Ch 8-3 Flashcards
What is the Calvin Cycle?
A light-independent process where CO₂ is reduced into sugars using ATP and NADPH from the light reactions.
Where does the Calvin Cycle occur?
In the stroma of the chloroplast.
What enzyme catalyzes the fixation of CO₂ to ribulose bisphosphate (RuBP)?
Rubisco
What are the three phases of the Calvin Cycle?
Carbon fixation, reduction, and regeneration.
What molecule is produced in the Calvin Cycle and used as a building block for glucose?
Glyceraldehyde-3-phosphate (G3P).
How many turns of the Calvin Cycle are required to produce one molecule of G3P?
Three turns.
What is photorespiration?
: A process where rubisco binds O₂ instead of CO₂, wasting energy and carbon
In what conditions does photorespiration occur?
When CO₂ levels are low, typically in hot and dry climates.
What is the alternative carbon fixation strategy used by C4 plants?
CO₂ is initially fixed into a 4-carbon compound with spatial separation of steps.
What is the alternative carbon fixation strategy used by CAM plants?
CO₂ is fixed at night, stored as an organic acid, and used during the day with temporal separation of steps.
Which organic molecule is essential in regenerating RuBP?
ATP
What is the net output of the Calvin Cycle for every three CO₂ molecules?
One G3P molecule.
What percentage of organic material from photosynthesis is used for cellular respiration in plants?
Approximately 50%.
What percentage of organic material from photosynthesis is used for cellular respiration in plants?
Approximately 50%.
Where is excess organic material from photosynthesis stored in plants?
As starch in seeds, tubers, and fruits.
How does photosynthesis contribute to Earth’s atmosphere?
A: It produces most of the oxygen in the atmosphere and fuels heterotrophs.
Which of the following is the initial reactant in the Calvin Cycle?
A) G3P
B) CO₂
C) ATP
D) NADPH
B) CO₂
What is the enzyme that fixes CO₂ in the Calvin Cycle?
A) Rubisco
B) ATP synthase
C) P700
D) Chlorophyll a
A) Rubisco
The Calvin Cycle requires how many turns to produce one G3P molecule?
A) One
B) Two
C) Three
D) Six
C) Three
In the Calvin Cycle, ATP is primarily used in which phase?
A) Carbon fixation
B) Reduction
C) Regeneration
D) Light-dependent reactions
C) Regeneration
Which molecule exits the Calvin Cycle to form glucose?
A) RuBP
B) ATP
C) G3P
D) NADPH
C) G3P
What is photorespiration?
A) A process that generates glucose
B) Rubisco binding O₂ instead of CO₂
C) A process to increase CO₂ levels
D) Production of ATP in photosynthesis
B) Rubisco binding O₂ instead of CO₂
Which of the following uses spatial separation to avoid photorespiration?
A) C3 plants
B) C4 plants
C) CAM plants
D) Algae
B) C4 plants
What occurs in CAM plants to minimize water loss?
A) Stomata open during the day
B) CO₂ is fixed during the night
C) Excess CO₂ is released
D) Water is stored in leaves
B) CO₂ is fixed during the night
Which phase of the Calvin Cycle involves the production of G3P?
A) Carbon fixation
B) Reduction
C) Regeneration
D) Light reactions
B) Reduction
How many molecules of ATP are used per turn in the Calvin Cycle?
A) One
B) Two
C) Three
D) Six
C) Three
Which product of photosynthesis is used by nearly all organisms?
A) Oxygen
B) NADPH
C) Glucose
D) Water
A) Oxygen
Which molecule serves as the primary electron carrier in the Calvin Cycle?
A) ATP
B) NADP+
C) G3P
D) RuBP
B) NADP+
Where are the enzymes of the Calvin Cycle located?
A) Thylakoid membrane
B) Mitochondria
C) Stroma
D) Cytoplasm
C) Stroma
What is the fate of the G3P molecules not used for glucose synthesis?
A) Recycled into RuBP
B) Converted to NADPH
C) Used in light reactions
D) Released as oxygen
A) Recycled into RuBP
What is the main product of the Calvin Cycle that serves as a precursor for glucose?
A) NADPH
B) ATP
C) G3P
D) CO₂
C) G3P
True or False: The Calvin Cycle is also called the light-independent reactions.
T
True or False: The Calvin Cycle occurs in the thylakoid membrane.
False (It occurs in the stroma.)
True or False: Photorespiration produces no useful energy or carbohydrates.
T
True or False: ATP and NADPH from the light reactions are used in the Calvin Cycle.
T
True or False: G3P is the first stable product of carbon fixation in the Calvin Cycle.
False (3-phosphoglycerate is the first stable product.)
True or False: Rubisco can bind both CO₂ and O₂.
T
True or False: CAM plants close their stomata during the day to conserve water
T
True or False: C4 plants separate carbon fixation and the Calvin Cycle spatially.
T
True or False: Glucose is directly produced in the Calvin Cycle.
False (G3P is produced and later converted to glucose.)
True or False: The Calvin Cycle requires three molecules of ATP for each turn.
T
True or False: Only heterotrophs depend on the oxygen produced by photosynthesis.
False (Both autotrophs and heterotrophs use oxygen for respiration.)
True or False: The Calvin Cycle regenerates RuBP at the end of each turn.
T
True or False: The Calvin Cycle is an anabolic process.
T
True or False: The Calvin Cycle can function without light if ATP and NADPH are present.
T
True or False: Most of the organic material created in photosynthesis is stored as glucose.
False (It is stored as starch in plants.)
