Cell Biology and Structure

The microglia act much like white blood cells by attacking and destroying pathogens that invade the brain. These are extremely small cells of the central nervous system that remove cellular waste and provide protection against microorganisms.

Centrosomes are organelles found only in animal cells. They contain centrioles and play a crucial role in cell division by organizing microtubules. Plant cells do not have centrosomes - they use different structures for cell division. Mitochondria and lysosomes are organelles found in both plant and animal cells.

Cancer is a class of diseases in which a group of cells display uncontrolled growth, invasion that intrudes upon and destroys adjacent tissues, and sometimes metastasis, or spreading to other locations in the body via lymph or blood. These three malignant properties of cancers differentiate them from benign tumors, which do not invade or metastasize.

Tracheids are elongated cells with tapered ends, resembling spindles. This shape facilitates water movement between cells through pits in their walls.

The epidermis is typically 1-2 cell layers thick in most plant organs. This outer protective layer covers stems, roots, and leaves.

Chloroplast is a semi-autonomous cell organelle, which contains its own DNA and protein-synthesising machinery.

They are associated with mitochondria and take part in aerobic respiration.

They contain digestive enzymes like hydrolase.

Goblet cells, located throughout the epithelial layer, secrete mucus that helps protect the epithelial layer from digestion.

Macrophages and leukocytes move by pseudopodial movement.

A tumour is an abnormal growth of tissue that serves no physiological purpose, often referred to as a 'neoplasm.' The key distinction from normal tissue growth is that tumours are uncontrolled and unwanted - they don't contribute to bodily function. Tumours can be benign (non-cancerous) or malignant (cancerous), but both represent unwanted cellular proliferation.

A tissue is a group of cells that work together to perform a specific function in an organism. Examples include muscle tissue, nerve tissue, and connective tissue. Tissues combine to form organs, not the other way around.

Golgi body of the spermatid forms the acrosome of the sperm during spermiogenesis.

The vacuolar membrane is specifically called the tonoplast (Option C). It surrounds the vacuole and regulates transport of materials into and out of the vacuole. Plasmalemma (A) is another name for the plasma membrane (cell membrane). Middle lamella (B) is the pectin layer between plant cell walls. Chromoplast (D) is a type of plastid, not a membrane.

Dictyosomes (the plant equivalent of Golgi apparatus stacks) originate from vesicles budded from the endoplasmic reticulum. These vesicles fuse to form the dictyosomes, which then modify and package proteins and lipids.