The protein that forms the thick filaments in muscle sarcomeres is:
A. Troponin
B. Actin
C. Myosin
D. Tropomyosin
Answer: Option C
Solution (By JKExamLibrary)
Myosin is the motor protein forming thick filaments; its heads bind to actin thin filaments and generate force via the cross-bridge cycle. Actin forms thin filaments, troponin and tropomyosin regulate contraction. The sliding filament theory describes muscle shortening without filament length change.
Explanation:
Innate (natural) immunity is non-specific, present at birth, and provides the first line of defense. It includes physical barriers (skin), phagocytes, and chemical defenses. Adaptive immunity is acquired and specific.
Explanation:
The nephron is the microscopic structural and functional unit that filters blood and forms urine. It consists of the renal corpuscle (glomerulus + Bowman's capsule) and tubules. Alveoli are lung units, neurons are nerve cells, hepatocytes are liver cells. Each kidney contains about one million nephrons.
Explanation:
Reptiles generally have a three-chambered heart with two atria and one partially divided ventricle; crocodiles are an exception with a four-chambered heart. Amphibians have a three-chambered heart with two atria and one undivided ventricle. Mammals and birds have four-chambered hearts. This adaptation reflects their metabolic demands and evolutionary advancement.
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