Cell Biology and Structure

Chemoheterotroph is the most common nutritional mode in prokaryotes. They use organic molecules as an energy source (for example, sugar) and use organic molecules as a carbon source (for example, proteins, sugars, fats, nucleic acids, etc.).

Correct answer. Thiomargarita namibiensis and Epulopiscium fishelsoni are up to half a millimetre long and are visible to the unaided eye; Epulopiscium fishelsoni reaches 0.7 mm.

When starved of amino acids, Myxobacteria detect surrounding cells in a process known as quorum sensing. They migrate towards each other and aggregate to form fruiting bodies up to 500 micrometres long and contain approximately 1,00,000 bacterial cells. About one in 10 cells migrate to the top of these fruiting bodies and differentiate into a specialised dormant state called myxospores, which are more resistant to drying and other adverse environmental conditions than ordinary cells.

It is an obligate aerobe.

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.

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.

Auramine O can be used to stain acid-fast bacteria (e.g. Mycobacterium), where it binds to the mycolic acid in its cell wall) in a way similar to Ziehl-Neelsen stain. It can also be used as a fluorescent version of Schiff reagent.

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.

Ribosomes are non-membranous organelles composed of ribosomal RNA and proteins. They are the site of protein synthesis and are not enclosed by any membrane, unlike organelles such as sphaerosomes and glyoxysomes which are membrane-bound.

A nucleoid is the region within prokaryotic cells where DNA is located, lacking a surrounding nuclear membrane. It is not a true nucleus but contains the genetic material. Capsid is the protein coat of viruses. Chromatin is the complex of DNA and proteins in eukaryotic nuclei. Nucleoplasm is the gel-like material within the nucleus.

Protoplasm is called the physical basis of life because it performs all vital activities - metabolism, growth, reproduction, response to stimuli. It includes cytoplasm and nucleoplasm. Cytoplasm is just the portion outside the nucleus. Kinoplasm and ectoplasm are specialized regions of cytoplasm involved in movement and structural functions respectively, not the entire living substance.