1 Photosynthesis Energy & Life copyright cmassengale

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Photosynthesis

Energy & Lifecopyright cmassengale

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The Photosynthesis Equation

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Redox Reactions

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Redox Reaction

The transfer of one or more electrons from one reactant to another

Two types:1. Oxidation is the loss of e-

2. Reduction is the gain of e-

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Oxidation Reaction

The loss of electrons from a substance or the gain of oxygen.

Example: Burning“Breaking Down Compounds”

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Reduction Reaction

The gain of electrons to a substance or the loss of oxygen.

“Building Up Compounds”

Question: If electrons are gained, what happens to the CHARGE of the molecule?

Would photosynthesis be considered an

oxidation reaction or a reduction reaction?

Why?


Photosynthesis

Photosynthesis is the REDUCTION of

Carbon Dioxide (CO2) into

Glucose (C6H12O6)


6CO2 + 6H2O 6O2 + C6H12O6

Reduction

PHOTOSYNTHESISThe Reactions

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Photosynthesis• Anabolic (small molecules combined)

consume energy to build molecules from simpler ones

• Endergonic (stores energy)absorbs free energy from its surroundings

• Carbon dioxide (CO2) requiring process that uses light energy (photons) and water (H2O) to produce organic macromolecules (glucose).

6CO2 + 6H2O C6H12O6 + 6O2glucose

SUNphotons

Electron Carriers

Electron carriers are molecules that will “pick up” one or two

hydrogen ions and electrons and carry them to another location.

Examples: Photosynthesis = NADP +

Cellular Respiration = NAD + & FAD+


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Photosynthesis Overview


1st Step of Photosynthesis• Light-Dependent Reactions

–Requires light (Energy Source)–Occurs in the Thylakoids

•In the Chlorophyll (inside the Thylakoids)

•Across the Membrane of the Thylakoids

Light-Dependent Reactions• These reactions use water molecules to

produce oxygen gas.• They use energy from light to produce

ATP and NADPH (an electron carrier).• They convert

–ADP into ATP–NADP+ into NADPH

Light-Dependent Big Idea

Light is absorbed by chlorophyll to split water

molecules and give off oxygen.

This “charges up” the energy molecules ATP and

NADPH.

2nd Step of Photosynthesis

• Calvin Cycle – a.k.a. Light-Independent Reactions or

Carbon Fixation

–Does NOT require light•Uses Energy Storage Molecules (ATP & NADPH)

–Occurs in the Stromacopyright cmassengale 16

Calvin Cycle (Light-Independent Reactions)

• Uses CO2 and the “Left-over” Hydrogen from NADPH.

• Produces Glucose (C6H12O6).

• These reactions use the ATP and NADPH produced in the light-dependent reactions to produce high-energy sugars.

Calvin Cycle Big Idea (Light-Independent)

Energy is used from ATP and NADPH.

The “left-over” hydrogens from the water are carried to the

stroma by NADPH.

They are combined with CO2 to make glucose.

Light Dependent Calvin Cycle• Energy Source= Light• Occurs in the Thylakoids

(Chlorophyll & membranes)

• Changes ADP into ATP• Changes NADP into

NADPH• Uses H2O

• Produces Oxygen Gas

• Energy Source = ATP and NADPH

• Occurs in the Stroma• Changes ATP into ADP• Changes NADPH into

NADP• Uses CO2 & “left-over” H

from NADPH• Produces Glucose

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Photosynthesis Overview


Light Dependent Reaction


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Thylakoid membranes

• Light Dependent reactions occur here

• Photosystems are made up of clusters of chlorophyll molecules integrated into the thylakoid membrane

• The two photosystems are: Photosytem I &

Photosystem II copyright cmassengale

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• Occurs across the thylakoid membranes

• Uses light energy• Produce Oxygen from

water• Convert ADP to ATP• Also convert NADP+ into the energy carrier NADPH

Light Dependent Reactions


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Photosystem II

•Discovered Second but OCCURS FIRST•Contains about equal amounts of chlorophyll a and chlorophyll b•Photosystem II absorbs light energy•SPLITS H2O into O2

•Excites Electrons!copyright cmassengale

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Photosynthesis Begins

Electrons are energized and passed to the Electron Transport Chain

Lost electrons are replaced from the splitting of water into 2H+, free electrons, and Oxygen

2H+ pumped across thylakoid membrane (active transport)


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Noncyclic Electron Flow

P700

Photosystem IP680

Photosystem II

PrimaryElectronAcceptor

ETC

H2O

1/2O2 + 2H+

ATPPhoton

2e-

2e-

2e-SUN

H2O is split in PSII & ATP is made

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Photosystem I

•Discovered First but occurs SECOND•Almost completely chlorophyll a•MAKES NADPH


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Photosystem I• High-energy electrons are

moved to Photosystem I through the Electron Transport Chain

• Energy is used to transport H+ from stroma to inner thylakoid membrane

• NADP+ converted to NADPH when it picks up 2 electrons & H+


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P700

Photosystem IP680

Photosystem II



ETC

EnzymeReaction

H2O

1/2O2 + 2H+

ATP

NADPH

Photon

2e-

2e-

2e-

2e-

2e-

SUN

Photon

The energy carrier NADPH is made in PSI

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• ADP + ATP• NADP+ + H NADPH• Oxygen comes from the

splitting of H2O, not CO2

H2O 1/2 O2 + 2H+

P

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ChemiosmosisH+ H+

ATP Synthase

H+ H+ H+ H+

H+ H+high H+

concentration

H+ADP + P ATP

PS II PS IE

TC

low H+

concentration

H+ThylakoidSpace

Thylakoid

SUN (Proton Pumping)

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Chemiosmosis• Powers ATP synthesis• Takes place across the

thylakoid membrane• Uses ETC and ATP synthase

(enzyme)• H+ move down their

concentration gradient through channels of ATP synthase forming ATP from ADP

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Light Reaction Summary

Reactant: H2O

Also Needed: Light Energy, Chlorophyll, ADP & NADP

Products:• O2 (PS II; released into atmosphere)

• ATP (chemiosmosis)

• NADPH (PS I; used in the Calvin Cycle)


Light Dependent Reaction Simulation

• http://www.youtube.com/watch?v=RFl25vSElaE

• Video http://www.youtube.com/watch?v=v590JJV96lc

• Rap http://www.youtube.com/watch?v=pE82qtKSSH4

• Light Dependent Claymation http://www.youtube.com/watch?v=CLf4yu8Iwo0


http://www.youtube.com/watch?v=RFl25vSElaE

http://www.youtube.com/watch?v=RFl25vSElaE

http://www.youtube.com/watch?v=v590JJV96lc

http://www.youtube.com/watch?v=pE82qtKSSH4

http://www.youtube.com/watch?v=CLf4yu8Iwo0

The Calvin Cycle


REMEMBER

• The following were produced during the Light-Dependent Reaction:–O2 (released into the atmosphere)

–NAPDH & ATP (used for ENERGY in the Calvin Cycle)


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2nd Step of Photosynthesis

Calvin Cycle • aka Light Independent

Reaction, Dark Reaction, Carbon Fixation or C3 Fixation

• Uses energy (ATP and NADPH) from light reaction to make sugar (glucose).

• Occurs in the stroma • Uses 6 CO2

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Chloroplast

GranumThylakoid

STROMA– where Calvin Cycle occursOuter Membrane

Inner Membrane

Calvin Cycle• RuBP (a 5-carbon sugar)

attaches to each CO2 forming a temporary 6-carbon sugar

• This 6-carbon sugar splits apart into 2 3-carbon sugars called PGA

• PGA exchanges Hydrogen and Oxygen to transform into G3Ps (a different 3-carbon sugar)


Calvin Cycle (continued)• 2 G3Ps combine to form Glucose (C6H12O6)

• The other G3Ps combine to become RuBP molecules

• To produce 1 Glucose molecule–6 turns of the cycle–Uses 18 ATP and 12 NADPH–“Fixes” 6 CO2 molecules into a usable form for organisms


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Calvin Cycle (C3 fixation)

6CO2

6C-C-C-C-C-C

6C-C-C 6C-C-C

6C-C-C-C-C

12PGA

RuBP

12G3P

(unstable)

6NADPH 6NADPH

6ATP 6ATP

6ATP

C-C-C-C-C-CGlucose

(6C)(36C)

(36C)

(36C)

(30C)

(30C)

(6C)

6C-C-C 6C-C-C

C3

glucose

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Calvin Cycle

Remember: C3 = Calvin

Cycle

C3

Glucose

• Big Idea: 6 CO2 molecules are “fixed” into Glucose (C6H12O6)

• ADP & NADP+ are reused in the next light-dependent reaction

More Videos• Calvin Cycle Claymation

https://www.youtube.com/watch?v=hhkpJwSDxQQ • Calvin Cycle Animation

https://www.youtube.com/watch?v=E_XQR800AgM• Crash Course Biology: Photosynthesis

https://www.youtube.com/watch?v=sQK3Yr4Sc_k


https://www.youtube.com/watch?v=hhkpJwSDxQQ

https://www.youtube.com/watch?v=E_XQR800AgM

https://www.youtube.com/watch?v=sQK3Yr4Sc_k

How do these large trees get all their mass?

• Complete the Life Science Assessment Probe – Giant Sequoia Tree

Documents

1 Photosynthesis Energy & Life copyright cmassengale