Lecture 27 Flashcards
Photosynthesis energy input
solar energy
Photosynthesis provides what
glucose and oxygen that we depend on for life
Photosynthesis equation
6CO2 + 6H2O -> C6H12O6 + 6O2
Photosynthesis parts
Part 1. Photosystem, which captures Solar energy and converts it into ATP
Part 2. Calvin cycle, which uses ATP to rearrange CO2 to make carbs (glucose)
Where does photosynthesis occur
in the chloroplasts of the plant
How may chloroplasts per plant cell
20-100
Stroma of the chloroplast
gel like and filled with enzymes
thylakoids of the chloroplast
flat sac-like structures
Granum of the chloroplasts
stack of thylakoids
Do photosynthetic prokaryotes have chloroplasts?
no, they are like free-living chloroplasts themselves
How is light captured by the plant to make ATP
light is captured by specialized molecules
Specialized molecules that capture molecules in plants to make ATP
Chlorophyll a and b
Chlorophyll a and b have what type of ions
they have a center Mg2+ (magnesium) ion and other groups (such as R) controlling alternating double bonds that move electrons around
Chlorophyll a and b have
different light absorption frequencies, so they only become excited at certain wavelengths because molecular structure determines this sensitivity
Why is chlorophyll a and b green
because green is not absorbed and bounces back to our eyes
Light energy has
properties of both waves and particles
short wavelengths have higher energy
what do photons do
they excite electrons in chlorophyll atoms
How do photosystems make ATP
by transferring excited electron energy (makes proton gradient)
What are photosystems
they are thylakoid membrane complexes of proteins and chlorophyll that establish H+ proton gradient
How some electron energy is transferred in photosystems
some chlorophyll molecules act as receiving antennas, passing energy from one to another chlorophyll
collection focuses on special chlorophyll molecules in reaction center that pass electrons out of photosystem
Photosystem II steps
PS II rxn center has chlorophyll a molecule sensitive to 680nm wavelength
P680 transfers electrons to Qb (plastoquinone), which binds to stromal H+ to become QbH2
the missing electron from P680 is replaced by breaking H2O into O2 and H+
O2 diffuses out of cell and is released into air as waste
QbH2 takes H+ to cytochrome b/f which transfers the H+ to lumen
Resulting in building a H+ gradient across membrane which can fuel ATP synthesis
