Free cell biology MCQ exam model for premedical students

Explanation:

(Correct): The cell is the smallest unit capable of carrying out life functions.

• Tissue is a group of cells.

• Organ consists of tissues.

• Organelles are components within cells.

• System is a group of organs.

Explanation:

(Correct): The plasma membrane is a phospholipid bilayer with embedded proteins.

• Cell wall has a rigid structure.

• Cytoplasm is semi-fluid but not mosaic.

• Nuclear membrane is double-layered but not described by this model.

• Mitochondrial membrane has a different composition.

Explanation:

(Correct): Facilitated diffusion uses carrier proteins but no ATP.

• Active transport requires ATP.

• Endocytosis requires energy.

• Exocytosis requires energy.

• Na⁺/K⁺ pump uses ATP.

Explanation:

(Correct): Actin filaments enable cell movement and muscle contraction.

• Microtubules help in spindle formation and transport.

• Intermediate filaments provide tensile strength.

• Centrioles organize microtubules.

• Ribosomal fibers do not exist.

Explanation:

(Correct): Ribosomes translate mRNA into proteins.

• Lipids are synthesized in smooth ER.

• ATP is produced in mitochondria.

• DNA replication occurs in the nucleus.

• Digestion occurs in lysosomes.

Explanation:

(Correct): Gap junctions allow ions and small molecules to pass directly.

• Tight junctions prevent leakage.

• Desmosomes provide mechanical strength.

• Hemidesmosomes anchor cells to basement membrane.

• Adherens junctions provide cell adhesion.

Explanation:

(Correct): DNA synthesis occurs during S (synthesis) phase.

• Cell growth occurs in G₁.

• Preparation for mitosis.

• Nuclear division occurs.

• Cytoplasm division.

Explanation:

(Correct): Lysosomes contain hydrolytic enzymes that can digest the cell.

• Peroxisomes detoxify harmful substances.

• Mitochondria produce energy.

• Golgi modifies proteins.

• Nucleolus produces rRNA.

Explanation:

(Correct): Mitochondria generate ATP through oxidative phosphorylation.

• Ribosomes synthesize proteins.

• Lysosomes digest cellular waste.

• Golgi apparatus modifies and packages proteins.

• Endoplasmic reticulum is involved in protein and lipid synthesis.

Explanation:

(Correct): Prokaryotes lack a true membrane-bound nucleus.

• Ribosomes are present (70S).

• Cell membrane is present.

• Cytoplasm is present.

• Most prokaryotes have a cell wall.