All Free Biology MCQs with Answers

• A. Mitochondria
• B. Dictyosome
• C. Lysosome
• D. Peroxisome

Explanation: Mitochondria have their own DNA. They are doublemembraned organelles found in eukaryotic cells responsible for producing energy through cellular respiration.

• A. Plasmodesmata
• B. Plastoquinones
• C. Endoplasmic reticulum
• D. Plasmalemma

Explanation: Plasmodesmata are microscopic channels that connect the cytoplasm of adjacent plant cells. They allow for the direct transport of various substances, such as ions, nutrients, and signaling molecules, between the cells.

• A. Muramic acid
• B. Calcium pectate
• C. Phosphoglycerides
• D. Hemicellulose

Explanation: The middle lamella is primarily composed of calcium pectate, which acts as a cementing agent between plant cells. It is rich in pectin, aiding in cell adhesion.

• A. Callose deposits
• B. Cellulosic microfibrils
• C. Proteinaceous filaments
• D. Calcium carbonate granules

Explanation: The cytoskeleton is a network inside the cell made up of protein filaments such as microtubules, microfilaments, and intermediate filaments. It helps maintain cell shape, provides support, and plays a role in movement of organelles and vesicles.

• A. Peroxisomes
• B. Mitochondria
• C. Proplastids
• D. Glyoxysomes

Explanation: In germinating seeds, fatty acids are degraded exclusively in glyoxysomes. Glyoxysomes are specialized peroxisomes found in plant cells that are involved in the conversion of stored fats (lipids) into carbohydrates during seed germination.

• A. Lacks a membrane and contains air
• B. Is membrane-bound and contains storage proteins and lipids
• C. Is membrane-bound and contains water, nutrients, and waste products
• D. None of these

Explanation: A vacuole in a plant cell is a membrane-bound organelle that primarily stores water. It also contains nutrients, ions, and waste products, playing a crucial role in maintaining cell pressure and storage.

• A. Magnesium
• B. Calcium
• C. Copper
• D. Manganese

Explanation: Ribosomes are composed of two subunits, a small subunit and a large subunit, which remain united with the help of magnesium ions. Magnesium ions play a crucial role in stabilizing the ribosome's structure and facilitating protein synthesis.

• A. Glycolipids
• B. Proline
• C. Phospholipids
• D. Cholesterol

Explanation: Proline is an amino acid, not a component of the cell membrane. Membrane structure is mainly composed of lipids and proteins, while proline is involved in protein synthesis.

• A. Both chloroplasts and mitochondria contain DNA.
• B. The mitochondria are generally smaller than chloroplasts.
• C. Both chloroplasts and mitochondria contain an inner and an outer membrane
• D. Both chloroplasts and mitochondria have an internal compartment - the thylakoid space bounded by the thylakoid membrane

Explanation: This statement is incorrect. Only chloroplasts have an internal compartment known as the thylakoid space. Mitochondria have a different internal structure, with the inner membrane forming cristae, but no thylakoid space is present.

• A. Movement of chromosomes towards poles
• B. Cytoplasmic cleavage
• C. Crossing over
• D. Transcription

Explanation: The centromere is crucial during cell division as it is the region where spindle fibers attach to chromosomes, facilitating their movement toward opposite poles during mitosis and meiosis. This ensures that each daughter cell receives the correct number of chromosomes.