The Fundamental Unit of Life Test - 25

• Bacterial cells are primitive cells hence, called prokaryotic cells. 
• They do not possess membrane-bound organelles like mitochondria, lysosomes, etc. They also do not have a well-defined membrane-bound nucleus. 
• Onion peel cell is an eukaryotic cell with a well-defined membrane-bound nucleus, other membrane-bound organelles like mitochondria, vacuole, etc. 

The nucleus contains a viscous liquid called nucleoplasm. It contains chromosomes and nuclei. It is surrounded by a nuclear membrane and it helps in the exchange of material between nucleus and cytoplasm. So, the correct answer is option B.

• The nucleus regulates all cellular activities by controlling the enzymes required for cellular processes. 
• Enzymes are proteins and protein synthesis is controlled by the nucleus.
• The mRNA required for protein synthesis is made from DNA, which is situated in the nucleus. 

2% of silver nitrate is used to stain the Golgi complex. Silver gets impregnated inside the Golgi complex and distinguishes morphology.
The silver nitrate stain enables us to visualize the Golgi body by turning it black against a pale yellow background. 

The given diagram is plant cell because cell is surrounded by the cell wall and have single large vacuole at the center of the cell whereas nucleus (P) is present at the side of the vacuole. The nucleus is called as the regulatory body of the cell or brain of the cell because it contains the genetic material and controls the cellular activities by controlling the protein synthesis. Whereas Q represents the vacuole, R represents the mitochondria, S represents the cytoplasm. 

• RNA is found everywhere- nucleus, nucleolus, mitochondria, chloroplasts, ribosomes, cytoplasm, etc. RNAs are 3 different types- mRNA, tRNA and rRNA. mRNA and tRNA are found in the cytoplasm and rRNA in the nucleus.
• The ribosomes can be free within the cytoplasm of a cell or attached to the endoplasmic reticulum but do not present inside the nucleus. RNA and ribosomes act together resulting in the synthesis of proteins.

 Hence, the correct answer is option C.

Water always moves from a region of higher water potential to a region of lower concentration of water molecules. In case, the concentration of solutes in the medium is less than the concentration of solutes in the cell sap, the medium is said to be hypotonic in comparison to the cell sap. Such a medium will have more number of water molecules relative to the number of water molecules inside the cell. Thus, the concentration of water molecules in the medium will be higher than the concentration of water molecules of the cell sap, and water will move into the cell along the concentration gradient.

Humans are complex organisms made up of more than trillions of cells, each with their own structure and function. Thus, Option D is correct.

Eukaryotic cells have a membrane-bounded nucleus. Nuclear pore protein complexes act as a channel that helps in the transport of molecules from nucleoplasm to outside the nucleus. It is also involved in chromatin organization, gene expression regulation and DNA repair, etc.

Coverslip is fixed on the microscopic slide, where the sample is mounted.
It is mounted in such a way that no air bubbles are trapped.
When air bubbles are trapped, the microscopic view will not look clear and the bubbles will be seen in the view.