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Mitochondrion and Chloroplasts (A Mitochondrion (Outer membrane = 50%…
Mitochondrion and Chloroplasts
A Mitochondrion
Plural = Mitochondria
Singular = Mitochondrion
Is a membrane enclosed organelle found in most eukaryotic cells, Mitochondia is described as cellular power plants because they generate most of the ATP.
Outer membrane = 50% protein
Contains large pore-forming proteins called Porin
Permeable to large molecules - even some proteins
Inner membrane = more than 75%
Contains cardiolipin but not cholesterol: Cardiolipin can stop protons crossing the membrane
Impermeable to even small molecules
Evolved by endosymbiosis
Inner membrane proteins with five types of functions
Those that preform redox reactions of oxidative phosphorylation
ATP synthase, which generate ATP in the matrix
Specific transport proteins that regulate metabolite passage into and out of the matrix
Protein import machinery
Mitochondria Fusion and Fission protein
Mitochondrial Matrix
Contains Circular DNA, Ribosomes and enzymes
RNA and proteins can be synthesised in the matrix of the mitchondrion
To make functional mitochondria we use proteins coded by the nucleus and by the DNA of the mitochondrion. The mitochondria DNA codes for 13 protein subunits and ribosomal and transfer RNA in mammals
Main roles
Make ATP from the krebs cycle and the electron transport chain, using oxygen as the final electron acceptor.
Roughly 32 molecules of ATP per molecule of glucose
ATP Can be formed by glycolysis or oxidative phosphorylation in mitochondria
Accounts for 160kg of ATP in our bodies per day, the body contains approx 250g of ATP
Mitochondrial Functions
Heme biosynthesis
Steroid synthesis
Metabolism of fatty acids
Regulation of the cellular redox state
Calcium homeostasis
Amino acid and protein metabolism
Carbohydrate metabolism
Involved in programmed cell death
Hibernating animals have specialised mitchondria in their brown fat: these have a specialised channel protein that allows protons to return through the membrane and not make ATP.
The energy associated with this is lost as heat
Other mitochondria
Hydrogenosomes
related closely to unicellular eukaryotes, lack an electron transport chain. They synthesise ATP from pyruvate breakdown via simple fermentation. (Roughly 4 mol of ATP per mole of glucose)
Endosymbiotic Origin of Mitochondria
Early prokaryotic cell (that could use oxygen) was engulfed by a primitive cell.
By- products of oxygen metabolism (radicals) cause damage to molecules in the mitochondria
Photosynthesis converts energy from sunlight into chemical energy stored in carbohydrates using the chloroplasts.
Low energy electrons are removed from a donor molecule
Takes place in chloroplasts.
Have a double membrane
Outer membrane contains porins and is permeable to large molecules.
Inner membrane contains light- absorbing pigment, electron carriers, and ATP - synthesising enzymes
Chloroplast structure:
Inner membrane: folded into flattened sacs (thylakoids), arranged in stacks called grana
Self replicating organelles with their own DNA
Site of carbon dioxide fixation is the stroma
Evolved by endosymbiosis
Photosynthesis is a
REDOX
reaction transferring an electron from water to carbon dioxide
Oxidizes water to oxygen; Respiration reduced oxygen to form water
Respiration removes high energy electrons from reduced organic substrates to from ATP and NADH
Photosynthesis uses low energy electrons to form ATP and NADPH, which are then used to reduce carbon dioxide to carbohydrate.