All Free Biology MCQs with Answers

• A. None of these
• B. Both primary and secondary cell wall
• C. Primary cell wall
• D. Secondary cell wall

Explanation: The primary cell wall facilitates the transport of water, nutrients, and allows upright growth in plants. The primary cell wall is a relatively thin and flexible layer that surrounds plant cells. It is composed of cellulose, hemicellulose, and pectin, which provide structural support while allowing water and nutrients to pass through.The secondary cell wall, on the other hand, is a rigid and thick layer that forms inside the primary cell wall in certain plant cells, such as xylem cells. While the secondary cell wall provides additional strength and support to these specialized cells, it is not directly involved in the transport of water, nutrients, or upright growth in plants.Therefore, the correct answer is the primary cell wall.

• A. Actin
• B. Myosin
• C. Tubulin
• D. Keratin

Explanation: Microtubules are made up of tubulin dimers (α and β). Tubulin is a type of polypeptide.

• A. 3
• B. 2
• C. 5
• D. 6

Explanation: The ribosome is a cell organelle that is present in large numbers in all living cells and serves as the site of protein synthesis via translation of mRNA. Ribosomes occur both as free particles in prokaryotic and eukaryotic cells, and as particles attached to the membranes of the endoplasmic reticulum in eukaryotic cells.Each ribosome has two subunits.

• A. 5 mM
• B. 0.02 mM
• C. 1 mM
• D. 0.5 mM

Explanation: 1 mM is the threshold concentration at which the ribosomal units can either or detach. Increasing the concentration to 1 mM or higher would allow for the small and large subunits to bind to each other.

• A. Chloroplast
• B. Mitochondria
• C. Endoplasmic reticulum
• D. Nucleus

Explanation: The nucleus is a double membrane-bound organelle. The membrane of the nucleus is called the nuclear envelope and is composed of an inner membrane and an outer membrane. At certain points, these two are continuous with each other, resulting in the formation of pores called nuclear pores. The nuclear pores are selective and allow the transport of materials between the nucleus and the cytoplasm.

• A. Chromoplast
• B. Leucoplast
• C. None of these
• D. Chloroplast

Explanation: Leucoplasts are colorless plastids that store starch or lipids. Chloroplasts contain a green-colored pigment called chlorophyll and are the site for photosynthesis. Chromoplasts contain colored pigments and are found in fruits and petals of flowers.

• A. Smooth endoplasmic reticulum
• B. Rough endoplasmic reticulum
• C. Rough and smooth endoplasmic reticulum both
• D. Mitochondria

Explanation: The rough endoplasmic reticulum is connected to the nuclear membrane whereas the smooth endoplasmic reticulum is connected to the cell membrane.

• A. Exocytosis
• B. Pyrolysis
• C. Phagocytosis
• D. Endocytosis

Explanation: Exocytosis is a process by which the contents of a cell vacuole are released to the exterior through the fusion of the vacuole membrane with the cell membrane. This fusion increases the surface area of the membrane. During phagocytosis or endocytosis, a portion of the cell membrane is used up in making the vesicle.

• A. None of these
• B. Chloroplast
• C. Vacuoles
• D. Mitochondria

Explanation: Chloroplasts and mitochondria have their own genetic material and can synthesize their own proteins so they are self-replicating organelles but vacuoles don't have such abilities.

• A. Mitochondria
• B. Nucleolus
• C. Ribosome
• D. Golgi apparatus

Explanation: The nucleolus is a dark membrane-less structure present inside the nucleus which is responsible for the production and assembly of ribosomes. Vacuoles, mitochondria, and Golgi apparatus are all present in the cytoplasm of cells.