Cell Structure MCQs for NEET — Zoology Questions with Answers

Assertion (A) and Reason (R) both are true, but reason (R) is not a correct explanation of the assertion (A). Animal cells do possess centrioles, and some algae also have centrioles, but the presence of centrioles in algae does not explain why animal cells have centrioles.

The protoplasmic region surrounding the centriole is called the centrosphere. It is a specialized region that plays a crucial role in cell division and the organization of microtubules in the cell.

The correct pairing of organelles and their functions is as follows:

1. Mitochondria (P) - ATP formation and storage (4)
2. Chloroplast (Q) - Photosynthesis (3)
3. Lysosome (R) - Suicide bag (1)
4. SER (S) - Synthesis of steroids (2). This is because mitochondria are known as the powerhouse of the cell, chloroplasts carry out photosynthesis, lysosomes contain enzymes that digest cellular waste, and SER is involved in lipid and steroid synthesis.

The correct matching is:

1. Robert Hook (P) - Cell (3): He discovered the cell.
2. Robert Brown (Q) - Nucleus (4): He discovered the cell nucleus.
3. Schleiden (R) - Cell theory (1): He co-founded the cell theory along with Schwann.
4. Camillo Golgi (S) - Golgi apparatus (2): He discovered the Golgi apparatus.

Chloroplasts have a double-layered membrane structure, lysosomes have a single-layer membrane, and the nucleolus is a non-membrane-bound structure. Hence, P corresponds to 2, Q corresponds to 1, and R corresponds to 3.

Lysosomes, often referred to as 'suicidal bags,' actually have a single-layer membrane structure, not a double-layer. This makes option o1 the false assertion.

The main difference between active and passive transport is that active transport requires energy in the form of ATP to move substances against their concentration gradient, whereas passive transport does not require energy and occurs along the concentration gradient.

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.