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. How does an increase in surface area affect the force of friction between two surfaces?

A. Increases friction
B. Decreases friction
C. Has no effect on friction
D. Causes unpredictable changes in friction

Correct answer: A

Rationale: An increase in surface area typically increases the force of friction between two surfaces. This is because with a larger surface area in contact, there are more points of contact between the surfaces, leading to a greater frictional force resisting motion. As a result, the correct answer is that an increase in surface area increases the force of friction between two surfaces. Choice B is incorrect because a greater surface area increases the frictional force. Choice C is incorrect because an increase in surface area results in more contact points and greater friction. Choice D is incorrect as the relationship between surface area and friction is predictable - an increase in surface area generally leads to an increase in frictional force.

3. Which structure contains the genetic material (DNA) of the cell?

A. Cytoplasm
B. Nucleus
C. Cell wall (only present in plant cells)
D. Golgi apparatus

Correct answer: B

Rationale: The nucleus is the organelle that contains the genetic material (DNA) of the cell. It acts as the control center of the cell, regulating gene expression and coordinating cellular activities. The cytoplasm is the fluid-filled space within the cell where organelles are suspended, but it does not contain the genetic material. The cell wall is a rigid structure found in plant cells that provides support and protection, but it does not house the DNA. The Golgi apparatus is involved in processing and packaging proteins for secretion, but it does not contain the genetic material of the cell.

4. What is the general formula for an alcohol?

A. CₙH₂ₙ
B. CₙH₂ₙ₊₂
C. CₙH₂ₙ₋₁
D. CₙH₂ₙO

Correct answer: D

Rationale: The correct general formula for an alcohol is CnH2n+1OH, which can be simplified to CnH2nO. In this formula, 'n' represents the number of carbon atoms, '2n' represents the number of hydrogen atoms, and 'O' represents the oxygen atom present in the hydroxyl group of the alcohol. Therefore, the correct general formula for an alcohol is CnH2nO. Choice A, CₙH₂ₙ, does not account for the oxygen atom, which is essential in alcohols. Choice B, CₙH₂ₙ₊₂, does not include the oxygen atom or the necessary hydrogen atoms for the hydroxyl group. Choice C, CₙH₂ₙ₋₁, lacks the oxygen atom and also does not fulfill the requirements of the hydroxyl group. Thus, the most accurate representation of the general formula for an alcohol is CnH2nO.

5. What is the primary function of the spleen, an organ associated with the lymphatic system?

A. Regulating blood sugar levels
B. Filtering blood and destroying old red blood cells
C. Producing digestive enzymes
D. Secreting hormones

Correct answer: B

Rationale: The spleen is primarily responsible for filtering blood and destroying old or damaged red blood cells. It also aids in storing blood and producing specific types of white blood cells, contributing to maintaining blood quality and immune system function. Choices A, C, and D are incorrect because the spleen is not involved in regulating blood sugar levels, producing digestive enzymes, or secreting hormones. These functions are carried out by other organs in the body.