1. So…how do we get the energy we need to survive?
Unit 4 Cell Energetics!
So…how do we get the energy we need to survive?

2. Part 4: Photosynthesis overview, chloroplast structure & pigments
Unit 4 Cell Energetics!
Part 4: Photosynthesis overview, chloroplast structure & pigments

3. Where does energy originally come from??
Make sure to state energy comes from the sun (except in deep sea conditions where chemicals power life from sulfur vents…cool!)

4. Photosynthesis is the process by which certain organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
What does it need? (Input)
What does it make? (Output)
Light
energy
PHOTOSYNTHESIS 6
CO2 +
H2O
Carbon dioxide
Water
C6H12O6 O2
Glucose
Oxygen gas

5. PS vs CR Photosynthesis Cellular Respiration Inputs: Outputs:
Make a table!!
Photosynthesis
Plants & some bacteria
Inputs:
Light energy
H2O
CO2
Outputs: O2
C6H12O6
Cellular Respiration
Plants & animals
Inputs:
C6H12O6 O2
Outputs:
CO2
H2O
ATP

6. Chloroplast structure
Be able to ID the following:
Inner membrane*
Outer membrane*
Granum
Thylakoid
Stroma
*supports the endosymbiotic theory

7. Endosymbiotic Theory?
A larger cell (pre-eukaryote) engulfed a smaller prokaryote  the smaller one provided energy  instead of “eating” the small bacteria they became bffs
Evidence that supports this:
Chloroplasts & mitochondria have their OWN DNA!!! 
Chloroplasts & mitochondria have ribosomes & cytoplasm!
Chloroplasts & mitochondria have two layers of membrane!

9. Leaf Anatomy
Mesophyll  chloroplast-rich cells found under the epidermis
Stomata  openings under the leaf that allow gas to pass in & out

10. Chloroplasts… Found in mesophyll
1 mesophyll cell may have 30 chloroplasts! (remember the pond scum?)

11. Photosynthesis Overview
Light reactions (LDR)
Depend on light
Occur in Thylakoid Membrane
Light Independent reactions (LIR)
Does NOT need light
Occurs in the Stroma

12. Electromagnetic spectrum

13. Photosynthesis background
Pigments
this is what absorbs the light energy from the sun it excites electrons making it unstable
Photosystems (PS 1 & PS 2)
Made of pigments & proteins

14. Pigments Chlorophyll Chlorophyll a  main pigment  blue-green
Chlorophyll b  accessory pigment  yellow-green
Other accessory pigments  absorb different wavelengths of light
Carotenoids  yellow-orange
Xanthophyll yellow
Rhodophyll  red
Fucoxanthin  brown
Why are plants green?
Why are plants changing color?

15. Unit 4 Cell Energetics! Part 5 LDR, ETC & Gradients

16. Photosynthesis Overview
Light reactions (LDR)
light energy  chemical energy (ATP and NADPH) and produce O2

17. LDR
Inputs?
Outputs?
Location?

18. Light Dependent Reaction (LDR)/Photophosphorylation

19. Photosystems Consist of There are 2
Pigments (chlorophyll b, carotenoids & xanthophyll)
Proteins!
There are 2
Photosystem 1
The last photosystem in the Light Dependent Reaction (LDR)
Photosystem 2
The FIRST photosystem in the LDR
Photosystem 2 comes first, but has the #2 after it because we discovered it second…

20. Photosystems Process:
Photon (light energy) absorbed by pigments  excites e- in pigment e- jump to higher levels  eventually reaches the reaction center (chlorophyll a)  transfers energy to the reaction center  passed back down through an ETC in LDR

26. Summarize the flow of energy:
Electron Carriers
Act like a car to transport electrons
NADP+ is an “empty” car
NADPH is a “full” car
Summarize the flow of energy:
Light energy to photosystem 2  electrons excited  electron passed to ETC  electrons hit photosystem 1  electrons then go to ANOTHER ETC  electrons end up in the electron carrier (NADPH)

27. But WHY??????

28. Cytochrome complex synthase reductase
LIGHT
REACTOR
NADP+
ADP
ATP
NADPH
CALVIN
CYCLE
[CH2O] (sugar)
STROMA
(Low H+ concentration)
Photosystem II
H2O
CO2
Cytochrome
complex O2 1
1⁄2 2
Photosystem I
Light
THYLAKOID SPACE
(High H+ concentration)
Thylakoid
membrane
synthase Pq Pc Fd
reductase
+ H+
NADP+ + 2H+ To
Calvin
cycle P 3 H+
2 H+
+2 H+

29. ETC, Chemiosmosis & ATP Synthase
ATP synthesis in light reactions
electrons (e-) are passed along a chain of proteins (called the ETC) in the membrane  H+ pumped into Thylakoid space (chemiosmosis)  this is active transport!
H+ diffuse back across the membrane through ATP synthase  powers the phosphorylation of ADP to produce ATP (photophosphorylation)

30. Photophosphorylation http://vcell. ndsu. nodak

31. Light Dependent RXN animation

32. Part 4 Light Independent Reaction
Cell energetics
Part 4 Light Independent Reaction

33. Photosynthesis Overview
Light Independent Reactions (LIR…aka: Dark reactions and Calvin Cycle)
Using ATP and NADPH from the light reactions form sugar from CO2

35. Calvin Cycle/Light Independent Reactions
Occur in the dark or the light
Occurs in the stroma
3 steps
Carbon fixation
Reduction
Regeneration of RuBP

36. Step 1: Carbon Fixation RuBP
5 C sugar w/2 Phosphates
Rubisco (nickname for an enzyme) adds CO2
Creates an unstable 6 C molecule that splits
Creates 2 3-C molecule

37. Step 2: Reduction
3-C molecule gets phosphorylated by ATP (gets it’s energy)
Electron carrier adds an electron (MORE energy!)
Produces G3P (PGAL)
some G3P  glucose
most G3P  regenerate RuBP
Adds a phosphate & energy, then electron carrier adds MORE energy new name PGAL or G3P (some of which makes glucose…but most goes to regenerate RuBP

38. Step 3: Regeneration of RuBP
1 G3P moves out to eventually become glucose
G3P  rearranged into RuBP
Requires input of 3 ATP
Takes 6 turns of cycle  1 glucose