ch. 10 photosynthesis. history jan van helmont mass of plant, container and soil, document mass of...
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Ch. 10 PHOTOSYNTHESIS
History
Jan Van Helmont Mass of plant, container and soil, document mass of water –
new growth was greater Joseph Priestley
Mint plant keeps candle lit inside jar, plants produce oxygen Also discovered/named oxygen
Jan Ingenhousz Plants only produce oxygen if in the light
Melvin Calvin Steps of dark reactions using radioactive tracers
CARBON DIOXIDE COMING INTO PLANT – CREATING CARBOHYDRATES ….. BIOMASS
Energy Flow
Energy flow is one directional From sun (solar energy) to chemical then
mechanical energy….. Eventually heat Elements/ nutrients/ matter cycles
C cycle, N cycle, Water cycle, etc. Food webs
Autotrophs = self feeding; photoautotrophic and chemoautotrophic
Heterotrophs = other feeding; herbivores, carnivores, omnivores, detritivores, decomposers, parasites, etc.
Leaf Structure
Chlorophyll is a chemical/ pigment
Chloroplasts are structures that contain chlorophyll Many layers (Membranes)
Other plastids chromoplast leukoplast amyloplasts
Specialized cells/ tissues
From chloroplast to leaf
Light Reactions
Require light to occurRequire waterLight energy is used to split a water
moleculeThylakoid is site of reactionProvides H for NADPH, e- and Generates oxygen that is released
Light Reaction Details
Photons (units of light), at just below 500 reach chloroplast and strike chlorophyll on thylakoid membrane
e- on chlorophyll are excited e- are passed to primary acceptor Heat is given off Water is split Oxygen helps oxidize reaction, O loses H and
e- returns to chlorophyll NADPH and ATP are generated
Noncyclic electron flow
Cyclic electron flow
Dark Reactions
Occurs in stroma of chloroplastDoes not require dark ( or light )Needs NADPH and ATP from light
reactionsUses CO2
Generates glycerol 3 phosphate (1/2 of a glucose…. aka PGAl )
Details of Calvin cycle
Phase 1: CO2 is incorporated, called ‘carbon fixation’
Phase 2: phosphorylation, ATP spent, e- from NADPH reduce the C chain so it stores more potential energy
6 molecules with 3 C are made – 5 are recycled and one is released as a future glucose
Phase 3: cycles
Summary
Rubisco is the enzyme that catalyzes the first step of Calvin cycle – since in all chloroplasts of all cells of all leaves, it’s the most abundant protein on Earth.
sunlight6CO2 + 6H2O C6H12O6 + 6O2
chlorophyll
Compare and contrast
PHOTOSYNTHESIS Chloroplast stroma and inner
membrane ETC and cycle ETC first CO2 in, O2 out Fixes C into chains Stores energy
RESPIRATION Mitochondria matrix and inner
membrane ETC and cycle ETC last C cpd in, CO2 out Breaks C bonds Releases energy
Alternatives
C3 plants ( rice and wheat; grasses) Close stomata, hot dry weather,
less sugar – do photorespiration
Photorespiration – process adds O2 by rubisco and this product then splits releasing CO2
C4 plants Sugar cane and corn Make 4 C cpd first then Calvin –
making PEP that can fix CO2 easily, even when hot.
CAM Succulent plants like cactus and
pineapples Crassulacean Acid Metabolism
make and store organic acids to be broken down to CO2 and used over night when cooler