Introduction to Photosynthesis Day 2 Unit 3 Introduction to Photosynthesis

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

Agenda Lecture on Photosynthesis Homework: ATP Energy Molecule

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. . .

Photosynthesis

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

Focus The light Reaction

Cell Chloroplasts

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

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

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

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

H2O O2 and H+

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

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

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

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

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

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.

A chemiosmotic gradient? What?

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

H+ H+ H+ H+ H+ H+ H+ H+ H+ ATP Synthase ATP ADP Pi

So what?

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

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

video Photosynthesis