All Free Biology MCQs with Answers

• A. AMP
• B. ATP
• C. ADP
• D. All of these

Explanation: "The explanation for this question will be added soon!".

• A. symplast
• B. nucleoplasm
• C. RER
• D. SER.

Explanation: Smooth endoplasmic reticulum (SER) is a system of smooth membranes (i.e., membranes not having ribosomes) within the cytoplasm of plant and animal cells. It forms a link between the cell and nuclear membranes. It is the site of important metabolic reactions, including phospholipid and fatty acid synthesis. In animal cells lipid­like steroidal hormones are also synthesized.

• A. A layer present between cell wall and membrane of bacteria
• B. Cell wall of bacteria
• C. Bacterial cell glyco­engineered to possess N-­glycosylated proteins
• D. A layer surrounding the cell wall of bacteria.

Explanation: 'Glycocalyx' is a sticky, gelatinous material that collects outside the cell wall of bacteria to form an additional surface layer. When this layer is firmly attached to the surface of the cell, it is called a 'capsule'. If it is loosely distributed around the cell, the glycocalyx is called a 'slime layer'.

• A. Chromoplast
• B. Elaioplasts
• C. Aleuroplasts
• D. Amyloplasts

Explanation: Chromoplasts are yellow or reddish in color because of the presence of carotenoid pigments. They do not contain stored food material. Chromoplasts are formed either from leucoplasts or chloroplasts. Chromoplasts provide color to many flowers for attracting pollinating insects. They provide bright red or orange colors to fruits for attracting animals for dispersal.

• A. Ribosomes
• B. Chromosomal organization
• C. Cell wall
• D. Cell membrane

Explanation: E.coli (bacteria) is a prokaryote while Chlamydomonas (algae) is a eukaryote. Ribosomes of both groups differ being 70S in prokaryotes and 80S in eukaryotes. Prokaryotic chromosomes lack histone proteins unlike eukaryotic ones. Cell wall organization also differs as bacterial cell wall is rich in muramic acid while algal cell wall is cellulosic. It is the cell membrane which has similar organization in both the groups.

• A. Golgi complex
• B. Peroxisome
• C. Vacuole
• D. Lysosome

Explanation: While each of the membranous organelles is distinct in terms of its structure and function, many of these are considered together as an endomembrane system because their functions are coordinated. The endomembrane system include endoplasmic reticulum (ER), Golgi complex, lysosomes and vacuoles. Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components, these are not considered as part of the endomembrane system.

• A. D (outer membrane) - gives rise to inner membrane by splitting
• B. B (inner membrane) - forms infoldings called cristae
• C. C (crista) - possesses single circular DNA molecule and ribosomes
• D. A (matrix) - major site for respiratory chain enzymes

Explanation: Each mitochondrion is a double membrane­ bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e., the outer compartment and the inner compartment. The inner compartment is called the matrix. The outer membrane forms the continuous limiting boundary of the organelle. The inner membrane forms a number of infoldings called the cristae towards the matrix. The cristae increase the surface area. The two membranes have their own specific enzymes associated with the mitochondrial function.

• A. Grana
• B. Pyrenoid
• C. Stroma
• D. Both grana and stroma

Explanation: Chlorophyll in chloroplasts is located in the grana. Grana are stacks of thylakoid membranes inside the chloroplasts where the photosystems containing chlorophyll are embedded. They are responsible for capturing light energy during photosynthesis.

• A. Proteins can also undergo flip-flop movements in the lipid bilayer
• B. Many proteins remain completely embedded within the lipid bilayer
• C. Proteins in cell membranes can travel within the lipid bilayer
• D. Proteins can remain confined within certain domains of the membranes

Explanation: The incorrect statement is A. In the fluid mosaic model, proteins are generally considered to be too large to undergo spontaneous flip-flop movements in the lipid bilayer. Instead, they can undergo lateral diffusion within the membrane.An improved model of the structure of cell membrane was proposed by Singer and Nicolson (1972) widely accepted as fluid mosaic model. According to this, the quasi-fluid nature of lipid enables lateral movement (Flip-flop) of proteins within the overall bilayer. This ability to move within the membrane is measured as its fluidity.

• A. Chloroplast
• B. Mitochondria
• C. Lysosome
• D. Endoplasmic reticulum.

Explanation: The proteins formed on ribosomes pass into the ER lumen where they are modified. Then the modified proteins move on into the transitional area, where the ER buds off membranous sacs (the transport vesicles) that carry the proteins to the Golgi apparatus.