All Free Biology MCQs with Answers

• A. Provides mechanical shape
• B. Maintains cellular homeostasis
• C. Regulates passage of molecules
• D. Prevents from osmotic lysis

Explanation: The cell membrane in animal cells does not prevent the cell from osmotic lysis. Animal cells do not have a cell wall like plant cells, and they are susceptible to osmotic lysis in a hypotonic environment where water can enter the cell freely, causing it to swell and potentially burst.

• A. Heads of phospholipid molecules
• B. Cholesterol molecules
• C. Tails of phospholipid molecules
• D. Glycoproteins

Explanation: Glycoproteins are proteins that have carbohydrate chains (oligosaccharides) attached to them. These carbohydrate chains extend outward from the plasma membrane into the extracellular space. Glycoproteins often act as receptors on the cell surface, allowing the cell to recognize and interact with specific molecules, such as hormones, growth factors, or signaling molecules.

• A. It helps in the transport of proteins between various regions of cytoplasm.
• B. It forms cytoplasmic framework for biochemical activities.
• C. It is involved in the formation of lysosomes.
• D. It is involved in the formation of cell wall.

Explanation: The endoplasmic reticulum (ER) is not involved in the formation of the cell wall. The cell wall is a rigid structure that surrounds the plasma membrane of plant cells. It is made up of cellulose, hemicellulose, and pectin. The ER is not involved in the synthesis of these molecules.

• A. Mitochondria
• B. Endoplasmic Reticulum
• C. Nucleus
• D. Chloroplast

Explanation: The endoplasmic reticulum (ER) is a single-membrane-bound organelle. This means that it is surrounded by a single layer of phospholipids. The ER is a network of interconnected tubules and sacs that is found in the cytoplasm of eukaryotic cells. It is the largest organelle in the cell, and it can account for up to 20% of the cell's volume. All the other organelles given in the options are surrounded by a double membrane.

• A. Lysosomes
• B. Golgi bodies
• C. Smooth endoplasmic reticulum
• D. Rough endoplasmic reticulum

Explanation: The smooth endoplasmic reticulum (SER) is involved in the synthesis of steroids. Steroids are a class of lipids that play important roles in the body, including regulating metabolism, reproduction, and inflammation. The SER contains enzymes that are responsible for the synthesis of cholesterol, which is the precursor for all steroids. The SER also contains enzymes that are responsible for the modification of cholesterol to form different types of steroids. Cells that produce steroids, such as the adrenal glands and the ovaries, are abundant in SER.

• A. E. coli
• B. C. botulinum
• C. T. pallidum
• D. All of these

Explanation: All of these are bacteria and belong to the prokaryotic group. Hence, all of them have 70S ribosomes. And 70S ribosome has 2 subunits: 50S and 30S.

• A. Mitochondria
• B. Lysosomes
• C. Cell membrane
• D. Golgi apparatus

Explanation: The modification of proteins and lipids into glycoproteins and glycolipids is one of the functions of the Golgi apparatus. The Golgi apparatus is an organelle found in eukaryotic cells that is responsible for processing and sorting proteins and lipids. The Golgi apparatus is divided into three main regions: the cis-Golgi, the medial-Golgi, and the trans-Golgi. The cis-Golgi is the region where proteins and lipids are imported from the endoplasmic reticulum. The medial Golgi is the region where proteins and lipids are modified. The trans-Golgi is the region where proteins and lipids are sorted and exported from the Golgi apparatus. The modification of proteins and lipids in the Golgi apparatus involves a variety of processes, including:Glycosylation: The addition of sugar molecules to proteins and lipids.Phosphorylation: The addition of phosphate groups to proteins.Adenylation: The addition of adenosine molecules to proteins.Proteolytic cleavage: The removal of amino acids from proteins.The modification of proteins and lipids in the Golgi apparatus is essential for the proper functioning of cells. For example, glycoproteins are important for cell-cell recognition and adhesion. Glycolipids are important for the formation of cell membranes.

• A. Golgi apparatus
• B. Cell wall
• C. Lysosomes
• D. None of these

Explanation: Lysosomes are most abundant in those animal cells which exhibit phagocytic activity. Phagocytic cells are cells that engulf and destroy foreign particles, such as bacteria. Lysosomes are organelles that contain enzymes that break down cellular waste products and foreign substances. Phagocytic cells, such as macrophages and neutrophils, have a large number of lysosomes. This is because they need to be able to break down the foreign particles that they engulf. The lysosomes fuse with the phagosome, which is the vesicle that contains the foreign particle, and the enzymes in the lysosomes then break down the particle. The abundance of lysosomes in phagocytic cells is an important adaptation that allows these cells to defend the body against infection.

• A. Grave's disease
• B. Addison's disease
• C. Glycogenosis type Il disease
• D. Tay-Sachs disease

Explanation: Tay-Sachs disease is a rare, inherited disorder that is caused by the accumulation of a fatty substance called GM2 ganglioside in the brain cells. This accumulation of GM2 ganglioside leads to the death of brain cells, which results in progressive neurological decline. Tay-Sachs disease is usually diagnosed in infants and young children. The first symptoms of the disease typically appear between 4 and 6 months of age. These symptoms can include:Vision problems: Infants with Tay-Sachs disease may develop nystagmus, which is a condition in which the eyes make involuntary movements. They may also develop cataracts, which are cloudy areas in the lens of the eye.Developmental delays: Infants with Tay-Sachs disease may have delayed development. They may not reach their developmental milestones on time, such as rolling over, sitting up, or walking.Seizures: Infants with Tay-Sachs disease may develop seizures.Behavioral changes: Infants with Tay-Sachs disease may become irritable and withdrawn. They may also have difficulty sleeping.

• A. Endoplasmic reticulum
• B. Ribosomes
• C. Mitochondria
• D. Lysosomes

Explanation: Due to the large size of mitochondria as compared to endoplasmic reticulum, lysosomes, and ribosomes, it can be visualized easily with the help of light microscope.It appears as rods or vesicles under light microscope.