Why does the Rough Endoplasmic Reticulum look 'rough' under a microscope ?
- A.Due to the presence of ribosomes on its surface
- B.Due to the absence of ribosomes on its surface
- C.Due to the presence of lysosomes on its surface
- D.Due to the presence of mitochondria on its surface
Correct answer
Explanation
The correct answer is A, Due to the presence of ribosomes on its surface. The endoplasmic reticulum (ER) is a network of membrane tubes and sacs inside the cell. Part of it is studded on the outside with tiny granules called ribosomes, which give it a dotted, rough look under an electron microscope; this part is the rough ER. Ribosomes are the sites of protein synthesis, so the rough ER makes proteins and passes them on to the Golgi apparatus for packing and dispatch. It is plentiful in cells that secrete proteins, such as those of the pancreas. Option B is wrong because the absence of ribosomes is what makes the smooth ER smooth; the smooth ER makes lipids and steroids and helps detoxify drugs in liver cells. Option C is wrong because lysosomes are separate sacs of digestive enzymes, not attached to the ER. Option D is wrong because mitochondria are free organelles that make energy (ATP) and do not sit on the ER surface. Exam tip: rough ER, ribosomes, proteins; smooth ER, no ribosomes, lipids.
Practice Questions
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- A.1,2 and 3
- B.2 and 4
- C.1 and 3 only
- D.1 only
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- A.Joule
- B.Watt-hr
- C.Newton-metre
- D.kg-metre/sec²
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- A.Magnesium
- B.Zinc
- C.Aluminium
- D.Lead
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Read the full explanation →In an electric circuit, a wire of resistance 10 Ω is used. If this wire is stretched to a length double of its original value, the current in the circuit would become :
- A.half of its original value.
- B.double of its original value.
- C.one-fourth of its original value.
- D.four times of its original value.
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Read the full explanation →Which one of the following scientists mentioned that an electron in an atom could revolve in certain stable orbits without the emission of radiant energy ?
- A.Ernest Rutherford
- B.J.J. Thomson
- C.Niels Bohr
- D.Albert Einstein
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