Question

Study the following and choose the correct statements.
• Sarcoplasmic reticulum is the store house of calcium ions.
• Thin filament of a myofibril is formed by actin, troponin and myosin molecules.
• Thick filaments of myofibril are held together by M-line.
• The portion of myofibril between two successive M-lines is called sarcomere.

• A. I, III
• B. II, IV
• C. I, II
• D. III, IV

Hint:

Muscle facts: \[ \boxed{ \begin{aligned} &\text{SR} &&\rightarrow \text{Stores Ca}^{2+} &\text{Thin filament} &&\rightarrow \text{Actin + Tropomyosin + Troponin} &\text{Thick filament} &&\rightarrow \text{Myosin} &\text{Sarcomere} &&\rightarrow \text{Between two Z-lines} \end{aligned} } \]

Answer 1

The Correct Option is A

Step 1: Examine each statement. \[ \begin{aligned} I. &\text{True} &&\text{Sarcoplasmic reticulum stores Ca}^{2+}\text{ ions.} II. &\text{False} &&\text{Thin filament contains actin, troponin and tropomyosin, not myosin.} III. &\text{True} &&\text{Thick filaments are held together by the M-line.} IV. &\text{False} &&\text{Sarcomere extends between two successive Z-lines.} \end{aligned} \]

Step 2: Identify the correct statements. \[ \boxed{\text{I and III}} \]

Step 3: Choose the correct option. Hence, \[ \boxed{(A)} \] is the correct answer.