Photosynthesis

Journey Into a Leaf

Plant Stomata

Water and Oxygen

Overall Equation Is this a Redox Reaction?

Overall Equation Is this a Redox Reaction? Yes: electrons are still transferred from one molecule to another

Questions About Plants Why 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 You need to know 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 energy What 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?