All Free Biology MCQs with Answers

• A. Solution
• B. Gelatin material
• C. Cytoskeleton
• D. Cytosol

Explanation: The correct answer is Cytosol. The cytosol is the aqueous component of the cytoplasm, containing dissolved ions, small molecules, and proteins, where cellular processes occur. The other options are incorrect: a 'Solution' is a general term for a mixture of solutes and solvents, 'Gelatin material' is a protein substance unrelated to cell structure, and the 'Cytoskeleton' is a network of fibers providing structural support, not a fluid component.

• A. 60-80%
• B. 20-40%
• C. 40-80%
• D. 20-60%

Explanation: The plasma membrane is the outermost covering of an animal cell. Cell membrane is composed of lipids and proteins;60-80% are proteins, while 20-40% are lipids.

• A. Mitochondria
• B. Lysosomes
• C. Endoplasmic reticulum
• D. Golgi Apparatus

Explanation: The endoplasmic reticulum is a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions including the synthesis, folding, modification, and transport of lipids and proteins.

• A. Monosome
• B. Polysomes
• C. Polypeptide
• D. Lysosome

Explanation: Polysome is defined as the cluster of ribosomes held together by a strand of mRNA that each of them is translating.•Polysomes/Polyribosomes can be found in three forms: free, cytoskeletal-bound, and membrane-bound.

• A. Endoplasmic reticulum
• B. Ribosomes
• C. Nucleus
• D. Plastids

Explanation: Ribosomes are made of proteins and ribonucleic acid. Ribosomes consist of two major components: the small and large ribosomal subunits. The tinier subunit is the place the mRNA binds and decodes, whereas the bigger subunit is the place the amino acids are included.

• A. Plastids
• B. Chromoplasts
• C. Mitochondria
• D. Leucoplasts

Explanation: Mitochondria are membrane-bounded organelles that generate the energy needed to power cells' biochemical reactions which are stored in a small molecule called ATP. They are present in both plants and animals.

• A. Engulfing
• B. Pinocytosis
• C. Phagocytosis
• D. None of the given options

Explanation: Phagocytes are cells that have the ability to ingest, and sometimes digest, foreign particles, such as bacteria, carbon, dust, or dye. They engulf foreign bodies by extending their cytoplasm into pseudopods (cytoplasmic extensions like feet), surrounding the foreign particle and forming a vacuole. Pinocytosis is a process by which liquid droplets are ingested by living cells. Phagocytosis is hence called cell eating and pinocytosis is called cell drinking.

• A. Nucleus
• B. Cytosol
• C. Nucleolus
• D. Endoplasmic Reticulum

Explanation: Molecules of rRNA are synthesized in a special region of the cell nucleus called the nucleolus, which appears as a dense area within the nucleus and contains the genes that encode rRNA.

• A. Floating in the cytosol
• B. Localized in the nucleus
• C. Bound to rough endoplasmic reticulum
• D. Both floating in the cytosol and bound to rough endoplasmic reticulum

Explanation: Ribosomes are essential organelles for protein synthesis and exist in two primary forms within the cell. Free ribosomes float in the cytosol and are responsible for synthesizing proteins that will function within the cytosol. In contrast, ribosomes bound to the rough endoplasmic reticulum (RER) typically synthesize proteins destined for secretion or incorporation into cellular membranes. Therefore, the correct answer is that ribosomes are present both floating in the cytosol and bound to the rough endoplasmic reticulum.Option A is incorrect because while ribosomes do float in the cytosol, this answer does not account for the ribosomes on the RER. Option B is incorrect because ribosomes are not active in protein synthesis within the nucleus. Option C is incorrect because while ribosomes are bound to the RER, this answer does not account for those that float freely in the cytosol.

• A. Primary cell wall
• B. Secondary cell wall
• C. Middle lamella
• D. All contain cellulose

Explanation: The correct answer is the Middle lamella because it is made up mainly of pectin and does not include cellulose, which is a significant component of both the primary and secondary cell walls. Options like Primary cell wall and Secondary cell wall are incorrect because they both contain cellulose, which provides structural integrity to plant cells. The option All contain cellulose is also incorrect, as it implies that all mentioned structures contain cellulose, which is not the case for the middle lamella.