1. By Ganyaza Z

2. Review
 What
is photosynthesis?
 Process
by which energy from sunlight is used
to convert water and carbon dioxide into highenergy carbohydrates (sugars and starches)
and oxygen as a waste product
 Who
uses photosynthesis?
 Plants
and other producers

4. Jan van Helmont

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1643
Belgian physician
Do plants grow by taking material out of the
soil?
Mass of soil
Mass of seed
Watered regularly
@ end of 5 yrs, tree was 75 g, soil the same
Conclusion: Mass came from water
Accounts to the “hydrate” portion of
carbohydrate produced but what made the
“carbo-” portion

5. Joseph Priestly
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1771
English minister
Bell jar, candle, plant
Jar over candle flame
died out
Jar over candle with live
sprig of mint flame
didn’t die
Conclusion: Plant
releases oxygen

6. Jan Ingenhousz
 1779
 Dutch
scientist
 Aquatic
plants produce
bubbles only when light is
present
 Conclusion:
Plants need
sunlight to produce oxygen

7. Julius Robert Mayer
 1845
 German
scientist
 Proposed
that plants
convert light into energy
into chemical energy

8. 
The experiments performed by van Helmont, Priestly,
and Ingenhousz led to work by other scientists who
finally discovered that in the presence of light, plants
transform carbon dioxide and water into carbohydrates,
and they also release oxygen

Hill, R. (May 1999). "Oxygen Produced by Isolated
Chloroplasts". Proceedings of the Royal Society of
London. Series B, Biological Sciences 127 (847):
192–210

9. Review Sunlight
 White
light
 ROYGBIV
 Combo
of all colors
 Pigments
 Chemicals
that absorb electromagnetic radiation
(visible light)
 Light absorbing molecules
 Electromagnetic
spectrum
 Electrons=energy

10. Structures and molecules

Chloroplast

Chlorophyll

Thylakoids

11. Chloroplast (found in cells in leaves)

Concentrated in the cells of the
mesophyll (inner layer of tissue) in
leaf

Stomata

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Tiny pores on surface of leaf
Allows carbon dioxide and
oxygen in and out of the leaf
Veins

Carry water and nutrients from
roots to leaves

Deliver organic molecules
produced in leaves to other
parts of the plant

12. Chloroplast

Cellular organelle where
photosynthesis takes place

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Double membrane
Outer membrane
Stroma (fluid filled space)
Inner membrane
Thylakoids
Granum
Intermembrane space
Contain chemical
compound called
Chlorophyll

This molecule gives
chloroplast its green color

13. Structure of Chloroplast

Structures organize the many
reactions that take place in
photosynthesis

Stroma

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Thick fluid enclosed by the inner
membrane
Thylakoids
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Disc-like sacs suspended in the
stroma
Has membrane that surrounds
inner thylakoid space
Grana (sing. Granum)

Stacks of thylakoids

16. Chlorophyll
Plants principle pigment
 2 types

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Chlorophyll a
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Absorbs light in the blue-violet and red regions of visible spectrum
Chlorophyll b

Absorbs light in the blue and red regions of the visible spectrum
Chlorophyll does NOT absorb light well in the green portion of
the visible spectrum
 Green light reflected by leaves
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This is why plants look green…they reflect green light
Carotene
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Secondary plant pigment
Red and orange pigments
Absorb light in other regions of the spectrum other than red and
orange

17. 2 main stages
 Light
Dependent Rxn
 Light-Independent
or Calvin Cycle

18. Photosynthesis Overview

#1 “Light-Dependent” reactions

Convert the E in sunlight to chemical energy

Rxns depend on molecules made in membranes of thylakoids

Chlorophyll in membr. captures light E

Chloroplast use E to remove e- from water

Splits water into oxygen (waste) and hydrgen ions
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e- taken are used to make high-E molecule NADPH (similar to NADH)
Chloroplast also use captured E to make ATP
Overall Product: convert light E into chemical energy stored in compounds ATP and NADPH

19. Photosynthesis Overview
# 2 “Light- Independent” Reactions aka
The Calvin Cycle

Makes sugar from atoms of CO2 and H+ ions and High-E e- carried by NADPH

Enzymes for these reactions are dissolved in the stroma (outside thylakoid)

ATP made by light Rxns provides E to make sugar (glucose)

Called light independent, b/c unlike unlike the light reactions, these do NOT require light tp
begin

However, this cycle does require two things made by the light reactions: ATP and NADPH

This means that the calvin cycle cannot necessarily continue in the dark

20. List of references

^ "photosynthesis". Online Etymology Dictionary.

(http://bioenergy.asu.edu/photosyn/study.html).

21. REFERENCES
Bryant DA, Frigaard NU (November 2006). "Prokaryotic photosynthesis
and phototrophy illuminated". Trends Microbiol. 14 (11): 488–96]
Buick R (August 2008). "When did oxygenic photosynthesis
evolve?". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 363 Olson
JM (May 2006). "Photosynthesis in the Archean era". Photosyn.
Res. 88 (2): 109–17.
Online Sources
http://bioenergy.asu.edu/photosyn/stuy.html
http://hdgc.epp.cmu.edu/teachersguide/teachersguide.htm