Final answer:
A biological catalyst that speeds up chemical reactions in living organisms is an enzyme, which is a protein that lowers the activation energy of reactions.
Step-by-step explanation:
A biological catalyst that speeds up chemical reactions in living organisms is known as an enzyme. Enzymes are essential for life because most chemical reactions in organisms occur too slowly under normal conditions to sustain life. They function by lowering the activation energy required for a reaction to proceed, therefore increasing the rate at which the reactions occur. An enzyme interacts with a specific substrate to catalyze a reaction without being consumed in the process.
In summary, the correct answer to the question is b) Enzyme. This is because enzymes are proteins that act as catalysts within living organisms, speeding up biochemical reactions necessary for life processes.