Photosynthesis

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Photosynthesis: Just the Notes

Turning Light into Life

 

What is Photosynthesis?

Autotrophs convert Sunlight Chemical Energy

 

Plants  provide:

Chemical energy on which all life depends

Oxygen plants created our atmosphere

Materials shelter, clothing, medicine

Food for (almost) all other life forms    

 

CO2 + H2O C6H12O6 + O2

       Materials Required for Photosynthesis:

        Sunlight provides energy

        Carbon Dioxide provides carbon

        Water provides electrons

        Oxygen waste product after electrons removed from water

        & enzymes to put everything together!
 

Where does photosynthesis take place?

Leaf Structures

      Cuticle & epidermis protect plant

      Stomates allow gases in and out

      Veins in leaf transport water, nutrients

    Xylem - water & minerals up from roots

    Phloem - food from leaves to plant

Leaf Structures

      Mesophyll = middle leaf
      Palisade layer is where most photosynthesis takes place
      Cells have many chloroplasts
      Spongy mesophyll allows gases to circulate

  

 

n    Link:  Narrate this movie!

 

Photosynthesis: The Process

2 Phases

 Organelle:  Chloroplasts

Input: Light, Water, CO2

Output: Sugar, O2

 

 

Phase 1: The Light Reactions

Purpose convert light energy from the sun to chemical energy (ATP)

 

Requires:  Light

Water

Electron carriers (NADP+)

Chlorophyll

Enzymes

 

Produces:  

ATP

O2 as waste

Electron-rich carriers
(NADPH)

 

Different Colors of Light :  Different Energy for Reactions

 

Pigments and Color

Pigments - molecules that absorb some colors of light and reflect other colors of light

The color you see is the color that is reflected.

 

Chlorophyll a

Chlorophyll a absorbs blue & red light

Chlorophyll a reflects green/yellow light

Thats why leaves look green!

 

Clusters of chlorophyll form photocenters in chloroplasts that absorb light energy

 

Link:  Light Reactions - the Basics

 

Chlorophyll

1.  Chlorophyll absorbs light energy from the sun Energy excites electrons in chlorophyll to high energy state electrons bounce out of photosystem

 

2.  High energy electrons are passed down electron transport chain ATP; the energy is used to make ATP (chemiosmosis)

 

3.  Electrons are energized again and passed to an electron carrier (NADP+)

 

Its a 7-Ticket Ride for the electrons!

 

Electrons excited in step 1 are replaced by electrons from water:

2 H2O 4 H+    4 e-     O2

 

  

Products of the Light Reactions

Input

Light Energy excites e-

H2O donates e-

NADP+  carries e-
 

Output

ATP - Energy for reactions

O2 - waste product

NADPH - provides electrons for CO2 sugar

 

Links to helpful animations:

summary leaf to NADPH and ATP

Light reactions in 4 stages

Animation of photosystems II and I

A close up of ATP synthase

 

 

Phase 2: The Calvin Cycle

 

Products of Phase 1 are used in Phase 2

ATP  Energy

NADPH e-(electrons)

 

Stage 2:  Calvin Cycle


Purpose: M
ake sugar from carbon dioxide


Location: Stroma of chloroplast


Requires        

ATP*

Electrons (NADPH)*

CO2

Enzymes

 

Produces Glucose

 

 

Link to Calvin cycle animation

 

Calvin Cycle

CO2 enters cycle by becoming attached to a 5-Carbon ribulose-bi-phosphate (RuBP)

6-Carbon molecule (unstable)

2  3-Carbon molecules

 

Calvin Cycle

Energy provided by (ATP ADP)

Electrons from NADPH used

3-Carbon compound leaves Calvin cycle

2     3-Carbon groups combine to  become glucose

remaining 3-Carbon groups continue through cycle to regenerate starting 5-Carbon RuBP

6 CO2 to produce 1 glucose

 

 

Important molecules are recycled

ATP ADP

NADPH NADP+

5-Carbon RuBP recycles
 

Photosynthesis Summary

Input:

Light

Water

CO2

 

Output:

Glucose

O2

 

Show your appreciation for
a green plant today!

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