Photosynthesis

I. Introduction

A. Goal of photosynthesis

To construct food using light energy

Food = Glucose

Converting radient energy (sun) to

Chemical energy.

I. Introduction

B. Photosynthetic organisms

Called Autotrophs

Examples – Plants, Algae

II. The Physics of LightA. Light travels in wave

Wavelength – distance peak to peak

Frequency – height of wave

II. The Physics of LightB. Visible Light

spectrum

II. The Physics of Light

C. Energy in light

Highest energy =

Short wavelength

High frequency

III. Photosynthesis and Pigments

A. Pigments absorb some colors and reflect others

1. Reflected colors is what we see

III. Photosynthesis and Pigments

A. Pigments absorb some colors and reflect others

2. Absorbed colors raises electrons to higher energy levels – generates heat

III. Photosynthesis and PigmentsB. Pigments in plants

1. Chlorophyll A – absorbs from ends of visible spectrum

2. Chlorophyll B – absorbs toward the middle of the spectrum

III. Photosynthesis and PigmentsB. Pigments in plants

3. Carotenoids – Aid Chlorophyll.

Orange and yellow in color

III. Photosynthesis and PigmentsC. Chloroplast structure

Double membrane

Filled with dense solution – Stroma

Thylakoid membranes

Thylakoids stack up = Grana (granum)

III. Photosynthesis and PigmentsC. Chloroplast structure

III. Photosynthesis and PigmentsD. Chloroplasts – locations

Green areas – mainly leaves

IV. Photosynthesis ProcessA. Two parts

1. Light Reactions (Sun necessary)Goal – convert sun energy to

chemical energy2. Dark Reactions (No light needed)

Goal – Build Glucose

IV. Photosynthesis ProcessB. The Light Reaction

1. Photosystem 2Pigments receive sun energyElectrons are raised to high energy level

Electrons passed down anElectron transport chain,

loosing energy as they goElectron Energy used to convert

ADP to ATPElectrons are passed to next step

Lost electrons are replaced by splitting water

IV. Photosynthesis ProcessB. The Light Reaction

2. Photosystem 1Receives electrons from P2Electrons energized by sunTwo directions for electrons

a. Non-cyclic flowElectrons become part of

NADPH (Chem. Energy)

IV. Photosynthesis ProcessB. The Light Reaction2. Photosystem 1Two directions for electons

b. Cyclic flowEnergized Electrons Make H move through enzymeATP SynthaseMakes lots of ATP!Used electrons cycle back

IV. Photosynthesis ProcessB. The Light ReactionSummary of light reactions

Photosystem 2Sends ATP energy to Dark Reactions

Photosystem 1 Non-cyclic – Sends NADPH to Dark R.

(High energy electron carrier) Cyclic – Sends ATP to Dark Reactions

Key – Light reactions convert sun energy tochemical energy to power the dark reactions

IV. Photosynthesis ProcessB. The Dark Reactions

Called the Calvin Cycle

This is the “Glucose Machine”

Powered by ATP and NADPH from

the light reactions

CO2 provides carbon to make Glucose

Oxygen is the waste product

(Given off from light reaction)