photosynthesis. journey into a leaf plant stomata
TRANSCRIPT
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?