Biology
The structure and function of mitochondria
Mitochondria are oval-formed organelles. They have an internal and external membrane and an intermembrane space between them—the external layer porins the proteins which permit the development of particles into and out of the mitochondrion. The space inside the internal membrane is known as the matrix; it contains proteins of the Krebs, DNA, and RNA (Van Wijk, 2016). The inner membrane is organized into cristae to build the surface region accessible for energy creation. The mitochondrion aids in cellular respiration and ATP synthesis.
The structure and function of chloroplasts
Chloroplasts are oval-formed, have two layers, an external and an internal layer, which is isolated by an intermembrane space. There are additionally many disc molded sacs called thylakoids inside the stroma, which contain chlorophyll, the shade that retains light during photosynthesis (Van Wijk, 2016). It likewise contains ribosomes and a nucleoid. The function of chloroplasts is to carry out the photosynthesis process by converting light energy to energy stored as sugar and other organic molecules.
How ancient bacteria ended up inside eukaryotic cells to give rise to mitochondria and chloroplasts
The mitochondria seem to have evolved from the Alphaproteobacteria, most of which are intracellular parasites, which suggests how they ended up inside the first eukaryotic cell. Mitochondria and chloroplasts resemble these tiny bacteria which are making their living inside eukaryotic cells. They must have been prokaryotes that ended up inside a eukaryotic cell host through phagocytosis, or they might have been parasites of the host cells. The prokaryotes then evolved to the current day mitochondria and chloroplast inside a eukaryotic cell (Lane, 2017).
Pieces of evidence supporting endosymbiosis theory
- Many similarities between mitochondria, chloroplasts, and photosynthetic bacteria such that they appear to be slightly different, and they may be said to have arisen via evolution.
- The very close range of sizes of mitochondrion and chloroplasts; they range from about 1 to 10 microns in size, if there were a large difference between the sizes, the theory would be false.
- It has been proven that the mitochondria and chloroplasts have their own DNA and that they divide independently of the cells they live in.
- As a result of the independent dividing, and the fact that the mitochondria have their own DNA, only one mitochondrial DNA is inherited by one’s mother since the egg cell and not the sperm cell has DNA (Lane, 2017).
The role of endosymbiosis in the evolution of eukaryotes
Endosymbiosis suggests that cells are inundated yet not absorbed; that they live respectively in a correspondingly benefitting relationship called symbiosis. As indicated by Margulis, mitochondria rose from endocytosis of aerobic microbes and chloroplasts from endocytosis of microscopic photosynthetic organisms. The two of them required anaerobic bacteria that would not exist in an aerobic relationship. Margulis argued that the aerobic bacteria were ingested by the anaerobic one, and each had an endurance advantage as long as their partnership sustained. The aerobic bacteria took care of the toxic oxygen from the anaerobic microorganisms and the previously ingested food and secured the high-impact symbiote (Lane, 2017). Thus, eukaryotic cells were shaped with twofold membranes; the internal lipid bilayer as the cell’s plasma layer and the external one originated from the cell that inundated it.
References
Lane, N. (2017). Serial endosymbiosis or singular event at the origin of eukaryotes?. Journal of theoretical biology, 434, 58-67.
Van Wijk, K. (2016, June). 2016 Mitochondria & Chloroplasts. Gordon Research Conferences.