MARCH 2020 PAPER 12:

Which cell structures contain RNA? 


1 centrioles 
2 mitochondria 
3 nucleus 
4 ribosomes 


A 1, 2, 3 and 4 
B 1 and 2 only 
C 2, 3 and 4 only 
D 3 and 4 only

ANSWER C

The centrioles do not contain RNA.

Mitochondria has a prokaryotic background thus it contains features similar to those of prokaryotes. Since prokaryotes contain RNA formed by transcription and translation( because prokaryotes also carry out the processes of protein synthesis), mitochondria which are evolved from prokaryotes, also contain RNA.

The nucleus is basically the site of transcription where gene is transcribed to form mRNA. The mRNA is a form of RNA. Therefore, the nucleus contains RNA.


Ribosome is basically a complex structure made up of rRNA and proteins. rRNA is a form of RNA. Thus, ribosome is also the correct option available.



5 It is possible for a bacterium to synthesise a eukaryotic protein. 

This involves introducing a eukaryotic gene into the bacterial DNA. The eukaryotic gene is then translated by the bacterium. 

What explains why a bacterial cell can produce a eukaryotic protein but cannot produce a 
eukaryotic glycoprotein? 


A Bacteria do not have rough endoplasmic reticulum. 
B Bacteria do not have a nuclear envelope. 
C Bacteria do not have mitochondria. 
D Bacteria do not have Golgi bodies

ANSWER D

For option A, it is correct that rough endoplasmic is not present in bacterial cells. Rough endoplasmic reticulum contains ribosomes which are responsible for translation of mRNA. But even if it is absent, ribosomes are still present in the cytoplasm of the bacteria where translation can occur. Rough endoplasmic reticulum is not responsible for attaching a carbohydrate chain to a protein to form a glycoprotein. 

Nuclear envelope does not play a role in the synthesis of either proteins or glycoproteins. It is involved in the entry and exit of substances that are required for within the nucleus or used outside the nuclear envelope. Though this statement is correct it does not account for the correct option here.

It is correct that bacterial cells do not have mitochondria which is involved in synthesizing ATP for active processes(energy requiring processes). But mitochondria are not directly the reason for why glycoproteins can not be made. The role of mitochondria that is the provision of energy is still carried out in bacterial cells. It is membrane associated. So there must be lack of something else that is required for glycoprotein synthesis.


This statement is correct because it is the Golgi body that basically modifies the protein in different ways to produce functional proteins. The Golgi body basically attaches the carbohydrate chain to a protein to form a glycoprotein.

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