Which of the following processes does not generate ATP?
a. photophosphorylation
b. the Calvin-Benson cycle
c. oxidative phosphorylation
d. substrate-level phosphorylation
e. All of the above generate ATP

Verified step by step guidance

1. Understand the processes listed: photophosphorylation, the Calvin-Benson cycle, oxidative phosphorylation, and substrate-level phosphorylation.
2. Recall that photophosphorylation occurs in photosynthetic organisms and involves the conversion of light energy into chemical energy, generating ATP.
3. Remember that oxidative phosphorylation is part of cellular respiration, where ATP is produced using energy derived from the electron transport chain.
4. Recognize that substrate-level phosphorylation is a direct method of forming ATP by transferring a phosphate group to ADP from a phosphorylated intermediate.
5. Consider the Calvin-Benson cycle, which is part of the photosynthetic process but primarily focuses on carbon fixation and does not directly generate ATP.

Key Concepts

ATP Generation Processes

ATP (adenosine triphosphate) is the primary energy currency of the cell, generated through various metabolic processes. Key processes include photophosphorylation, oxidative phosphorylation, and substrate-level phosphorylation, each utilizing different mechanisms to produce ATP. Understanding these processes is essential for identifying which ones do not contribute to ATP synthesis.

Calvin-Benson Cycle

The Calvin-Benson cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis. Its primary function is to fix carbon dioxide into organic molecules, specifically glucose, but it does not directly produce ATP. Instead, it relies on ATP and NADPH generated from light-dependent reactions, making it crucial to distinguish its role in energy metabolism.

Photophosphorylation vs. Oxidative Phosphorylation

Photophosphorylation occurs in photosynthetic organisms, where light energy is converted into chemical energy, producing ATP through the electron transport chain in chloroplasts. In contrast, oxidative phosphorylation takes place in mitochondria, where ATP is generated from the transfer of electrons through a series of proteins, driven by the oxidation of nutrients. Both processes are vital for ATP production, but they operate in different cellular contexts.