Photosynthesis Flashcards
U3L4 (15 cards)
What is Photosynthesis?
Photosynthesis is the process of converting radiant energy from the sun into chemical energy for plants in the form of Glucose.
Whats the chemical formula for glucose?
6H2O + 6CO2 + Radiant Energy -> C6H12O6 + 6O2
What are the similarities between photosynthesis and cellular respiration?
They both use Cytochrome complexes to generate a proton gradient.
They use ATP synthase
They use similar energy carriers
(NADH in humans v. NADPH in plants).
Where does photosynthesis take place?
Photosynthesis takes place in the Chloroplasts of the leaf. The chloroplasts of the leaf are typically found in the mesophylls.
Where do the Light reactions (light dependent reactions) take place?
They take place in the Thylakoids (inside the chloroplast).
An entire stack of Thylakoids is called granum.
What’s a photon?
A photon is light travelling as a bundle of energy.
Chlorophyll can absorb photons.
What happens to Photons?
Photons are absorbed by an excitable electron on an atom that is part of a pigment molecule (chlorophyll). the electron moves from a low energy level to a higher one. This makes it turn into an electron accepting molecule.
What is Chlorophyll a/b?
Chlorophyll a/b is a pigment that’s found in plants. They can absorb most wavelengths with the exception of absorbing yellow and green. This is why leaves appear green to humans.
What are some other pigments?
Carotenoids, Phycobilin and Xanthophylls.
How is radiant energy converted to chemical energy?
Chlorophyll in the Thylakoid excites its electrons using radiant energy.
This energy is then transferred to a primary electron acceptor via redox.
What do protein complexes in the thylakoid contain?
They typically contain:
Antennae pigments (chlorophyll B)
Reaction center: molecule of Chlo. a
A primary electron acceptor
These complexes are called photosystems.
What are photosystems referred to as?
They are called P700/PSI or P680/PSII.
The numbers correspond to the wavelength at which their absorption spectrum peaks.
What happens in the photoexcitation process?
Photons are absorbed by antenna pigments, which causes it to move from a ground state to an excited state.
Excitation energy is then passed along the chlorophyll until it reaches the excitation center.
Chlorophyll a in the reaction center absorbs the energy.
the high energy of chlorophyll causes it to release two electrons.
the primary electron acceptor takes the electrons from chlorophyll a.
What happens in the non-cyclic electron pathway?
(light dependent reaction)
Photosystem II acquires electrons by using the sun’s energy to hydrolyze water (breaking the molecule into O2 and H+). This is called photolysis.
This causes the electrons to be energized. They then move along the ETC, interacting with the cytochrome complexes and pumping hydrogens across the membrane to form a proton gradient.
The de-energized electrons interact with PSI and have photons added to them. This energizes them and forms NADPH (using NADP+).
Pressure builds up on the gradient and suddenly, hydrogen gets pumped through the ATP synthase to cause equilibrium.
What is produced at the end of the non-cyclic pathway?
1 ATP and 1 NADPH.
These can now be used to synthesize glucose.
