All Free Biology MCQs with Answers

• A. Cell wall
• B. Cell wall and vacuole
• C. Nucleolus and vacuole
• D. Cell membrane

Explanation: Plant cell walls are made largely of cellulose which forms strong, highly rigid, almost indigestible coverings that protect the cell and give it shape.

• A. Nerve cell
• B. Cardiac cell
• C. Red blood cell
• D. None of above

Explanation: Red blood cells lack mitochondria and are therefore unable to carry out oxidative phosphorylation.

• A. Plasma membrane
• B. Endomembrane
• C. Plasmalemma
• D. Tonoplast

Explanation: Vacuole is single membrane bounded organelle. This single membrane around vacuole is known as tonoplast.

• A. Golgi Apparatus
• B. Lysosomes
• C. RER
• D. SER

Explanation: The Rough Endoplasmic Reticulum (RER) is an organelle that has a continuous connection with the nuclear membrane in eukaryotic cells. The RER is a network of membrane-bound flattened sacs, studded with ribosomes on its cytoplasmic surface. These ribosomes are responsible for protein synthesis.

• A. Galactose
• B. Phospholipids
• C. Glucose
• D. Carbohydrate

Explanation: Phospholipids: This option is the correct answer. The fluid mosaic model of the plasma membrane states that protein molecules float in a fluid phospholipid layer. Phospholipids are the main components of the plasma membrane, forming a bilayer structure. The hydrophilic (water-loving) phosphate heads of the phospholipids face outward, interacting with the watery environment, while the hydrophobic (water-fearing) fatty acid tails face inward, creating a barrier.

• A. Gas vacuoles - Green bacteria
• B. Large central vacuoles - Animal cells
• C. Protists - Eukaryotes
• D. Methanogens - Prokaryotes

Explanation: Large central vacuoles are a feature of plant cells, used for storage and maintaining cell rigidity. This is a mismatch as animal cells have small, scattered vacuoles.

• A. Ribosome
• B. Chloroplast
• C. Mitochondrion
• D. Lysosome

Explanation: The mitochondrion is called the "powerhouse of the cell" because it breaks down carbohydrates through cellular respiration and produces ATP. Ribosomes make proteins, chloroplasts perform photosynthesis, and lysosomes carry out digestion, but ATP formation mainly occurs in mitochondria.

• A. Lysosome
• B. Microbodies
• C. Ribosome
• D. Mesosome

Explanation: Lysosomes contain powerful hydrolytic enzymes used for intracellular digestion. They break down worn-out organelles, foreign particles, and macromolecules.

• A. Centrioles, spindle fibres and chromatin
• B. Centrosome, nucleosome and centrioles
• C. Cilia, flagella and peroxisomes
• D. Spindle fibres, centrioles and cilia

Explanation: Spindle fibres, centrioles, and cilia all contain microtubules. Microtubules are crucial for their structure and function.

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

Explanation: Lysosomes are enclosed by a single membrane and contain hydrolytic enzymes that help in digestion processes within the cell.