the stratum corneum the outermost layer of the epidermis is primarily composed of

ATI TEAS 7

TEAS 7 science practice

1. What is the primary composition of the stratum corneum, the outermost layer of the epidermis?

A. Keratinized dead cells
B. Melanocytes
C. Langerhans cells
D. Merkel cells

Correct answer: A

Rationale: The stratum corneum, the outermost layer of the epidermis, is primarily composed of keratinized dead cells. These cells are flattened, fully keratinized, and lack nuclei, serving a protective function for the skin. Melanocytes are responsible for producing melanin, providing skin pigmentation. Langerhans cells are involved in the immune response within the skin. Merkel cells are associated with sensory functions in the skin, particularly in touch sensations. Therefore, the correct answer is A as it accurately reflects the main constituent of the stratum corneum, which acts as a barrier against external factors.

2. What is the function of the myelin sheath in a neuron?

A. To transmit electrical impulses
B. To insulate and speed up electrical signals
C. To produce neurotransmitters
D. To protect the neuron from damage

Correct answer: B

Rationale: The myelin sheath serves to insulate neurons and accelerate the transmission of electrical signals along the axon. This insulation helps in the efficient conduction of nerve impulses by preventing signal loss or leakage. Choice A is incorrect because the myelin sheath does not transmit electrical impulses itself but rather helps in the conduction. Choice C is incorrect as the myelin sheath is not responsible for producing neurotransmitters. Choice D is also incorrect as the primary function of the myelin sheath is not to protect the neuron from damage. Therefore, the correct answer is B, as it accurately describes the function of the myelin sheath in a neuron.

3. Which of the following statements is true about the dependent variable?

A. A factor that remains constant during the experiment
B. A factor with data typically plotted on the x-axis
C. A factor that is measured during an experiment
D. A factor with data typically plotted on the y-axis

Correct answer: C

Rationale: The correct answer is C. The dependent variable is the factor that is being measured or observed in an experiment. It is the outcome that is affected by changes in the independent variable. In graphical representations, the dependent variable is usually plotted on the y-axis, not the x-axis. Choice A is incorrect because a factor that remains constant is referred to as a constant, not a dependent variable. Choice B is incorrect as the independent variable's data is typically plotted on the x-axis. Choice D is incorrect because the dependent variable's data is usually plotted on the y-axis. Therefore, choice C accurately describes the dependent variable.

4. Which indicator is commonly used to distinguish between acidic and basic solutions?

A. Methyl orange
B. Phenolphthalein
C. Universal indicator
D. All of the above are common indicators.

Correct answer: B

Rationale: Phenolphthalein is commonly used to differentiate between acidic and basic solutions. It changes color, turning pink in basic solutions and remaining colorless in acidic solutions due to a specific pH range. While methyl orange and universal indicator are also indicators used for pH testing, phenolphthalein is especially known for its distinctive color change in response to acidic and basic solutions, making it the correct choice. Methyl orange is typically used in titrations for a sharp color change at a specific pH, and the universal indicator is a mixture of indicators displaying a range of colors depending on the pH value, not specifically tailored to acidic and basic distinctions.

5. What is the function of introns in eukaryotic genes?

A. They code for protein sequences.
B. They are involved in gene regulation.
C. They are removed during mRNA processing.
D. They are non-functional remnants of ancient DNA.

Correct answer: C

Rationale: A) Introns do not code for protein sequences. Exons are the segments of DNA that code for proteins. B) While introns can indirectly influence gene regulation, their primary function is not directly involved in gene regulation. C) Introns are non-coding regions of DNA that are transcribed into pre-mRNA but are removed during mRNA processing through a process called splicing. This allows only the exons to be included in the mature mRNA that will be translated into proteins. D) While introns were once thought to be non-functional remnants of ancient DNA, research has shown that they can have regulatory functions and play a role in gene expression.