Nokea
What is the most basic unit of structure in living things?
- A. Cell
- B. Organelle
- C. Oxygen
- D. Pigment
Correct Answer: A
Rationale: The cell is indeed the most basic unit of life, forming the foundation of all living organisms. Cells are the building blocks of all living things, containing organelles that perform specific functions. While oxygen is essential for life, it is not a structural unit. Similarly, pigment is a component found within cells but is not the fundamental unit of structure. Therefore, the correct answer is 'A: Cell.'
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How does the respiratory system facilitate gas exchange between air and blood?
- A. Diffusion
- B. Exhalation
- C. Inspiration
- D. Ventilation
Correct Answer: A
Rationale: The correct answer is 'Diffusion.' Diffusion is the process by which gases are exchanged between air in the alveoli and blood in the capillaries. Oxygen moves from the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli through diffusion. Exhalation is the process of expelling air from the lungs, inspiration is the process of inhaling air into the lungs, and ventilation refers to the overall movement of air in and out of the lungs. While these processes are essential for the respiratory system to function, they are not directly responsible for the gas exchange between air and blood, which is primarily achieved through diffusion.
Which structure protects the lungs?
- A. Femur
- B. Ribcage
- C. Scapula
- D. Skull
Correct Answer: B
Rationale: The ribcage is the correct answer. It protects the lungs by providing structural support and shielding them from injury. The femur is a bone in the thigh and does not protect the lungs. The scapula is a shoulder blade bone, and the skull protects the brain, not the lungs.
Why is the lining of the stomach covered with rugae?
- A. Rugae increase the output of gastric juices.
- B. Rugae increase the surface area of the stomach.
- C. Rugae increase the permeability of the stomach walls.
- D. Rugae increase the types of nutrients that can diffuse.
Correct Answer: B
Rationale: Rugae are folds in the stomach lining that increase its surface area. This increased surface area allows for more efficient digestion and absorption of nutrients in the stomach. Choice A is incorrect because rugae do not directly affect the output of gastric juices. Choice C is incorrect because rugae do not impact the permeability of the stomach walls. Choice D is incorrect because rugae do not influence the types of nutrients that can diffuse.
An atom has 17 protons, 20 neutrons, and 17 electrons. What is its mass, in amu?
- A. 17
- B. 20
- C. 37
- D. 54
Correct Answer: C
Rationale: The atomic mass of an atom is the sum of the protons and neutrons in its nucleus. In this case, the atom has 17 protons and 20 neutrons, totaling 37 particles in the nucleus. Electrons are not considered in the atomic mass calculation as their mass is negligible compared to protons and neutrons. Therefore, the mass of the atom in atomic mass units (amu) is 37.
Which of the following is the base that will bind with cytosine?
- A. Adenine
- B. Cytosine
- C. Guanine
- D. Thymine
Correct Answer: A
Rationale: Adenine is the correct answer as it is the base that binds with cytosine through hydrogen bonding in DNA, forming the A-T base pair. Cytosine always pairs with guanine to form the G-C base pair. Thymine pairs with adenine in DNA, not with cytosine.