Which one of the following is an organelle that is NOT found in prokaryotic cells?
- A.Cell wall
- B.Mitochondria
- C.Plasma membrane
- D.Ribosome
Correct answer
Explanation
The correct answer is B, Mitochondria. Prokaryotic cells such as bacteria have no membrane-bound organelles, so they lack mitochondria.
Prokaryotes have no true nucleus: their DNA lies in a region called the nucleoid, and they have no mitochondria, chloroplasts, endoplasmic reticulum or Golgi body. Bacteria carry out respiration on their plasma membrane, which does the work that mitochondria do in eukaryotic cells. In fact, mitochondria are thought to have come from bacteria that were taken into early eukaryotic cells, which is why they have their own DNA and 70S ribosomes.
A is wrong because most bacteria have a cell wall, made of peptidoglycan.
C is wrong because every cell, prokaryotic or eukaryotic, is bounded by a plasma membrane.
D is wrong because prokaryotes have ribosomes, of the smaller 70S type, to make proteins; eukaryotes have 80S ribosomes in the cytoplasm.
Exam tip: prokaryote = no nucleus, no membrane-bound organelles, 70S ribosomes; eukaryote = true nucleus, mitochondria, 80S ribosomes.
Practice Questions
View allWhich one of the following cell organelles contains DNA?
- A.Golgi apparatus
- B.Mitochondrion
- C.Lysosome
- D.Endoplasmic reticulum
Show answer
Mitochondria carry their own small, circular DNA and their own ribosomes. Mitochondria are the powerhouses of the cell, where aerobic respiration makes ATP.
Read the full explanation →Which set of vegetables is underground stem or modified stem of a plant?
- A.Potato, artichoke, round gourd
- B.Onion, garlic, carrot
- C.Potato, onion, garlic
- D.Potato, garlic, turnip
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All three are underground modified stems: the potato is a stem tuber, and onion and garlic are bulbs. A stem can be told from a root by its nodes and buds.
Read the full explanation →A sound wave having frequency of 300 Hz is travelling in an unknown medium. Its wavelength is not known. It travels a distance equal to 150 times its wavelength in time t. The value of t is :
- A.0.5 s
- B.1 s
- C.1.5 s
- D.2 s
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A wave moves forward by one wavelength in each cycle, so 150 wavelengths take 150 cycles, and 150 cycles at 300 per second take half a second.
Read the full explanation →A body floats in a liquid if the buoyant force is :
- A.equal to its weight.
- B.less than its weight.
- C.greater than its weight.
- D.zero.
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A floating body is in equilibrium, so the upward buoyant force exactly balances its weight. By Archimedes' principle, a body in a liquid is pushed up by a force equal to the weight of the liquid it displaces.
Read the full explanation →Which of the following are the different parts of a human brain ?
- A.Forefront brain, Standard brain and Hind brain
- B.Fore brain, Median brain and Rear brain
- C.Fore brain, Mid brain and Hind brain
- D.Precursor brain, Mean brain and Hind brain
Show answer
These are the three main divisions of the human brain. The fore brain is the largest part.
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