| Criteria | Mitochondrial Protein Synthesis | Cytoplasmic Protein Synthesis (Animal Cells) | Remarks |
| Location | Occurs in the mitochondrial matrix | Occurs in the cytoplasm and on the rough endoplasmic reticulum (RER) | Spatial separation reflects different proteomes and cellular roles |
| Ribosomes Involved | Mitochondrial ribosomes (55S–60S, prokaryote-like) | Cytoplasmic ribosomes (80S, eukaryotic) | Mitoribosomes resemble bacterial ribosomes structurally and functionally |
| Genetic Material Source | Encoded by mitochondrial DNA (mtDNA) | Encoded by nuclear DNA (nDNA) | mtDNA codes for only 13 polypeptides; rest of the mitochondrial proteome is nuclear-encoded |
| mRNA Features | Lacks 5′ cap and poly-A tail; often polycistronic | Typically monocistronic with 5′ cap and 3′ poly-A tail | Reflects simpler, prokaryote-like gene expression system in mitochondria |
| Initiation Mechanism | Uses unique mitochondrial initiation factors (e.g., mtIF2); bacterial-like mechanism | Uses eukaryotic initiation factors (eIFs) and scanning model | Initiation machinery differs significantly |
| Genetic Code Used | Modified genetic code (e.g., UGA codes for tryptophan) | Universal genetic code | Genetic code deviations are critical for mitochondrial specificity |
| Translation Inhibitors | Sensitive to antibiotics targeting bacterial translation (e.g., chloramphenicol, tetracycline) | Sensitive to eukaryotic inhibitors (e.g., cycloheximide) | Useful for selectively blocking mitochondrial vs. cytoplasmic translation in experiments |
| Protein Targeting | Translates proteins for use in oxidative phosphorylation complexes | Produces all structural and functional proteins of the cell | Proteins synthesized in cytoplasm may be imported into mitochondria via targeting signals |
| Evolutionary Origin | Derived from endosymbiotic α-proteobacteria | Result of eukaryotic genome evolution | Mitochondrial synthesis retains bacterial features due to evolutionary origin |
