About from <span>1.8 to 1.3 million years ago,</span>
Nervous System
<span>Respiratory System
</span><span>Circulatory System
</span><span>Digestive System
</span><span>Urogenital System
</span><span>Endocrine System
</span><span>Immune System</span>
Answer:
In eukaryotes, the Krebs cycle reactions take place in the mitochondrial matrix, a dense solution that surrounds the mitochondria crests: in addition to water, the matrix contains all the enzymes necessary for the biochemical reactions of the cycle, coenzymes, and phosphates.
Explanation:
