Biology 140 notes Feb 12, 2009

Organelles and the origin of Eukaryotes Mitochondrion and chloroplast: Mitochondrion- has 4 main compartments inner membrane, inner membrane, and inter-membrane space. This is the organelle that produces ATP. Inner membrane ?cristae? made up of phospholipids bilayer. ATP main energy storage molecule in eukaryotic cells. We ingest the carbohydrates which are turned into ATP which is where we really get our energy not the actual carbohydrates. Chloroplast ? Also double membrane organelle. Exclusive to plant cells only. Thylakoid ?the light reaction in photosynthesis occurs here. They are green and are stacked on top of each other. Thylakoid membrane is where chlorophyll is embedded. This membrane is therefore the ?structural unit of photosynthesis.? The Thyladoid membrane is the most abundant membrane on Earth. Cellulose is the most organic molecule on Earth. This thylakoid membrane is where the light dependent reaction occurs. The stroma is where the light independent reaction occurs. Origin of Eukaryotes Mitochondrian and chloroplasts are now known to have been independent bacteria prokaryotic cells that were ingested and now a part of a eukaryotic cell. Origin of the nucleus and endoplasmic reticulum. ? In-folding of membrane leads to nucleus and ER. It?s hypothesized that the nuclear membrane is the consequence of in folding membrane. This causes the DNA to cluster. Over time a nucleus was formed with an in folding of the membrane causing a double membrane (nuclear envelope) around the DNA I.E. nucleus. Symbiosis: living together (usually in a mutually beneficial situation). Ex. Lichens is algae and fungus who have a symbiosis relationship. The fungus gets carbohydrates from algae because it cannot produce its own food. We are not sure what algae get from fungi. Possibly habitat or nutrients. Endosymbiosis: a mutually beneficial interdependence between two species, one of which resides permanently inside the other?s body. Mitochondrian and chloroplasts were at one time interdependently living bacteria that were engulfed and became organelles. The pre-Cambrian Era: Origin of Eukaryotes occurred only after oxygen accumulated in atmosphere. Origin of cyanobacteria (3.5 bya) origin of eukaryotes (2.0 BYA) accumulation of oxygen in atmosphere about 2.5 BYA. Oxygen is highly electronegative and combines with almost any other element. However at that time oxygen was toxic and could kill things. A bacterium with infolded membrane capable of aerobic metabolism (?respiration?) Origin of Mitochondrion ? Aerobic metabolism results in a more complete breakdown of carbohydrates than does anaerobic metabolism. More ATP is formed. This was a huge adaptation with a great selective benefit. Bacterium with infolded membrane capable of aerobic metabolism. Mitochondrian thought to have evolved from purple bacteria. Origin of mitochondrian. Basically the predator engulfs this ATP making factory so it can get food easier. And the mitochondrian is able to obtain carbohydrates from the bigger cell without having to search for it. Double membranes result from engulfing of bacterium. Sequence of endoxymbiotic events leading to origin of mitochondrion and chloroplasts. Primary endosymbiosis ( secondary endosymbiosis ( tertiary endosymbiosis Two membranes ( three membranes ( four membranes Evidence in support of the endsymbiotic theory (for both mitochondria and chloroplasts): They divide independently of host cell, under their own genetic control and DNA. They have DNA similar to bacterial DNA (i.e. occurs as small loops; DNA not complexed with histone) Have tRNA and RNA polymerase similar to bacteria. Have small, unique ribosome?s similar to bacteria. Protein synthesis is inhibited by antibiotics specific for bacteria. Antibiotics can break down cell walls. You could potentially break down your protein producing mitochondria in your body but they usually leave eukaryotic cells alone.