All Free Biology MCQs with Answers

• A. Cellulose
• B. Hemicellulose
• C. Middle lamella
• D. All of the above

Explanation: Option C is correct since the middle lamella is the layer of material between adjacent plant cells. It cements the cells together and contains pectins, which are also used as gelling agents in food.

• A. Mesosomes
• B. Lysosomes
• C. Peroxisomes
• D. All of these

Explanation: Lysosomes are membrane-bound organelles that contain digestive enzymes produced by the cell. These enzymes are initially produced in an inactive form to prevent them from digesting the cell itself. When activated, lysosomal enzymes help to break down and recycle cellular waste and foreign material and also play a role in processes such as apoptosis (programmed cell death) and autophagy (self-eating of cellular components).

• A. Structures that degrade parts of their own cells to recycle cellular components
• B. Organelles that help in the removal of old and damaged cellular components
• C. Lysosomes that aid in extracellular digestion
• D. Vesicles that sequester cellular components for degradation by lysosomes

Explanation: The correct answer is that autophagosomes are vesicles that sequester cellular components for degradation by lysosomes. They play a crucial role in cellular homeostasis by capturing and transporting damaged organelles and proteins to lysosomes, where they are broken down and recycled. Option A and B incorrectly describe autophagosomes as lysosomes, while Option C describes a function not directly related to autophagosomes' primary role.

• A. They contain enzymes which help in conversion of fatty acids into carbohydrates
• B. They are abundant in soybeans but absent in peas
• C. They are single membranous organelles
• D. They are present throughout the life of a plant, providing energy through the Glyoxylate cycle

Explanation: Glyoxysomes are specialized peroxisomes found in plant cells, particularly in the germinating seeds of plants rich in lipids. They contain enzymes necessary for the glyoxylate cycle, which converts fatty acids into carbohydrates, providing energy for the growing seedling. This function is crucial during the early stages of seed germination, but glyoxysomes are not present throughout the plant's life cycle. They are absent in lipid-poor seeds such as peas. Therefore, the statement that glyoxysomes are present throughout the life of a plant is incorrect, making Option D the correct choice. Options A, B, and C are all true statements about glyoxysomes.

• A. Active transport
• B. Passive transport
• C. Diffusion
• D. Both options B and C are correct

Explanation: Passive transport and diffusion both refers to the transport without the need of energy, in the form of ATP.

• A. Homogenisation, centrifugation
• B. Centrifugation, Homogenisation
• C. Both A and B
• D. None of the above

Explanation: Cell fractionation is a process designed to separate and isolate cellular components, such as organelles. The first step is homogenization, where cells are broken open to release their contents. This is followed by centrifugation, where the homogenate is spun at various speeds to separate the components based on their size and density. Option A correctly describes this sequence. Options B, C, and D are incorrect because they do not reflect the necessary order of operations in cell fractionation.

• A. Capsule of bacteria
• B. Nucleus
• C. Cell membrane
• D. Mitochondria

Explanation: The correct answer is the capsule of bacteria because it is an external structure, unlike the protoplasm, which refers to the internal contents of a cell. The protoplasm of bacteria includes components like cytoplasm and nucleoid, but not external structures such as the capsule. The other options are incorrect because they either describe internal structures (like the nucleoid for a nucleus) or features not found in bacteria (such as mitochondria), which are irrelevant in this context.

• A. Viral fever
• B. Common cold
• C. Asthma
• D. Malaria

Explanation: Glycophorin is a sialoglycoprotein of the membrane of a red blood cell. Directly, it is not related to any of the diseases, but some of its variations have resistance to malaria, a mosquito-borne infection.

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

Explanation: This option is correct because lysosomes play a vital role in defense activity as they are full of powerful hydrolytic enzymes. They kill the antigen by secreting the digestive enzyme over it so that it could be digested.

• A. Schwann
• B. Scheilden
• C. Robert Hooke
• D. Both Options A and B are correct

Explanation: The cell was discovered by Robert Hooke in 1665, in a Cork piece, in which he saw small compartments. He named them "cells" because they resembled small rooms "cellulae" (Latin) in which Monks used to live. Scheilden and Schwann coined the cell theory AFTER the cell had been discovered and named.