Question

The immune system (select the MOST CORRECT statement)

		The second exposure to a given antigen leads to a rapid adaptive immune response that reaches its peak (as measured by antibody concentration in plasma) within 3-4 days.
		Granzymes are synthesized by both cytotoxic T cells and Natural Killer Cells and are stored in secretory vesicles.
		Granzymes are specialized enzymes that can diffuse across the plasma membrane of cells without the help of a channel or carrier protein.
		Both a) and b) are correct and c) is incorrect
		a), b) and c) are all correct

Digestion of food (select the MOST CORRECT statement)

		Cnidarians such as Hydra have a gastrovascular cavity and use both extracellular and intracellular digestion.
		The gastrovascular cavity of Hydra is used for both nutrient absorption and gas exchange.
		Birds have a structure called the gizzard that is specialized for the absorption of nutrients.
		Both a) and b) are correct and c) is incorrect
		a), b) and c) are all correct

Answer 1

The immune system

Ans: Both a) and b) are correct and c) is incorrect

a. Correct statement

On secondary exposure, the antigen raises about twice as high as the highest primary response and about 6 times the residual primary response. So the statement "The second exposure to a given antigen leads to a rapid adaptive immune response that reaches its peak (as measured by antibody concentration in plasma) within 3-4 days" is correct.

b. Correct statement

Granzymes are serine proteases released by cytoplasmic granules within cytotoxic T cells and natural killer (NK) cells. They induce apoptosis in the target cell, thus eliminating cells that have become cancerous or are infected with viruses or bacteria. So the statement 'Granzymes are synthesized by both cytotoxic T cells and Natural Killer Cells and are stored in secretory vesicles' is correct.

c. Incorrect statement

Perforin is able to polymerize and form a channel in target cell. When perforin creates a transmembrane pore for granzymes, the granzymes enter and digest the cell from the inside out. Granzymes can diffuse across the plasma membrane only with the help of this perforin protein. So the statement "Granzymes are specialized enzymes that can diffuse across the plasma membrane of cells without the help of a channel or carrier protein" is incorrect.

Digestion of food

Ans: Both a) and b) are correct and c) is incorrect

a. Correct statement - Cnidarians such as Hydra has a gastrovascular cavity and use both extracellular and intracellular digestion.

Cnidarians carry out extracellular and intracellular digestion, where enzymes break down the food particles and cells lining the gastrovascular cavity absorb the nutrients.

b. Correct statement - The gastrovascular cavity of Hydra is used for both nutrient absorption and gas exchange. The gastrovascular cavity is a structure found in Cnidarians such as Hydra. It is responsible for both the digestion of food and the transport of nutrients throughout the body.

The cavity has only one opening to the environment. Food goes in and waste comes out that same opening, making it a two-way digestive tract.

c. Incorrect statement - Gizzard is a muscular, thick-walled part of a bird's stomach especially for grinding food, to make it more digestible. So the statement "Birds have a structure called the gizzard that is specialized for the absorption of nutrients" is not correct.