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Photosynthesis

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Which of the following statements accurately describes the relationship between photosynthesis and cellular respiration?
photosynthesis uses solar energy to convert inorganics to energy-rich organics; respiration breaks down energy-rich organics to synthesize ATP
Stomata
openings in the leaf for gas exchange, CO2 enters, water vapor exits
Carbon Dioxide
In photosynthesis, used to make sugar and other organic molecules.
Carbon atoms present in CO2 end up
sugar molecules and water
carotenoids and chlorophylls
pigments
role of pigments in photosynthesis
capture light energy
The pigment molecules responsible for photosynthesis are located in the
thylakoid membrane of the chloroplast
Chlorophyll
...
chlorophyll is located in
thylakoids, which are in chloroplasts in the mesophyll cells of a leaf
granum vs crista
the granum only has photosynthetic pigments
Antenna Complex
in the thylakoid membrane
primary role is to harvest photons and transfer light energy to the reaction-center chlorophyll
Reaction Center
...
when chloroplast pigments absorb light
electrons get excited
During photosynthesis, photons raise electrons to higher energy levels. These excited electrons belong to what compound?
chlorophyll
action spectrum
(Engelmann), the wavelengths of light most effective in driving photosynthesis
High-energy photons
have short wavelenghts
Light that is visible to humans occupies what part of the electromagnetic spectrum?
small middle portion
Colors of light most useful in photosynthesis are
red, violet, and blue
Chlorophyll a+b
absorb red and blue, reflect green
Carotenoids
accessory pigment,
absorb blue and green, reflect yellow, orange, red
absorption spectrum
The wavelengths that are absorbed, not all of which are used for photosynthesis.
The light reaction four stages:
capture of a photon by a pigment,
charge separation, (splitting of water?)
electron transport,
and chemiosmosis.
flow of electrons in photosynthesis
H2O → NADPH → Calvin cycle
Both mitochondria and chloroplasts
use chemiosmosis to produce ATP
photosystem
formed by the reaction center, light-harvesting complexes, and primary electron acceptors that cluster, and is located in the thylakoid membrane?
Where do the electrons entering photosystem II come from?
water
P680 and P700
the electron acceptor associated with Photosystem II, filled by electrons derived from water
P700
the electron acceptor associated with Photosystem I
Photosystem I
receives electrons from the thylakoid membrane electron transport chain
O2 is produced in
the light-dependent reactions involving photosystems I and II
During photosynthesis in chloroplasts, O2 is produced from _____ via a series of reactions associated with _____.
H2O, Photosystem II
Electron Transport Chain (in photosynthesis)
transport electrons from photosystem II to photosystem I
electrochemical gradient aka chemiosmosis
the ETC pumps protons from the stroma to the (lumen of the) thylakoid
The energy used to produce ATP in the light reactions of photosynthesis comes from _____.
movement of H+ through a membrane
thylakoid membrane
electrochemical gradient locations are separated by the thylakoid membrane.
During what stage of photosynthesis are ATP and NADPH converted to ADP + Pi and NADP+?
the light-independent reactions
What is the role of NADP+ in photosynthesis?
It is reduced and then carries electrons to the Calvin cycle. (aka It is the source of NADPH for the Calvin cycle)
Calvin Cycle: light independent or dependent?
Calvin cycle is light independent
The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. Why?
The Calvin cycle requires products (NADPH and ATP) only produced when the photosystems are illuminated.
The "dark" reaction (light independent) in photosynthesis is limited by
CO2, temperature, and light
Calvin cycle occurs in
stroma
Phases of Calvin Cycle
1. Fixation (CO2+Rubisco)
2. Reduction (G3P produced)
3. Regeneration (Rubisco made from G3P)
Rubisco
the enzyme in plants that first captures (reacts with) CO2 to begin the Calvin cycle
To reduce six molecules of carbon dioxide to glucose via photosynthesis, how many molecules of NADPH and ATP are required?
12 NADPH 18 ATP
Calvin Cycle
CO2 is reduced (requires ATP and NADPH)
ATP is hydrolyzed (consumed)
NADPH is oxidized
CO2 acceptor regenerated by G3P (Rubisco)
How many carbon atoms are in a molecule of RuBP?
5
G3P
-It is produced from glucose during glycolysis.
-It is a 3-carbon sugar.
-For every three molecules of CO2, six molecules of G3P are formed but only one molecule exits the cycle to be used by the plant cell.
-the remaining five molecules must be recycled to regenerate three molecules of RuBP
CO2 and 5-carbon Sugar (Rubisco)
6-carbon product, so unstable that it decomposes immediately into two 3-carbon phosphoglycerates.
Production of one molecule of 3-phosphoglyceraldehyde requires how many turns of the Calvin cycle?
3
Calvin Cycle products
produces glucose, final product G3P
relationship between the light reactions and the Calvin cycle?
The light reactions produce ATP and NADPH, both of which are used in the Calvin cycle.
(NADPH provides reducing power by donating electrons and ATP provides energy when it is converted to ADP.)
T/F CO2 fixation occurs within the stroma.
T (fixation is during Calvin Cycle, which occurs in stroma)
T/F Light-driven electron transport in the chloroplast pumps H+ into the intermembrane space between the outer and inner membranes.
F
Which of the following statements about photosynthesis is true?
The light-dependent reactions produce the energy-rich compounds that are used to run the light-independent reactions
Photorespiration
"undoes" photosynthesis (decreases rate)
consumes energy, releases fixed CO2
Photorespiration vs Carbon Fixation (Rubisco)
O2 and CO2 compete at rubsico active site,
when O2 and Rubisco react (instead of CO2 which would initiate Calvin Cycle's carbon fixation) then photo respiration is allowed to occur
Photorespiration vs. Carbon Fixation (concentrations of CO2 and O2)
Photorespiration occurs when
-CO2 low
-O2 high
water preservation vs CO2 delivery
when its hot
close stomata and halt CO2 delivery (and photosynthesis)
or risk dehydration
Which of the following organisms have the greatest problem with photorespiration?
C3 plants
Why are C4 plants more suited to hot climates than C3 plants?
Unlike C3 plants, they keep fixing carbon dioxide even when the concentration of carbon dioxide in the leaf is low
The immediate products of C3 and C4 photosynthesis are, respectfully:
3-phosphoglycerate; oxaloacetic acid
The use of non-C3 and non-CAM plants as crops may be limited in some regions because on hot, dry days, they close their stomata. What happens as a result of closing their stomata?
-It reduces water loss.
-It prevents carbon dioxide from entering the leaf.
-In a process called photorespiration, rubisco binds oxygen instead of carbon dioxide.
-It builds up oxygen from the light reactions in the leaf.
How is photosynthesis similar in C4 plants and CAM plants?
In both cases, rubisco is not used to fix carbon initially.
Which of the following is mismatched?

A) Photosystem I - uses the P700 molecule in its photocenter
B) PGA - a 3-carbon compound
C) antenna complex - contains hundreds of pigment molecules
D) CAM plants - open their stomata during the day and close them at night to avoid photorespiration
E) C4 plants - expend ATP to concentrate CO2 in bundle-sheath cells to avoid photorespiration
D
The primary form of sugar transported from the site of photosynthesis to the rest of the plant is:
sucrose