Mitochondria - notes from first year PDF

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notes from first year...

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Mitochondria Mitochondria are membrane bound organelle that are present within eukaryotic cells and its main function is to synthesize ATP. The quantity is determined by the cells need of ATP (the number of ATP is tissue specific) for example, sperm cells need a lot of ATP. The mitochondria are placed in the spiral shape of the sperm cell as it needs to contract. mitochondria are dynamin organelles as they have multiple functions such as, producing ATP, plays a role in metabolism, calcium signalling etc. Mitochondria are never the same shape they constantly change, and they are referred as the power house of all cells in the eukaryotes. Mitochondria have their own genome as well as nuclear genome, and the mitochondria and the associated DNA is only passed on by the mother. Structure: Mitochondria contain the smooth outer membrane and a markedly folded or tubular inner mitochondrial membrane, this has a large surface and encloses the matrix space. The inner membrane folds are known as the cristae and the intermembrane is located between the two different types of membranes. Mitochondria number and shape varies depending on the cell type and need of mitochondria also, its affected by the number of cristae the mitochondria have. So, the tissues which require intensive oxidation metabolism e.g. heart muscle, they have mitochondria which has high number of cristae. The shape is dependent on the functional status. Mitochondria are described as the power house (mobile). Both the membranes are rich in protein as protein is needed for mitochondrial functions and carrying out reactions of the electron transport chain. Function: Most important function of the mitochondria is to produce energy in the form of ATP. It does this by converting the nutrition's (food intake) into charged molecules and these combine with oxygen and produce ATP this process is known as the oxidative phosphorylation). Another function of mitochondria is to maintain the calcium ion concentration within the compartments of the cell. It helps in building blood parts such as testosterone and estrogen. Mitochondria within the liver cells have enzymes that detoxify ammonia. History of mitochondria: It's said that the mitochondria developed during an early phase of evolution from aerobic bacteria which entered symbiosis with primeval anaerobic eukaryotes. The mitochondrial genome became smaller and smaller over time. In humans the genome is still around 16,569 base pairs which code for two rRNAs and 22 tRNAs and 13 proteins (only them 13 are produced in the mitochondrion) mitochondria and chloroplast both evolved from endosymbiotic bacteria.

https://alevelbiology.co.uk/notes/mitochondria-structure-and-functions/ Localization of metabolic functions within the mitochondria:   

Outer membrane: phospholipids synthesis, fatty acid desaturation and fatty acid elongation. These are the functions carried out in the outer membrane. Matrix: pyruvate oxidation, TCA cycle, beta-oxidation of fats, DNA replication, RNA and protein synthesize (translation) Inner membrane: electron transport, oxidative phosphorylation, pyruvate import, fatty acyl coA import, metabolite transport. This has a high proportion of phospholipids which can make the membrane more permeable to ions.

Aerobic respiration: Macromolecules are broken down and goes through a multiple of oxidation reactions: 1) Glycolysis 2) Pyruvate oxidation 3) TCA cycle- Electron transport/ATP synthesis TCA cycle: The reactions produce reduced co-factors NADH and FADH2 and for each cycle the energy released by each oxidation are reduced by coenzymes. Each pyruvate produces 3CO2, (4 NADH, 1FADH2) reduced enzymes, 1ATP. The substrates involved in the TCA cycle are Acetyl COA, oxidized coenzymes, ADP and Pi. Electron transport: Electron transport is when coenzymes are reoxidised so NADH and FADH2 by the transfer of electrons to oxygen, where oxygen is the final electron acceptor. During the process of electron transport the NADH and FADH2 are reoxidised to NAD and FAD. The product consumed is oxygen and the two end products are water and carbon dioxide. The electron transport chain is an ordered series of reversible oxidized electron carriers which function together. And the transport takes place in the inner membrane of the mitochondrion and produces many ATP molecules. A) complex 1: this receives 2 electrons from NADH and this passes them to CoQ via the FMN and an FE-S protein. During this process 4H+ exit the matrix by complex 1. B) complex 111: passes electrons from CoQH2 to cytochrome c via cytochrome c via cytochromes b and c and an Fe-S protein. The CoQH2 carries 2H+ across the inner membrane and 2 more H+ exit the matrix. C) complex 1V receives electrons from the cytochrome c and via cytochrome a and a3, passes them to molecular oxygen, this reduces to water as 2 more H+ exit the matrix by complex 1V. D) ATP synthase uses the energy from the proton gradient generated during the transport to synthesize ATP from ADP and Pi. Across the inner membrane= energy stored as an electrochemical proton gradient....