Final answer:
Chemotaxis is the cellular process for detecting chemical concentration gradients and determining direction of movement. Phagocytes utilize chemotaxis to locate pathogens, engulf them through phagocytosis, and then degrade them with enzymes.
Step-by-step explanation:
The process that many cells rely on to detect differences in concentrations of chemicals and determine movement direction is chemotaxis. This is a form of cellular response where cells move toward higher concentrations of certain chemicals, seen as positive chemotaxis, or move away from them, known as a negative chemotaxis. The process is crucial for various functions such as how bacteria move toward nutrients or how immune cells, like phagocytes, locate and attack pathogens.
As for the mechanism by which a phagocyte destroys a bacterium that it has ingested, it is through the process of phagocytosis followed by degradation using enzymes. Phagocytes such as macrophages engulf bacteria and then use enzymes to break down the ingested bacterium within specialized compartments called lysosomes.
It's worth noting that some of the other mechanisms of molecule movement across cell membranes include osmosis, active transport, facilitated diffusion, and endocytosis, of which phagocytosis is a specific type.