Zoology MCQs for NEET — Practice Questions with Answers

Chlorophyll is present in the thylakoid membranes of the chloroplast. Thylakoids are membranous sacs inside the chloroplast where the light-dependent reactions of photosynthesis occur. The presence of chlorophyll in these membranes is crucial for the absorption of light energy.

The false assertion is that 'Thylakoid lumen is not covered by thylakoid membrane.' In reality, the thylakoid lumen is the space inside the thylakoid membrane. The thylakoid membrane encloses the thylakoid lumen and is essential for the light-dependent reactions in photosynthesis.

In plant cells, vacuoles are membrane-bound structures that store various substances and help in excretion. The membrane surrounding the vacuole is called the tonoplast. Vacuoles play a key role in maintaining cell turgor, storage of nutrients, and waste products.

The middle lamella is a pectin layer which cements the cell walls of two adjoining plant cells together. It is primarily composed of calcium pectate.

The stroma of chloroplasts in higher plants contains enzymes necessary for the dark reactions (Calvin cycle) of photosynthesis, which are responsible for the synthesis of glucose from carbon dioxide and water.

Prokaryotic ribosomes are 70S in size, which consist of two subunits: a larger 50S subunit and a smaller 30S subunit.

The plasma membrane is primarily composed of a phospholipid bilayer with embedded proteins. This structure allows it to be selectively permeable, controlling the movement of substances in and out of the cell.

The cell theory, which states that the cell is the structural and functional unit of organisms, was proposed by Matthias Schleiden and Theodor Schwann in the 19th century. Their work laid the foundation for modern cell biology.

The fluid-mosaic model describes the structure of the plasma membrane. According to this model, the membrane is composed of a lipid bilayer with proteins embedded within it. The lipids provide fluidity and elasticity, while the proteins act as channels, carriers, or receptors. This combination of lipids and proteins allows the membrane to be both flexible and selectively permeable.

The nucleolus is a spherical structure found within the nucleus of eukaryotic cells. It is primarily involved in the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomes. The nucleolus does not contain chromatin but is associated with specific chromosomal regions called nucleolar organizing regions. Its main function is to produce and assemble the components needed for protein synthesis.