Nokea
What term describes the functional unit of a skeletal muscle responsible for muscle contraction?
- A. Myofibril
- B. Sarcomere
- C. Tendon
- D. Myoglobin
Correct Answer: B
Rationale: The correct answer is B, 'Sarcomere.' The sarcomere is indeed the functional unit of a skeletal muscle responsible for muscle contraction. It is composed of actin and myosin filaments that interact to generate muscle contraction. Choice A, 'Myofibril,' is incorrect as myofibrils are composed of sarcomeres, not the functional units themselves. Choice C, 'Tendon,' is incorrect as tendons connect muscles to bones and do not directly participate in muscle contraction. Choice D, 'Myoglobin,' is incorrect as myoglobin is a protein that stores oxygen in muscle cells and is not directly involved in muscle contraction.
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Which of the following organs is responsible for churning and mechanically breaking down food?
- A. Small intestine
- B. Large intestine
- C. Stomach
- D. Esophagus
Correct Answer: C
Rationale: The correct answer is C, the stomach. The stomach is responsible for churning and mechanically breaking down food. It contains muscles that contract and relax to mix food with digestive juices, breaking it down into smaller particles. This mechanical digestion process helps prepare the food for further digestion and absorption in the small intestine. The small intestine is primarily responsible for the absorption of nutrients, not for mechanical digestion. The large intestine absorbs water and salts, and the esophagus is a muscular tube that transports food from the mouth to the stomach, not involved in churning or breaking down food.
What is the periodic table?
- A. A table of elements that are arranged in order of increasing atomic number.
- B. A table of elements that are arranged in order of increasing atomic mass.
- C. A table of elements that are arranged in order of their reactivity.
- D. A table of elements that are arranged in order of their color.
Correct Answer: A
Rationale: The periodic table is a tabular arrangement of the chemical elements, organized based on their atomic number, electron configurations, and recurring chemical properties. Elements are placed in rows (periods) and columns (groups) with similar properties. The elements are listed in order of increasing atomic number, which is the number of protons in the nucleus of an atom. This arrangement reveals a periodic repetition of chemical properties, forming the basis of the periodic law. Choice B, which suggests arranging elements based on increasing atomic mass, is incorrect because the periodic table is primarily organized by atomic number, not atomic mass. Choices C and D are also incorrect as the periodic table is not based on reactivity or color of elements, but rather on atomic number and properties.
A rocket blasts off from Earth. What is the main force propelling the rocket upwards?
- A. Gravitational force
- B. Air resistance
- C. Thrust from the rocket engine
- D. Normal force from the launchpad
Correct Answer: C
Rationale: The main force propelling the rocket upwards is the thrust from the rocket engine. Thrust is the force produced by the rocket engine pushing exhaust gases in the opposite direction, following Newton's third law of motion (action and reaction). This thrust overcomes the force of gravity and allows the rocket to lift off and move upwards. Choice A, gravitational force, is incorrect as gravity pulls objects towards the Earth, and in this case, the rocket is moving against gravity. Choice B, air resistance, is incorrect because it opposes the motion of the rocket and is more relevant during descent rather than ascent. Choice D, normal force from the launchpad, is incorrect as this force acts perpendicular to the surface and does not propel the rocket upwards.
The adrenal cortex produces a group of steroid hormones called corticosteroids. What is a MAJOR function of corticosteroids?
- A. Regulate insulin sensitivity and blood sugar levels
- B. Control blood pressure and electrolyte balance
- C. Stimulate the immune system and inflammatory response
- D. Promote growth and development during puberty
Correct Answer: B
Rationale: Corticosteroids, produced by the adrenal cortex, primarily function to control blood pressure and electrolyte balance. One of the key corticosteroids, aldosterone, plays a crucial role in regulating sodium and potassium levels in the body. This regulation is essential for maintaining blood pressure and electrolyte balance. Choices A, C, and D are incorrect because corticosteroids do not primarily regulate insulin sensitivity and blood sugar levels, stimulate the immune system and inflammatory response, or promote growth and development during puberty. While corticosteroids can have effects on insulin sensitivity, immune response, and growth, their major role is in maintaining blood pressure and electrolyte balance.
Why are noble gas elements generally unreactive?
- A. They are too large and cannot form bonds easily.
- B. They lack valence electrons in their outermost shell.
- C. They have strong bonds within their own molecules.
- D. They have already achieved stable electron configurations.
Correct Answer: D
Rationale: The correct answer is D. Noble gas elements are generally unreactive because they have already achieved stable electron configurations by having a full outer electron shell. This full shell makes them very stable and unlikely to gain, lose, or share electrons with other elements. Choices A, B, and C are incorrect because noble gases are not unreactive due to being too large to form bonds easily (A), lacking valence electrons in their outermost shell (B), or having strong bonds within their own molecules (C).