Why is the cell theory considered a scientific theory ?

The correct answer is theory is well-supported and established with data and can be revised.

Explanation:

A theory is considered a scientific theory when it fulfills the conditions:

1. Well-explained by facts based on the repeated experiments and observation.

2. Supported with data.

3. Can be revised or modified if needed with new discoveries and  inventions.  

Since cell theory was given by Schwann a zoologist, who observed that all animals are made of cells and Schleiden a botanist, who observed that plants are made of cells.

This theory was later supported and revised by Rudolf Virchow based on the experiments and found that all cells arise from pre-existing cells. Afterwards this theory has revised many times with the development in the technology.

Thus, theory is well-supported and established with data and can be revised is the correct answer.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

the endomembrane system i think