molecular oxygen, which picks up protons and electrons to form water.

7.11 The Complete Respiratory Chain Electrons enter the chain from two sources, but they follow the same pathway from Q onward.

(H+), against their concentration gradient, across the inner membrane of the mitochondrion from the mitochondrial matrix to the intermembrane space (the space between the inner and outer mitochondrial membranes). This occurs because the electron carriers contained in the three large protein complexes are arranged such that protons are taken up on one side of the membrane (the mito-chondrial matrix) and transported along with electrons to the other side (the intermembrane space) (Figure 7.12). Thus, the protein complexes act as proton pumps. Because of the positive charge on the protons (H+), this transport causes not only a difference in proton concentration, but also a difference in electric charge, across the membrane, with the inside of the organelle (the matrix) more negative than the intermembrane space.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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