PHOTOSYNTHESIS
SBI 4UDATE: ______________________
OVERVIEW OF PHOTOSYNTHESIS
INTRODUCTION:
metabolic process occurring in green plants, algae, some protists and cyanobacteria
Photosynthesis is an ______________ PROCESS (building organic molecules which store radiant energy as chemical potential energy)
Recall: Cellular Respiration is a _______________ PROCESS
Summary Reaction for Photosynthesis:
CO2:
used in light__________________ reactions (sometimes called ________ reactions)
enters through stomata and goes to mesophyll cells
H2O:
used in light____________________ reactions (sometimes called ________ reactions)
enters through veins of leaf and goes to mesophyll cells
chlorophyll:
light absorbing ___________ coloured pigment that begins the process of photosynthesis
found in _______________
primary function: convert ___________ energy into ___________ and __________ in order to be used to convert __________ to ___________ molecules
Note: if any of the raw materials is absent, photosynthesis will NOT occur
Chloroplast
organelle involved in photosynthesis
contains its own:
(a) ________________________
(b) ________________________
You should be able to:
- label a diagram of a chloroplast
- explain the structure/function of the chloroplast
OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis consists of two complex series of events;
(1) __________________________________
(2) __________________________________
Light Dependent Reactions
capturing light energy
occur within the __________ membrane of the chloroplast
produces:
(1) ______________________
(2) ______________________
(nicotinamide adenine dinucleotide phosphate, a coenzyme; similar to NADH)
Light Independent Reactions OR _____________________________________________________
occur in either the presence or absence of __________
occur within the ______________ of the chloroplast
uses ATP and NADPH from the light reactions to form organic molecules like glucose, from CO2
produces:
(1) ______________________
(2) ______________________
completely enzyme catalyzed
LIGHT
Electromagnetic (EM) radiation
Travels in wave packets called ____________
Photons with short wavelength = ________________
Photons with large wavelength = ___________________
Light is a mix of photons of different energies
Most of it we cant see
If passed through spectroscope, photons can separate from one another
Called Electromagnetic Spectrum
Light Photosystems (briefly)
Photosystems
Clusters of photosynthetic pigments embedded in thylakoid membrane
They absorb photons of particular wavelengths
Through light reactions they convert ADP to ATP and NADP+ to NADPH
Occurs in the stroma
PHOTOSYNTHETIC PIGMENTS
Chlorophyll
found within _________________
___________ pigments
contain:
(1) _____________________________
(2) _____________________________
chlorophyll a: absorbs _______________ and _____________ wavelength photons (reaction centre of a photosystem)
chlorophyll b: absorbs _______________ and _____________ wavelength photons (accessory pigment)
Carotenoids
_____________ and _____________ pigments (accessory pigments)
absorb only in the ______________ end of the spectrum
Excess energy absorber to protect chlorophyll and dissipate it as heat
E.g. -carotene from carrots
Photosynthetically Active Radiation
Ideal wavelengths for photosynthesis
Ranges from __________________________________
Combination of chlorophyll a and b, and all of the other accessory pigments that help out
(LIGHT DEPENDENT REACTIONS)PHOTOSYSTEMS
- consists of:
(1) _________________________________________________________
_________________________________________________________
(2) _________________________________________________________
_________________________________________________________
Location of Photosystems: __________________________________________
Photosystem I: ___________________________________________________
Photosystem II: __________________________________________________
There are two separate light powered systems in the membranes of the thylakoid disc:
(1) _____________________________________
(2) _____________________________________
Cyclic Photophosphorylation
used by prokaryotes (eg bacterial photosynthesis)
involves only ___________________ (PS I)
PS I contains ______________
chlorophyll a electrons return to chlorophyll a
product = __________ (no NADPH is made)
Description:
(1) PS I (P700) absorbs ___________ energy, causing the two ____________ to become excited.
(2) The two excited electrons enter an _______________________________.
(3) The two excited electrons are captured by the protein _________________, causing some of their energy to be lost.
(4) The two excited electrons are then captured by the _____________________ protein complex and lose more energy. At this point, enough energy has been lost to add a P to ADP forming ________.
(5) The passing of electrons from cytochrome b6-f complex to the next electron carrier, ___________________(Pc) results in further lowering of the energy in the electrons to almost the ground state
(6) The passing of the two electrons to ______ returns the electrons to both the _______________ molecule and the __________ state.
Non-Cyclic Photophosphorylation
used in photosynthesis of green plants
involves both ___________________ (PS I) and ___________________ (PS II)
chlorophyll a electrons are passed along to make ____________ and are replaced by __________ electrons
Description:
(1) PS II absorbs __________ energy causing two electrons of chlorophyll P680 to become excited.
(2) A Z protein, associated with PS II and facing the thylakoid _________, splits __________ into ____________, _____________ and ______________. Two __________ are used to replace the excited electrons in chlorophyll P680. ___________ leaves the chloroplast as a byproduct.
The _________ remain in the thylakoid space add to the proton gradient that powers chemiosmosis.
(3) The two excited __________ travel through a series of proteins within the _______________________________.
(4) As the two excited ____________ move from the excited reaction centre of PS II to ___________________(PQ), energy is lost.
(5) This energy is used to move _________ protons from the _____________ to the ____________. This creates a proton gradient for chemiosmosis.
(6) The increase in proton concentration within the thylakoid lumen drives protons out of the lumen to the ________ via a special protein called _____________. This proton motive force is used to produce ___________.
(7) The electrons continue to move from PQ to other components of the electron transport chain (cytochrome b6-f complex to Plastocyanin to PS I) eventually replacing the 2 electrons that were lost by PS I when it was struck by photons.
(8) The two excited electrons from PS I pass through another electron transport chain containing the protein _________________(Fd).
(9) The two excited electrons are then captured by ___________________, which uses the two electrons and protons from the stroma to reduce ___________ to ___________.
(10) The ____________ and ________ are used to drive light independent reactions.
(LIGHT INDEPENDENT REACTIONS)Calvin Cycle
reactions that convert ________________ into _______________ molecules
occur in the ___________ of chloroplasts
(Summarize the 3 phases listed below:)
(1) Carbon Fixation: ____________________________________________________________________________________________________________________________________________________________________________________
(2) Reduction Reactions:
____________________________________________________________________________________________________________________________________________________________________________________
(3) Regeneration of RuBP:
____________________________________________________________________________________________________________________________________________________________________________________
