Difficulty: Easy
Correct Answer: Cytosol
Explanation:
Introduction / Context:
The eukaryotic cell interior contains many membrane-bound organelles. These structures do not float in empty space; instead, they are bathed in a complex aqueous solution rich in ions, metabolites, proteins, and cytoskeletal elements. Identifying this compartment helps frame discussions about metabolic channeling, diffusion, and intracellular transport.
Given Data / Assumptions:
Concept / Approach:
The cytosol constitutes the fluid phase of the cytoplasm outside organelles. It contains enzymes for glycolysis, parts of signaling pathways, ribosomes, and a dynamic cytoskeleton network. Organelles such as mitochondria, ER, and Golgi are suspended within this cytosolic matrix, enabling exchange and trafficking via vesicles and motor proteins.
Step-by-Step Solution:
Verification / Alternative check:
Cell fractionation separates cytosol from organelles by centrifugation, confirming its distinct composition and enzyme content. Fluorescence microscopy shows soluble proteins diffusing throughout the cytosol around organelles.
Why Other Options Are Wrong:
Common Pitfalls:
Using “cytoplasm” and “cytosol” interchangeably. Cytoplasm includes cytosol plus organelles (except the nucleus in some definitions), while cytosol is the soluble fraction alone.
Final Answer:
Cytosol
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