what of the following cations is found at the center of a heme

ATI TEAS 7

Practice Science TEAS Test

1. Which of the following cations is found at the center of a heme?

A. Cr (III)
B. Cu (II)
C. Iron (II)
D. Iron (III)

Correct answer: C

Rationale: The correct answer is Iron (II) (Fe2+), which is the cation found at the center of a heme group. Heme contains an iron (II) ion that is coordinated within the porphyrin ring structure. This iron ion is crucial for the function of heme in binding and transporting oxygen in hemoglobin and myoglobin. Choice A (Cr (III)) is incorrect as chromium is not typically found at the center of a heme group. Choice B (Cu (II)) is incorrect as copper is not the cation typically present in heme. Choice D (Iron (III)) is also incorrect as heme predominantly contains iron (II) at its center, not iron (III).

2. Which part of the brain is responsible for regulating heart rate, breathing, and swallowing?

A. Cerebrum
B. Cerebellum
C. Medulla oblongata
D. Thalamus

Correct answer: C

Rationale: The correct answer is C, the medulla oblongata. This part of the brain, located at the base of the brainstem, is primarily responsible for regulating essential functions like heart rate, breathing, and swallowing. Choices A, B, and D are incorrect. The cerebrum is associated with higher brain functions such as thinking and voluntary movements, the cerebellum controls coordination and balance, and the thalamus serves as a relay station for sensory information. Therefore, the medulla oblongata specifically governs the autonomic functions critical for survival.

3. What type of tissue is bone composed of?

A. Epithelial tissue
B. Connective tissue
C. Hard connective tissue
D. Muscle tissue

Correct answer: B

Rationale: Bone is composed of connective tissue. Connective tissues are characterized by having cells scattered within an extracellular matrix. In the case of bone, the extracellular matrix is mineralized, giving bone its hardness and strength. Choice A, epithelial tissue, is not correct as bone is not primarily composed of epithelial cells. Choice C, hard connective tissue, is not a recognized category of tissue in the scientific classification; bone is classified under connective tissue. Choice D, muscle tissue, is incorrect as bone and muscle tissues are distinct types of tissues with different structures and functions.

4. What is insulin, where is it produced, and what is its function?

A. Produced in the liver, regulates fat storage
B. Produced in the pancreas, regulates blood sugar
C. Produced in the stomach, aids in digestion
D. Produced in the kidneys, controls hydration

Correct answer: B

Rationale: Insulin is a hormone produced in the pancreas. Its primary function is to regulate blood sugar levels by facilitating the uptake of glucose by cells for energy. The other choices are incorrect as insulin is not produced in the liver (Choice A), stomach (Choice C), or kidneys (Choice D), and its function is not related to fat storage, digestion, or hydration. Therefore, the correct answer is B.

5. What is the principle behind optical fibers used in communication?

A. Reflection of light within the fiber
B. Refraction of light due to different densities within the fiber
C. Total internal reflection guiding light through the fiber core
D. Diffraction of light around bends in the fiber

Correct answer: C

Rationale: Optical fibers used in communication rely on the principle of total internal reflection guiding light through the fiber core. Total internal reflection occurs when light traveling through the core of the fiber is reflected back into the core due to the higher refractive index of the core compared to the cladding. This reflection ensures that the light remains confined within the core and propagates along the fiber without significant loss, allowing for efficient transmission of signals over long distances in optical communication systems. Choice A is incorrect because optical fibers do not primarily rely on simple reflection; instead, they utilize total internal reflection to guide light. Choice B is incorrect as the primary principle is not the refraction of light due to different densities within the fiber, but rather total internal reflection. Choice D is incorrect as diffraction is not the main principle behind optical fibers, which mainly rely on total internal reflection to guide light through the fiber core.