1. HBio: Photosynthesis

2. Leaf Anatomy Cuticle – waxy coating to prevent desiccation
Epidermis – outer layer of protective cells
Vascular Bundle - vein
Xylem – delivers water from roots
Phloem – delivers sugars from leaves
Mesophyll
Palisade – tightly packed photosynthetic cells
Spongy – loose arrangement of photosynthetic0 cells w/air spaces
Stoma – openings allow for gas exchange
Guard Cells – regulate stoma

3. Homework: Draw or describe the carbon cycle
Explain how it relates to photosynthesis

4. Do Now:
Homework on Desk
Grab your clickers!

5. Which leaf structure is responsible for gas exchange?
Epidermis
Cuticle
Mesophyll
Guard cells
Xylem
Phloem

6. Which leaf structure is responsible for transport of water?
Epidermis
Cuticle
Mesophyll
Guard cells
Xylem
Phloem

7. Which leaf structure is responsible for synthesis of sugars?
Epidermis
Cuticle
Mesophyll
Guard cells
Xylem
Phloem

9. Which process increases C in the atmosphere?
Reforestation
Coal formation
Burning fossil fuels

10. Chloroplasts
Chloroplasts found in cells of mesophyll (interior tissue of leaf)
CO2 enters and O2 exits through stomata (pores)
Chlorophyll - green pigment absorbs light energy found in thylakoid membranes
Thylakoids stacked in grana
Stroma – fluid in chloroplast

11. Electromagnetic Spectrum

12. Spectrophotometer
Measures the ability for a pigment to absorb various wavelengths of light
Directs a beam of light of different wavelengths through a solution of the pigment and measures the fraction of the light transmitted at each wavelength
Absorption spectrum plots a pigment’s light absorption vs. wavelength

13. ALL wavelengths are equally effective for photosynthesis
True
False
Cannot be determined

14. The colors of light most useful in photosynthesis are
green, yellow, and orange
red, violet, and blue
infrared, red, and yellow
red, white, and blue

15. Big Picture: Energy Cycles
All energy ultimately comes from sun
Light reactions of photosynthesis
Take place in thylakoid
Carbon fixation -all C in living things ultimately from CO2
Dark reactions of photosynthesis
Take place in stroma
Photosynthesis and cellular respiration are reverse reactions

16. Redox Redox Rxns w/ transfer of e Oxidation – loss of e
Reduction – gain of e
Both photosynthesis and cellular respiration use redox rxns in a series of steps
Electron transport chain (ETC) breaks the fall of electrons into several Energy releasing steps using proteins in the cell membrane

17. Photosystem
Photosystem – reaction center surrounded by light harvesting complexes called pigments (chlorophyll a, chlorophyll b, xanthrophyll, carotenoids, etc)
Pigment – absorbs photon E transferred from pigment to chlorophyll a rxn center
Rxn Center – protein complex w/ primary e acceptor
2 photosystems used in light reactions
Photosystem II – p680 chlorophyll a rxn center
Photossystem I – p700 chlorophyll a rxn center

18. Light Reactions: Non-Cyclic e flow
Photons absorbed by pigments and funneled to p680 in PSII excites e to higher energy state
E is captured by primary e acceptor
Enzyme splits H2O  2e + 2 H+ + O (will form O2)
Excited e passes thru etc to rxn center in PSI
Exergonic rxns in etc provide E for synthesis of ATP
Photons excite e in p700 in PSI excites e to higher energy state
E is captured by primary e acceptor and passed down 2nd etc
NADP+ transfers 2e from etc to form NADPH

19. OR Light Reactions: Cyclic e flow
Uses PSI only! (not PSII)
Excited e from primary e acceptor to 1st etc produces ATP and e falls back to replace lost e from p700
No water splitting
No production of NADPH
Increases production of ATP for Calvin Cycle (req. more ATP then NADPH)

20. Chemiosmosis
etc passes e thru carrier proteins in thylakoid membrane creating a H+ gradient (pumps H+ from stroma (pH8) into thylakoid space pH5)
Chloroplasts – photophosphorylation
ATP synthase embedded in same membrane (as H+ diffuse down gradient ADP is phosphorylated into ATP on stroma side of thylakoid)
NADPH also made on stroma side of membrane

21. Classwork:
Draw a flowchart (or diagram) of the light dependent reactions

22. Do Now Good Morning! Grab your Clicker
Take out your photosyntehsis pogil
Have out your homework ws (light reactions)

23. The light dependent reactions take place in the
Cloroplast membrane
Thylakoid
Stroma
Cytoplasm

24. NADP+  NADPH is an example of
Reduction
Oxidation
Chemiosmosis
Photophosphorylation
None of the above

25. During what stage of photosynthesis is O2 produced?
Photosystem I
Photosystem II
ETC
Photophosphorylation
O2 is not produced

26. The photophosphorylation of ATP is due to
Chemiosmosis of H+
ATP synthase
Electron Transport Chain
All of the above
None of the above

27. Dark Rxns: Calvin Cycle
Anabolic rxns – consuming E to build sugar
C enters Calvin cycle as CO2
C exits Calvin cycle as 3C sugar called G3P
Uses ATP as E source (ATP) from light rxns
Uses NADPH as reducing agent to add high E e (NADPH from light rxns)
Phase I: Carbon Fixation
CO2 + RuBP (5C sugar)  2 3- phosphoglycerate
Phase II: Making Sugar
Each 3-phosphoglycerate + P (from ATP)  1,3-biphosphoglycerate + 2e (from NADPH)  G3P
Phase III: Regenerating RuBP
(5) G3P + 3ATP  3 RuBP (ready for C fixation phase I)
3 molecules CO2  1 molecule G3P
6 molecules CO2  2 G3P (Glucose)
Must go thru Calvin Cycle 6x to make 1 molecule of glucose!

28. Alternate Methods of C Fixation
Hot/Dry day – stomata close to prevent water loss
Stomata close – limits CO2 from entering leaves, O2 builds up from light rxns
Photorespiration occurs on hot/dry days
No ATP produced nor sugar
Due to excess O2 instead of CO2 a 2C compound is produced and rearranged and released as CO2
No advantage

29. Alternate Methods: C4 Plants
Minimizes Photorespiration
Forms a 4C compound as 1st product (instead of 3)
Ex. Sugar cane, corn, grass
Photosynthesis occurs between 2 separate cells
Mesophyll cells
CO2 reacts with Phophonolpyruvate (PEP)  Oxaloacetate (4C cmpd)
Bundle Sheath Cells
4C cpmd  CO2  Calvin Cycle

30. Alternate Methods: CAM Plants
Succulent plants ex. Cacti and pinapple
Photosynthesis occurs in same cell, but at different times
Stomata open at night and close during day
Crassulacean Acid Metabolism (CAM)
Calvin cycle produces organic acids at night and mesophyll cell store in vacuoles until morning
During day light rxns supply ATP and NADPH for Calvin cycle, then CO2 is released from organic acids stored in vacuoles