Photosynthesis Overview

HOMEWORK! READ CHAPTER 10…

Stuff about photosynthesis you need to know

• Plants take sunlight energy to make carbohydrates!

• Electrons! They rule the world!– Take electrons from something?

• You take its energy!

• It usually falls apart!

– Give something electrons? • You give it energy!

• It makes the molecule bigger too!

Highlights!

• Plants use energy from the sun to make carbohydrates

• Photosynthesis uses water, carbon dioxide and sun-catching pigments.

• The process gives off oxygen

Photosynthesis is really two processes!

1. The light reactions 2. The Calvin Cycle

Calvin?

Light Reactions• Electrons from water

get put onto NADP+.• This makes NADPH

• Oxygen is released• H+ goes through ATP

synthase and makes ATP

Electrons are given to NADP+

Electrons from water

Oxygen leaves

photon

PigmentMakes NADPH

H+ goes through ATP synthase, makes ATPATP

So Far…

IN:• Water

• Sun

• NADP+

OUT:• Oxygen

• ATP

• NADPH

Calvin Cycle

• Takes NADPH, ATP, and CO2 to make carbohydrate! Often glucose: C6H12O6

More Specifically

• The electrons from NADPH get put onto CO2

• This takes energy from ATP!

• When electrons get added, CO2 becomes CH2O.. A small carbohydrate!~

Review

• Light reactions make NADPH, Oxygen, and ATP

• Calvin Cycle makes carbohydrate out of NADPH, CO2, and ATP

Photosynthesis

IN:• Water

• CO2

• Sunlight

OUT:• Oxygen• Carbohydrate

Oxidation/ReductionOxidation is loss (OIL)Reduction is gain (RIG)

Oxidation Reactions:

H2O to H+ and O2

NADPH to NADP+

Reduction Reactions

CO2 to CH2O

NADP+ to NADPH

CO2 + H2O + sun C6H12O6 + O2

(Carbon Dioxide) CO2 GETS REDUCED, makes CH2O (a small

carbohydrate.)

Oxidized or Reduced in Photosynthesis?

• H20• NADP+• NADPH• CO2

2H2O GOES TO 4H+ AND O2 IT IS OXIDIZED.

NADP+ GOES TO NADPH (REDUCED) IN THE LIGHT DEPENDANT REACTIONS

NADPH GOES TO NADP+ (OXIDATION) IN THE LIGHT INDEPENDENT REACTIONS (CALVIN CYCLE)

CO2 GOES TO CARBOHYDRATE IN THE LIGHT INDEPENDENT REACTION (REDUCTION.)

Wavelengths of light

•The pigments of photosynthesis work best in only a few wavelengths of light. (Green does not absorb green wavelengths of light. Chlorophyll is green.)

•Accessory pigments help absorb the wavelengths of light that are not absorbed by chlorophyll. Makes it so that photosynthesis can take place in any wavelength of light.

Absorption by pigments

Action spectrum

Photorespiration• Rubisco can grab O2 as easily as it grabs CO2.

• When rubisco grabs O2, it all falls apart, and they call this photorespiration.

• Because oxygen is made in the light reactions of photosynthesis, this is a problem.

• Future nobel prize winning research available…

1. C3 plants: photosynthesis like we learned. (Rubisco bonds to

CO2)2. C4 plants: CO2 gets fixed

onto PEP. PEP does not bond to oxygen…

3. CAM plants: CO2 gets stored in the mesophyll cells (inside part of the plant.)