exam 3: lecture 10 photosynthesis Flashcards
definition of photosynthesis
the process by which organisms use light energy to make sugar and oxygen gas from carbon dioxide and water
-occurs in plants. algae, and some prokaryotes
-anabolic (small molecules combined)
-endergonic (stores energy) “CARBON FIXATION” (a gas is fixed to a molecule/sugar
-stored as carbohydrate in their bodies
6 CO2 + 6H2O—-light energy—-> C6H12O6 + 6O2
structures of the chloroplasts
stoma: small openings for CO2 ^ O2 to pass thru
(high CO2 outside;low O2 inside)
intermediate membrane: the space between the outer and inner membrane
thylakoid: 1 flattened sac/disc
granum: many flattened sacs on top of each other
grama: all stacks
plants in temperate zones: keep stomata open-allow CO2 in during the day
plants in desert: close stomata during the day
tracking oxygen atoms in photosynthesis
the oxygen from CO2 goes to glucose and water
the oxygen from H2O goes to O2
redox reactions in photosynthesis
CO2 is reduced into C6H12O6
H2O is oxidized into O2
At which wavelengths do most energy absorb? what gives the leaf their green color?
red and blue wavelengths (not much in the middle -green/yellow)
Mg in the middle of their structure
CHO in chlorophyll b
CH3 in chlorophyll a (methyl group)
how does the transfer of energy to the reaction center of a photosystem work?
a photon’s energy is absorbed by a chlorhyl molecule where it excites the e- into high energy
-light energy absorbed by antenna pigment is transferred from one to the next until it reaches the main reaction center chlorophyll
-the energy is then captured by an electron acceptor
*no chemical reaction, energy is being transferred through physical only
resonance transfer: wavelength energy
what happens in photosystem II
light absorption:
* after reaction center, energy is transfer to P680, bringing an e- to a high energy level
*energy is then passed to an acceptor molecule and replaced with an electron from H2O=> water is broken down to release O2
atp synthesis:
*high energy e- travels down the ETC, losing energy as it does
*the released energy is used to pump H+ from the stroma into the thylakoid interior-> a gradient
*H+ pass thru ATP synthase-> ATP production (chemiosmosis)
what happens in photosystem I?
light absorption:
*e- arrive at photosyste I and join P700 in the reaction center.
*energy energy is absorbed–> e- is bring to a high energy level and transferred to an acceptor molecule
NADPH formation:
*the high energy e- travel down the second ETC
*the e- is passed to NADP+ to make NADPH
non-cyclic photophosphorylation
involves 2 photosystems (p680,p700)
contain chlorophyll a and b
flow of electron is noncyclic (going down in one direction)
uses photolysis of water
h2o—> 2h+ +2e- +1/2 o-
end products are reduced nadph, atp, and o2
the reduced and oxidized form of nadp+
NADP+: nicotinamide adenine dinucleotide
NADPH: reduced
NADP+: oxidized
cyclic photophosphorylation
involves only photosystem 1 (at 700 nm)
end product is atp only
where does the production of ATP take place in photosynthesis?
thylakoid membrane
a summary of chemical processes of photosynthesis
h2o——light reaction (grana)——> O2
-make atp & NADPH
CO2—–calvin cycle (stroma)—–>sugars
-make adp+p & NADP+
calcin cycle is also called dark reaction bc it does not depend on light
what is light-independent reaction
aka calvin cycle
-takes place in the stroma of the chloroplast
-no light required but need end products (reduced NADPH & ATP)
-need an enzyme RUBISCO (ribulose diphosphate carboxylase) and carbon dioxide
What is the calvin cycle called now? + what happens
carbon reactions
CO2—–free energy of cleavage of P bonds of ATP + reducing power of NADPH—-> carbohydrate
