP exam.
Important concepts in red!

32. Calvin cycle broken down
Phase 3 regeneration of rubisco
5 molec. G3P rearranged to 3 molec rubisco
ATP net usage =9
NADPH net usage=6
Light reactions regenerate ATP and NADPH
G3P NOT used to make rubisco is starting material for other chem reactions

33. Calvin cycle visual

36. Video clips of PS mechanisms
Put the following terms in the correct order:
Electron transport chain, Calvin cycle, photosystem I, RuBP forms, photosystem II, split water, electron transport chain , carbon fixation, G3P forms, ATP synthase

37. Alternative forms of PS: C3 and C4
WHY? Dehydration
HOW? When stomata open to release oxygen, and gain carbon dioxide they also lose water (transpiration)
Photorespiration- use oxygen in place of carbon dioxide in calvin cycle, 2C compounds are made, sent to mitochondria and broken into carbon dioxide

38. Side effects of C3 plants
Produce less sugar from PS
Produce less ATP
Theory- this started when atmosphere had more carbon dioxide and less oxygen
Rice, wheat, soy beans

39. C4 alternate to carbon fixation

40. C4 PS in words (sugarcane)
2 types of PS cells
Mesophyll, bundle sheath cells
Carbon dioxide + PEP (phosphophenol pyruvate)  oxaloacetate, using enzyme PEP carboxylase
Oxaloacetate (4C) malate (4C)
4C compound to bundle sheath cells via plasmodesmata
4C releases carbon dioxide for calvin cycle

41. CAM PS

42. CAM PS in words Succulents, cacti, pinapples
Open stomata at night close during day
Carbon dioxide only enters cells at night
CAM- crassulacean acid metabolism- carbon fixation at night into organic acids
Organic acids stored in vacuoles until day when light can power PS

43. CHAPTER 9 CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY MAIN IDEA
How do cells use
Stored energy in food?

44. 2 methods
Catabolic pathway- metabolic pathways that release stored energy from complex molecules
Cellular respiration
Requires oxygen
More efficient than fermentation
Fermentation
Anaerobic
Alcohol or lactic acid are biproducts

45. THE BIG PICTURE
Like PS, you will not be tested on the recitation of each chemical step of Cellular respiration, but in order to answer the Q you do need to understand what is going on!

46. Reverse PS
C6H12O6 + 6O2  6CO2 + 6H2O + ATP/heat
Exergonic ΔG = -686kcal/mol glucose
-ΔG = products have less potential energy than reactants

47. ATP is a rechargable battery
Recharge ~10million molecules per second!
REDOX REACTIONS- reaction in which e- are passed from one reactant to another
Oxidation- loss of e- from a substance
Reduction- addtion of e- to a substance
Cellular respiration is a redox reaction

48. Electrons “fall” toward oxygen
Carbs and lipids are storage of e- associated with the H
CR is a controlled reaction!
1. H atoms taken from glucose
2. H passed to coenzyme NAD+ using enzymes called dehydrogenases
NADH is like a charged battery, waiting to be used to make ATP

49. Electron transport chain
A chain of proteins built into the inner membrane of mitochondria
ΔG = -53 kcal/mol glucose

50. HOW?? Electronegativity
Each step “down” the chain is more and more electronegative.
Last acceptor is oxygen- very greedy for e-

51. Cellular Respiration 3 steps

54. Vocab in the figure
Oxidative phosphorylation- energy released at each step stored in the form that the mitochondria can use for ATP synthesis
Substrate level phosphorylation- enzyme transfers a phosphate group from substrate to ADP

55. Glycolysis
1. Split sugar
2. Form 2 3-C sugars
3. Sugars modified into pyruvate molecules

56. Glycolysis movie 9.9

57. What to know of Glycolysis mechanism for the exam
Location of process
Net energy production
Oxygen independent process
How many ATP are used?
How many ATP are created?
What is the net production of ATP?
What method was used to create these ATP’s?

58. Classwork Task: Teaching
We may or may not do this exercise depending on time.
Classwork Task: Teaching
I will randomly split the class into two groups
Group 1 will have 1 class period to create an analogy/story that will help everyone understand and remember the mechanism of glycolysis.
Group 2 will have 1 class period to create an analogy/story that will help everyone understand and remember the mechanism of the Krebs cycle

59. Criteria for Teaching
1. You may NOT use ONLY chemical terms OR ONLY comparison terms
2. The teaching method is up to you- drawing/powerpoints/acting/handouts
3. You must present the lesson as an alter-ego (real or fictional) in about 20 min.
4. Ms. Bjelko will only assist with the lesson IF you are saying something totally incorrect.
***powerpoint must be accessible on 2003 version of the program…2007 will not open on Ms. Bjelko’s computer

60. Goal for Teaching
All students and Ms. Bjelko must be able to explain the mechanisms in both chemical terms and as some analogy
HINT: the stranger/sillier analogies are most likely to be remembered and the most fun to teach!!!

61. Where are we now???

62. Link to Krebs Cycle e- from acetate used to make NADH
From carboxyl group on pyruvate
Needed for Krebs cycle

63. Krebs Cycle Summary

64. Krebs cycle movie 9.12

65. What to know of Krebs cycle mechanism for the exam
Where does acetyl CoA come from?
Each step uses a different enzyme- names not vital
How many total chemical reactions must occur for the oxaloacetate (needed for the cycle to restart) to be re-formed ?
How many ATP molecules are made during this process?
What other energy/electron carrying molecules are formed in this process?
Where do the energy/electron carrying molecules go next?

66. Where are we now???

67. Electron transport chain- most of energy formation
Only 4 ATP formed so far, 2 from each step
Each step of the chain molecules are reduced and oxidized as electrons passed to and from them.
e- carried from the Krebs cycle to e- transport chain by NADH and FADH2 .
Cytochrome molecules (cyt) have a heme group- Fe surrounded by 4-C rings. Similar as in hemoglobin of RBC’s (Why would this be useful!- back to chemistry!)

68. Electron transport chain
Water produced
NO ATP produced DIRECTLY-
Chemiosmosis and ATP synthase make ATP

69. Chemiosmosis- energy coupling reaction using H+ gradient across mitochondrial membrane

70. Electron transport chain movie 9.15

71. Discovery of chemiosmosis
1961 Peter Mitchell proposed the idea
1981 it was confirmed in bacteria, mitochondria, and chloroplasts
1981 Peter Mitchell received Nobel Prize
And the point is…research scientists must be very patient!

72. Energy totals from cellular respiration

73. Krebs cycle and Electron transport chain are aerobic processes
What happens when there is no O?
FERMENTATION
Use e- from NADH made in glycolysis to transform pyruvate
Biproducts are either lactic acid or ethanol
Only 2 ATP formed compared to 38 with CR
Movies 9.17a (alcoholic) and 9.17b (lactic acid)

76. Faculative Anaerobes
Organisms/cells that can create energy using either CR or fermentation
Yeast, many bacteria, mammalian muscle cells
CR is much more efficient!!!

77. Evolution and Glycolysis
Early earth lacked oxygen  prokaryotes just used glycolysis
Oxygen would be the biproduct at that time
Evidence: Glycolysis widespread through living organisms
Evidence: glycolysis happens in cytosol- even prokaryotes can perform it
HOW could this have led to the evolution of CR?

78. Catabolism
Many carbohydrates can be hydrolized to be used for glycolysis
Beta oxidation- breaks fatty acids into 2-C fragments sent to Krebs cycle

79. Anabolic pathways (biosynthesis)
Using molecules to create needed materials for cells/the body
Amino acids obtained from protein used to make proteins for cell
About 10 of the 20 AA’s can be synthesized by modifying molecules taken from Krebs
Glucose made from pyruvate
Fatty acids from acetyl CoA
Extra proteins and carbs transformed into fats using intermediate steps of glycolysis and Krebs cycle

80. Controlling CR: the ON/OFF switches
DO NOT MAKE MORE THAN YOU NEED!
FEEDBACK INHIBITION- end product of a reaction acts as an inhibitor of the enzyme that starts chain reaction
TARGET KEY ENZYMES IN THE PROCESS

81. SUMMARY
Cellular respiration and fermentation RELEASE energy from the chemical compounds ingested
Remember: Energy is neither created nor destroyed, it is simply transferred and transformed.

82. The New Test
This is the first unit that clearly shows the edits made from the previous exam.
You will NOT be asked to recite a list of chemical reactions in order, but instead you will be presented with stories/diagrams showing you chemical reactions in order.
The questions will ask you to interpret the story/diagram, or make a prediction based on the story/diagram.
Teacher note: as much as the college board says you don’t have to know the mechanisms…if you don’t have a clue about them, you will STRUGGLE to answer their questions. The new predict/interpret questions are challenging to both teachers and students.