10 - Photosynthesis, chaper 10 Flashcards
Which of the following is mismatched with its location
- light reactions - grana
- electron transport chain - thylakoid membrane
- Calvin cycle - stroma
- ATP synthase - double membrane surrounding chloroplast
- splitting of water - thylakoid space
ATP synthase - double membrane surrounding chloroplast
Photosynthesis is a redox process in which
- CO2 is reduced and water is oxidized
- NADP+ is reduced and RuBP is oxidized
- CO2 NADP+ and water are reduced
- O2 acts as an oxidixing agent and water acts as a reducing agent
- G3P is reduced and the electon transport chain is oxidized
CO2 is reduced and water is oxidized
A chlorophyll a in SP1 has its electon holes filled by electrons from
- photosystem 1
- water
- NADPH
- accessory pigments
photosystem 1
CAM plants avoid photorespiration by
- fixing CO2 into organic compounds during the night; these compounds then release CO2 during the day
- performing the calin cycle at night
- fixing CO2 into four-carbon compounds in the mesophyll, which release CO2 in the bundle-sheath cells
- keeping their stomata closed during the day
fixing CO2 into organic compounds during the night; these compounds then release CO2 during the day
Chloroplasts can make carbohydrate in the dark if provided with
- ATP & NADPH and CO2
- an artificially induced proton gradient
- organic acids or four-carbon compounds
- a source of hydrogen
- photons and CO2
ATP & NADPH and CO2
In the cheiosmotic synthesis of ATP in cholorplasts, H+ diffuses through the ATP synthase
- form the stroma into the thylakoid space
- from the thylakoid space into the stroma
- from the intermembrane space into the matrix
- from the cytoplasm into the intermembrane space
- from the matrix into the dtroma
from the thylakoid space into the stroma“
Photosynthesis is comprised of two parts, what are they?
light reaction & Calvin cycle
Light reactions occurs where?
in the thylakoid space
___________ are on the interior of chloroplasts, they are vexcicle like structures in interconnected stacks called________
thylakoids; grana
the fluid filled space between thylakoids & inner mb
Stroma
How does light split H2O to form e- & O2
- e- reduces NADP+ to NADPH
- e- provides E’y to make ATM through chemiosmosis
There are two major classes of pigments, what are they and which colors do they absorb?
- Chlorophylls - a & b - absorb strongly in blue & red
- carotenoids - Beta-carotene - absorb blue & green
The accessory pigments carotenoids can be further broken down into 2 more classes, what are they and list their charateristics
- Carotenes - gives carrots their orange
- xanthophylls - yellow
**Carotenoids ** absorb colour not absorbed by chlorophyll a & b = extends range of wavelenghts
_____________ can bind down the damaging wavelenghts that could cause harm to the plants in the form of free radicals
carotenoids
__________ acts as a sunscreen by absorbing UV rays, stored int eh vacuoles of the plant
flavonoids
Describe cholorphyll a & b
- very similar in their structure and absorption spectrum
- long tails isoprene keeps them imbedded int the thylakoid mb
- head with large ring w/ Mg atom in the middl = where the light is absorbed
Describe fluorescence
where the energy state quickly goes up and then down -> some E’y released as heat - and some molecular movement - fluorescence
What are photosystems (PS)
- they are the light trapping componenets of the thylakoid mb
- 2 components antenna complex & reaction centre
Whare are other names for the photosystems
PS1 = P700
PS2 = P680
What is in the photosystems?
- PS1 & PS2
- rxn centre containing cholorplast a & b -> primary e- acceptor called pheophytin
In a rxn centre what is the e- acceptor called?
pheophytin
when light E’y hits a photosystem, what happens?
pigments transfer E’y to Chloroplast a which donates an e- to primary e- acceptor
Which photoreceptor is the 1st to absorb light?
PS 2
describe the the steps of photosynthetic electron tranfer
- photon -> PS2
- Photon E’y absorbed by pigments -> Chloroplast a
- E’y excited e- from Chl a -> primary e- acceptor
- excited e- get passed down to ETC PS1
- e- arrives @ PS1 another photon excites primary e- acceptor of PS1
- e- is passed down a short STC to NADP+ -> NADPH —> calvin cycle
- P680 regains an e- by oxidixing P680
- 2H+ gather in the thylakoid lumen
- 02 released through stroma
when a proton hits a chloroplast what can happen?
- flouresence & heat
- exciting pigment molecule
- e- -> electron accepting molecule
what does pheophytin do?
- receives excite e- from chlorophyll a
- acts as an e- acceptor
how does the P680 regain an e-?
by oxidixing H2O
contributes to the proton-motive force
Where in the chloroplast is the pH the highest?
thylakoid lumen
what does platoquinone do?
- connects excited e- in pheophytin w/ cytochrome complex
- lipid soluble
- delivery from pheophytin to cytochrome & others
__________ is the stream of protons through ATP synthase
photophosphorylation
why is plastocyanin important?
b/c it links PS1 & PS2
feeds PS1 with e-
what is the purpose of RuBP
- initial reactant w/ CO2 to from a 6-C cmpd
- 1st intermediate product of the 10 intermediates in glycolysis
__________ occurs in the stroma. Uses NADPH and ATP from light rxns to make a highly reduced 3-C cmpd -> other organic molecules
The calvin cycle
The calvin cycle happens in 3 steps, what are they?
- Fixation
- Reduction
- Regeneraction
In the calvin cycle what are the steps of carbon fixation?
- CO2 + RuBP via rubisco => 6-C cmpd
- step 1 happens 2 more times to make a total of 3 6-Carbon cmpds which break down to 6 3-Carbon cmpds
Certain chemicals can uncouple thylakoid mb, making it leaky to H+, how would this affect photosynthesis?
- stop working b/c no [] gradient
- calvin cycle cannot continue without ATP
What does rubisco do in the calvin cycle?
adds CO2 to RuBP
What happens in the calvin cycle during the reduction phase?
- becomes phospholorated (6 ATP -> 6 ADP + 6 Pi)
- reduced by NADPH to form 6 3-C cmpds called G3P
- 1 G3P is released from the cycle
What are the steps to the regeneration phase of the calvin cycle?
- 5 G3P regenerated -> 3 5-C RuBP
- requires 3 ATP
What happens to the G3P that is released from the calvin cycle
makes everything, CH2O, lipids, sugars neucleotides, cellulose
Where does the CO2 come from that eneters the cycle?
the atmosphere
How many turns of the calvin cycle produces 1 G3P?
3 turns
The light & dark rxns are intimately associated and can’t occur w/out each other. Why?
Excess of NADPH will bung up the system
What does photorespiration do?
- consumes O2 -> CO2
- decreases the rate of photosynthesis
- catalyzes the oxidation of RuBP -> CO2 + H2O
- bleeds carbon out of the cycle
What are guard cells?
pair of cells w/ openings
makes up the stroma so that plant can breathe
what happens when the temperature increases?
the stromata close = stops photosynthesis to conserve H2O
When the stromata close, how does this affect the plant?
rubisco binds to O2 instead of CO2 - competitive inhibitor
In chloroplasts
Select one:
A. Proton pumping requires ATP
B. Light causes the thylakoid lumen to become less acidic than the stroma
C. Light leads to the flow of protons out of the thylakoids
D. ATP is formed when protons flow in to the thylakoid lumen
E. Protons return passively to the stroma through proteins channels
In chloroplasts protons return passively to the stroma through proteins channels
Which statement about the Calvin cycle in NOT true?
Select one:
A. The concentration of G3P rises if the light is switched off
B. Carbon dioxide reacts with RuBP to eventually form G3P
C. ADP and NADP+ are formed by reducing Calvin Cycle intermediates
D. Rubisco catalyzes the reaction of carbon dioxide and RuBP
The concentration of G3P rises if the light is switched off
Photorespiration
Select one:
A. Is catalyzed by PEP carboxylase
B. Increases the yield of photosynthesis
C. Decreases the biomass of a plant
D. Takes place only in C4 plants
E. Is independent of light intensity
Photorespiration decreases the biomass of a plant
During photosynthesis, photosystem I functions to __________ and photosystem II functions to________.
Select one:
A. reduce H2O, reduce CO2
B. synthesize ATP, produce O2
C. reduce CO2, oxidize NADPH
D. reduce NADP+, oxidize H2O
During photosynthesis, photosystem I functions to reduce NADP+ and photosystem II functions to oxidize H2O
Which region of a chloroplast is associated with the capture of light energy?
Select one:
A. outer chloroplast membrane
B. inner chloroplast membrane
C. thylakoid membrane
D. cell membrane
thylakoid mb
Where in the chloroplast would you find the highest concentration of H+?
Select one:
A. in the cytoplasm
B. in the thylakoid space
C. in the intermembrane space
D. in the stroma
thylakoid space
In C4 photosynthesis
Select one:
A. 4 carbon compounds are formed by PEP carboxylase in bundle sheath cells
B. Carbon dioxide released from RuPB is transferred to PEP
C. Photosynthesis continues in lower levels than in C3 plants
D. Rubisco catalyzes the first step in the pathway
In C4 photosynthesis photosynthesis continues in lower levels than in C3 plants
