Final answer:
The term for a discrete macromolecular structure within the cytoplasm of eukaryotic cells that performs a specific job and is often membrane-enclosed is 'organelle'. Option a.
Step-by-step explanation:
The correct answer to the question is a) Organelle. Any discrete macromolecular structure in the cytoplasm of eukaryote cells that is enclosed within a membrane and performs a specific job is termed an organelle.
Examples of organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, and vacuoles in animal cells, as well as ribosomes, which despite not being enclosed by a membrane, are still considered organelles in eukaryotic cells.
These structures play crucial roles in cells, with some organelles like the mitochondria being responsible for producing energy, and chloroplasts allowing green plants to utilize sunlight to make sugars.
So Option a .