Part 5 — Mitochondria, Plastids, Ribosomes & Nucleus (Q101–125)

Q101.

The mitochondrial matrix contains:
A. Ribosomes and DNA ✅
B. Chlorophyll
C. Histones
D. None of these

Explanation:

A. Correct: Matrix has circular DNA, 70S ribosomes, enzymes of Krebs cycle.
B. Chlorophyll: In chloroplast, not mitochondria.
C. Histones: Found in eukaryotic nuclear DNA, not in mitochondria.
**D. Incorrect, as mitochondria do have DNA and ribosomes.

Q102.

Mitochondria are semi-autonomous because:
A. They have their own DNA and ribosomes ✅
B. They are part of the endomembrane system
C. They synthesize cellulose
D. They cannot make proteins

Explanation:

A. Correct: They contain mtDNA and 70S ribosomes → produce some proteins independently.
**B. Endomembrane system excludes mitochondria.
**C. Cellulose synthesis occurs in plants.
**D. They can synthesize proteins, so statement is false.

Q103.

The outer mitochondrial membrane is:
A. Highly folded
B. Smooth and permeable to small molecules ✅
C. Impermeable to all molecules
D. Connected to thylakoids

Explanation:

**A. Folding = inner membrane (cristae).
**B. Correct — outer membrane smooth, contains porins (permeable to ions/small molecules).
**C. Wrong, it is permeable.
**D. Thylakoids belong to chloroplasts.

Q104.

Which organelle is the site of photorespiration in plants along with chloroplast and mitochondria?
A. Nucleus
B. Peroxisome ✅
C. Lysosome
D. Ribosome

Explanation:

A. Nucleus: Genetic storage, not photorespiration.
B. Peroxisome (Correct): Works with mitochondria & chloroplast in glycolate pathway.
C. Lysosome: Digestion.
D. Ribosome: Protein synthesis.

Q105.

Which plastid type stores starch?
A. Elaioplast
B. Amyloplast ✅
C. Proteinoplast
D. Chromoplast

Explanation:

A. Elaioplast: Oil/fat storage.
B. Amyloplast (Correct): Starch storage.
C. Proteinoplast: Protein storage.
D. Chromoplast: Colored pigments.

Q106.

Chlorophyll is located in:
A. Stroma
B. Thylakoid membrane ✅
C. Cell wall
D. Cristae

Explanation:

A. Stroma: Enzymes of dark reaction, not pigments.
B. Thylakoid membrane (Correct): Embedded chlorophyll + photosystems.
C. Cell wall: Structural, no chlorophyll.
D. Cristae: In mitochondria.

Q107.

Which plastid type is found in ripened fruits?
A. Chloroplast
B. Chromoplast ✅
C. Leucoplast
D. Etioplast

Explanation:

A. Chloroplast: Found in green tissues.
B. Chromoplast (Correct): Pigments in flowers/fruits (carotenoids).
C. Leucoplast: Storage, non-pigmented.
D. Etioplast: Dark-grown tissue precursor.

Q108.

The 70S ribosome consists of:
A. 60S + 40S
B. 50S + 30S ✅
C. 70S + 20S
D. 80S + 10S

Explanation:

A. 60S + 40S: Eukaryotic 80S.
B. 50S + 30S (Correct): Prokaryotic ribosome.
C. 70S + 20S: Doesn’t exist.
D. 80S + 10S: Doesn’t exist.

Q109.

In eukaryotic cytoplasm, ribosomes are:
A. 70S
B. 80S ✅
C. 60S
D. 30S

Explanation:

A. 70S: Found in prokaryotes & organelles.
B. 80S (Correct): Eukaryotic cytoplasm ribosomes.
C & D: Subunits, not full ribosome.

Q110.

Which organelle assembles ribosomal subunits?
A. Nucleolus ✅
B. Chromatin
C. Golgi
D. ER

Explanation:

A. Nucleolus (Correct): Produces rRNA, assembles ribosome subunits.
B. Chromatin: DNA + proteins.
C. Golgi: Protein modification.
D. ER: Protein synthesis, not ribosome assembly.

Q111.

Which plastid develops into chloroplast upon exposure to light?
A. Chromoplast
B. Etioplast ✅
C. Leucoplast
D. Amyloplast

Explanation:

A. Chromoplast: Produces carotenoids, not green pigments.
B. Etioplast (Correct): Precursor in dark → light induces chlorophyll formation.
C. Leucoplast: Storage.
D. Amyloplast: Starch storage.

Q112.

Ribosomes are absent in:
A. Prokaryotes
B. Viruses ✅
C. Mitochondria
D. Cytoplasm

Explanation:

A. Prokaryotes: Have 70S ribosomes.
B. Viruses (Correct): Lack ribosomes, rely on host.
C. Mitochondria: Have 70S ribosomes.
D. Cytoplasm: Ribosomes abundant.

Q113.

Which pigment besides chlorophyll is present in chloroplast?
A. Anthocyanin
B. Carotenoids ✅
C. Xanthophylls ✅
D. Both B and C ✅

Explanation:

A. Anthocyanin: In vacuoles, not chloroplast.
B. Carotenoids: Yes.
C. Xanthophylls: Yes, subgroup of carotenoids.
**D. Correct — both are accessory pigments.

Q114.

Histone proteins are associated with:
A. Ribosomes
B. Nuclear DNA ✅
C. Mitochondrial DNA
D. Chloroplast DNA

Explanation:

A. Ribosomes: rRNA + ribosomal proteins, not histones.
B. Nuclear DNA (Correct): Wrapped around histone octamers.
C. Mitochondrial DNA: Naked, no histones.
D. Chloroplast DNA: Also naked.

Q115.

Which is NOT a function of the nucleus?
A. Storing genetic material
B. Controlling metabolism
C. Protein synthesis directly ✅
D. Regulating cell division

Explanation:

**A. Stores DNA: yes.
**B. Controls metabolism via mRNA production: yes.
C. Protein synthesis directly (Correct): Done by ribosomes, nucleus provides mRNA.
**D. Regulates cell cycle: yes.

Q116.

The nucleoplasm is also known as:
A. Karyolymph ✅
B. Cytosol
C. Stroma
D. Matrix

Explanation:

A. Karyolymph (Correct): Fluid inside nucleus.
B. Cytosol: Cytoplasm fluid.
C. Stroma: Chloroplast fluid.
D. Matrix: Mitochondrial interior.

Q117.

The nuclear pore complex allows:
A. Free diffusion of all molecules
B. Selective transport of RNA and proteins ✅
C. Only DNA exit
D. Only proteins entry

Explanation:

A. Free diffusion: Only for small molecules.
**B. Correct — selective for RNA export and protein import.
**C. DNA never exits.
**D. Proteins enter but not exclusive.

Q118.

Which plastid is involved in synthesis and storage of proteins?
A. Amyloplast
B. Proteinoplast ✅
C. Elaioplast
D. Chromoplast

Explanation:

A. Amyloplast: Starch.
B. Proteinoplast (Correct): Protein storage plastids.
C. Elaioplast: Lipids.
D. Chromoplast: Pigments.

Q119.

Mitochondria and chloroplasts support the endosymbiotic theory because:
A. They lack DNA
B. They possess prokaryotic-type DNA and ribosomes ✅
C. They are single-membraned
D. They are part of the endomembrane system

Explanation:

**A. False — they have DNA.
**B. Correct — circular DNA, 70S ribosomes = prokaryotic features.
**C. False — both double-membraned.
**D. False — independent from endomembrane system.

Q120.

The darkly stained, transcriptionally inactive chromatin is:
A. Euchromatin
B. Heterochromatin ✅
C. Plasmid
D. Nucleolus

Explanation:

A. Euchromatin: Active, lightly stained.
B. Heterochromatin (Correct): Inactive, condensed, dark-stained.
C. Plasmid: Prokaryotic DNA.
D. Nucleolus: Not chromatin.

Q121.

Which ribosomal subunit binds to mRNA first in prokaryotes?
A. 30S ✅
B. 50S
C. 70S
D. 80S

Explanation:

A. 30S (Correct): Small subunit recognizes mRNA.
B. 50S: Joins later.
C. 70S: Whole ribosome formed.
D. 80S: In eukaryotes.

Q122.

Chloroplast DNA is:
A. Circular, double-stranded ✅
B. Linear, single-stranded
C. Associated with histones
D. Absent

Explanation:

**A. Correct — cpDNA is circular, ds, histone-free.
**B. Wrong — not linear or ss.
**C. Histone proteins absent.
**D. DNA is present.

Q123.

Which organelle has both structural and genetic continuity?
A. Ribosome
B. Chloroplast ✅
C. Lysosome
D. Golgi

Explanation:

A. Ribosome: Non-membranous, no DNA.
B. Chloroplast (Correct): Has DNA, self-duplicates.
C. Lysosome: Single-membrane, no DNA.
D. Golgi: Forms anew, no DNA.

Q124.

Which subunit of ribosome contains peptidyl transferase activity?
A. Small subunit
B. Large subunit ✅
C. Both
D. None

Explanation:

A. Small subunit: mRNA binding.
B. Large subunit (Correct): rRNA functions as ribozyme for peptide bond formation.
**C. Not both.
**D. Not none.

Q125.

Nucleolus disappears during:
A. Metaphase of mitosis ✅
B. Interphase
C. Cytokinesis
D. G1 phase

Explanation:

**A. Correct — nucleolus disassembles in prophase, absent in metaphase, reappears in telophase.
**B. Interphase: nucleolus is present.
**C. Cytokinesis: after chromosome segregation, nucleolus reforms.
**D. G1: nucleolus is active.

Cell the unit of life, Class 11 Biology MCQs, Prokaryotic and eukaryotic cell, NCERT Biology Chapter 8, Cell organelles structure function, NEET UG Biology preparation, Online learning Class 11 Biology, Cell theory and nucleus, cell the unit of life MCQs for NEET, prokaryotic and eukaryotic cell NCERT questions, plant and animal cell Class 11 Biology, cell organelles structure function NEET UG, cytoskeleton cilia flagella centrioles MCQs, endomembrane system Class 11 MCQs, nucleus structure and function Class 11 NEET, online Class 11 Biology MCQs NEET

Part 5 — Mitochondria, Plastids, Ribosomes & Nucleus (Q101–125)