All Free Biology MCQs with Answers

• A. 22
• B. 23
• C. 21
• D. 24

Explanation: The egg and sperm cells, the reproductive cells or gametes, are haploid, meaning they contain only one set of chromosomes. In humans, the haploid number of chromosomes is 23.During meiosis, the process of cell division that produces gametes, the parent cell undergoes two rounds of cell division to produce four daughter cells, each with half the number of chromosomes as the parent cell. This ensures that when the egg and sperm fuse during fertilization, the resulting zygote will have the usual diploid number of chromosomes, which is 46 in humans.

• A. Microtubules
• B. Microfilaments
• C. A and B both
• D. None of these

Explanation: The cell cycle is the process by which a cell grows, duplicates its genetic material, and divides into two daughter cells. It consists of four main stages: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis). During G1, the cell prepares for DNA replication. In the S phase, DNA synthesis occurs, resulting in two identical copies of the cell's DNA. G2 is a preparation phase before cell division. Finally, during the M phase, the cell divides into two daughter cells through either mitosis (for somatic cells) or meiosis (for reproductive cells). Microtubules are dynamic structures that are assembled and disassembled during the cell cycle. They are involved in a variety of cellular processes including chromosome segregation during mitosis and meiosis, intracellular transport of organelles and vesicles, and maintenance of cell shape and polarity. The assembly and disassembly of microtubules are tightly regulated by a variety of cellular factors and play critical roles in maintaining cellular homeostasis. Microfilaments and intermediate filaments are also part of the cytoskeleton, but they do not undergo dynamic assembly and disassembly during the cell cycle.

• A. Cristae
• B. Microtubules
• C. Glyoxysome
• D. Intermediate filaments

Explanation: Intermediate filaments form an elaborate network in the cytoplasm of most cells, extending from a ring surrounding the nucleus to the plasma membrane which helps in maintenance of cell shape.

• A. Stomach
• B. Liver
• C. Pancreatic
• D. Muscle

Explanation: Golgi complex takes part in the formation of secretory vesicles and helps in the transportation of material within or outside the cells. The "β cells" in the pancreatic islets are involved in the storage of insulin secretory granules and instant secretion of insulin.

• A. Chloroplast
• B. Vacuole
• C. Cell membrane
• D. Endoplasmic Reticulum

Explanation: A cell membrane is described as a fluid mosaic model. The fluid mosaic model describes the structure of the cell membrane as a mosaic of components including phospholipids, cholesterol, proteins, and carbohydrates that gives the membrane a fluid character. Cell membrane, also called the plasma membrane, thin membrane that surrounds every living cell, delimiting the cell from the environment around it. Its structure is described by the fluid mosaic model.

• A. Starch
• B. Protein
• C. Lipid soluble molecules
• D. Ions

Explanation: Lipid soluble molecules can cross plasma more easily than starch, protein, and ions. The plasma membrane is a phospholipid bilayer, which is made up of two layers of fatty acids. Lipid soluble molecules, such as oxygen, carbon dioxide, and fat-soluble vitamins, can dissolve in the fatty acids of the plasma membrane and cross the membrane easily.

• A. They have a nitrogenous base in the head region
• B. They have fatty acids in the tail region
• C. They are amphipathic in nature
• D. They have a phosphate group in the head region

Explanation: In summary, the major reason why phospholipids are a crucial part of the lipid bilayer in plasma membranes is their amphipathic nature (option c). The hydrophilic head with the phosphate group interacts with water, while the hydrophobic tails with fatty acids cluster together away from water, forming a stable and functional barrier that defines the plasma membrane's structure and function. Phospholipids are amphipathic molecules. This means that they have a hydrophilic, polar phosphate head and two hydrophobic fatty acid tails. These components of the phospholipids cause them to orientate themselves.

• A. Flagella
• B. Cillia
• C. Pilli
• D. All of these options are correct

Explanation: The tail of the sperm contains the flagellum that confers motility upon the sperm. Thus, human sperm locomotes with the help of flagella that get energy from mitochondria.

• A. Lysozymes
• B. Lysosomes
• C. Mitochondria
• D. Nucleus

Explanation: Macrophages are phagocytes and need to carry out intracellular digestion, which is the function of lysosomes.

• A. 1:1
• B. 2:1
• C. 1:2
• D. 1:3

Explanation: Eukaryotic ribosomes are composed of almost equal amounts of RNA (ribonucleic acid) and protein; hence they are ribonucleoprotein particles. Hence, A is the correct option.