Ap Bio Calvin Cycle

Ap Bio Bushman

What part of photosynthesis is the Calvin cycle?

Light-independent

What are the three parts of the Calvin cycle?

Carbon fixation, reduction, and regeneration

What is glyceraldehyde-3-phosphate (G3P)?

A three-carbon sugar produced by the Calvin cycle that is used to make glucose and other organic compounds

Where does the carbon used in the Calvin cycle come from?

CO2 comes from the air

What products from the light-dependent reactions are required for the Calvin Cycle?

ATP and NADPH

What is the main product of the Calvin Cycle?

G3P (PGAL)

How is glucose formed from G3P?

Two G3P molecules combine to form one glucose molecule

What enzyme catalyzes the first step of the Calvin cycle?

Rubisco

Why is rubisco considered the most abundant protein on Earth?

It catalyzes carbon fixation in nearly all photosynthestic organisms

What molecule does CO2 attach to during carbon fixation?

Ribulose bisphosphate (RuBP)

How many carbons does RuBP have?

Five carbon

What unstable compound is formed when CO2 attaches to RuBP?

A six-carbon unstable sugar

What molecules are formed when the unstable six-carbon compound breaks down?

Two molecules of PGA (3-phosphoglycerate)

How many carbons does PGA have?

three

What phase of the Calvin cycle produces G3P?

the reduction phase

What molecules provide energy and electrons during the reduction phase?

ATP and NADPH

What type of reaction occues during the reduction phase?

A redox reaction

What is a redox reaction?

A chemical reaction in which the transfer of electrons happens between substances. One loses (oxidation) and one gains (reduction)

What happens during the regeneration phase?

RuBP is remade so the cycle can continue

How many turns of the Calvin cycle are needed to produce one G3P?

three

How many turns of the Calvin cycle are needed to produce one glucose?

Six

What is a stomata?

Microscopic openings in the epidermis of the leaves that allow for gas exchange

What gases move in and out of the stomata?

CO2 enters; O2 and H2O exit

How do gases move through the stomata?

By diffusing from high concentration to low concentration

Why do plants close their stomata on hot days

to prevent water loss

What happens to CO2 levels inside the leaf when stomata are closed?

CO2 levels decrease

What is photorespiration?

The process where Rubisco binds oxygen instead of CO2, wasting energy and carbon

What molecule does Rubisco bind to during photorespiration?

oxygen

Why does photorespiration occur more often when stomata are closed?

CO2 levels drop and O2 levels rise

Why is photorespiration considered inefficient?

It wastes time, energy, and carbon without producing sugar

Why might plants tolerate photorespiration instead of opening the stomata>

To avoid dying from dehydration

What types of plants are most classifed as?

c3 plants

What is the first stable intermediate in C3 plants?

PGA (3-carbon compound)

Why are C3 plants more prone to photorespiration?

They rely directly on Rubisco to fix CO2

What conditions are C4 plants adapted to?

Hot and dry enviornments

What enzymes initially fixes CO2 in C4 plants?

PEP carboxylase

What is the first stable intermediate in C4 plants?

OAA (oxaloacetate), a four-carbon compound

Why are C4 plants called "C4"?

Their first stable product has four carbons

How do C4 plants reduce photorespiration?

By delivering CO2 to bundle sheath cells with low oxygen levels

Two common C4 plants

Corn and sugarcane

Why are C4 plants more water-efficient than C3 plants?

They can keep their stomata closed more often

What does CAM stand for?

Crassulacean Acid Metabolism

What environments are CAM plants adapted for?

Hot, dry environments

When do CAM plants open their stomata?

NIght

Why do CAM plants open the stomata at night instead of during the day?

To reduce water loss

How is CO2 stored in CAM plants at night?

Add organic acids

What happens to the stored CO2 during the day?

It is released for use in the Calvin cycle

Do CAM plants produce ATP or NADPH at night?

No

When does the Calvin cycle occur in CAM plants?

Day