1. Photosynthesis

2. Photosynthesis
The process by which plants and other producers convert the energy of sunlight into the energy, stored in organic molecules. (Carbon Compounds) Plants and other photosynthetic organisms produce the food that start the food chain.

3. Pigment Chlorophyll For most plants chlorophyll is the main pigment
Gives green color

4. Types of Chlorophyll Pigments
Chlorophyll a – absorbs mainly blue-violet and red light; reflects green light
Chlorophyll b – (helper pigment) absorb mainly
blue and orange light; reflects yellow-green (looks light frees)
Carotenoids – (many types) absorb mainly blue-
green light; reflect yellow-orange
Xanthophyll - a yellow or brown carotenoid plant pigment that causes the autumn colors of leaves

5. Electromagnetic Spectrum
The range of types of electromagnetic energy; from the very short wavelength (gamma rays) to the very long wavelength (radio waves)

6. Electromagnetic Spectrum
ROYGBIV

7. Electromagnetic Spectrum
Plants use the same part of the electromagnetic spectrum that our eyes are able to see.

8. Electromagnetic Spectrum
Those wavelength that your eyes can see as different colors
Make a small fraction of the electromagnetic spectrum
Shorter wavelengths (violet/indigo) have more energy than longer wavelengths (red)
Actually shorter wavelengths can damage organic molecules like proteins and nucleic acids
This is why U.V. rays cause sunburns and can lead to skin cancer

9. Electromagnetic Spectrum
Substances can do one of only 2 things when struck by a particular wavelength of light:
Absorbed
Reflected
Pigments in the leaf’s chloroplast absorb blue-violet and red very well

10. Wavelength

11. Chloroplast

12. Photosynthesis
ATP and H2 generated from light dependent stage used to covert CO2 and H2O into organic compounds (like glucose)
6CO H2O C6H12O O2
This carbon fixation…turning inorganic to organic
Fixation requires energy—all comes from sun

13. Photosynthesis Two Main Stages
Stage I Light Reaction (Light Dependent)
Convert the energy in sunlight to chemical energy
Takes place in the thylakoid membrane
1st – Chlorophyll molecules in the membrane
capture light energy
2nd – Chloroplast use energy to remove eˉ (excites)
from water (photolysis)
This splits H⁺ + O₂
O₂ is the “waste product” for photosynthesis

14. Photosynthesis Stage 1
Photolysis – when a water molecule is split into its component elements
Hydrogen and water
Generates electrons in light dependent reaction

15. Results of Light Reaction – NADPH + ATP
Photosynthesis Stage 1
O₂ escape into the atmosphere via the stoma (on leaves)
3rd – Chloroplast use H₂O eˉ and H⁺ ions to
(make energy rich molecules) NADH
found in cellular respiration.
4th – (finally) ATP is made in chloroplast
Excited e⁻ from Photosystem II are used to generate a proton gradient
Results of Light Reaction – NADPH + ATP

16. Photosynthesis Stage 1
Transfer of excited electrons occurs between carriers in the thylakoid membrane

17. Photosynthesis Stage 1
In photosynthesis light-excited eˉ for the electron transport from chlorophyll travel down the chain. (P680/P700 are pigments)

18. Photosynthesis Stage 2
Stage II The Calvin Cycle (takes place in Stoma)
Makes sugar from the atoms in CO₂ + the H ions and high-energy eˉ carried by NADPH
Enzymes for the Calvin Cycle are located outside the thylakoids and are dissolved in the stoma
ATP made in Light Reaction provides energy to make sugar (carbohydrates or other carbon compounds)
Calvin Cycle AKA “Light Independent Reactions” because it does not require light to begin reaction

19. Photosynthesis Stage 2
ATP synthase in thylakoids generates ATP using the proton gradient.

20. Photosynthesis Stage 2
Ribulose biphosphate (RuBP), 5 carbon compound, binds with CO₂ in a process called carbon fixation.
Catalyzed by an enzyme called RuBP carboxylase (rubisco).
Result: 6 carbon compound
The unstable 6-carbon breaks down into 2 3 carbon compounds (Glycerate 3 – phosphate GP)
GP = what we called G3P!!!!!
Done by reducing NADP and ATP

21. Photosynthesis Stage 2
The 3 carbon molecules of GP are acted upon by ATP and NADPH from the light-dependent reaction to form 2 other 3-carbon molecules called triose phosphate (TP). This is a reduction reaction.
The molecules of TP then do one of 2 things: some leave the cycle to become sugar phosphates that may become more complex carbohydrates. The others continue in the cycle and reproduce RuBP.
ATP is used to regain RuBP

22. Calvin Cycle

23. The Calvin Cycle

24. Photosynthesis-rates
Photosynthesis does not occur at such a steady rate
Greatly affected by intensity of light, temperature, and CO2 levels
Can be measured directly via CO2 intake and O2 production amounts IF adjusted to account for respiration
Biomass (amount of plant/size) is an indirect method of measuring rate of photosynthesis—indirect b/c a lot of other potential factors

25. Photosynthesis O2 released + Photosynthesis Respiration O2 taken in --
Respiration
O2 taken in --
Day 1
Night 1
Day 2
Night 2

26. Photosynthesis
Light intensity—varies inversely with the square of the distance (farther away, less intense)
Enzymes at max rate
Rate of photosynthesis
intensity

27. Photosynthesis Temperature
Enzymes and other proteins begin to get denatured
Rate of photosynthesis
Temp

28. Photosynthesis CO2 concentration
Plateaus unless light intensity or temp. go up
Rate of photosynthesis
CO2

29. Photosynthesis Summary
Light Reaction – takes place in the thylakoid
membrane
Convert light energy to chemical energy (ATP) and NADPH
Calvin Cycle – takes place in the stroma; uses ATP and NADPH to convert CO₂ to sugar.