Final answer:
To create sketches of two 4-stranded antiparallel beta sheets with different topologies, draw zigzag lines with arrows indicating the direction from N-terminus to C-terminus, and label the termini. Then, for distinct topology, arrange the strands with hairpin turns and add hydrogen bonds with dashed lines.
Step-by-step explanation:
To sketch two 4-stranded antiparallel beta sheets with different topology, begin by understanding that beta sheets are composed of beta strands connected by hydrogen bonds. The antiparallel arrangement signifies that adjacent strands run in opposite directions, so the N-terminus of one strand is adjacent to the C-terminus of the neighboring strand.
For the first beta sheet, sketch four parallel zigzag lines to represent the polypeptide strands. Then add arrows pointing from the N-terminus to the C-terminus to show the directionality. Strands 1 and 3 will have arrows pointing left to right, while strands 2 and 4 will have arrows pointing right to left, indicating the antiparallel nature. Label the N and C termini at the ends of the strands respectively. Add dashed lines between the strands to represent hydrogen bonds.
For the second beta sheet with a different topology, consider a ribbon-like drawing with beta strands 1 and 4 running left to right, and strands 2 and 3 running right to left, with hairpin turns connecting strands 1 to 2 and 3 to 4. Again, label the N and C termini and draw dashed lines for hydrogen bonds, ensuring that the topology differs from the first beta sheet.