PHOTOSYNTHESIS

Photosynthesis uses sunlight to make energy and biomass.

CO2 + H2O → CH2O + O2hv

Biomass

Respiration is the opposite of photosynthesis

CH2O + O2 → CO2 + H2O

What would happen if the amountof respiration = the amount of photosynthesis?

Some photosynthesis occurs on land and some occurs in the ocean

All photosynthesis by plants and algae use chloroplasts. People think the chloroplast used to be a photosynthetic bacteria. Voet & Voet 1998

Many chlorophyllabsorb light and send the light energy to a reaction center.

If a plant lives in lowlight it has more chlorophyll perreaction center.

Brock, 2003

Voet & Voet, 1998

Different phytoplankton have different pigmentsthat absorb light at different wavelengths.

Why?

Photosynthesis takes place in a membrane

To make biomass

Voet & Voet, 1998

How do Plants get Energy from Photosynthesis?

2H2O → 4H+ + O2hv

membrane

Fewer H+

More H+

Make ATP

Protons (H+) flowingthrough the channelmechanically changethe enzyme, smashingthe ADP & P together.

Bonds broken2 O-H1 P-OBond formed2 O-H1 P-O

Statistics

8 photons are used per 1 O2 produced.For every O2 produced 4 ATP are madeAnd 2 NADPH.1 NADPH can produce 3 ATP.

3 CO2 to biomass uses 9 ATP and 6 NADPH.Need 22 photons for 3CO2 to biomass. (At max efficiency)

Energy of a photon = h* velocity /wavelengthPlanck’s constant h = 6.63*10-34 J*s

The speed of light in a vaccuum (like space) is:3 * 108 m/s.

Let’s pick a pigment…

Voet & Voet, 1998

Like chlorophyll b at 450 nm.

How much energy is used to make biomass?

Energy of a photon = h*velocity/wavelength

E = 6.63*10-34 J/s *( 3 * 108 m/s) /(450 *10-9 m)

E = 4.42 *10-19 J per photon

22 photons per 3 CO2 to biomass:22* 4.42*10-19 J = 9.72*10-18 J

That’s for 3 molecules of CO2.

1951 kJ of light energy per mol of CO2 to biomass.

Brock, 2003

We think photosynthesisevolved to use hydrogensulfide (H2S) as an electronand proton donor.

An organism needs twice as much light to use H2O instead of H2S.

A bacteria that can useH2S for photosynthesis.

Why do all trees and algae use 2H2O → O2 + 4H+ ?

Phytoplankton in Puget Sound: DiatomsChlorophyll autofluoresces

Little predators are consumed by big predators.This is a copepod.

http://www.biosci.ohiou.edu/faculty/currie/ocean/gallery/calanoid-copepod.jpg

Chlorophyll of the world

Satellite image with false color. Integrated over 30 days

Phoyosynthesisunder the ice

Photosynthesis in permanent ice cover

English (1961) Arctic Inst. N.Amer., Sci Rep. 15

Huge productivity at the ice edge.

Normal ocean bloom-- 3 mg/m3 chlorophyll max

Arctic ocean ice edge--20 mg/m3 maximum

From lots of nutrients and light.

(Nutrients have halfA year to accumulate.)

http://www.free-people-world.com/4/animals-world/wild-nature/1/2004 03 01 archives.html

Order of Events

1.) Snow melts-- this allows light to pass thru ice

2.) Ice algae bloom.

3.) Specially adapted predators scrap algae off ice

4.) Ice melts

5.) Water column phytoplankton get light

6.) Huge bloom of phytoplankton

Ice algae predator-- amphipod

http://www.sfos.uaf.edu/research/arcdiv/

http://www.sfos.uaf.edu/research/arcdiv/

Lots of Shallow Shelf

http://www.sfos.uaf.edu/research/arcdiv/

Why bacteria are important in the Arctic…Arctic OceanNormal Ocean

Cold bacteria can not metabolize as fast

Bacteria eat allBottom is shallower

Lots of “food” makes it to the bottom

Temperature in the Northern Hemispherehas increased

SOURCE: Michael E. Mann [Geophys. Res. Lett., 30, 1820 (2003)]

Arctic ice extent has decreased

Pink line = average

Wang et al (2005) Deep sea Research II

1998 was a warmyear.

Less ice.

Earlier bloom.

What is going to happen to the Arctic ecosystem???