H+ ions cannot cross the membrane directly. However, the thylakoid membrane contains a protein called ATP synthase that spans the membrane and allows H+ ions to pass through it. Powered by the gradient, H+ ions pass through ATP synthase and force it to rotate, almost like a turbine being spun by water in a hydroelectric power plant. As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP. This process, which is known as chemiosmosis (kem ee ahz MOH sis), enables light-dependent electron transport to produce not only NADPH (at the end of the electron transport chain), but ATP as well.
Summary of Light-Dependent Reactions The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH. What good are these compounds? As we will see, they have an important role to play in the cell: They provide the energy needed to build high-energy sugars from low-energy carbon dioxide.
ZOOMING IN
LIGHT-DEPENDENT REACTIONS
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis