Nokea
Which structure in the skin is responsible for producing melanin?
- A. Sudoriferous gland
- B. Melanocyte
- C. Sebaceous gland
- D. Hair follicle
Correct Answer: B
Rationale: The correct answer is B: Melanocyte. Melanocytes in the skin are responsible for producing melanin, the pigment that gives skin its color and provides protection against harmful UV radiation. Sudoriferous glands produce sweat, sebaceous glands produce sebum (oil), and hair follicles are associated with hair growth. However, the specific function of producing melanin is attributed to melanocytes, making them the correct answer in this context.
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Which hormone regulates the sleep-wake cycle?
- A. Cortisol
- B. Melatonin
- C. Thyroxine
- D. Insulin
Correct Answer: B
Rationale: The correct answer is B: Melatonin. Melatonin, produced by the pineal gland, is the hormone that regulates the sleep-wake cycle. It helps signal to the body when it's time to sleep and wake up, playing a crucial role in maintaining a healthy sleep pattern. Choice A, Cortisol, is known as the stress hormone and plays a role in the body's response to stress, not specifically in regulating the sleep-wake cycle. Choice C, Thyroxine, is a hormone produced by the thyroid gland that regulates metabolism, not the sleep-wake cycle. Choice D, Insulin, is a hormone produced by the pancreas that regulates blood sugar levels, not the sleep-wake cycle.
Which of the following statements is NOT true about DNA?
- A. DNA contains the nucleotides A, T, C, G and is read 5' to 3'.
- B. DNA contains genetic information and is tightly coiled with proteins to form chromosomes.
- C. DNA contains the nucleotides A, T, C, G and is read 3' to 5'.
- D. DNA is a double-stranded molecule connected by hydrogen bonds.
Correct Answer: C
Rationale: The correct answer is C because DNA is typically read from the 5' end to the 3' end, not from 3' to 5'. Choices A, B, and D are all true statements about DNA. DNA contains the nucleotides A, T, C, G and is read in a 5' to 3' direction. DNA also contains genetic information and is tightly coiled with proteins to form chromosomes. Additionally, DNA is a double-stranded molecule connected by hydrogen bonds.
What type of joint connects the bones of the skull?
- A. Hinge joint
- B. Fibrous joint
- C. Ball-and-socket joint
- D. Pivot joint
Correct Answer: B
Rationale: The correct answer is B: Fibrous joint. Fibrous joints connect the bones of the skull, providing stability with little to no movement. These joints are made of fibrous connective tissue, which holds the bones tightly together and prevents movement, making them ideal for the structure of the skull.
Choice A: Hinge joint is incorrect because hinge joints allow movement in a single plane like the elbow or knee, which is not characteristic of the joints in the skull.
Choice C: Ball-and-socket joint is incorrect as this type of joint allows for a wide range of movement in multiple planes, such as the hip and shoulder joints, which is not the case for skull bones.
Choice D: Pivot joint is incorrect as pivot joints allow rotation around a central axis, as seen in the joint between the first and second cervical vertebrae (atlas and axis), but not in the skull bones.
Which part of the brain is responsible for voluntary muscle movements?
- A. Medulla oblongata
- B. Cerebrum
- C. Hypothalamus
- D. Thalamus
Correct Answer: B
Rationale: The question inquires about the brain region responsible for voluntary muscle movements. The correct answer is the Cerebrum. The cerebrum is the main part of the brain involved in voluntary muscle control and motor coordination. The Medulla oblongata is primarily responsible for regulating vital functions like breathing and heart rate, not voluntary muscle movements. The Hypothalamus plays a role in regulating body temperature, thirst, hunger, and other homeostatic processes. The Thalamus serves as a relay station for sensory information but is not directly responsible for voluntary muscle movements.
What is the primary mode of CO2 transport in the body?
- A. Bicarbonate
- B. Carbamino compounds
- C. None of these
- D. Plasma
Correct Answer: A
Rationale: The correct answer is A: Bicarbonate. In the body, the primary mode of CO2 transport is as bicarbonate. Carbon dioxide is converted to bicarbonate in red blood cells as part of the bicarbonate buffer system, which helps maintain the pH balance in the blood. Bicarbonate is then transported in the plasma to the lungs where it is converted back to carbon dioxide for exhalation. While carbamino compounds also play a role in CO2 transport by binding to amino groups on proteins, bicarbonate is the main mode of transport for carbon dioxide in the body. Options B, C, and D are incorrect as they do not represent the primary mechanism of CO2 transport in the body.