chapter 7 - photosynthesis almost all plants are photosynthetic autotrophs, as are some bacteria and...
TRANSCRIPT
Chapter 7 - Photosynthesis
• Almost all plants are photosynthetic autotrophs, as are some bacteria and protists
– They generate their own organic matter through photosynthesis..
(a) Mosses, ferns, andflowering plants
(b) Kelp
(c) Euglena(d) Cyanobacteria
Meso-phyll
Vein
Stomata
Leaf cross section Mesophyll cell
Chloroplast
Innermembrane
Outermembrane
Grana Stroma Thylakoid Thylakoidspace
• Photosynthesis occurs in the chloroplasts, which:– Are found in the cells of the mesophyll– Contain stroma, a thick fluid– Contain thylakoids, membranous sacs in stacks
called grana..
• The reactants and products of the reaction..
The Overall Equation for Photosynthesis
Lightenergy
Carbondioxide
WaterPhoto-
synthesis Glucose Oxygengas
• Photosynthesis is a two-step process:– Light reactions – require sunlight energy
to split water molecules into 2H and O2
– Calvin Cycle (dark reactions) – hydrogen generated from the light reactions is used to reduce CO2 to generate sugar – does not require sunlight• Leaves absorb CO2 through stomata..
LightChloroplast
Lightreactions
Calvincycle
NADP
ADP+ P
• Chlorophyll molecules absorb photons– Electrons in the pigment gain energy
– The energy is released and used..
Excitedstatee
Heat
Light
Photon
Light(fluorescence)
Chlorophyllmolecule
Groundstate
1 2
(a) Absorption of a photon
(b) fluorescence of isolated chlorophyll in solution
(c) Fluorescence of a glow stick
• The light reactions in the thylakoid membrane
2NADP+ 2NADPH2
– 2H2O O2 ..
Light Light
To Calvin Cycle
Stroma
Thylakoidmembrane
Electron transport chainATP
synthase
Inside thylakoid
1/2
NADPADP + P
Light Reactions
• The Calvin cycle– Functions like a sugar factory within a
chloroplast– Regenerates the starting material with each turn
6NADPH2 6NADP + 12H
6CO2 C6H12O6
The Calvin Cycle: Making Sugar From Carbon Dioxide
Input
3 CO2
6 3-PGA
6
6 ADP + 6
6
6 NADP
6 G3P
Glucose andother compoundsOutput
5 G3P
3
3 ADP
3 RuBP
Calvincycle
1 G3P
• Photosynthesis has an enormous impact on the atmosphere– It swaps CO2 in the atmosphere for O2
Why do we need the O2?..