chapter 7: photosynthesis Flashcards
What is a chloroplast
Green portion
Mesophyll tissue
Chloroplast: organelle in algae & plants with chlorophyll-containing membranous thylakoids
Produces glucose
What is the role of NADP+/NADPH
-Electrons are needed to reduce CO2
-Carried by NADP+ coenzyme of oxidation-reduction reaction
-Water splits during photosynthesis
-Oxygen is released
-Hydrogen atoms & electrons taken up by NADP+
-NAPDH reduces CO2 to carbohydrate
how do plants convert solar energy
Wavelength & energy contents
Most radiation reaching Earth is within the visible-light range, the rest is filtered out
-ozone layer
Organisms evolved to use them
what is the absorption spectrum
For photosynthetic pigments, a graph of how much solar radiation is absorbed versus the wavelength of light
Plants contain chlorophylls a and b
what are carotenoids
accessory photosynthetic pigment of plants & algae often yellow or orange in color
what is the photosystem
consists of pigment complex & electron acceptor molecules within thylakoid
how do electrons flow in light reactions
-Two photosystems: photosystem I (PS I) and photosystem II (PS II)
-Electrons typically follow noncyclic pathway -> begin with PS II
what are the ways plants fix carbon dioxide
- CO2 fixation
- CO2 reduction
- Regeneration of RuBP
how does co2 fixation work
CO2 is attached to 5-carbon RuBP by the enzyme RuBP carboxylase
Results in 6-carbon molecule
Splits into two 3-carbon molecules (3PG)
Accelerated by RuBP carboxylase (Rubisco)
how does co2 reduction work
Each two 3PC undergoes reaction to G3P two steps
1. Energy is required in the form of ATP, which is hydrolyzed to ADP
2. Substrate BPG is reduced, while the coenzyme NADPH is oxidized
how does the regeneration of RuBP work
Calvin cycle reactions multiplied by 3
Three turns to allow one G3P molecule to exit
Takes five G3P to reform three RuBP
ATP
what is the importance of G3P
-most important molecule to sustain for life
-molecule used to make glucose, phosphate groups, synthesize fatty acids, produce amino acids
what are C3 plants
C3 plant: plant that fixes carbon dioxide via the Calvin cycle; the first stable product of C3 photosynthesis is a 3-carbon compound
what is photorespiration
Photorespiration: series of reactions that occurs in plants when carbon dioxide levels are depleted but oxygen continues to accumulate; enzyme RuBP carboxylase fixes oxygen instead of carbon dioxide
-stomata close to conserve water
-Disadvantageous ☹
-3PG produced at reduced rate
-Much higher metabolic cost
how does C4 photosynthesis work
Fix CO2 to PEP (3 carbon molecule) using enzyme PEPCase
Result is 4 carbon molecule
Pumped into bundle sheath cells
Partitioning CO2 uptake & fixation
how does CAM photosynthesis work
Night: CAM plants use PEPCase to fix some CO2 Stored in large vacuoles
Day: C4 molecules release CO2 to Calvin Cycle when NADPH and ATP are available
Conserves water; stomata only open at night
difference between c3 and c4 plant
c3
-no interbundle sheath cells with chloroplasts
c4
-more cyclically organized
-more packed together
-strictly palisade mesophyll cells
-interbundle sheath with chloroplasts
c4 plants advantages
C4 high light intensity, high temperatures, limited rain fall
c3 plants advantages
C3 plants rain, wide range of temperatures (better than C4 below 25 °C) and humid environments
CAM plants advantages
CAM plants do well in arid environments
What is the ultimate destination for the energized electrons during the light reactions of photosynthesis?
a.
They are taken up by NADPH to produce NADP+
b.
They are taken up by NAD+ to produce NADH
c.
They are taken up by NADP+ to produce NADPH
d.
They are taken up by NADH to produce NAD+
c.
They are taken up by NADP+ to produce NADPH
Which is most closely associated with the Calvin cycle?
a.
Oxygen production
b.
Carbon dioxide fixation
c.
Carbon dioxide production
d.
ATP production
e.
Removal of electrons from water for passage through an electron transport system
b.
Carbon dioxide fixation
The function of sunlight in photosynthesis is to
a.
Reduce NADPH to NADP
b.
Fix O2 in the Calvin cycle
c.
Combine carbon dioxide and water to form ATP and NADPH
d.
Excite electrons in chlorophyll
e.
Split water releasing oxygen
d.
Excite electrons in chlorophyll
The fixation of carbon dioxide in the first step of the Calvin cycle is facilitated by which enzyme?
a.
RuBP carboxylase
b.
PEP carboxylase
c.
Glyceraldehyde-3-phosphate (G3P)
d.
Lactate dehydrogenase
a.
RuBP carboxylase
Photorespiration occurs mainly in
a.
CAM plants
b.
C4 plants
c.
All of the answer choices
d.
C3 plants
d.
C3 plants
