Photosynthesis Case Study Objectives

Components of the thylakoid membrane

Photosystem II, b6f proton pump, Photosystem I, and ATP synthase.

Sides of the thylakoid membrane

Thylakoid space on the inside and surrounding stroma on the outside.

Where is light energy absorbed?

By chlorophyll and other pigments in photosystems.

Rate-dictating factors for light-dependent reactions

Light intensity, wavelength, and availability of water and NADP+.

Source of electrons for light-dependent reactions

The splitting of water molecules.

Final electron acceptor in light reactions

NADP+, which is reduced to form NADPH.

Proton movement in light-dependent reactions

Active transport into the thylakoid space and facilitated diffusion out through ATP synthase.

What drives ATP synthesis in chloroplasts?

The proton gradient across the thylakoid membrane.

Location of ATP synthesis

The stroma, via ATP synthase.

Inputs of light-dependent reactions

Water, light energy, NADP+, and ADP.

Outputs of light-dependent reactions

Oxygen, ATP, and NADPH.

Location of the Calvin cycle

The stroma of the chloroplast.

Inputs of the Calvin cycle

CO2, ATP, and NADPH.

Outputs of the Calvin cycle

G3P (glucose precursor), ADP, and NADP+.

Importance of recycling Calvin cycle outputs

To regenerate RuBP and sustain continuous carbon fixation.

How is O2 produced in photosynthesis?

Through the photolysis of water at Photosystem II.

Effect of photosynthetic ETC disruption on ATP

ATP production drops as the proton gradient is lost.

Effect of Calvin cycle disruption on NADP+

NADP+ levels drop while NADPH accumulates.

Gas relationship in photosynthesis vs respiration

Photosynthesis uses CO2 and makes O2; respiration uses O2 and makes CO2.

Purpose of additional photosynthetic pigments

To absorb broader wavelengths of light and maximize energy capture.

Why plants reflect green light

Chlorophyll poorly absorbs green wavelengths, reflecting them instead.

Effect of ETC disruption on molecule concentrations

O2 and ATP production decrease, while H2O and NADP+ accumulate.

Effect of Calvin cycle disruption on molecule concentrations

CO2 accumulates, while ATP and NADPH levels rise due to lack of consumption.

Predicting light absorption and reflection

Pigments absorb specific wavelengths and reflect colors that match their unabsorbed wavelengths.

Using light absorbance graphs

Plants photosynthesize better at wavelengths where pigment absorbance is high.

Experimental design for photosynthetic rates

Measuring O2 production or CO2 consumption under different light colors and intensities.

Effect of changing photopigments

Alters the absorption spectrum, enabling efficient light utilization across different wavelengths.

Independent variable in light experiments

Typically the color/wavelength of light or light intensity.

Dependent variable in photosynthetic rate experiments

Rate of oxygen production or carbon dioxide consumption.

General herbicide mechanism in chloroplasts

Disrupting the electron transport chain or inhibiting Calvin cycle enzymes.

Role of accessory pigments

Absorb light wavelengths missed by chlorophyll a and protect the plant from photo-damage.