Cell Biology and Structure

Apoptosis is a precisely regulated, programmed cell death process characterized by cell shrinkage, chromatin condensation, DNA fragmentation, and formation of apoptotic bodies without inflammation. It is fundamentally different from necrosis (A), which is uncontrolled cell death resulting from injury, causing membrane rupture and inflammation. Cell cycle arrest (D) may precede apoptosis but is not its defining feature. Membrane leaky syndrome (C) is not a standard biological term and does not describe apoptosis. Option B correctly identifies apoptosis as programmed cell death.

Yes, it is correct. Some of the white blood cells, which are phagocytic in nature, move through the tissues by amoeboid movements to reach the places of infection.

This is the correct option. Ions have the least percentage (1%) of the total cellular mass in a cell of a living organism.

The capsular polysaccharides are polymerised outside the cell wall.

The shape-determining part of a cell is the cell wall. It is made up of peptidoglycan, which is a polymer of NAG, NAM and DAPA.

Nucleus or nucleus-like structures like nucleoid are required to divide and produce daughter cells. Cells incapable to produce daughter cells lack nucleus

Nucleus was the first organelle to be discovered. It was first noticed by Antonie van Leeuwenhoek.

Assembled ribosomal units are the largest sub-units that can pass through nuclear pores.

Nuclear pores provide aqueous channels through the envelope. These are composed of multiple proteins called nucleoproteins.

During telophase, when the two daughter nuclei are formed, there is no RNA Pol II transcription. So, the protein components like paraspeckles instead form a perinucleolar cap. Thus, they are absent in telophase.

Promyelocytic leukemia bodies are found in nucleoplasm. These are non-membrane-delineated bodies. They are involved in assemblage of nuclear bodies.

Perichromatin fibrils are located next to the transcriptionally active chromatin and is hypothesised to be the site of active pre-mRNA processing.

Catalysome refers to an organelle, found in adipose tissue, that functions in lipid metabolism; may represent a specialized type of mitochondrion.

Centrioles are cylindrical organelles composed of microtubules that organize spindle fibers during cell division. They are present in animal cells and play a crucial role in mitosis and meiosis. Most plant cells lack centrioles, using alternative mechanisms to organize their microtubules. Bacteria and viruses do not have centrioles.

Cell walls are extracellular structures found in plant cells, fungi, and some protists, but are absent in animal cells. Animal cells rely on their cytoskeleton and extracellular matrix for structural support instead. Mitochondria, nucleus, and centrosomes are all present in animal cells.