Nokea
Through which of the following transport mechanisms do water molecules enter cells?
- A. Facilitated diffusion
- B. Electrochemical gradients
- C. Gated channels
- D. Proton pumps
Correct Answer: A
Rationale: Water molecules enter cells through facilitated diffusion. Facilitated diffusion is the passive movement of molecules across a cell membrane with the help of specific transport proteins. In the case of water, it moves through specialized channels called aquaporins using this mechanism, allowing it to cross the membrane more efficiently than by simple diffusion. While electrochemical gradients, gated channels, and proton pumps play roles in transporting other substances and ions, they are not directly involved in the transport of water molecules into cells.
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To accurately measure the density of a series of small irregular solids made of plastic, wood, fiberglass, and glass, which of the following laboratory tools will a student need?
- A. Graduated cylinder, water, weighing balance
- B. Weighing balance, Bunsen burner, metric ruler
- C. Graduated cylinder, spectrophotometer, water
- D. Graduated beaker, metric ruler, water
Correct Answer: A
Rationale: To measure the density of irregular solids, a student needs a graduated cylinder to measure the volume of the solids by water displacement, water for the displacement method, and a weighing balance to measure the mass of the solids. Density is calculated by dividing the mass by the volume.
Why is nitrogen gas an extremely stable molecule?
- A. resonance bonds
- B. ionic bonds
- C. triple covalent bonds
- D. hydrogen bonds
Correct Answer: C
Rationale: The correct answer is C - triple covalent bonds. Nitrogen gas (N2) is composed of two nitrogen atoms held together by a triple covalent bond. This bond is very strong and requires a significant amount of energy to break, making nitrogen gas a stable molecule. Triple covalent bonds involve the sharing of three pairs of electrons, resulting in a very stable configuration. Resonance bonds, ionic bonds, and hydrogen bonds are not present in the structure of nitrogen gas, hence they do not contribute to its stability.
What distinguishes endocrine and exocrine glands from one another?
- A. The biochemistry of their secretions
- B. The presence or absence of ducts
- C. The presence or absence of nerve innervation
- D. The effect their secretions have on the target cell
Correct Answer: B
Rationale: The correct answer is B. The presence or absence of ducts is the key factor that distinguishes endocrine and exocrine glands. Endocrine glands secrete hormones directly into the bloodstream without ducts, while exocrine glands secrete substances through ducts to the external environment or onto a surface. Choice A is incorrect because both types of glands can have different biochemistries in their secretions. Choice C is incorrect because both types of glands can receive nerve innervation. Choice D is incorrect as it does not differentiate between endocrine and exocrine glands based on the effect of their secretions on target cells.
Which of the following triangular areas of the human body is described as the perineum?
- A. The area between the nipples on the chest and the belly button.
- B. The area on the back between the neck and the two shoulder blades.
- C. The area that contains the orifices of the urinary, digestive, and reproductive systems.
- D. The area between the edges of the eyes and the chin.
Correct Answer: C
Rationale: The perineum is the specific triangular region in the pelvic area that houses the openings of the urinary, digestive, and reproductive systems. It is essential for supporting these vital bodily functions. The other options describe different anatomical areas that are not related to the perineum. Understanding the location and function of the perineum is crucial for healthcare professionals to provide accurate assessments and care to patients.
When an organism with an unknown genotype is crossed with another organism displaying the recessive trait (aa), the Punnett square shown above illustrates the outcomes. What is the unknown genotype?
- A. a
- B. Aa
- C. AA
- D. aa
Correct Answer: B
Rationale: In the provided Punnett square, the recessive trait (aa) is displayed. This means the known organism must be homozygous recessive (aa). When crossed with the unknown genotype, which is represented by a capital letter (A), it results in a 50% chance of producing heterozygous offspring (Aa). As the recessive trait is expressed in the outcomes, the unknown genotype must carry the dominant allele (A) alongside the recessive allele (a), making it heterozygous (Aa). Therefore, the correct answer is B, Aa.