Explanation

Surplus red blood cells, needed to meet an emergency, are mainly stored in the spleen.

Explanation

Nipah Virus (NIV) is a zoonotic virus, meaning it can be transmitted from animals to humans. The natural host of NIV is the fruit bat of the Pteropus genus. The virus can spread to humans through:

• Direct contact with infected bats
• Contact with infected pigs or other animals
• Contact with contaminated food or drinks
• Human-to-human transmission through close contact with an infected person

Explanation

• Chlorosis in older leaves occurs due to the deficiency of Magnesium.
• Chlorosis is a condition in which the leaves produce an insufficient amount of chlorophyll, causing yellowing of the leaves.
• Magnesium is the main component of chlorophyll, so its deficiency causes insufficient production of chlorophyll in leaves.

Explanation

• Endotoxin is a component of the outer membrane of Gram-negative bacteria, and it is specifically associated with the presence of Lipopolysaccharides (LPS).
• LPS is a complex molecule composed of a lipid A anchor, a core oligosaccharide, and a repeating O-antigen polysaccharide chain. 
• The lipid A portion of LPS is responsible for its endotoxic activity, which can trigger a strong immune response and cause septic shock.

Explanation

• Peptidoglycan, also known as murein, is a polymer of N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc) that forms the cell wall of bacteria.
• It is composed of a backbone of alternating GlcNAc and MurNAc residues, cross-linked by short peptides.

Explanation

• Erythrocytes, also known as red blood cells, have an average lifetime of 100 to 120 days in humans.
• They are produced in the bone marrow and can be recycled by macrophages.
• The average time for an erythrocyte to complete a cycle of circulation is 60 seconds, or one minute.

Explanation

• M13 is a bacteriophage (a virus that infects bacteria) that is commonly used for phage display techniques.
• Phage display is a laboratory technique used to display peptides or proteins on the surface of phages, such as M13, to select and evolve specific binders or enzymes.

Explanation

• The statement that is wrong is: Mycobacterium tuberculosis stains blue because of the thick lipid layer.
• Mycobacterium tuberculosis actually stains red or pink, not blue, due to its unique cell wall composition, which includes a waxy substance called mycolic acid. This makes it resistant to the Gram stain and causes it to appear red or pink.

The other statements are correct:

• Streptococcus pyogenes stains blue because of its thick peptidoglycan layer, which retains the crystal violet dye.
• Escherichia coli stains pink because of its thin peptidoglycan layer, which allows the safranin counterstain to dominate.
• Mycoplasma pneumoniae is not visible in the Gram stain because it lacks a cell wall, making it unable to retain the dyes.

Explanation

The earliest recorded pandemic, the Black Death, was speculated to be caused by the bubonic plague.

Explanation

• Cell signaling refers to the process by which cells communicate with each other and respond to their environment. It involves the transmission and reception of signals, which can occur through both intercellular and intracellular pathways.
• Intercellular signaling refers to the communication between different cells, where signals are transmitted through the extracellular space, such as through hormones, neurotransmitters, or other signaling molecules.
• Intracellular signaling refers to the communication within a cell, where signals are transmitted through various signaling pathways, such as protein-protein interactions, phosphorylation cascades, and gene regulation.