NEET Practice Questions (MCQs) with Answers & Solutions

The centriole is the organelle that directs the formation of the bipolar spindle during cell division. Centrioles are cylindrical structures that help in the organization of microtubules in the spindle apparatus, which is essential for the segregation of chromosomes during mitosis and meiosis.

Red Blood Cells (RBCs) in humans lack a nucleus. During their maturation, RBCs lose their nucleus to provide more space for hemoglobin, which allows them to efficiently transport oxygen throughout the body.

In plants, phloem is responsible for the transport of nutrients, mainly sugars, throughout the plant. Sieve tubes are the main conductive cells in the phloem, and they lack a nucleus at maturity. This helps in the efficient flow of nutrients. Companion cells are closely associated with sieve tubes and help in their functioning, but they do have a nucleus.

The kinetochore is a protein structure on the centromere that serves as the attachment point for spindle fibers during cell division. It is disc-shaped and plays a critical role in the proper segregation of chromosomes. The centromere itself holds the sister chromatids together.

Bacteria often contain small, circular DNA molecules known as plasmids, which are separate from the main bacterial chromosome. Plasmids can replicate independently and often carry genes that confer advantageous traits, such as antibiotic resistance.

The cell wall of fungi is primarily composed of chitin. Chitin is a long-chain polymer of N-acetylglucosamine, a derivative of glucose, and it provides structural strength to the cell wall. Unlike plant cell walls, which are made of cellulose, fungal cell walls do not contain cellulose but instead rely on chitin.

Chloroplasts are not considered a part of the endomembrane system. The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles. Chloroplasts are involved in photosynthesis and are a type of plastid, which is an organelle found only in plant cells and some protists. They have their own DNA and are thought to have originated from endosymbiotic cyanobacteria.

Paramecium is a unicellular organism that possesses cilia. Cilia are hair-like structures that cover the surface of Paramecium and are used for movement and feeding. They beat in coordinated waves, allowing the organism to move through water efficiently.

Chlamydomonas is a genus of green algae consisting of unicellular flagellates. It is a well-known example of a unicellular organism. Spirogyra, Mushroom, and Chiton are multicellular organisms.

Theodor Schwann, a German physiologist, is credited with the discovery that animal cells had a thin layer around them, which he later identified as the cell membrane in 1839. This discovery was a significant contribution to the cell theory.