A cell is unable to synthesize lipids. Which of its cell organelles might be defective?
- (a)Smooth endoplasmic reticulum
- (b)Golgi bodies
- (c)Lysosomes
- (d)Mitochondria
Correct — A, Smooth endoplasmic reticulum. The smooth endoplasmic reticulum (SER) is the site of lipid (fat) and steroid synthesis in the cell, so if a cell cannot make lipids, its smooth ER is the organelle likely to be defective. The Golgi bodies package and dispatch materials, lysosomes carry out intracellular digestion, and mitochondria generate ATP — none of these is the primary lipid-synthesising organelle.
- (b)Golgi bodies — The Golgi apparatus modifies, sorts and packages materials for secretion; it does not synthesise lipids, so its failure would not stop lipid production.
- (c)Lysosomes — Lysosomes are the cell's digestive sacs, breaking down waste and worn-out parts; they play no role in making lipids.
- (d)Mitochondria — Mitochondria are the powerhouses that produce ATP by respiration; they are not the site of lipid synthesis.
The endoplasmic reticulum comes in two forms. The smooth ER (without ribosomes) synthesises lipids and steroids and helps detoxify drugs; the rough ER (studded with ribosomes) makes and processes proteins. A defect in lipid synthesis therefore points to the smooth ER.
The question maps a lost function (lipid synthesis) onto the responsible organelle. Knowing the division of labour — SER for lipids, RER for proteins, Golgi for packaging, lysosomes for digestion, mitochondria for ATP — makes the smooth ER the clear answer.
- Smooth endoplasmic reticulum synthesises lipids and steroids and helps detoxify substances.
- Rough endoplasmic reticulum (ribosome-studded) synthesises and processes proteins.
- The Golgi apparatus modifies, sorts and packages proteins and lipids for secretion.
- Lysosomes digest waste; mitochondria produce ATP through respiration.
Lipid synthesis is the smooth ER's job — so option (a) is the defective organelle.
- Mixing up smooth ER (lipids) with rough ER (proteins).
- Assuming the Golgi 'makes' lipids — it only packages and modifies them.
A defect-to-organelle item — no lipid synthesis points to the smooth endoplasmic reticulum.
Which of the following cell organelles play the most significant role in protein synthesis?
- (a) Lysosome and Centrosome
- (b) Endoplasmic reticulum and Ribosome
- (c) Golgi apparatus and Mitochondria
- (d) Lysosome and Mitochondria
Answer(b) Endoplasmic reticulum and Ribosome
Same theme — organelle functions. That item pairs the (rough) endoplasmic reticulum and ribosomes with protein synthesis; this one uses the complementary fact that the smooth ER handles lipid synthesis.
In mitochondria, ATP synthesizing chemical reactions take place in the
- (a) Outer membrane.
- (b) Matrix.
- (c) Inner membrane.
- (d) DNA of mitochondria.
Answer(c) Inner membrane.
Same concept — matching an organelle to its function. That item locates ATP synthesis in the mitochondrion's inner membrane, just as this one locates lipid synthesis in the smooth ER.
- practice — not a real PYQ
Which part of the endoplasmic reticulum is chiefly associated with protein synthesis and processing?
- (a)smooth ER
- (b)rough ER
- (c)the ER lumen only
- (d)the nuclear envelope
Answer(b) rough ER — it is studded with ribosomes.
- practice — not a real PYQ
The 'powerhouse of the cell' that produces ATP is the
- (a)Golgi body
- (b)mitochondrion
- (c)lysosome
- (d)smooth ER
Answer(b) mitochondrion.