Final answer:
Proteolytic cleavage is a form of protein activation or modification rather than degradation, making statement D false in the context of protein modification.
Step-by-step explanation:
The question asks which statement concerning protein modification is false.
Among the options given, statement D is false because proteolytic cleavage is a specific type of protein modification where a protein is cleaved to become active or be part of a signaling pathway, whereas protein degradation refers to the process of breaking down a protein into its amino acids for disposal or recycling.
Proteolytic cleavage can be part of a protein's activation process while degradation is the breakdown of a protein when it is no longer needed or if it is damaged.
Ubiquitination involves attaching ubiquitin to a protein, often tagging it for degradation, but this process is considered a modification until the protein is actually degraded by the proteasome.
Allosteric effects can indeed positively or negatively affect protein functions, making changes to the protein's activity without altering its primary structure. Protein phosphorylation is a reversible covalent modification that can alter protein function in various ways, including changing the protein's activity, stability, or location within the cell.