Sample 1Medium
A figure shows a sausage-shaped organelle bounded by two membranes. The outer membrane (A) is smooth. The inner membrane (B) forms a number of infoldings (C) towards the inside. The dense, homogeneous space enclosed by the inner membrane is labelled D. Which labelled part contains a single circular DNA molecule and 70S ribosomes?
- A
A, the outer membrane
- B
B, the inner membrane
- C
D, the matrix
- D
C, the cristae
Show the answer
The answer is C.The organelle is a mitochondrion: smooth outer membrane, inner membrane folded into cristae, and an inner compartment called the matrix. The matrix has a single circular DNA molecule, a few RNA molecules, 70S ribosomes and what is needed to make proteins.
- A.
The outer membrane is a smooth limiting boundary. It does not contain DNA or ribosomes.
- B.
The inner membrane carries the enzymes of respiration, but the DNA and ribosomes lie in the compartment it encloses.
- D.
Cristae are infoldings that increase the surface area of the inner membrane. They do not hold the DNA.
NCERT: Class 11 Biology, Chapter 8
Sample 2NEET level
Assertion (A): Mitochondria are a part of the endomembrane system. Reason (R): The functions of mitochondria are not coordinated with those of the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles. Choose the correct answer from the options given below.
- A
Both A and R are true and R is the correct explanation of A
- B
Both A and R are true but R is not the correct explanation of A
- C
A is true but R is false
- D
A is false but R is true
Show the answer
The answer is D.The endomembrane system comprises the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles. Mitochondria, chloroplasts and peroxisomes are not part of it because their functions are not coordinated with these, so A is false and R is true.
- A.
A is false: mitochondria are excluded from the endomembrane system.
- B.
A is false, so this cannot be the answer.
- C.
A is false and R is true, not the other way round.
NCERT: Class 11 Biology, Chapter 8 (Cell: The Unit of Life), Eukaryotic Cells – Endomembrane System