Nokea
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.
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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.
What presents the correct order of cellular respiration?
- A. Glycolysis, Acetyl-CoA, Citric Acid Cycle, Electron Transport Chain
- B. Citric Acid Cycle, Glycolysis, Acetyl-CoA, Electron Transport Chain
- C. Glycolysis, Acetyl-CoA, Electron Transport Chain, Citric Acid Cycle
- D. Glycolysis, Citric Acid Cycle, Electron Transport Chain, Acetyl-CoA
Correct Answer: A
Rationale: The correct order of cellular respiration is Glycolysis, Acetyl-CoA, Citric Acid Cycle, and Electron Transport Chain. Glycolysis initiates the breakdown of glucose in the cytoplasm, leading to the formation of pyruvate. This pyruvate is then converted to Acetyl-CoA in the mitochondria, which enters the Citric Acid Cycle to generate energy-rich molecules like NADH and FADH2. Finally, the Electron Transport Chain, located in the inner mitochondrial membrane, utilizes these energy carriers to produce ATP through oxidative phosphorylation. Choice B is incorrect because it starts with the Citric Acid Cycle, which comes after Glycolysis. Choice C is incorrect as it places the Citric Acid Cycle before the Electron Transport Chain. Choice D is incorrect by placing Acetyl-CoA last instead of before the Citric Acid Cycle.
An atom has 17 protons, 20 neutrons, and 17 electrons. What is its mass, in amu?
- A. 17
- B. 20
- C. 37
- D. 54
Correct Answer: C
Rationale: The atomic mass of an atom is the sum of the protons and neutrons in its nucleus. In this case, the atom has 17 protons and 20 neutrons, totaling 37 particles in the nucleus. Electrons are not considered in the atomic mass calculation as their mass is negligible compared to protons and neutrons. Therefore, the mass of the atom in atomic mass units (amu) is 37.
In an experiment where five tropical plants are kept at varying humidity levels in a greenhouse for three months, while one plant is left outside in normal conditions, with plant height measured weekly, what serves as the control of the experiment?
- A. Plant height for each tropical plant
- B. The plant left outside in normal conditions
- C. Humidity level readings in the greenhouse
- D. Amount of time used to study plant height
Correct Answer: B
Rationale: The correct answer is B. The plant left outside in normal conditions acts as the control in the experiment. It provides a standard reference point for comparison to assess the impact of the varying humidity levels on the growth of the tropical plants. Choice A is incorrect because it refers to the dependent variable being measured, not the control. Choice C is incorrect as humidity levels in the greenhouse are part of the experimental conditions, not the control. Choice D is incorrect as the time used for studying plant height is a parameter of the experiment and not the control.
At which of the following ages would ossification most likely take place to replace cartilage at the growth plate?
- A. 5
- B. 18
- C. 42
- D. 91
Correct Answer: B
Rationale: Ossification, the process where cartilage is replaced by bone, typically occurs during adolescence, around the age of 18. This is when the growth plates in the bones close, and the bones stop growing in length, leading to the replacement of cartilage with bone tissue. Choice A (5) is incorrect because ossification primarily occurs during adolescence, not early childhood. Choice C (42) is incorrect as ossification is completed well before this age, usually during the late teens or early twenties. Choice D (91) is incorrect as ossification is a process that occurs earlier in life, typically during adolescence, and is not a process that occurs in advanced age.