Proteomics is the large-scale study of proteins, particularly their structures, functions, interactions, and modifications. It aims to characterize the
proteome, which is the entire complement of proteins produced or modified by an organism, system, tissue, or cell at a particular time and under specific conditions.
Key aspects of proteomics include:
- Identification and quantification of proteins.
- Determination of protein structures and post-translational modifications.
- Analysis of protein interactions and protein networks.
- Study of protein function and localization.
Let's analyze the options:
(a) "Set of proteins in a specific region of the cell": This is a part of proteomics (e.g., organellar proteomics), but proteomics is broader, encompassing the entire proteome.
(b) "Biomolecules": Too general. Biomolecules include nucleic acids, carbohydrates, lipids, in addition to proteins.
(c) "Set of proteins": This is closer, but option (d) is more precise.
(d) "The entire set of expressed proteins in the cell" (or organism/tissue): This correctly defines the proteome, which is the subject of proteomics. It emphasizes "expressed" proteins, reflecting the dynamic nature of the proteome.
Therefore, proteomics refers to the study of the entire set of expressed proteins in a cell, tissue, or organism.
\[ \boxed{\text{The entire set of expressed proteins in the cell}} \]