Similarities in Structure of Mitochondria & Chloroplasts | Sciencing
Similarities in Structure of Mitochondria & Chloroplasts. By Drew Lichtenstein Evolutionary Relationships Between Prokaryotes & Eukaryotes. misjon.info! This tutorial introduces mitochondria. Other sections include plants, animal systems, invertebrates, vertebrates, and microorganisms. Like mitochondria, chloroplasts also have their own DNA and ribosomes. Endosymbiosis (endo-= within) is a relationship in which one organism lives inside.
Difference Between Chloroplast and Mitochondria | Structure, Function, Comparison
Both chloroplasts and mitochondria generate ATP by chemiosmosis, but they use different sources of energy. Mitochondria transfer chemical energy from food to ATP. Chloroplasts transform light energy into the chemical energy of ATP. Mitochondria can be found in animal cells and Chloroplasts can be found in plant cells. In mitochondria, protons are pumped to the intermembrane space and drive ATP synthesis. In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into stroma.
History[ edit ] Schimper, Mereschcowsky, Wallin and The Symbiogenesis Theory InFrench botanist Andreas Franz Schimper — observed that the division of chloroplasts was similar to that of the free-living cyanobacteria. Schimper would later propose in a footnote that symobiotic union of organisms lead to the evolution of green plants.
He was the first to study and describe the potential endosymbiotic nature in these cells. While conducting research on lichen, Russian biologist and botanist Konstantin Mereschcowsky — formulated the symbiogenesis theory. Inhe first suggested the idea of plastids originating as endosymbionts, which argued that symbiosis was the main driving force of evolution.
Difference Between Chloroplast and Mitochondria
Mereshcowsky published his finding of mitochondria in his work, Symbiogenesis and the Origin of Species in collaboration with Ivan Wallin. Mereschocowky proposed that smaller and less complex cells formed symbiotic relationships with larger complex cells. Mereshcowsky believed that many large complex cells like chloroplasts evolved through this process.
Alongside Mereschocowsky, he published his works in "Symbiogenesis and the Origin of Species". American biologist Ivan Emanuel Wallin — proposed, after studying and working with mitochondria, that species derived from bacteria have origins in endosymbiosis. He was the first to suggest the idea that the eukaryotic cell was composed of microorganisms. Chemiosmotic generation of ATP in chloroplasts and mitochondria.
In mitochondria, electron transport generates a proton gradient across the inner membrane, which is then used to drive ATP synthesis in the matrix. In chloroplasts, the proton gradient is more The Chloroplast Genome Like mitochondriachloroplasts contain their own genetic system, reflecting their evolutionary origins from photosynthetic bacteria. The genomes of chloroplasts are similar to those of mitochondria in that they consist of circular DNA molecules present in multiple copies per organelle.
However, chloroplast genomes are larger and more complex than those of mitochondria, ranging from to kb and containing approximately genes.
The chloroplast genomes of several plants have been completely sequenced, leading to the identification of many of the genes contained in the organelle DNAs. These chloroplast genes encode both RNAs and proteins involved in gene expression, as well as a variety of proteins that function in photosynthesis Table In contrast to the smaller number of tRNAs encoded by the mitochondrial genome, the chloroplast tRNAs are sufficient to translate all the mRNA codons according to the universal genetic code.
In addition to these RNA components of the translation system, the chloroplast genome encodes about 20 ribosomal proteins, which represent approximately a third of the proteins of chloroplast ribosomes.
Some subunits of RNA polymerase are also encoded by chloroplasts, although additional RNA polymerase subunits and other factors needed for chloroplast gene expression are encoded in the nucleus. The chloroplast genome also encodes approximately 30 proteins that are involved in photosynthesisincluding components of photosystems I and II, of the cytochrome bf complex, and of ATP synthase.
- Compare and Contrast: Chloroplasts and Mitochondria
- Chloroplasts - Show Me the Green
- Mitochondria - Turning on the Powerhouse
In addition, one of the subunits of ribulose bisphosphate carboxylase rubisco is encoded by chloroplast DNA. Rubisco is the critical enzyme that catalyzes the addition of CO2 to ribulose-1,5-bisphosphate during the Calvin cycle see Figure 2.
Not only is it the major protein component of the chloroplast stroma, but it is also thought to be the single most abundant protein on Earth, so it is noteworthy that one of its subunits is encoded by the chloroplast genome. As with mitochondria, these proteins are synthesized on cytosolic ribosomes and then imported into chloroplasts as completed polypeptide chains.
They must then be sorted to their appropriate location within chloroplasts—an even more complicated task than protein sorting in mitochondria, since chloroplasts contain three separate membranes that divide them into three distinct internal compartments.
Protein import into chloroplasts generally resembles mitochondrial protein import Figure Proteins are targeted for import into chloroplasts by N-terminal sequences of 30 to amino acids, called transit peptides, which direct protein translocation across the two membranes of the chloroplast envelope and are then removed by proteolytic cleavage.
The transit peptides are recognized by the translocation complex of the chloroplast outer member the Toc complexand proteins are transported through this complex across the membrane.
They are then transferred to the translocation complex of the inner membrane the Tic complex and transported across the inner membrane to the stroma. As in mitochondriamolecular chaperones on both the cytosolic and stromal sides of the envelope are required for protein import, which requires energy in the form of ATP. In contrast to the presequences of mitochondrial import, however, transit peptides are not positively charged and the translocation of polypeptide chains into chloroplasts does not require an electric potential across the membrane.
Proteins are targeted for import into chloroplasts by a transit peptide at their amino terminus. The transit peptide directs polypeptide translocation through the Toc complex in the chloroplast outer membrane more Proteins incorporated into the thylakoid lumen are transported to their destination in two steps Figure They are first imported into the stroma, as already described, and are then targeted for translocation across the thylakoid membrane by a second hydrophobic signal sequencewhich is exposed following cleavage of the transit peptide.
The hydrophobic signal sequence directs translocation of the polypeptide across the thylakoid membrane and is finally removed by a second proteolytic cleavage within the lumen. When the energy from the Sun hits a chloroplast and the chlorophyll molecules, light energy is converted into the chemical energy found in compounds such as ATP and NADPH.
Those energy-rich compounds move into the stroma where enzymes fix the carbon atoms from carbon dioxide CO2. The molecular reactions eventually create sugar and oxygen O2. Plants and animals then use the sugars glucose for food and energy. Animals also breathe the oxygen gas that is released. Different Chlorophyll Molecules Not all chlorophyll is the same. Several types of chlorophyll can be involved in photosynthesis.
You will hear about chlorophyll a and b most often.
All chlorophylls are varieties of green and have a common chemical structure called a porphyrin ring. There are other molecules that are also photosynthetic. One day you might hear about carotenoids in carrots, phycocyanin in bacteria, phycoerythrin in algae, or fucoxanthin in brown algae.