All Free Biology MCQs with Answers

1801. Which of the following cell organelles does not contain DNA?

• A. Nucleus
• B. Lysosomes
• C. Chloroplast
• D. None of these

Explanation: Lysosomes contain hydrolytic digestive enzymes but do not contain their own DNA, whereas the nucleus and chloroplast contain DNA. Students may choose chloroplast because it is an organelle in plant cells, but chloroplasts retain their own genetic material as semi-autonomous organelles.

1802. DNA of mitochondria is__________?

• A. circular
• B. spring
• C. straight
• D. All of these

Explanation: Mitochondrial DNA is usually a circular, double-stranded DNA molecule, reflecting the bacterial ancestry proposed by the endosymbiotic theory. Students may choose straight DNA because nuclear chromosomes are generally linear, but mitochondrial DNA is distinct from nuclear DNA in this respect.

1803. Which organelles contain its own DNA?

• A. nucleus
• B. mitochondria
• C. chloroplast
• D. All of these

Explanation: The nucleus, mitochondria and chloroplasts contain their own DNA, so all three listed structures have genetic material. Students may choose mitochondria or chloroplasts because they are emphasized as semi-autonomous organelles, but the nucleus also contains the cell's main genome.

1804. They are present in the underground parts of the plants and stored food?

• A. leucoplast
• B. chromoplast
• C. chloroplast
• D. stem

Explanation: Leucoplasts are colourless plastids found commonly in underground plant parts and storage tissues, where they store starch, oils, or proteins. Chromoplasts contain coloured pigments and chloroplasts carry out photosynthesis, so students may select them by confusing different plastid types.

1805. Flagella are composed of________?

• A. micro tubules
• B. micro filaments
• C. intermediate filaments
• D. glycoproteins

Explanation: The core of a eukaryotic flagellum has a 9+2 arrangement of microtubules, which allows it to bend and produce movement. Microfilaments are involved in processes such as cell shape and contraction, so students may select them by confusing another cytoskeletal element with flagellar microtubules.

1806. Xylem and phloem are conducting tissues found in ..........?

• A. animals
• B. plants
• C. micro orgamnisms
• D. all the above

Explanation: Xylem and phloem are vascular conducting tissues found in plants. Xylem transports water and mineral ions mainly upward, while phloem transports sugars and other organic solutes from sources to sinks. Students may choose animals because animals also have transport systems, but animal blood vessels are not xylem or phloem.

1807. Which of the following endoplasmic reticulum has no ribosome on its surface?

• A. smooth
• B. rough
• C. both
• D. all of above

Explanation: Smooth endoplasmic reticulum lacks ribosomes on its cytoplasmic surface, whereas rough endoplasmic reticulum bears ribosomes and is involved in synthesis of secreted and membrane proteins. The absence or presence of ribosomes is the main structural distinction between the two forms. Students may choose rough by reversing the names, but rough ER is defined by its ribosome-studded appearance.

1808. which of the following is called protein synthesizing machine?

• A. mitochondria
• B. nucleus
• C. chromosomes
• D. ribosomes

Explanation: Ribosomes are protein-synthesizing machines because they read the codons of mRNA and join amino acids in the correct sequence to form a polypeptide. Students may choose the nucleus because it contains DNA, but the nucleus provides the genetic instructions rather than directly assembling the protein.

1809. Which of the following manufactures carbohydrates by the process of photosynthesis?

• A. chloroplast
• B. chromoplast
• C. leucoplast
• D. All of these

Explanation: Chloroplasts contain chlorophyll and the enzymes needed to convert light energy into chemical energy during photosynthesis, producing carbohydrates. Chromoplasts mainly contain coloured pigments, while leucoplasts are generally colourless storage plastids, so choosing all of them confuses plastid types.

1810. Vacuoles are fluid filled sacs surrounded by a membrane called__________?

• A. tonoplast
• B. nuclear membrane
• C. cell membrane
• D. cell wall

Explanation: The tonoplast is the selectively permeable membrane surrounding a plant-cell vacuole and controlling movement of substances into and out of its fluid contents. The cell membrane surrounds the entire cell, whereas the nuclear membrane surrounds the nucleus, so neither is the vacuole membrane.