Nokea
Which vitamin deficiency can lead to a condition called pernicious anemia, affecting vitamin B12 absorption in the digestive system?
- A. Vitamin A
- B. Vitamin B12 (cobalamin)
- C. Vitamin D
- D. Vitamin E
Correct Answer: B
Rationale: Pernicious anemia is caused by a deficiency in vitamin B12 (cobalamin). Vitamin B12 is essential for the production of red blood cells and for the proper functioning of the nervous system. Pernicious anemia occurs when there is a lack of intrinsic factor, a protein produced in the stomach that is necessary for the absorption of vitamin B12 in the digestive system. Vitamin A, Vitamin D, and Vitamin E deficiencies do not lead to pernicious anemia. Vitamin A deficiency can cause night blindness and skin issues, Vitamin D deficiency can lead to rickets or osteomalacia, and Vitamin E deficiency can result in neurological problems and muscle weakness.
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What are isotopes?
- A. Atoms of the same element with different numbers of protons.
- B. Atoms of the same element with different numbers of neutrons.
- C. Atoms of different elements with the same number of protons.
- D. Atoms of different elements with the same number of electrons.
Correct Answer: B
Rationale: Isotopes are atoms of the same element with different numbers of neutrons. While isotopes share the same number of protons, which determines the element, they differ in the number of neutrons. This variance in neutron count results in isotopes having different atomic masses. Choice A is incorrect because isotopes have the same number of protons (same element) but differ in the number of neutrons. Choice C is incorrect as it describes atoms of different elements, not isotopes of the same element. Choice D is also incorrect because isotopes can have different numbers of electrons, but what defines isotopes is the variation in neutron numbers.
What is the process of splitting a heavy nucleus into smaller nuclei, releasing a vast amount of energy called?
- A. Nuclear fusion
- B. Nuclear fission
- C. Radioactive decay
- D. Chain reaction
Correct Answer: B
Rationale: The correct answer is B: Nuclear fission. Nuclear fission is the process of splitting a heavy nucleus into smaller nuclei, releasing a vast amount of energy. This process is commonly used in nuclear power plants and nuclear weapons. It is a controlled chain reaction that generates energy. Option A, Nuclear fusion, is the process of combining two light nuclei to form a heavier nucleus, releasing energy. This process powers the sun and other stars. Option C, Radioactive decay, is the process by which an unstable atomic nucleus loses energy by emitting radiation. Option D, Chain reaction, is a self-sustaining reaction where the products of one reaction event stimulate further reaction events. While chain reactions can occur in both nuclear fission and fusion, the specific process of splitting a heavy nucleus into smaller ones is known as nuclear fission.
Two objects with equal masses collide head-on, both initially moving at the same speed. After the collision, they stick together. What is their final velocity?
- A. Zero
- B. Half their initial velocity
- C. Their initial velocity
- D. Twice their initial velocity
Correct Answer: C
Rationale: In an inelastic collision where two objects stick together after colliding, momentum is conserved. Since the two objects have equal masses and equal initial velocities but opposite directions, their momenta cancel out. Therefore, after the collision, the combined mass will move at the same speed as the initial velocity, but in the direction of one of the objects. Choice A ('Zero') is incorrect because momentum is conserved, and the objects must move after the collision. Choice B ('Half their initial velocity') is incorrect as the final velocity is the same as the initial velocity due to momentum conservation. Choice D ('Twice their initial velocity') is incorrect as the final velocity cannot be twice the initial velocity based on the conservation of momentum principle.
What is the function of introns in eukaryotic genes?
- A. They code for protein sequences.
- B. They are involved in gene regulation.
- C. They are removed during mRNA processing.
- D. They are non-functional remnants of ancient DNA.
Correct Answer: C
Rationale: A) Introns do not code for protein sequences. Exons are the segments of DNA that code for proteins.
B) While introns can indirectly influence gene regulation, their primary function is not directly involved in gene regulation.
C) Introns are non-coding regions of DNA that are transcribed into pre-mRNA but are removed during mRNA processing through a process called splicing. This allows only the exons to be included in the mature mRNA that will be translated into proteins.
D) While introns were once thought to be non-functional remnants of ancient DNA, research has shown that they can have regulatory functions and play a role in gene expression.
What are the fluid-filled sacs that cushion the brain within the skull called?
- A. Meninges
- B. Cerebrospinal fluid
- C. Dura mater
- D. Arachnoid mater
Correct Answer: B
Rationale: The correct answer is B, cerebrospinal fluid. Cerebrospinal fluid acts as a shock absorber, protecting the brain from impact and providing nutrients to brain cells. Meninges are the three protective layers of tissue that surround the brain and spinal cord. Dura mater and arachnoid mater are specific layers of the meninges, not the fluid-filled sacs that cushion the brain.