Download PPT

Photosynthesis
Chemical Cycling between Photosynthesis and
Cellular Respiration
– The ingredients for
photosynthesis are
carbon dioxide and water.
• CO2 is obtained from the
air by a plant’s leaves.
• H2O is obtained from the
damp soil by a plant’s
roots.
– Chloroplasts rearrange
the atoms of these
ingredients to produce
sugars (glucose) and
other organic molecules.
• Oxygen gas is a by-product
of photosynthesis.
– Both plants and animals
perform cellular respiration.
• Cellular respiration is a
chemical process that
harvests energy from
organic molecules.
• Cellular respiration occurs
in mitochondria.
– The waste products of
cellular respiration, CO2 and
H2O, are used in
photosynthesis.
The Basics of Photosynthesis
– Almost all plants are photosynthetic
autotrophs, as are some bacteria and protists.
• They generate their own organic matter through
photosynthesis.
Chloroplasts: Sites of Photosynthesis
– Chloroplasts
• Are found in the interior cells of leaves.
• Contain stroma, a thick fluid.
• Contain thylakoids, membranous sacs.
The Overall Equation for
Photosynthesis
– The reactants and products of the reaction
•Solar energy (sunlight) energizes electrons that are
then added to carbon dioxide to make sugar.
A Photosynthesis Road Map
– Photosynthesis is composed of two
processes:
•The light reactions
convert solar energy to
chemical energy.
•The Calvin cycle adds
that chemical energy to
carbon dioxide to make
the high-energy
molecule sugar.
The Nature of Sunlight
– Sunlight is a type of energy called radiation
• Or electromagnetic energy.
– The full range of radiation is called the
electromagnetic spectrum.
The Light Reactions
– Chloroplasts are chemical factories powered by
the sun that convert
solar energy
into
chemical energy.
- Chloroplasts absorb select
wavelengths of light that drive
photosynthesis.
http://www.youtube.com/watch?v=IJCVg9M-7S0
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Chloroplast Pigments
– Chloroplasts contain several pigments:
• Chlorophyll a
• Chlorophyll b
• Carotenoids
How Photosystems Harvest
Light Energy
– Light behaves as photons, discrete packets
of energy.
– Chlorophyll molecules absorb photons.
• Electrons in the pigment gain energy.
Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman
(www.whfreeman.com)
Check out: http://science.howstuffworks.com/light-stick.htm
Figure 7.9
– A photosystem
• Is an organized group of chlorophyll and other
molecules.
• Is a light-gathering antenna.
How the Light Reactions
Generate ATP and NADPH
– An electron transport chain
• Connects the two photosystems.
• Uses energy in electrons to make ATP
– Two types of photosystems cooperate in
the light reactions.
How the Light Reactions
Generate ATP and NADPH
http://www.youtube.com/watch?v=v590JJV96lc&feature=related
The Calvin Cycle
– The Calvin cycle
• Functions like a
sugar factory
within a chloroplast.
• Adds the energy and
H+ stored in ATP and
NADPH to carbon
dioxide to make sugar.
http://www.youtube.com/watch?v=mHU27qYJNU0
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
A review of photosynthesis