Transcript Photosynthesis Powerpoint

Today’s Objectives
• Given information and/or diagrams on
the process of photosynthesis, write
and/or identify the equation, raw
materials, sites, products, factors
affecting the process, and the role of
chlorophyll in the light and dark
reactions.
ATP: The Cell’s Currency
• Adenosine Triphosphate
• Energy from food is converted into
high energy bonds in ATP
• ADP + P + energy  ATP
Photosynthesis
• 6 CO2 + 6 H2O + Light Energy  C6H12O6 + 6 O2
• Basis of most of the earth’s food chains
• Produces and maintains all of the earth’s atmospheric
oxygen
• Most oxygen produced in the oceans
Photosynthetic Pigments
• Mostly chlorophyll a and chlorophyll b
• Accessory pigments:
• Carotenoids
• Anthocyanins
• Each pigment absorbs a particular
wavelength of light in the visible
spectrum
Photosynthesis:
Reactants & Products
Chloroplast Structure
Pigment Absorption
Pigments – protein molecules that
absorb specific colors of light.
• Most plants have
at least 3
pigments:
• 1. Chlorophyll A
• 2. Chlorophyll B
• 3. Carotenoids
* Why do leaves change color in the fall?
Overview of Photosynthesis
Step I: Light Reactions
• Involves the splitting of water
(photolysis)
• 12 H2O + Energy  6 O2 + 24 H+ +
24e• Requires light for the energy to split the
water molecule
• Also forms a highly energetic compound,
adenosine triphosphate (ATP)
Overview of the Light Reactions
• Think of the light reaction, as a
process by which organisms "capture
and store" radiant energy as they
produce oxygen gas. This energy is
stored in the form of chemical bonds
of compounds such as NADPH and
ATP.
Light Reaction = Electron Transport
When Sunlight is absorbed by Photosystem II, electrons
are “kicked out”.
Water is “split” to replace lost electrons.
Electrons are passed along a chain of molecules to
Photosystem I.
Energy from moving electrons is used to pump protons
inside the thylakoid.
Light Reaction - Analogy
Light-Dependent Reaction – Summary
• Water and Light are
converted into ATP &
NADPH.
• Occurs in the
Thylakoid Membrane.
• Oxygen is released as
a waste product.
• NADPH – an energy
(electron) carrying
molecule
Step II: Dark Reactions
• Does not require light but can happen at
any time of day.
• The energy from NADPH and ATP is used
for carbon fixation
• 6 CO2 + 24 H+ + 24 e- ------>
C6H12O6 + 6 H2O
• The chemical bonds present in glucose
also contain a considerable amount of
stored (potential) energy.
Dark Reaction – Calvin Cycle
• Energy stored from the
light reaction (ATP &
NADPH) is used to
power the production
of sugar.
• Carbon Dioxide and
Hydrogen are
converted into ½ of a
glucose = PGAL
Calvin Cycle – another diagram
Calvin Cycle (Light-Independent Reaction) –
Summary
• CO2 is converted into
carbohydrate (PGAL).
• Occurs in the Stroma.
• ATP and NADPH
provide the energy.
• PGAL = 3 carbon
sugar that is used to
make Glucose or other
carbohydrates.
Overview of the Dark Reactions
• Carbon dioxide is broken and “fixed” into
glucose or fructose molecules in the
CALVIN CYCLE!!!!
• Glucose subunits can make cellulose or
other polysaccharides, such as fruit sugars.
• The carbon skeleton in glucose also helps
to synthesize other important biochemical
compounds such as, lipids, amino acids,
and nucleic acids.
Diagram of Photosynthesis