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 controlling voluntary muscle movements?

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

Correct answer: A

Rationale: The correct answer is the Cerebrum. The cerebrum, the largest part of the brain, controls voluntary muscle movements, along with cognitive functions like thinking, perception, and decision-making. It is crucial for motor coordination and the regulation of voluntary movements. The Cerebellum (Choice B) is responsible for coordinating movement, balance, and posture, but not specifically for voluntary muscle movements. The Medulla oblongata (Choice C) is involved in controlling autonomic functions like breathing and heart rate, not voluntary muscle movements. The Thalamus (Choice D) acts as a relay station for sensory information but is not primarily responsible for controlling voluntary muscle movements.

3. Antidiuretic hormone (ADH) plays a crucial role in regulating water balance. When ADH levels are high, what happens to urine production?

A. Urine production increases significantly
B. Urine production decreases to conserve water
C. There is no change in urine production
D. The kidneys stop producing urine altogether

Correct answer: B

Rationale: When ADH levels are high, urine production decreases to conserve water. ADH acts on the kidneys to increase water reabsorption, leading to the production of concentrated urine and conservation of water in the body. Choice A is incorrect as high ADH levels lead to increased water reabsorption, reducing urine output. Choice C is incorrect since high ADH levels do influence urine production. Choice D is incorrect as the kidneys do not stop producing urine entirely but rather adjust the reabsorption of water based on ADH levels.

4. What is the formula to calculate kinetic energy?

A. Kinetic Energy = Mass × Velocity
B. Kinetic Energy = Force × Distance
C. Kinetic Energy = Power × Time
D. Kinetic Energy = Potential Energy ÷ Time

Correct answer: A

Rationale: Kinetic energy is the energy an object possesses due to its motion. The formula to calculate kinetic energy is KE = 0.5 × mass × velocity^2, which can also be written as KE = mass × (velocity)^2. Therefore, the correct formula is Kinetic Energy = Mass × Velocity. Choice B is incorrect because it represents the work formula. Choice C is incorrect as it represents the formula for work done. Choice D is incorrect as it does not accurately represent the formula for calculating kinetic energy.

5. In the reaction 2Na + 2H2O → 2NaOH + H2, what is the limiting reactant when 3 moles of sodium react with 2 moles of water?

A. Na
B. H2O
C. NaOH
D. H2

Correct answer: A

Rationale: The balanced chemical equation indicates that 2 moles of sodium react with 2 moles of water to yield 2 moles of sodium hydroxide and 1 mole of hydrogen gas. When 3 moles of sodium react with only 2 moles of water, sodium becomes the limiting reactant as it is present in excess compared to the available water molecules. This situation arises because not all sodium atoms can fully react with the limited amount of water, resulting in sodium being the limiting reactant in this specific case. Choice B (H2O), choice C (NaOH), and choice D (H2) are incorrect as they are not the limiting reactant in the given reaction scenario.