Cell Structure MCQs for NEET — Zoology Questions with Answers

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.

Mitochondria are known as the powerhouses of the cell because they generate ATP (adenosine triphosphate), which is the primary energy currency of the cell. Through the process of oxidative phosphorylation, mitochondria convert energy stored in nutrients into ATP, which is then used by the cell to perform various functions.

Ribosome synthesis takes place in the nucleolus, which is a prominent sub-nuclear structure that is not bound by a membrane and resides within the cell nucleus. The nucleolus is responsible for producing and assembling ribosome components.

The mitochondria are often referred to as the 'powerhouse of the cell' because they generate most of the cell's supply of adenosine triphosphate (ATP), which is used as a source of chemical energy.