Photosynthesis

Journey Into a Leaf

Plant Stomata

Water and Oxygen

Overall Equation

Is this a Redox Reaction?

Overall EquationIs this a Redox Reaction? Yes: electrons are still transferred from one

molecule to another

Questions About PlantsWhy do plants need water?

Why do they release oxygen?

Photosynthesis

To answer these questions we must first ask, how can solar light provide energy for plants?

Photosynthesis

How can solar light provide energy for plants? Shorter the

wavelength the greater the energy

Solar Radiation

Solar radiation is absorbed by chlorophyll (pigments in the thylakoids)

Why are plant leaves green?

All other colors (wavelengths) are absorbed

Chloroplast Pigments

Chlorophyll a

Chlorophyll b

Carotenoids

Many others…why?

Why reflect green?

Photosynthesis

Two Stages Light Reactions Calvin Cycle

You need to know The main purpose of

each stage Where they take

place

Photon Absorption

What happens when a photon is absorbed by a pigment?

The Photosystem

Energy (not electrons) is passed from one pigment to the next until it reaches the reaction center

Making ATP & NADPH

The pigment in the reaction center will give up its excited electron to an electron acceptor

Conversion of light energy to chemical energyWhat can cells do with captured electrons?

Electron Flow & Potential Energy

A Familiar Processes

The Calvin Cycle

Summary

Problem with Photosynthesis

Photorespiration When its hot out, stomata

close up…why is this a problem? CO2 can’t get into cell and O2 can’t leave

O2 then enters Calvin Cycle

Sugar production stops because there’s no carbon source

Photorespiration

The Oxygen Revolution

Was O2 always part of our atmosphere?

How do we know?

How and when did it happen?

What was the impact?