# DBT JRF 2020 — Question 7

Exam: DBT JRF 2020 · Section: A · Topic: Cell Biology · Difficulty: Easy

## Question

Synthesis of majority of lipids in a cellular system occurs in the

## Options

- **A.** mitochondria
- **B.** lysosomes
- **C.** endoplasmic reticulum
- **D.** nucleus

## Answer

Option C

## Explanation

Lipid biosynthesis is the major function of the smooth endoplasmic reticulum (SER). The SER houses key enzyme systems: fatty acid desaturases, phospholipid synthases (CDP-choline pathway for phosphatidylcholine), and cholesterol biosynthetic enzymes (HMG-CoA reductase). Steroid hormones (from cholesterol) are also synthesised in SER of adrenal cortex and gonads. The rough ER handles protein synthesis/processing; mitochondria synthesise some specialised lipids (cardiolipin); the Golgi completes sphingolipid synthesis — but the majority of cellular lipid biosynthesis is initiated and accomplished in the SER.

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