The organelle directly affected by the inability of oxygen to diffuse across the membrane is the mitochondria.

Here's why:

* Mitochondria are the powerhouses of the cell: They are responsible for cellular respiration, the process that uses oxygen to break down glucose and produce ATP (adenosine triphosphate), the energy currency of the cell.

* Oxygen is essential for cellular respiration: Mitochondria need a constant supply of oxygen to carry out this process. Without oxygen, they cannot function properly.

* Lack of oxygen leads to ATP depletion: If oxygen cannot enter the cell, the mitochondria will be unable to produce ATP. This will significantly impact the cell's ability to perform its functions and could eventually lead to cell death.

While other organelles might indirectly be affected by the lack of ATP, the mitochondria are the primary and most immediate target of the oxygen deprivation.