Photosynthesis
Defined: process by which light energy is
converted to chemical energy.
• Is this an example of metabolism?
• Is this a chemical reaction?
Autotrophs: self feeding
Energy: ATP
Light- Absorbing Structures
• Pigments: molecule
that contains a lightabsorbing structure
• Chlorophyll: primary
pigment involved with
photosynthesis
• Carotenoids: secondary
pigments in
photosynthesis
Color- absorption vs. reflection
• What visible light colors (wavelength) does
chlorophyll A and B absorb? Reflect?
Infrared (IR) light
• Invisible to human
eye
• “Night Vision”
• “Thermographic”
cameras
• Photosynthetic
Bacteria
Prokaryotes
– Lack organelles
– Single celled
Cyanobacteria
Who came first?
Endosymbiosis
Recap Story of Life
• Atoms  Molecules
• Molecules  Organic compounds: monomers
• Monomers  Polymers
– Amino acids  protein and enzymes
– Glycerol & fatty acids  lipids
• Phospholipids  selective permeability
• Maintain Homeostasis
• Photosynthesis- Carry out Metabolic Reactions
Photosynthesis Stages
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
Stages of Photosynthesis:
i. Absorb light energy (via pigments)
ii. Convert light energy  chemical energy
iii. Convert chemical energy  organic
compounds
Photosynthesis
Light Reaction Steps
Calvin Cycle (Light- Independent)
Occurs in the Thylakoid Membrane  Chloroplast
Occurs in the stroma  chloroplast
1.
2.
1.
3.
4.
5.
6.
7.
Light energy is absorbed
Water molecules are split into H+ ions, O- and
e-.
O- combine to form O2 that diffuses out of
thylakoid membrane
H+ ions travel down concentration gradient
through the transport protein ATP synthase via
facilitated diffusion.
ATP synthase uses energy from H+ gradient to
combine ADP + Pi  ATP (chemical energy)
Light energy excites electrons, which bounce
through the Electron Transport Chain (ETC)
and land on NADP+ reductase, enzyme.
NADP+ reductase combines e- + NADP+ 
NADPH
Inputs: H2O + light energy
Intermediates: H+ ions, Oxygen and Electrons
Outputs: ATP and NADPH
2.
3.
4.
CO2 is added to a 5-C compound via enzyme
RuBisCO to make a 6-C compound.
The resulting 6-C compound splits into two 3C compounds; phosphates from ATP and
electrons from NADPH are added.
One of the 3-C compounds is used to make
C6H12O6, a sugar to store energy for plant.
The other 3-C compound gets recycled back
into the mix to keep cycle going.
Inputs: ATP, NADPH and CO2
Intermediates: 3- carbon sugar
Outputs: C6H12O6
6.
7.
6.
2.
3.
4.
5.
+ 5 carbon compound
RuBi
sCO
Unstable 6 carbon compound
3 carbon simple
sugar (recycled)
organic compounds:
sucrose, starch