Question

Which of the following is a housekeeping protein?
A. Actin
B. Collagen
C. Fibrin
D. All of the above

Answer 1

All cells in the human body require a huge number of proteins to function properly. These proteins are sometimes called housekeeping proteins, suggesting that their expression is crucial for the maintenance of basic cellular function. Housekeeping proteins are defined in a variety of ways, each with varying degrees of strictness. Any definition of housekeeping genes, however, makes the assumption that they are anticipated to be expressed in every cell type in the organism.

Complete answer:
Option: A – Actin is a protein that serves as a housekeeper. They carry out the activities that are common to all cells. It is a microfilament of the cytoskeleton. Cell motility, structure, and integrity are all affected by it.
Thus, Option A is correct.
Option: B – Collagens are structural proteins which are found in the extracellular matrix of connective tissues and hence they do not serve the function of housekeeping proteins.
Thus, Option B is not correct.
Option C Fibrin is a strong protein material made up of long fibrous chains that is made up of fibrinogen, a soluble protein generated by the liver and present in the plasma. Fibrin is produced when fibrinogen and thrombin combine, which is the recognized mechanism for blood coagulation. It's also found in the extracellular matrix of living things. So, it's not a housekeeping protein.
Thus, Option C is also not correct.
Option: D - All of the above is not correct as actin in the options is a housekeeping protein
Thus, Option D is not correct.

Hence, Option A. Actin is the correct answer.

Note:
Actin is a multifunctional globular protein that forms microfilaments in the cytoskeleton and thin filaments in muscle fibres. It is a housekeeping protein found in virtually all eukaryotic cells, where it may be found in concentrations of over $100{\text{ }}\mu M$. It has a mass of $42{\text{ }}k\,Da$ and a diameter of $4$ to $7$ nm. Beta actins are well known actin proteins which serve as housekeeping proteins.