Photosynthesis

THE BIG PICTURE

Scientists discovered that in the

presence of light, plants transform CO2 and water

into carbohydrates and release oxygen.

_____________ + ____________ _______________ + ____________

Carbondioxide

WATER Sugars Oxygen

6 CO2_____________ + ____________ _______________ + ____________6 H2O C6H12O6 6 O2→

PHOTOSYNTHESIS: Reactants & Products

LIGHT ENERGY

6CO2 + 6H2O SUGAR + 6O2

In addition to water and carbon dioxide,

__________________

and

__________________

are needed for photosynthesis to happen.

chlorophyll

light energy

Because light is a form of ___________, any molecule that absorbs light also ___________the energy from the light.

ENERGY

ABSORBS

Pigments

• Chlorophyll A is the most important photosynthetic pigment.

• The pigments are embedded in the membranes of the chloroplast in groups called photosystems.

Chlorophyll a

Chlorophyll b

Absorption of Light byChlorophyll a and Chlorophyll b

SO WHAT WAVELENGTHS ARE BEST FOR PHOTOSYNTHESIS?

THE ONESCHLOROPHYLLABSORBS THE BEST________ and_______________

red

Blue-violet

Chlorophyll a

Chlorophyll b

Absorption of Light byChlorophyll a and Chlorophyll b

NEITHER KIND OF CHLOROPHYLL IS VERY GOOD AT ABSORBING _________ LIGHT!GREEN

That’s why leaves LOOK GREEN…..

Chlorophyll doesn’t absorb…. it ___________ GREEN light!REFLECTS

PHOTOSYNTHESIS OVERVIEW

Photosynthesis: The Chemical Process

• Occurs in two main phases.– Light reactions– Dark reactions (aka – the Calvin Cycle)

• Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments.

• Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.

PHOTOSYNTHESIS

Light-Dependent

Reaction

Light-IndependentReactions

CALVIN CYCLE

Light & Water

Oxygen

ATP

NADPH

Carbon Dioxide (CH2O)n

Factors that Affect Photosynthesis____________________

Water is one of the raw materials needed, so

A shortage of water can ________________

photosynthesis

AMOUNT OF WATER

Desert plants and conifers that live in dry conditions have a waxy coating on their leaves to prevent water loss.

slow or stop

Factors that Affect Photosynthesis

Photosynthesis enzymes function best between 0° C - 35° C

At temperatures above or below this

range, photosynthesis will slow or stop

Conifers in winter may carry outphotosynthesis only occasionally

TEMPERATURE

http://www.sustland.umn.edu/maint/images/evergreen10.jpg

Factors that Affect Photosynthesis

____________________

More light increases rate of photosynthesis

up to a certain level until plant reaches its

maximum rate of photosynthesis

LIGHT INTENSITY

THE BIG PICTURE

These experiments led to work by later

scientists who finally discovered that in the

presence of light, plants transform CO2 and water

into carbohydrates and release oxygen.

_____________ + ____________ _______________ + ____________

Carbondioxide

WATER Sugars Oxygen

6 CO2_____________ + ____________ _______________ + ____________6 H2O C6H12O6 6 O2→

•Photosynthesis is the process by which plants and few other organisms use to transform light energy into chemical energy.

•Plants use chlorophyll to collect the energy from the sun rays to create the food they need, the food we eat, the oxygen we, all living creatures need to breath, and fossil fuels, like coal, oil and gas that the industrialized world needs.

•Without this process, life on earth would end, and the only organisms left would be the chemosynthesis bacteria.

•Photosynthesis is basic in the maintenance of life on earth.

THE BIG PICTUREWhy Should You Care?