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Practice each question, then open the answer or worked solution.
Discuss briefly the role of nucleolus in the cells actively involved in protein
synthesis.
It contains small spherical bodies which are known as the nucleolus. It is not a membrane-bound structure. It is a site for active ribosomal RNA synthesis. It also receives and stores ribosomal proteins formed in the cytoplasm.
Explain the association of carbohydrate to the plasma membrane and its significance.
By glycosylation carbohydrates forms glycoproteins and glycolipids. They are biochemical involved in cell recognition and adhesion.
Comment on the cartwheel structure of centriole.
The centromere is an organelle usually containing two cylindrical structures called centrioles. The centrioles present in a centrosome lie perpendicular to each other in which each as an organization like the cartwheel. Each of the peripheral fibrils is a triplet. The adjacent triplets are also linked.
Briefly describe the cell theory.
Cell theory was given by Schleiden and Schwann, which stated –
a) Bodies of all the plants and animals are made up of cells.
b) The cells are structural and functional units of life.
The modern cell theory by Rudolf Virchow is all living organisms are composed of cells and products of cells and all arise from pre-existing cells.
Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
| Rough Endoplasmic Reticulum(RER) | Smooth Endoplasmic Reticulum(SER) |
| They have ribosomes attached to it
They help in the synthesis of proteins and enzymes It is mainly formed of cisternae and few tubules |
They have no ribosomes attached
Helps in synthesis of glycogen and lipids It is formed mainly vesicles and tubules. |
Give the biochemical composition of the plasma membrane. How are lipid molecules arranged in the membrane?
The plasma membrane is composed of proteins, lipids, water and carbohydrates. The ratio of lipids and proteins varies considerably in different types of cells. The major lipids are phospholipids that are arranged in a bilayer. They also contain cholesterol.
What are plasmids? Describe their role in bacteria.
Plasmids are smaller DNA present in the bacteria outside the genomic DNA. The plasmid DNA grants certain phenotypic characteristics like resistance to antibiotics to such bacteria. DNA is used to monitor bacterial transformation with foreign DNA.
What are histones? What are their functions?
Histones are highly alkaline proteins that are found in nuclei of eukaryotes. They package and order DNA into structural units. They also function as gene regulation.