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stomate
transpirationgas exchange
PHOTOSYNTHESIS!!
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Photosynthesis Overview
Energy for all life on Earth ultimately comes from photosynthesis.
6CO2 + 12H2O C6H12O6 + 6H2O + 6O2
Photosynthesis is carried out by:Cyanobacteria,Some protists,+ Land plants
• Chloroplasts– double membrane– stroma
• fluid-filled interior
– thylakoid sacs– grana stacks
• Thylakoid membrane contains– chlorophyll molecules– electron transport chain– ATP synthase
• H+ gradient built up within thylakoid sac
H+ H+
H+
H+
H+H+
H+ H+
H+H+
H+
outer membrane inner membrane
thylakoidgranum
stroma
thylakoid
chloroplast
ATP
6
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Pigments
Pigments: molecules that absorb visible light
Each pigment has a characteristic absorption spectrum, the range it is capable of absorbing.
--chlorophyll a – primary pigment--chlorophyll b – secondary pigment-- carotenoids – accessory pigments
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Why are plants green??
Two stages of photosynthesis:
1. Light-dependent reactions• Requires light as a source of energy
Step 1: chlorophyll uses energy from sun to split water molecules
Step 2: water molecules split into H & OStep 3: O2 released to atmosphere
Step 4: chlorophyll stores some light energy in ATP
Photo
phosphoryl
ation A process
Adding aphospate group
Using light
Light Reactions
O2
H2O
Energy BuildingReactions
ATP
produces ATP produces NADPH releases O2 as a
waste product
sunlight
H2O ATP O2lightenergy ++ + NADPH
NADPH
Thylakoid Structure
Non-cyclic
2. Light-Independent reactions (Calvin Cycle)• Part of photosynthesis that doesn’t require
light
Step 1: hydrogen which split from H2O combines with CO2 using energy stored in ATP
Step 2: this combination forms glucose (C6H12O6)
Step 3: water is formed (byproduct)
Making Sugar
The energy captured in the Lt-Dep is now used to fix CO2 and make sugar.
Calvin Cycle
sugars
CO2
SugarBuildingReactions
ADP
builds sugars uses ATP &
NADPH recycles ADP &
NADP back to make more
ATP & NADPHATP
NADPH
NADP
CO2 C6H12O6 ++ + NADPATP + NADPH ADP
Putting it all together
CO2 H2O C6H12O6 O2lightenergy + ++
SugarBuildingReactions
Energy BuildingReactions
Plants make both:energy
ATP & NADPH sugars
sunlight
O2
H2O
sugars
CO2
ADP
ATP
NADPH
NADP
*respiration occurs in plant cells also, when they need to release the energy stored in glucose
H2O
Energy cycle
Photosynthesis
Cellular Respiration
sun
glucose O2CO2
plants
animals, plants
ATPThe Great Circleof Life,Mufasa!
CO2 H2O C6H12O6 O2lightenergy + ++
even thoughthis equationis a bit of a lie…it makes a better story
CO2 H2OC6H12O6 O2ATPenergy+ ++
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