Question

Do eukaryotes that have chloroplasts also have mitochondria? Do eukaryotes that have mitochondria also have chloroplasts? Use the answers to these questions to explain why it is believed that the first endosymbiotic event was the introduction of the mitochondria into a proto-eukaryote

Answer 1

Animal and fungi cells are eukaryotic, but they do not have chloroplasts. They have mitochondria.

Plant cells contain both mitochondria and chloroplasts.

In fact, they have totally different functions, and without mitochondria plants would die pretty quickly. Mitochondria produce energy from organic compounds. Chloroplasts produce organic compounds from CO2, H2O and solar energy. Both are needed in plants.

In eukaryotes, the mitochondria and chloroplasts perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria. In prokaryotes similar processes occur across the cell membrane; endosymbionts are extremely rare.

Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis

The engulfed prokaryotic cell remained undigested as it contributed new functionality to the engulfing cell (e.g. photosynthesis)

Over generations, the engulfed cell lost some of its independent utility and became a supplemental organelle.

Mitochondria and chloroplasts are both organelles suggested to have arisen via endosymbiosis

Evidence that supports the extracellular origins of these organelles can be seen by looking at certain key features:

• Membranes (double membrane bound)
• Antibiotics (susceptibility)
• Division (mode of replication)
• DNA (presence and structural composition)
• Ribosomes (size)