1. Introduction to Photosynthesis
Day 2 Unit 3
Introduction to Photosynthesis

2. Warm Up
Get a computer Reading Comp 7 Use your notes but not each other 20 minutes

3. Agenda
Lecture on Photosynthesis Homework: ATP Energy Molecule

4. Unit Three LTs
I can describe why all living systems require a constant input of free energy and matter I can explain how photosynthesis provides living things with matter and free energy I can explain how cellular respiration provides living things with a useable source of free energy I can explain why living things must exchange matter with the environment, and describe how these exchanges take place* *: Winter break LT. . .

5. Photosynthesis

6. Photosynthesis: Two Stages:
Light Reactions (photo):
Energy from the sun is captured in the chemical bonds of energy carrier molecules
Energy transfer
Energy transformation (light to chemical energy)
OVERALL: spontaneous/exergonic, but released energy is used to do work/captured
Calvin Cycle/Dark Reactions (synthesis):
Captured energy is used to build sugars
Energy Transfer
OVERALL: non-spontaneous/endergonic; coupled with exergonic releases of energy from carrier molecules
6H2O + 6CO2+ LIGHT  C6H12O6 + 6O2

7. Focus
The light Reaction

9. Cell
Chloroplasts

10. The structure of a chloroplast
A SINGLE chloroplast
Stroma is the between the inner chloroplast and the grana space in the chloroplast, lumen is the space inside the thykaloid
The structure of a chloroplast

11. Stroma is the between the inner chloroplast and the grana space in the chloroplast, lumen is the space inside the thykaloid

13. The Electron Transport Chain
the Light Reactions, Part 1
The Electron Transport Chain

14. Light, Chlorophyll and the Electron transport chain
The Photosystems in the electron transport chain (ETC) are made of proteins called pigments
Main pigment/protein: chlorophyll
Three chlorophylls (A, B and C); A most important
Other pigments: carotenoids
These pigments ABSORB photons of light
Different pigments absorb different wavelengths/colors
When the pigment absorbs the photon of light, it captures its ENERGY
The energy is transferred from pigment to pigment
The energy EXCITES an electron in the final chlorophyll A
Energy transfer: LIGHTCHLORPHYLLELECTRON

16. H2O O2 and H+

17. Redox Reactions, Electrons and Energy
Redox=oxidation-reduction reaction (a type of chemical reaction) {remember LEO and GER!}
Involves the MOVEMENT OF ELECTRONS
One reactant molecule donates electrons, and is oxidized (LEO)
Second reactant molecule accepts electrons, and is reduced (GER)
This involves a CHANGE IN THE POTENTIAL ENERGY OF THE ELECTRONS
Analogy: rolling a ball down a hill
As the ball rolls, it loses potential energy
That energy doesn’t go away—it is transferred to kinetic energy

18. Potential Energy of the Ball Converted to Kinetic Energy
High Potential Energy
Potential Energy of the Ball Converted to Kinetic Energy
Low Potential Energy

19. Redox Reactions and Photosynthesis
Each photon (light particle) energizes ONE chlorophyll electron
This electron (and its energy) is transferred from molecule to molecule in the electron transport chain in a series of REDOX reactions
As it is transferred, the electron loses energy
Just like the ball rolling down hill loses energy
This energy is USED to do work
The ETC pumps hydrogen ions into the thylakoid compartment

20. An electron in the ETC is like a ball rolling down a hill—its potential energy decrease as it is transferred into kinetic energy e-
Energy of the electron

21. At the end of the ETC, the electron (and its remaining energy) is used to join a H+ ion to a molecule called NADP+, forming an energy carrier molecule called NADPH. . . e-
NADP+ H+
NADPH NOW CONTAINS SOME OF THE SUN’S ENERGY! + +
NADPH

22. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ e- H+ H+
Movement of an e- through the ETC results in the pumping of H+ ions into the thylakoid
Result: a difference in concentration of H+ ions across the membrane. This is called a chemiosmotic gradient.

23. A chemiosmotic gradient?
What?

25. The H+ Gradient
Just like water behind a dam, the chemiosmotic gradient contains POTENTIAL ENERGY
In a dam:
Potential energy of water used to generate electricity
In the thylakoid:
Potential energy of the gradient used to by an enzyme called ATP Synthase to make ATP
H+ ions actually flow through the enzyme
The flow of H+ ions provides the energy necessary to join inorganic phosphate (Pi) to ADP, making ATP

26. H+ H+ H+ H+ H+ H+ H+ H+ H+
ATP Synthase
ATP
ADP Pi

27. So what?

28. At the end of the Light Reactions, you have two energy carrier molecules
NADPH ATP

29. INPUTS and OUTPUTS of Light Reaction
6H2O + 6CO2+ LIGHT  C6H12O6 + 6O2
Inputs:
Water
Light
Outputs:
Energy carrier molecules
Oxygen

30. video
Photosynthesis