Nokea
Which structure protects the lungs?
- A. Femur
- B. Ribcage
- C. Scapula
- D. Skull
Correct Answer: B
Rationale: The ribcage is the correct answer. It protects the lungs by providing structural support and shielding them from injury. The femur is a bone in the thigh and does not protect the lungs. The scapula is a shoulder blade bone, and the skull protects the brain, not the lungs.
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Not all cells in the pancreas secrete insulin because of the hormone somatostatin, which inhibits the release of insulin by all cells. What type of intercellular chemical signal does this illustrate?
- A. Autocrine
- B. Neuromodulator
- C. Paracrine
- D. Pheromone
Correct Answer: C
Rationale: The correct answer is C: Paracrine. Somatostatin acts in a paracrine manner by inhibiting the release of insulin from nearby cells within the pancreas. Paracrine signaling involves the secretion of signals that act on neighboring cells, as seen in this scenario where somatostatin affects nearby pancreatic cells without entering the bloodstream or affecting distant cells. Autocrine signaling involves cells responding to substances they themselves release, which is not the case here. Neuromodulators are chemicals that modulate the activity of neurons, not directly related to this scenario. Pheromones are chemicals released into the environment to communicate with individuals of the same species, not relevant to the signaling within the pancreas.
How does the respiratory system facilitate gas exchange between air and blood?
- A. Diffusion
- B. Exhalation
- C. Inspiration
- D. Ventilation
Correct Answer: A
Rationale: The correct answer is 'Diffusion.' Diffusion is the process by which gases are exchanged between air in the alveoli and blood in the capillaries. Oxygen moves from the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli through diffusion. Exhalation is the process of expelling air from the lungs, inspiration is the process of inhaling air into the lungs, and ventilation refers to the overall movement of air in and out of the lungs. While these processes are essential for the respiratory system to function, they are not directly responsible for the gas exchange between air and blood, which is primarily achieved through diffusion.
How do killer T cells recognize infected cells?
- A. The B cells flag the infected cells with amino acids.
- B. Tiny bits of the virus's RNA are left around the cell.
- C. Macrophages show up to help consume the infected cell.
- D. The T cells have receptors that recognize the proteins the virus leaves on the surface of the cell.
Correct Answer: D
Rationale: Killer T cells recognize infected cells by detecting viral proteins displayed on the surface of these cells. The T cells possess receptors specifically designed to identify these viral proteins, allowing them to target and eliminate the infected cells. Choice A is incorrect because B cells are not directly involved in the recognition process of infected cells by killer T cells. Choice B is incorrect because tiny bits of the virus's RNA being left around the cell is not how killer T cells primarily recognize infected cells. Choice C is incorrect because while macrophages play a role in immune responses, they do not directly assist in the recognition of infected cells by killer T cells.
If a biochemist isolates a large amount of pyruvate, which part of the cell is he working with?
- A. Chloroplasts
- B. Cytoplasm
- C. Mitochondria
- D. Nucleus
Correct Answer: B
Rationale: The correct answer is B: Cytoplasm. Pyruvate is a product of glycolysis, a metabolic pathway that takes place in the cytoplasm of the cell. Therefore, a biochemist isolating a large amount of pyruvate would be working with the cytoplasm of the cell. Choice A, Chloroplasts, is incorrect because pyruvate is not produced in chloroplasts, which are responsible for photosynthesis. Choice C, Mitochondria, is incorrect as pyruvate is produced in the cytoplasm before entering the mitochondria for further metabolism. Choice D, Nucleus, is incorrect as the nucleus is not involved in the production or isolation of pyruvate, which is a metabolic intermediate.
Which statement confirms that the cell membrane is selectively permeable?
- A. Receptors are found on a cell's surface.
- B. Cells communicate with each other using cell signals.
- C. Environmental changes can cause a cell to expand or shrink.
- D. Sodium ions must travel through ion channels to enter the cell.
Correct Answer: D
Rationale: The correct answer is D because selective permeability is demonstrated by the fact that specific ions, such as sodium, require ion channels to cross the cell membrane. This process allows the cell to control what substances can enter or exit, highlighting the selective nature of the cell membrane. Choices A, B, and C do not directly relate to the concept of selective permeability of the cell membrane. Receptors on a cell's surface (Choice A) are involved in cell signaling rather than selective permeability. Cell communication through signals (Choice B) and environmental changes affecting cell size (Choice C) are not directly related to the selective permeability of the cell membrane, which specifically refers to the regulation of substances passing through the membrane.