Which of the following statements best predicts the effect of increasing the permeability of the mitochondrial membranes to large molecules? A ATP production will increase because of an increase in the rate at which proteins diffuse out of mitochondria. B ATP production will increase because of an increase in the mixing of mitochondrial and cytosolic substances. C ATP production will decrease because of an increase in the occurrence of uncontrolled chemical reactions. D ATP production will decrease because of an increase in the surface area of the mitochondrial membranes.
The correct answer and explanation is:
Correct Answer: C. ATP production will decrease because of an increase in the occurrence of uncontrolled chemical reactions.
The mitochondria are essential organelles responsible for producing energy in the form of adenosine triphosphate (ATP). This energy production occurs primarily through a process called oxidative phosphorylation, which takes place across the inner mitochondrial membrane. The structure and selective permeability of the mitochondrial membranes are critical to maintaining the efficiency and control of this process.
Increasing the permeability of the mitochondrial membranes to large molecules would disrupt this delicate balance. The inner membrane is usually impermeable to most ions and molecules, which allows the mitochondria to create and maintain a proton gradient between the intermembrane space and the matrix. This gradient drives the ATP synthase enzyme to produce ATP. If the membrane becomes permeable to large molecules and other substances, this gradient will collapse.
When large molecules and ions can move freely across the membrane, controlled conditions inside the mitochondria are lost. Enzymes and substrates needed for specific steps in cellular respiration may leak out, and unwanted substances from the cytosol may enter. These disturbances can lead to unregulated or uncontrolled chemical reactions. Such reactions may interfere with the carefully coordinated steps of ATP production, reducing the efficiency or even halting ATP synthesis altogether.
Therefore, the decrease in ATP production is not due to a beneficial increase in diffusion or surface area, but rather due to the breakdown of controlled environments and the loss of compartmentalization. This leads to chemical chaos within the mitochondria, disrupting energy production and potentially damaging the cell. Hence, choice C best predicts the outcome of increased mitochondrial membrane permeability.