mitochondria Flashcards
functions
- obtaining energy from food
- oxidative phosphorylation
- cell biology in human disease
the powerhouse of the cell - ATP is produced via areobic respiration:
all cells can make ATP - occurs via glycolysis in bacteria and in simple cells
Eukaryotic cells make ATP via oxygen in respiration
Mitochondrial proteins
the get their proteins fro various processes :
transmembrane transport
contain small circular DNA and ribosomes that resemble those in bacteria- this means that they can make some of their own proteins
Mitochondrial energy metabolism
pyruvate and fatty acids enter the mitochondria and are converted into :
Acetyl CoA in the kreb’s cycle (citric acid cycle)
krebs cycle produces NADH and CO2
NADH is a product of oxidative phosphorylations = produces ATP & H2O
mitochondrial membranes
surrounded by a double membrane - there is a clear distinction between the 2
both membranes have specific functions
outer membrane is smooth and continuous
krebs cycle occurs in the mitochondria :
the inner membrane has a high surface area - lots of folds and projections called cristae THIS IS WHERE ATP IS MADE !!
Mitochondria have very different proteins and lipids compared to the rest of the cell
some are very similar to bacterial lipids and proteins
the inner membrane is enriched in CARDIOLIPIN- this lipid isn’t found anywhere else in the cell
CARDIOLIPIN:
has 4 fatty acid tails (most have 2)
FUNCTION : increase the selectivity and impermeability of the inner membrane
matrix
large internal space contains highly concentrated mixture of 100s of enzymes including the ones for the oxidation of pyruvate and fatty acids and the ones needed for the citric acid cyclea
also contains several identical copies of the mitochondrial DNA ,genome, special mitochondrial ribosomes , RNA and various enzymes required for expression of mitochondrial genes
inner membrane :
SURFACE AREA AND PROTON GRADIENT
ATP is formed on the inner surface of the INNER membrane
when the proton gradient is used to push together phosphate and ADP into ATP]
1) electron transport drives the pump that pumps protons across the membrane
2) protein gradient is harnessed by ATP synthase to make ATP
proton gradient in terms of pH
has a lot of energy - it has a electrical energy because its a separation of change and conc energy because it has a high conc outside the membrane
-log(pH of protein gradient)=pH
Protons go down their electrical and con gradient from one side of the inner membrane to the other
as they do that the energy which is released is used to make ATP (transmembrane process )
why does the proton gradient exist ?
energy from food in the krebs cycle : NADH and FADH2 to pump protons across the membrane
as the high transport electrons NADH and FADH2 are pumped down the electron transport chain - the energy created allows the pumping of proteins across the membrane
the
the pumping of protons across the membrane releases energy used for making ATP
this process is called CHEMIO-OSMOTIC COUPLING : generation of the proton gradient (change in pH)
the electron transport chain
NADH produced from the citric acid cycle contains high energy electrons that are fed into the electron transport chain which sets up a pH gradient
the general mechanism in oxidative phosphorylation :
high energy electrons are passed down the electron transport chain via redox reactions (ie. Fe2+ to Fe3+)
the energy released is used to pump protons across the inner mitochondrial membrane
outer membrane and inter-membrane space
OUTER MEMBRANE :
it contains a large channel - forming proteins(porin) the outer membrane is permeable to all membranes
other proteins in this membrane include enzymes involved in mitochondrial lipid synthesis subsequently metabolised in the matrix
INTER-MEMBRANE SPACE :
this space contains several enzymes that used ATP passing out of the matrix to phosphorylate other nucleotides
