The Fundamental Unit of Life Test - 20

Viruses can be made into crystals i.e., they can be crystallised. Crystallisation is the process of transformation of viral components into organised solid particles. Crystallisation is used to study structural characteristics of biomolecules through X-rays, laser beams etc.

If concentration of water molecules in surrounding medium is higher than water molecules concentration in the cell, it will result in movement of water into the cell. This will result in cell getting swelled up.

Chromosomes are thin, thread like structures present in the nucleus and visible during all division. Each chromosome is made up of DNA (deoxyribonucleic acid) and proteins. DNA stores all the information necessary for cell to function, to grow and to reproduce.

Ribosomes are responsible for protein synthesis. Enzymes are composed of protein. Hence, options (iii) and (iv) are incorrect.

Endoplasmic reticulum (ER) is a membranous network enclosing a fluid-filled lumen which almost fills up the intracelluar cavity. ER serves as channel for the transport of materials (especially proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus. ER also functions as a cytoplasmic framework providing the site for some biochemical activities of the cell.
Mitochondrion is the site of energy generation.

Movement of water molecules from a region of higher concentration to a region of lower concentration through a semipermeable membrane.

When a cell is placed in a hypertonic solution i.e., a solution in which concentration of water molecules outside the cell is lesser than the concentration of water molecules inside the cell, the cell will loss water by the process of osmosis (exosmosis). Although water crosses the cell membrane in both directions, but more water leaves the cell than enters resulting in the shrinkage of cell cytoplasm. This phenomenon of shrinkage of cell cytoplasm when put in a hypertonic solution is called plasmolysis.

Lysosomes and vacuoles are cell organelles that are enclosed by a single membrane.
Lysosomes contain hydrolytic enzymes, for digestion of non-functional cell organelles and pathogens. It is also called the 'suicide bag' of the cell.
Vacuoles: They are conspicuous in plant cell than animal cell. In plant cell they occupy about 70% - 80% of the cell volume and are centrally placed. The single membrane covering the vacuole of the plant cell is called tonoplast. It contains cell sap.

• Golgi apparatus gives out small vesicles from their terminals. These small vesicles are lysosomes. Hence, Golgi apparatus is involved in the formation of lysosomes. 
• Nucleus, mitochondria, and plastid have DNA. Hence, they are able to make their own structural proteins using transcription and translation process. 
• Mitochondria produces and stores energy in the form of ATP thus, it is called as the powerhouse of the cell as it provides energy currency to the cell. 
• Protoplasm contains the nucleus, cytoplasm and cell membrane whereas cytoplasm does not contain a nucleus. Cytoplasm is a part of protoplasm.

RER has ribosomes on the surface and ribosomes are responsible for protein synthesis and thus for enzymes synthesis as well. Hence, option ‘a’ is correct and option ‘b’ is incorrect. ER has no role to play in destruction of plasma membrane. The undefined nuclear region in prokaryotes is called nucleoid.

Smooth endoplasmic reticulum (SER) plays a crucial role in detoxifying many poisons and drugs in a cell by metabolising the toxic substances such as aspirin, insecticides, petroleum products, pollutants etc.

Endoplasmic reticulum synthesise both lipids and proteins. However, RER mainly synthesise proteins and SER mainly synthesise lipids.

The undefined nuclear region of prokaryotes are also known as nucleoid.

Golgi apparatus is involved in repackaging of many biomolecules.

Vacuoles are single membrane bound, fluid filled sacs present in the cytoplasm. Vacuoles are meant for the storage of food, water and other substances. In plant cells, vacuoles are full of cell sap and provide turgidity and rigidity to the cell. In single- celled organisms like Amoeba, the food vacuole contains the food items that the Amoeba has consumed. In some unicellular organisms, specialised vacuoles also play important roles in expelling excess water and some wastes from the cell (osmoregulation).