VISUAL SKILLS This computer model shows the four parts of ATP synthase, each part consisting of a number of polypeptide subunits (the structure in gray is still an area of active research). Using Figure 9.14 as a guide, label the rotor, stator, internal rod, and catalytic knob of this molecular motor.

Verified step by step guidance

1. Identify the four main parts of ATP synthase in the image: rotor, stator, internal rod, and catalytic knob.
2. Locate the rotor, which is the part that rotates as protons (H+) flow through it. In the image, this is the circular structure at the bottom of the ATP synthase complex.
3. Find the stator, which holds the rotor in place and prevents it from rotating. This is the structure that spans the membrane and is connected to the rotor.
4. Identify the internal rod, which connects the rotor to the catalytic knob. This is the vertical structure that runs through the center of the ATP synthase complex.
5. Locate the catalytic knob, which is the part of the ATP synthase where ADP and inorganic phosphate (Pi) are combined to form ATP. This is the bulbous structure at the top of the ATP synthase complex.

Key Concepts

ATP Synthase Structure

ATP synthase is a complex enzyme composed of multiple subunits that facilitate the synthesis of ATP from ADP and inorganic phosphate. It consists of a rotor, stator, internal rod, and catalytic knob, each playing a crucial role in the enzyme's function. The rotor spins as protons flow through it, driving the mechanical movement necessary for ATP production.

Proton Gradient

The proton gradient is a difference in proton concentration across a membrane, created during cellular respiration. This gradient generates potential energy, which ATP synthase harnesses to produce ATP. Protons flow back into the mitochondrial matrix through ATP synthase, causing the rotor to turn and catalyze the conversion of ADP to ATP.

Chemiosmosis

Chemiosmosis is the process by which ATP is produced in mitochondria and chloroplasts, driven by the movement of protons across a membrane. This movement occurs due to the proton gradient established by electron transport chains. The energy released as protons flow back through ATP synthase is used to synthesize ATP, linking the processes of electron transport and ATP production.