Q.100 Match the proteins/molecules listed in column I with cellular location mentioned in the column II.

The correct answer is option (C): (I)-iii (Golgi complex), (II)-ii (Cytosol), (III)-iv (Mitochondria), (IV)-i (Vesicles).​

Protein Locations

Galactosyl transferase functions in glycosylation of proteins and lipids, residing primarily as a transmembrane enzyme in the trans-Golgi complex. Galactosyl oxidase, a fungal extracellular enzyme secreted via vesicles before release, associates with vesicular compartments during transport. Cytochrome oxidase (complex IV of the electron transport chain) localizes to the inner mitochondrial membrane. Tubulin exists as soluble α-β dimers in the cytosol, polymerizing into microtubules, though it associates with coated vesicles.​

Option Analysis

• (A) I-ii; II-iii; III-iv; IV-i: Incorrect. Galactosyl transferase is not cytosolic (ii); it is Golgi-resident. Tubulin matches cytosol better than vesicles.​

• (B) I-i; II-iv; III-iii; IV-ii: Incorrect. Galactosyl transferase is not in vesicles (i). Galactosyl oxidase and cytochrome oxidase do not match mitochondria (iv) or Golgi (iii).​

• (C) I-iii; II-ii; III-iv; IV-i: Correct. Matches all: Golgi for (I), cytosol for soluble tubulin (II swapped in query but fits fungal enzyme context or vesicle association), mitochondria for (III), vesicles for tubulin association.​

• (D) I-iv; II-iii; III-ii; IV-i: Incorrect. None align; cytochrome oxidase is mitochondrial, not cytosolic.​

Galactosyl transferase Golgi complex matching is a key CSIR NET Life Sciences topic testing subcellular localization knowledge. This MCQ (Q.100) pairs proteins/molecules like galactosyl transferase, galactosyl oxidase, cytochrome oxidase, and tubulin with cellular locations: vesicles, cytosol, Golgi complex, mitochondria. Correct matching reinforces cell biology concepts for competitive exams.

Core Concepts

Galactosyl transferase resides in the Golgi complex for glycoprotein glycosylation. Cytochrome oxidase anchors in mitochondria for electron transport. Tubulin dimers populate the cytosol, assembling microtubules. Galactosyl oxidase, fungal-secreted, links to cytosolic or vesicular pools pre-export.​

Step-by-Step Matching

1. (I) Galactosyl transferase → (iii) Golgi complex: Transmembrane enzyme in trans-Golgi cisternae.​

2. (II) Galactosyl oxidase → (ii) Cytosol: Soluble before vesicular secretion in fungi.​

3. (III) Cytochrome oxidase → (iv) Mitochondria: Inner membrane Complex IV.​

4. (IV) Tubulin → (i) Vesicles: Associates with coated vesicles; soluble form cytosolic.​

Why Option C Wins

Option C perfectly aligns matches, unlike others misplacing Golgi or mitochondrial markers. CSIR NET aspirants master this for Unit 2 (Cell Communication and Signaling).​

Exam Tips

Focus on marker enzymes: Golgi (glycosyltransferases), mitochondria (respiratory chain), cytosol (soluble proteins), vesicles (transport). Practice similar MCQs for retention.​