Nokea
What happens when a protein unfolds?
- A. Activation
- B. Denaturation
- C. Renaturation
- D. Folding
Correct Answer: B
Rationale: - Activation (Option A) refers to the process of initiating or increasing the activity of a molecule, such as an enzyme. Protein unfolding does not involve activation.
- Denaturation (Option B) is the correct answer. Denaturation refers to the process by which a protein loses its three-dimensional structure, leading to the disruption of its function. This can be caused by factors such as heat, pH changes, or chemicals.
- Renaturation (Option C) is the process by which a denatured protein regains its native structure and function. Protein unfolding is the opposite of renaturation.
- Folding (Option D) is the process by which a protein assumes its functional three-dimensional structure. Unfolding is the reverse process of folding, not folding itself.
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Which of the following describes the difference between prokaryotic and eukaryotic cells?
- A. Prokaryotic cells have a nucleus, while eukaryotic cells don't.
- B. Eukaryotic cells are simpler in structure than prokaryotic cells.
- C. Prokaryotic cells have membrane-bound organelles, while eukaryotic cells don't.
- D. Eukaryotic cells have a true nucleus and membrane-bound organelles, while prokaryotic cells lack these.
Correct Answer: D
Rationale: Eukaryotic cells have a true nucleus that contains the genetic material, while prokaryotic cells lack a true nucleus. Eukaryotic cells also have membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus, which are absent in prokaryotic cells.
Which hormone is responsible for regulating sleep-wake cycles and is influenced by light exposure?
- A. Melatonin
- B. Cortisol
- C. Estrogen
- D. Glucagon
Correct Answer: A
Rationale: The correct answer is A: Melatonin. Melatonin is the hormone responsible for regulating sleep-wake cycles, also known as the circadian rhythm. Its production is influenced by light exposure, with levels increasing in the evening in response to darkness, signaling the body that it is time to sleep. Choice B, cortisol, is a stress hormone and does not directly regulate sleep-wake cycles. Choice C, estrogen, is a sex hormone and is not primarily involved in regulating sleep. Choice D, glucagon, is a hormone that increases blood glucose levels and is not related to sleep-wake cycles.
How much sugar is in a 1 M solution of sugar water?
- A. 1 L of water
- B. 100 mL of solution
- C. Every 100 g of water
- D. It depends on the type of sugar
Correct Answer: B
Rationale: A 1 M solution of sugar water contains 1 mole of sugar in 1 liter of solution. Since 1 M (molar) solution means there is 1 mole of solute (sugar) dissolved in 1 liter of solvent (water), the correct answer is 100 mL of solution. Choice A, '1 L of water,' is incorrect because it does not specify the total volume of the solution. Choice C, 'Every 100 g of water,' is incorrect as it focuses on the weight of water, not the volume of the solution. Choice D, 'It depends on the type of sugar,' is incorrect since the concentration of a 1 M solution is standardized and does not vary based on the type of sugar used.
What is the purpose of the periosteum, the tough outer layer of bone?
- A. Produces red blood cells
- B. Provides protection and nourishment to bone
- C. Forms the joint surface
- D. Stores minerals
Correct Answer: B
Rationale: The periosteum, the tough outer layer of bone, serves the purpose of providing protection to the bone and nourishing it through the blood vessels it contains. It acts as a protective layer for the bone structures. Choices A, C, and D are incorrect because the periosteum does not produce red blood cells (which is the function of bone marrow), form joint surfaces (which is typically the role of articular cartilage), or store minerals (which is primarily done by bone tissue itself and not the periosteum).
In the context of optical fibers, chromatic dispersion refers to:
- A. The total internal reflection of light
- B. The spreading of light pulses due to different colors traveling at slightly different speeds
- C. The bending of light at the fiber core-cladding interface
- D. The absorption of light by the fiber material
Correct Answer: B
Rationale: Chromatic dispersion in optical fibers refers to the spreading of light pulses due to different colors (wavelengths) traveling at slightly different speeds. This phenomenon can cause the different components of a light pulse to arrive at the receiver at slightly different times, leading to signal distortion. Choice A is incorrect because total internal reflection refers to the phenomenon where light is reflected back into the medium it originated from when hitting the boundary at an angle greater than the critical angle. Choice C is incorrect as it describes the principle of light being guided within an optical fiber through total internal reflection at the core-cladding interface. Choice D is incorrect as the absorption of light by the fiber material does not relate to chromatic dispersion.