AP Biology Flashcards: Photosynthesis
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 24 cards to help you master important concepts.
What is the immediate result of electrons passing through the electron transport chain (ETC) between the photosystems?
As electrons pass through the ETC, an electrochemical proton gradient is established across the thylakoid membrane.
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What is the immediate result of electrons passing through the electron transport chain (ETC) between the photosystems?
As electrons pass through the ETC, an electrochemical proton gradient is established across the thylakoid membrane.
What is an electron transport chain (ETC)?
An electron transport chain is a series of protein complexes that transfer electrons, a process which is present in both chloroplasts and mitochondria.
What is the overall purpose of photosynthesis?
Photosynthesis is a process that uses light energy, carbon dioxide, and water to capture and store energy by producing carbohydrates and oxygen.
Where specifically within the chloroplast do the light-dependent reactions take place?
The light-dependent reactions occur in the thylakoid membranes, which are organized in stacks called grana.
What is the role of chlorophylls in photosynthesis?
Chlorophylls absorb light energy, which excites electrons in photosystems I and II.
What is photophosphorylation?
Photophosphorylation is the process where a proton gradient drives the synthesis of ATP from ADP and inorganic phosphate via ATP synthase.
What happens to the electrons in photosystems I and II when they absorb light energy?
When chlorophylls in photosystems I and II absorb light energy, their electrons become excited and are transferred through an electron transport chain.
What is the stroma?
The stroma is the fluid-filled space within the chloroplast where the Calvin cycle occurs.
What molecule is split to replace the electrons lost from photosystem II?
Water is split to replace the electrons that are excited and lost from photosystem II.
What are the two main products of photosynthesis?
The main products of photosynthesis are carbohydrates (for energy storage) and oxygen.
What is the carbon source for the carbohydrates produced in the Calvin cycle?
The Calvin cycle uses carbon dioxide (CO2) from the atmosphere to produce carbohydrates.
What is the primary function of the light-dependent reactions?
The light-dependent reactions capture light energy to produce ATP and NADPH.
What is the specific role of the proton gradient in the light-dependent reactions?
The proton gradient across the thylakoid membrane provides the energy to drive the synthesis of ATP via the enzyme ATP synthase.
In photosystem I, what molecule do the transferred electrons ultimately reduce?
In photosystem I, electrons are transferred to NADP+ to form NADPH.
In which type of organisms did photosynthesis first evolve?
Photosynthesis first evolved in prokaryotic organisms.
What is the function of the energy captured in ATP and NADPH?
The energy captured in ATP and NADPH powers the production of carbohydrates from carbon dioxide in the Calvin cycle.
How do the light-dependent reactions and the Calvin cycle relate to each other?
The ATP and NADPH produced during the light-dependent reactions are used to power the production of organic molecules from CO2 in the Calvin cycle.
Where specifically within the chloroplast does the Calvin cycle take place?
The Calvin cycle occurs in the stroma of the chloroplast.
What two energy-carrying molecules are produced by the light-dependent reactions?
The light-dependent reactions produce ATP and NADPH, which are high-energy molecules.
What are thylakoids?
Thylakoids are membrane-bound compartments inside chloroplasts where the light-dependent reactions occur; they are often organized in stacks called grana.
How do chloroplasts capture energy from light?
Chloroplasts capture energy from light when chlorophylls absorb photons, causing electrons within photosystems to become excited.
What are the three main inputs for the entire process of photosynthesis?
The main inputs for photosynthesis are light energy, carbon dioxide, and water.
What is ATP synthase?
ATP synthase is an enzyme that uses the energy from a proton gradient to synthesize ATP from ADP and inorganic phosphate.
How are photosystems I and II connected?
Photosystems I and II, embedded in the thylakoid membranes, are connected by the transfer of electrons through an electron transport chain (ETC).