Small changes in protein structure may lead to big changes in protein structures. A. secondary; tertiary
B. primary; secondary
C. primary; tertiary
D. tertiary; secondary

B. primary; secondary

Explanation:

Small changes in primary structure can result in large changes in protein shape and function. Secondary structure describes regions where the polypeptide is folded into localized shapes. There are two types of secondary structure (alpha helix and Beta pleated sheet).

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