Mitochondria Flashcards
what membrane binds mitochondria?
double membrane
cristae?
invaginations formed by the innner membrane
intermembrane space?
space between membranes
inside of mitochondrion?
mitochondrial matrix
which organelle generates most of the energy of the cell?
the mitochondria
how is most nutrients delivered to the mitochondria?
most nutrients delivered to the cell are broken down in the cytoplasm to simple constituents which are transported to the mitochondria
when the constituents are further oxidised, what is produced?
carbon dioxide and water, releasing energy captured in the form of ATP
Where are mitochondria often located?
close to sites of high ATP utilisation
adenosine?
adenine AND the sugar
where is the energy released coming from?
by the hydrolysis of the phosphoanhydride bonds
ATP –>
ADP +Pi –> AMP + Pi
what is glucose converted to in glycolysis?
pyruvate (x2)
pyruvate is converted into what during the link reaction?
acetyl coA
(you decarboxylate - remove a C and then the 2 C’s left are converted to acetyl CoA
what are fatty acids?
they are a long chain of carbons and a carboxylic acid
What are fatty acids metabolised via?
Beta oxidation.
What happens during beta oxidation of fatty acids?
It removes two carbons at a time and these two carbons are converted to acetyl-CoA
Describe the amino acid metabolism
Removal of amino group
Remainder of amino acid is in the carbon skeleton and different amino acid carbon skeletons can enter at different points of the metabolic cycle
Describe what the removal of an amino group means for different animals:
Ammonia converted to urea [in mammals, amphibians and sharks ]
Ammonia converted to uric acid [in birds, reptiles and insects ]
Ammonia excreted directly [in most fish]
what cycle does acetyl CoA feed into?
the citric acid cycle
what is the citric acid cycle also known as?
the tricarboxylic acid cycle or the krebs cycle
stage 2 of respiration?
acetyl-coA oxidation
what are the end products of the krebs cycle?
NADH and FADH2
Describe the number of CO2 given off as waste during decarboxylation’s:
one per pyruvate in the link reaction
TWO per pyruvate in TCA cycle
stage 3 of respiration?
oxidative phosphorylation
what are the roles of NADH and FADH2 in oxidative phosphorylation?
they carry the electrons for the electron transport chain
what happens to ADP and O2 during oxidative phosphorylation?
converts ADP + Pi to ATP
O2 is reduced to H20
What happens to NADH during the electron transport chain?
NADH–>NAD+ + H+ + 2e-
what happens to FADH2 during oxidative phosphorylation?
FADH2 –> FAD + 2H+ + 2e-
outline the electron transport chain:
High energy electrons pass through complexes in the inner membrane each with a higher redox potential than the last i.e. a greater affinity for electrons
final electron acceptor?
oxygen
show equation representing oxygen as the final electron acceptor:
2H+ + 1/2 O2 + 2e- –> H2O
Complex 1 of the electron transport chain in oxidative phosphorylation?
NADH dehydrogenase
Complex 2 of the electron transport chain in oxidative phosphorylation?
succinate dehydrogenase
Complex 3 of the electron transport chain in oxidative phosphorylation?
cytochrome b-c1 complex
complex 4 of the electron transport chain in oxidative phosphorylation?
cytochrome oxidase
other than the 4 complexes involved in the electron transport chain, what else is involved?
coenzyme Q (or ubiquinone)
AND cytochrome C
where are mitochondria often located?
close to sites of high ATP utilisation
how do fatty acids become acetyl coA?
Beta oxidation, in mitochondrial matrix
why does the electron pass down through the complexes?
the transfer of electrons goes from a lower to higher affinity BECAUSE it is energetically favourable
what is the energy released for?
used to pump H+ into the intermembrane space
where is the electrochemical gradient generated?
across the inner mitochondrial membrane
environment in inner mitochondrial membrane compared to matrix?
more acidic
ATP synthase?
enzyme that utilises energy from the electrochemical gradient to regenerate ATP from ADP + Pi
chemiosmosis?
hydrophilic pathway for H+ to flow down electrochemical gradient - it is energetically favourable
what does the H+ cause?
causes rotation of the transmembranous rotor domain stalk (attached)
how do we create energy from electron transport chain?
enzymatic head held still by an arm attached to the membrane
the mechanical energy as the stalk grinds against the head is converted to chemical energy
describe the structure of the outer membrane of the mitochondria?
it contains large pores made of proteins called porins and is therefore permeable to molecules of <5 kDa
how do oxygen and carbon dioxide move?
via simple diffusion
control across the inner membrane?
more tightly controlled than outer
electrochemical gradient used for?
to drive transport of other compounds
describe transport of pyruvate and inorganic phosphate?
transport is driven by H+ gradient… they are co-transported in the same direction (symporter)
describe the transport of ATP and ADP:
they are co-transported in opposite directions using the charge gradient - antiporter
where are most of the proteins destined for the mitochondria encoded and by what?
encoded in the nucleus and produced by cytosolic ribosomes
MTS?
mitochondria targeting sequence
what mediates the passage into the mitochondria?
TOM and TIM membranes
TOM and TIM membranes, what do these stand for?
Translocases of the Outer (TOM) and Inner Mitochondrial membranes (TIM)
when does transport occur?
post-translational
it is energy requiring
what do mitochondria possess?
their own genetic systems
describe mitochondrial genomes:
they are circular, vary in size and number of genes encoded
describe the size of human mitochondrial DNA:
it is approx. 16.5 kb and encodes 2 rRNA, 22 tRNAs and 13 peptides
what can canine mtDNA be used for?
to determine breed origins and also in forensics
where do transcription ans translation occur for mitochondria and what are these processes carried out by?
occur in the matrix and carried out by comp;exes unique to the organelle
mitochondrial DNA inheritance?
maternally inherited
how do mitochondria grow and divide?
by fission
where did mitochondria originate from?
endosymbiosis
what do mitochondria have of their own?
own fission, own genome, own translation and own transcription processes
apoptosis?
release of cytochrome c (& other pro-apoptotic molecules) from the intermembrane space which triggers cells to undergo programmed cell death
what store does mitochondria act as?
as a calcium store
what do mitochondria regulate?
regulation of the cellular redox state
how do mitochondria regulate the cellular redox state?
electron carriers produce reactive oxygen species
extensive network of antioxidant defences
imbalance between ROS production and removal - cellular damage disrupt functions and promote cancer
ROS?
Reactive oxygen species
Haeme synthesis - mitochondrial functions:
many enzymes and carrier molecules have a co-ordinated haeme group at their active site - this is synthesised in the mitochondria
steroid synthesis - mitochondrial functions:
some steps of steroid synthesis occur in the mitochondria
what cell specific functions occur in the mitochondria?
e.g. mitochondria in hepatocytes contain enzymes that detoxify ammonia
4 exmples of the clinical relevance - mitochondrial toxicity?
TCA cycle inhibitors
Electron transport inhibitors
Uncoupling agents
Mitochondrial transporter inhibitors
tca cycle?
tricarboxylic acid cycle
give one example of a tca cycle inhibitor:
arsenite inhibits pyruvate dehydrogenase (pyruvate to acetyl CoA)
give a second example of a tca cycle inhibitor:
2-fluorocitrate irreversibly inhibits aconitase in the 2nd step (of 8) in the TCA cycle
how can environmental toxins inhibit electron transport?
they can prevent the passing of electrons by binding to one or more of the proteins that carry electrons.
give one example of electron transport inhibitors:
rotenone (an insecticide) binds to NADH dehydrogenase complex (complex I) of the electron transport chain
give a second example of electron transport inhibitors:
cyanide ions bind tightly to the iron atom of cytochrome c oxidase (complex IV) and block electron transport
give an example of uncoupling agents:
2,4-dinitrophenol (used in making dyes) is a low molecular weight organic compound which uncouples electron transport from ATP synthesis
give an example of mitochondrial transporter inhibitors:
the transporter which brings ADP out of the mitochondria is inhibited by bongkrekic acid (an antibiotic from mould)
explain how a lipid soluble weak acid acts as uncoupling agents - where is it found?
sits in the inner membrane and acts as a H+ carrier i.e. it dissipates the electrochemical gradient and therefore although electrons are transported, no gradient builds up and no ATP is synthesised.
pH of intermembrane space?
pH 7
pH of matrix?
8
