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Photosynthesis

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lovelle navos

on 3 February 2014

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Transcript of Photosynthesis

Powered by light, chlorophyll produces organic compounds and oxygen from carbon dioxide and water
Hydrogen extracted from water is incorporated into sugar and is released into the atmosphere
Water is then split and electrons are transferred with H+ from water to carbon dioxide, reducing its sugar
Therefore photosynthesis is a redox reaction
Also, light boosts potential energy of electrons as they move from water to sugar
Powered by light, chlorophyll produces organic compounds and oxygen from carbon dioxide and water
Hydrogen extracted from water is incorporated into sugar and is released into the atmosphere
Water is then split and electrons are transferred with H+ from water to carbon dioxide, reducing its sugar
Therefore photosynthesis is a redox reaction
Also, light boosts potential energy of electrons as they move from water to sugar
Light reaction turns solar energy to chemical energy
Light energy is absorbed by chlorophyll in thylakoids that drive the transfer of electrons and hydrogen from water to NADP +, forming NADPH
NADPH, an electron acceptor provides energized electrons, reducing power to the Calvin Cycle
Also generates ATP by phosphorylation for the Calvin Cycle
Occurs in the thylakoids
Light reaction turns solar energy to chemical energy
Light energy is absorbed by chlorophyll in thylakoids that drive the transfer of electrons and hydrogen from water to NADP +, forming NADPH
NADPH, an electron acceptor provides energized electrons, reducing power to the Calvin Cycle
Also generates ATP by phosphorylation for the Calvin Cycle
Occurs in the thylakoids
Two Main Steps of Photosynthesis:
Two Main Steps of Photosynthesis:
Photosynthesis
light
What is photosythesis?
It is the conversion of light into chemical energy that is stored in sugars or other organic compounds
This process is a series of chemical reactions that require carbon dioxide, water, and light to produce glucose, oxygen, and water
The following equation summarizes photosythesis:
6CO2 + 6H2O + light energy ---> C6H12O6 + 6O2
Introduction to Photosynthesis:
What is an autotroph?
Autotrophs are living organsims that can produce its own food from carbon dioxide and other inorganic raw materials from the environment to create oxygen.
They are the producers of the biosphere
Ex.) plants, algae, some protists, and cyanobacteria
What are heterotrophs?
Heterotrophs are organisms that are consumers of the biosphere
They depend on autotrophs in order to live
Many heterotrophs feed on plants and animals
Others decompose and feed on the dead
They create carbon dioxide for plants, but cannot make their own food
Ex.) humans, bears, dears, rabbits, and mice
Autotrophs can be separated by the source of energy that drives their metabolism
Photoautotrophs:
are used as the energy source
photosynthesis occurs in pants, algae, some protists, and some prokaryotes
Chemautotrophs:
harvest energy from oxidizing inorganic substances, including sulphur and ammonia
are unique to bacteria
What is chloroplast?
Chloroplast is the site where photosynthesis occurs in plants
Any green part of a plant has chloroplast
Leaves are the major site of photosynthesis for most plants
Its colour comes from the the absorption of light energy from chlorophyll
Inside the chloroplast
Photosynthesis takes place in the chloroplast of the plant

thylakoid- membrane sacs that have internal
aqueous space and mmay be stacked into
columns called grana
stroma- the fluid in chlorplast that surrounds the grana and where the Calvin Cycle takes place
photosystem- a cluster of pigment and protein that absorbs all the light energy (found in thylakoids)
Oxygen exits
and carbon dioxide enters the leaf through microscopic pores called the stomata
Veins deliver water from the roots and carry sugar from the mesophyll cells to other plant areas
Pathway of Photosynthesis
Pathway of Photosynthesis
Light Dependent Reaction
Light Independent Reaction
Calvin Cycle incorporates carbon dioxide from the atmosphere into an organic molecule and uses energy from the light reaction to reduce new carbon piece to sugar
Begins with the incoporation of carbon dioxide into an organic molecule
Occurs in stroma
Calvin Cycle incorporates carbon dioxide from the atmosphere into an organic molecule and uses energy from the light reaction to reduce new carbon piece to sugar
Begins with the incoporation of carbon dioxide into an organic molecule
Occurs in stroma
The process of light reaction starts off with protons striking the photosynthetic membrane where the absorption of light, the electron transport chain (transfer of energy), and chemiosmosis (making of ATP) all occur. In th end, the products are ATP, NADPH, and oxygen.
PHOtosystem I and Photosystem II
Are clusters of proteins and pigment molecules where light is absorbed
Cytochrome B6-f
The enzyme which transfers electrons between the two photosystems and introduces the protons to the thlakoid lumen
PHotosystem I
Is struck by photons and releases two electrons, which are replaced by two electrons from Photosystem II
Ferredoxin
Iron containing protein that carries the two electrons to the NADP reductase
NADP Reductase
Uses the two electrons and H+ ions from the stroma to reduce NADP+ to NADPH, and NADPH goes to the Calvin Cycle
atp synthase
Protons move through the ATP synthase to create ATP and is called phosphorylation and the ATP then goes to the Calvin Cycle
The Calvin Cycle is part of the light independent reaction and
converts carbon dioxide into sugars. This part of
photosynthesis occurs in
the stroma through three
phases: Carbon Fixation,
Reduction, and RuBP
regeneration
Phase 1: Carbon Fixation
In this stage, carbon dioxide is added to the 5 carbon molecule, RuBP, to create a highly unstable 6 carbon molecule
This 6 carbon molecule immediately breaks into two 3 carbon molecules
PHASE 2: REduction
C4 and CAm plants
Some plants face the problem of dehydration due to hot weather so they have alternative ways to undergo the Calvin Cycle
C4 PLants
C4 plants fix carbon dioxide with a 4-carbon compound called Phosphpeonylpyruvate to create oxaloacetate
Cam PLants
CAM plants open their stomata at night and store carbon dioxide into an acid within the mesophyll cells
During the day the light reaction supplies ATP and NADPH to the Calvin Cycle
Each six molecules of PGA is phosphorylated by an ATP for form six molecules of 1,3-bisphosphoglycerate
Then NADPH molecules reduce six molecules of 1,3-bisphosphoglycerate to six molecules of glyceraldehyde 3-phosphate (G3P), a sugar
Then one molecule of G3P exits the cycle as a final product
Phase 3: Regeneration of Rubp
Finally, five out of the molecules of G3P are rearranged to regenerate three molecules of RuBP
Three molecules of ATPare used and this regenerates the whole cycle
For more information check this out
Thank You!
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