All Free Biology MCQs with Answers

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

Explanation: Option A: Lysosomes are another type of cell organelle that contains enzymes that can break down waste products and foreign invaders. However, lysosomes do not produce hydrogen peroxide.Option B: Mitochondria are the powerhouses of the cell, responsible for producing ATP, the cell's energy currency. They do not produce hydrogen peroxide.Option C: Peroxisomes are small, membrane-bound organelles that are found in most eukaryotic cells. They contain enzymes that carry out oxidation reactions, which can produce hydrogen peroxide as a byproduct. Hydrogen peroxide is a reactive molecule that can damage cells. Peroxisomes are small organelles that contain enzymes involved in various metabolic processes, including the breakdown of fatty acids and the detoxification of harmful substances. One of the enzymes present in peroxisomes is called catalase, which facilitates the breakdown of hydrogen peroxide into water and oxygen. This prevents the accumulation of hydrogen peroxide, which can be damaging to cells if it builds up in high concentrations. Option D: Glyoxysomes are a type of peroxisome that is found in plant cells. They are involved in the breakdown of fatty acids to produce carbohydrates. They do not produce hydrogen peroxide. describes organelles that contain hydrolytic enzymes that break down endocytosed foreign particles or even intracellular fragments.

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

Explanation: The Golgi complex is crucial for cells involved in secretion, such as stomach, liver, and pancreatic cells, where it helps in forming secretory granules for proteins, enzymes, and other substances. Muscle cells, however, are specialized for contraction and movement rather than secretion. Thus, they do not rely on the Golgi complex for forming secretory granules, making option D (Muscle) the correct answer. In contrast, the other cell types depend on the Golgi complex for their secretory functions.

• A. A and B
• B. B and C
• C. A and C
• D. A and D

Explanation: ATP synthesis is seen in both chloroplasts and mitochondria. The inner membrane of mitochondria is folded to increase surface area.Both mitochondria and chloroplasts have small, circular DNA, all kinds of RNA and 70S ribosomes.Oxidative phosphorylation takes place only in mitochondria.

• A. Endoplasmic reticulum
• B. Chloroplast
• C. Golgi apparatus
• D. Mitochondria

Explanation: Mitochondria and chloroplasts are both considered semi-autonomous organelles, as they have their own circular DNA and 70S ribosomes. Mitochondria are present in both plant and animal cells, but chloroplasts are present in autotrophic eukaryotes only.

• A. Flagella
• B. Cell wall
• C. Central vacuole
• D. Chloroplast

Explanation: Plants cells are generally equipped with a cell wall, central large vacuole and chloroplast while it generally lacks flagella.

• A. Globular proteins
• B. Cholesterol
• C. Traces of carbohydrates
• D. Phospholipid

Explanation: Cholesterol is a type of lipid that is a major component of eukaryotic cell membranes. It helps maintain membrane fluidity and stability by interacting with phospholipids. Cholesterol is present in large amounts (around 20-40 mol%) in eukaryotic plasma membranes, but it is universally absent in the membranes of prokaryotes. Therefore, the correct option is cholesterol as it is not present in all types of cell membranes.

• A. Provides mechanical support
• B. Maintain cellular homeostasis
• C. Regulate passage of molecules
• D. Prevent from osmotic lysis

Explanation: The animal cell membrane provides mechanical support., maintain homeostasis and regulate passage of molecules across the membrane. It does not prevent the animal cell from osmotic lysis, it is the function of the cell wall, which is absent in animal cells.

• A. Head of phospholipid molecules
• B. Tail of phospholipid molecules
• C. Cholesterol molecules
• D. Glycoprotein

Explanation: The correct answer is Glycoprotein. Glycoproteins, which are proteins with carbohydrate chains attached, are embedded in the plasma membrane and play a key role as receptor sites. They can recognize and bind to various signaling molecules, including hormones, which initiates cellular responses.

• A. Nucleus
• B. Cell membrane
• C. Chromosome
• D. Mitochondria

Explanation: The correct answer is the cell membrane, which is crucial for cellular life as it forms the outer boundary of the cell, providing structural support and regulating the movement of substances in and out of the cell. It ensures the cell maintains homeostasis, protecting its internal environment and allowing it to interact with its surroundings.

• A. Glycosylation of proteins
• B. Synthesis of lipids
• C. Synthesis of proteins
• D. Synthesis of ribosomes

Explanation: Secretory proteins are synthesized on RER, then transferred to Golgi apparatus through SER for final processing and packaging and finally released as secretory vesicles via cell membrane.