What is photosynthesis?
The process by which plants, algae, and some bacteria use energy from sunlight to synthesize organic molecules from CO2.
What are the two stages of photosynthesis?
The light-dependent reactions and the light-independent reactions (the Calvin cycle).
Where do the light-dependent reactions occur?
On the thylakoid membranes inside chloroplasts.
Where does the Calvin cycle occur?
In the stroma of the chloroplast.
What are the products of the light-dependent reactions?
ATP and NADPH.
What do the light-dependent reactions provide to the Calvin cycle?
ATP (energy) and NADPH (hydrogen atoms and electrons).
What does the Calvin cycle produce?
Carbohydrate molecules (sugars) built from CO2.
What is the overall equation for photosynthesis?
6CO2 + 12H2O + light energy → glucose + 6H2O + 6O2.
What are the three layers of a leaf that light must pass through to reach chloroplasts?
The cuticle, the epidermis, and the mesophyll cells.
What are mesophyll cells?
Cells that fill the interior of a leaf and contain numerous chloroplasts where photosynthesis occurs.
What are photons?
Tiny packets of light energy that have properties of both particles and waves.
How does wavelength relate to the energy of a photon?
Shorter wavelengths carry more energy; longer wavelengths carry less energy.
What is visible light?
The portion of the electromagnetic spectrum with wavelengths between about 400 nm (violet) and 740 nm (red) that human eye pigments can absorb.
What is a pigment?
A molecule that absorbs light energy.
What is chlorophyll?
The primary pigment in plants that absorbs red and blue light and reflects green light — making plants appear green.
What are the two versions of chlorophyll in plants?
Chlorophyll a and chlorophyll b.
What is a photosystem?
A complex of chlorophyll molecules and proteins embedded in the thylakoid membrane that captures light energy.
What is the antenna complex?
The portion of a photosystem containing light-harvesting pigment molecules that channels excitation energy to the reaction center.
What is the reaction center?
The specific chlorophyll a molecule in a photosystem that receives excitation energy from the antenna complex and passes it as a high-energy electron to the electron transport system.
What is the electron transport system?
A series of electron-carrier proteins embedded in the thylakoid membrane that use the energy of excited electrons to pump protons across the membrane.
What does photosystem II produce?
ATP — it captures light energy, excites an electron, and uses the electron transport system to pump protons that drive ATP synthesis.
What does photosystem I produce?
NADPH — it re-energizes electrons from photosystem II using a second photon of light and passes them to NADP+ to form NADPH.
What molecule is split in photosystem II and what is released as a by-product?
Water (H2O) is split to replace lost electrons — oxygen gas (O2) is released as a by-product.
What is chemiosmosis?
The process by which protons diffuse back across the thylakoid membrane through ATP synthase, driving the formation of ATP.
