Question

1. figure 9.3 is a diagrammatic representation of a small portion of a relaxed muscle cell (the bracket indicates the portion that has been enlarged). first, select a different color for each of the structures with a coding circle. color the coding circles and the corresponding structures on figure 9.3. when you have finished, bracket and label an a band, an i band, and a sarcomere. then, match the numbered lines (1, 2, and 3) in part b to the cross sections in part c.

thin myofilaments
thick myofilaments
z discs
(figure 9.3 includes diagrams labeled a, b, c with muscle cell structures and cross - sections)

Explanation:

To solve the matching of numbered lines in part B to cross - sections in part C:

1. Recall the structure of muscle filaments in cross - section:

• Thick myofilaments (myosin) in cross - section appear as a central bundle (like in part C, section 1: dots arranged in a circle, representing thick filaments).
• Thin myofilaments (actin) around thick filaments: In section 2 of part C, the circles are arranged in a pattern consistent with thin filaments alone (no thick filaments in the center).
• At the Z - disc region (where thin filaments are anchored), the cross - section (part C, section 3) shows a mix of thin filaments and the Z - disc structure (the more complex arrangement with both small dots and circles, representing the area with thin filaments and Z - disc - associated structures).
• Line 1 in part B: Looking at the arrangement, it should correspond to the cross - section with thick myofilaments (part C, 1). Line 2 in part B (likely through the I - band or thin - filament - only region) corresponds to part C, 2. Line 3 in part B (through the A - band or region with both thick and thin filaments and Z - disc - related) corresponds to part C, 3.
• So, 1 in B matches 1 in C (thick myofilaments cross - section), 2 in B matches 2 in C (thin myofilaments cross - section), 3 in B matches 3 in C (Z - discs and associated thin filaments cross - section).

Answer:

1 in B matches 1 in C; 2 in B matches 2 in C; 3 in B matches 3 in C.