Chapter 10 [Light Independent Reactions]

What are the inputs of the Light-independent reactions of photosynthesis?

-ATP

-CO2

-NADPH

Q//when might it be disadvantageous for a leaf to have open stomata?

In hot, dry, or windy conditions, open stomata can cause a plant to lose water faster than it can replace it, putting the leaf at risk of drying out or overheating. Keeping stomata open during those times is basically like leaving a window open during a heat wave—everything valuable escapes. Open stomata can also make the leaf more vulnerable to pollutants or pathogens in the air, since they act as tiny entry points for spores or harmful gases. So whenever water loss or exposure outweighs the benefit of taking in more CO₂, having open stomata becomes a disadvantage.

In the fixation phase of the Calvin-Benson cycle, CO2 is added to a ___ carbon compound to generate two ____ carbon compounds.

5, 3

What are the inputs of the reduction phase of the Calvin-Benson cycle?

-6 ATP

-6 NADPH

-A 3 carbon compound

Q//In your own words, why is the regeneration phase of the Calvin-Benson cycle necessary?

The regeneration phase of the Calvin-Benson cycle is necessary because it restores the molecule ribulose-1,5-bisphosphate (RuBP), which is needed to capture carbon dioxide and begin the cycle again. Without regeneration, the cycle would stop after producing a few sugar molecules, since RuBP would be used up. By rearranging and converting some of the intermediate molecules back into RuBP, the cycle can continue operating, allowing the plant to keep fixing carbon dioxide and producing sugars over time.

The Calvin-Benson cycle must turn ___ times to make one net molecule of G3P and ____ times to make one net molecule of glucose.

3, 6

In glycolysis G3P is _______ to form 3PGA, but in the Calvin-Benson cycle 3PGA is _______ to form G3P.

oxidized, reduced

Q//In your own words, why do plant cells use ATP to make glucose if they will be breaking down some of that glucose to make ATP?

Plant cells use ATP to make glucose because glucose serves as a long-term storage form of energy, while ATP is a short-term, immediately usable form. ATP is unstable and can't be stored for long, so plants use the energy from ATP (produced in the light reactions) to build glucose molecules during the Calvin-Benson cycle. Glucose can then be stored as starch or used later for energy through cellular respiration when sunlight isn't available. In other words, plants "invest" ATP to create glucose so they can have a stable energy supply for growth, repair, and survival over time.