Sb: ch. 8 photosynthesis part 2
True or false: Water is oxidized during the light reactions of photosynthesis.
True
The role of the light-harvesting complex is to ______.
absorb photons of light
The end product of phase 2 of the Calvin cycle is G3P. This molecule is used to synthesize _____ and to regenerate the starting material _____ bisphosphate.
carbohydrates, ribulose
What are the three phases of the Calvin cycle?
carbon fixation, reduction, regeneration
The light reactions of photosynthesis require water to supply two ______ that are transferred to P680+.
electrons
The incorporation of carbon from CO2 in the atmosphere into an organic molecule is called carbon
fixation
In plants, which of the following is polymerized to form starch?
glucose
What is produced at the end of the second phase of the Calvin cycle?
glyceraldehyde 3-phosphate
Which of the following is the primary output of the Calvin cycle?
glyceraldehyde 3-phosphate
Which of the following are components of both PSI and PSII?
light harvesting complex and reaction center
The products of the light reactions that are used by the Calvin cycle to make carbohydrates are
NADPH and ATP
Which of the following are products of the light reactions of photosynthesis that are used as reactants in the Calvin cycle?
NADPH and ATP
Sequence the phases of the Calvin cycle from first (on top) to last.
1. carbon fixation 2. reduction and carbohydrate production 3. regeneration of ribulose bisphosphate
Based on the Z scheme, how many photoactivation events occur during photosynthesis?
2
What is the product of the carbon fixation reaction catalyzed by rubisco in the Calvin cycle?
3-phosphoglycerate
What molecule is reduced in the Calvin cycle?
CO2
In C4 plants, the first product of carbon fixation is
a four-carbon molecule
In hot dry conditions, rubisco can attach O2 to RuBP in a process called ______. which ultimately produces CO2.
photorespiration
The G3P produced at the end of the second phase of the Calvin cycle is directly used for which of the following?
regenerate ribulose bisphosphate make glucose or other carbohydrates
In the last phase of the Calvin cycle, what molecule is regenerated so that the next cycle can occur?
ribulose bisphosphate
Why does CO2 enter CAM plants at nighttime?
Because the stomata of CAM plants are only open at night
How do CAM plants avoid water loss?
CAM plants close their stomata during the day and open them at night.
In the first phase of the ______, atmospheric carbon dioxide is fixed into a five carbon sugar.
Calvin Cycle
Carbon dioxide is incorporated into a molecule of ribulose biphosphate to form an unstable 6-carbon intermediate that immediately splits into two 3-carbon molecules. This process is called
Carbon fixation
Which of the following differentiates PEP carboxylase from rubisco?
PEP carboxylase does not bind oxygen
What enzyme is responsible for carbon fixation?
Rubisco
What happens during photorespiration?
Rubisco attaches O2 to RuBP, and CO2 is produced.
Both PEP carboxylase and rubisco can fix carbon dioxide. However, PEP carboxylase:
does not bind oxygen
When a pigment molecule absorbs a photon of light, a(n) ______ is boosted to a higher energy level.
electron
What is the role of the reaction center in a photosystem?
it transfers a high-energy electron to another molecule
Several dozen pigment molecules anchored to transmembrane proteins make up the ____ harvesting complex of a photosystem.
light
What part of a photosystem contains dozens of pigment molecules that absorb light photons?
light harvesting complex
Which of the following conditions affect the way the Calvin cycle operates in photosynthetic organisms?
light intensity, temperature, water availability
PSI and PSII have two main components: a(n) harvesting complex and a(n) center.
light reaction
During photosynthesis, water is ______.
oxidized
The light-harvesting complex is composed of several dozen ________ molecules that are anchored to transmembrane proteins.
pigment
Which of the following will remove a high energy electron from P680* and transfer it to a more stable molecule?
reaction center
In the Calvin cycle, CO2 is ______.
reduced
The Calvin cycle is affected by certain environmental conditions, including light intensity, _______ availability, and ______
water temperature
The model for photosynthesis that incorporates two photoactivation events and shows the series of energy changes during the light reactions of photosynthesis is called the _____ scheme.
z
What is the source of electrons used to reduce the C-O bond of 3-phosphoglycerate during the Calvin cycle?
NADPH
In some plants, carbon fixation yields a four-carbon molecule instead of 3GP as the first product. Such plants are known as ______ plants.
C4
Which of the following summarizes the events of the first phase of the Calvin cycle?
Atmospheric carbon dioxide is fixed into a five carbon sugar.
A product of the Calvin cycle is used to produce _______ molecules that may be linked together to form a polysaccharide called starch.
Glucose
Which of the following happens to the molecule formed by the addition of carbon dioxide to ribulose bisphosphate?
It is immediately split into two more stable three carbon molecules.
What is carbon fixation?
The incorporation of carbon into an organic molecule that is not a gas
Which of the following is the purpose of phase 3 of the Calvin cycle?
To create a new 5-carbon sugar for the "next" Calvin cycle
Why is water required for the light reactions of photosynthesis?
To replace the electrons lost from P680
What happens when a photon of light is absorbed by a pigment molecule?
an electron is boosted to a higher level
