By Ganyaza Z

Review

What is photosynthesis? Process by which energy from sunlight is used

to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) and oxygen as a waste product

Who uses photosynthesis? Plants and other producers

Jan van Helmont 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

Joseph Priestly

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

Jan Ingenhousz

1779 Dutch scientist Aquatic plants produce

bubbles only when light is present

Conclusion: Plants need sunlight to produce oxygen

Julius Robert Mayer

1845 German scientist Proposed that plants

convert light into energy into chemical energy

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

Review Sunlight White light

ROYGBIV Combo of all colors

Pigments Chemicals that absorb electromagnetic radiation

(visible light) Light absorbing molecules

Electromagnetic spectrum Electrons=energy

Structures and molecules

Chloroplast

Chlorophyll

Thylakoids

Chloroplast (found in cells in leaves)

Concentrated in the cells of the mesophyll (inner layer of tissue) in leaf

Stomata 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

Chloroplast

Cellular organelle where photosynthesis takes place 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

Structure of Chloroplast

Structures organize the many reactions that take place in photosynthesis

Stroma Thick fluid enclosed by the inner

membrane

Thylakoids Disc-like sacs suspended in the

stroma

Has membrane that surrounds inner thylakoid space

Grana (sing. Granum) Stacks of thylakoids

Chlorophyll Plants principle pigment 2 types

Chlorophyll a 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 This is why plants look green…they reflect green light

Carotene Secondary plant pigment Red and orange pigments Absorb light in other regions of the spectrum other than red and

orange

2 main stages Light Dependent Rxn Light-Independent or Calvin Cycle

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

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

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

List of references

^ "photosynthesis". Online Etymology Dictionary.

 (http://bioenergy.asu.edu/photosyn/study.html).

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