What is the liquid substance within the outer cell wall of bacteria called?

The correct answer is protoplasm, which refers specifically to the living contents of a cell, including the cytoplasm and the nucleus. In the context of bacteria, the protoplasm includes the cytoplasm and various cellular organelles, all situated within the cell membrane, but outside the cell wall. This substance is crucial for maintaining the cell's metabolic functions and is where many cellular activities occur.

Cytoplasm, while it constitutes a major part of the protoplasm, is just one component and does not encompass the entirety of the living material within the cell. Plasma might refer to a fluid component in biological contexts, but in terms of bacterial structure, it is not the term used to describe the cell's inner content. Cell sap usually refers to the fluid found in vacuoles of plant cells, not bacteria. Therefore, protoplasm is the term that best fits the description of the liquid substance within the outer cell wall of bacteria, capturing the comprehensive nature of the cell's living material.