Science TEAS Practice Test

Correct Answer: A

Rationale: The correct answer is A: The sinoatrial node. The SA node is known as the heart's natural pacemaker as it initiates electrical impulses that regulate the heart rate. It is located in the right atrium and generates rhythmic electrical signals that stimulate the cardiac muscle to contract. The left ventricle (B), aorta (C), and tricuspid valve (D) do not serve as electrical stimulators of the cardiac muscle. The left ventricle is a chamber that pumps oxygenated blood, the aorta is the largest artery that carries blood away from the heart, and the tricuspid valve controls blood flow between the right atrium and right ventricle.

Correct Answer: C

Rationale: The correct answer is C: Covalent. In DNA, sugar and phosphate molecules are joined together by covalent bonds. Covalent bonds involve sharing of electrons between atoms, providing a strong and stable connection. This type of bond is essential for the structural integrity of the DNA molecule. A: Hydrogen bonds are important in DNA structure, but they connect the nitrogenous bases, not sugar and phosphate. B: Ionic bonds involve the transfer of electrons between atoms, not sharing, and are not typically involved in connecting sugar and phosphate in DNA. D: "Overt" is not a recognized type of chemical bond; it is an incorrect distractor.

Correct Answer: C

Rationale: The correct answer is C: Circulatory system. This system, composed of the heart, blood vessels, and blood, is responsible for transporting nutrients, gases, and wastes throughout the body. The heart pumps blood carrying oxygen and nutrients to cells and removes waste products. The blood vessels distribute these substances to tissues and organs. The respiratory system (A) is responsible for gas exchange but not for transporting nutrients and wastes. The digestive system (B) processes food and absorbs nutrients but does not transport gases. The nervous system (D) coordinates body functions and transmits signals but does not transport nutrients, gases, or wastes.

Correct Answer: D

Rationale: The correct answer is D: Help red blood cells transport oxygen. Hemoglobin is a protein in red blood cells that binds to oxygen in the lungs and releases it in tissues. It does not transport oxygen itself, but it aids red blood cells in carrying oxygen. Choice A is incorrect because hemoglobin carries oxygen, not transports it. Choice B is incorrect because hemoglobin binds to oxygen, not to red blood cells. Choice C is incorrect because hemoglobin primarily transports oxygen, not carbon dioxide.

Correct Answer: D

Rationale: Density is considered an intensive property because it remains constant regardless of the amount of the substance present. Intensive properties do not depend on the quantity of the material. Density is defined as mass per unit volume, so it is independent of the amount of the substance. On the other hand, mass and volume (choices A and C) are extensive properties that change with the amount of the substance, making them not intensive. Weight (choice B) is also not an intensive property as it depends on the gravitational force acting on the object, which can vary.