mitochondria 1 (hekimi) Flashcards
which biological comopent is thought to be a key determinant of life span in c elegans (and maybe in humans)
the electron transport chain
explain this
diagram shows the impact of mutating the iron sulphur protein of the mitochondrial complex 3 in the elctron transport chain. as we can see, a simple single amino acid substitution leads to a significant change in lifespan
which worm is often used in labs for experiments? why?
-c elegans
-their lifespan is only around 3 weeks, so we can see long term effects of tests on them
what is coenzyme Q?
-enzyme in the ETC
-mostly hydrophobic, but amphipatic, cause hydrophobic head
-a bunch of different enzymes are involved in its biosynthesis
which CoQ deficiency leads to Charcot-Marie-Tooth disease?
COQ7
what is Charcot-Marie-Tooth disease?
neuropathy of the peripheral nervous system characterized by progressive loss of muscle tissue and touch sensation across various parts of the body
explain this image. why is there such a large diversity in phenotype?
-showing us the different mutations in genes coding for enzymes that are involved in the biosynthesis pathway of coenzyme Q
-multiple different phenotypes possible, because different cell types have different mitochondrial activity. some rely more on specific enzymes present in the coenzyme Q synthesis pathway than others, so the mutations of specific genes involved affect some cell types more than others
true or false, coenzyme Q supplements work very well
false. coenzyme Q supplements dont work well, as their ingestion has no effect. this is due to the fact that when ingested, very little is actually taken up by the gut, therefore we are not changing amount of coenzyme Q enough to be able to make a significant change
the professor is currently working on a project to make coenzyme Q a useful supplement that we can take. explain
-CoQ in water simply floats on top, like a layer of fat, which is why its hard for our body to take it up
-he found a way to solubize CoQ with CF (carrier factor)
true or false, mitochondrial and cytoplasmic ribosomes are the same
false theyre different
true or false, mitochondrias have their own nucleus, ribosomes and DNA
FALSE, they have their own ribosomes and DNA but not nucleus
what are christae
folds in the mitochondria
true or false, the mitochondria is spacious
false, filled with stuff
what is the shape of the mitochondria?
-it is NOT bean shaped
-they are complex, dynamic filaments
-green filaments are all mitochondria surrounding nucleus
what are metazoans?
ancestral eukaryotic cells that give rise to all metazoans
what is the theory on how the mitochondria developed in eukaryotic cells
-ancestral cell (ancestral to all metazoans) symbiosis event with a prokaryote capable of oxidative phosphorylation.
-this drive for symbiosis was likely due to the fact that the eukaryotic cell wanted to be able to to aerobic respiration (using oxygen to produce ATP)
what is the ancestor of the inner mitochondrial membrane
the membrane of the prokaryote that underwent symbiosis with the ancestral eukaryotic cell. this is where all the machinary to make ATP is present
what helped prove the endosymbiosis theory?
-sequence analysis of the protein (superoxide dismutase) found inside the mitochondria, and also inside the cytoplasm (sequencing a protein, by peeling amino acids off one by one)
-we saw that the sequence for the chicken liver mitochondria supreoxide dismutase (which uses manganese) greatly resembled the sequence for the e coli (iron and manganese), and not the sequence of the superoxide dismutase of the bovine erythrocyte (which is a cytoplasmic protein, not mitochondrial)
-matches with proteins found in prokaryotes, proving that there are prokaryotic origins to the mitochondria
whats superoxide dismutase? where is it present?
-converts the superoxide anion into hydrogen peroxide
-helps protect cells from oxidative damage by neutralizing superoxide radicals (O₂⁻)
-there are several isoforms of it in the cell, and theres always one in the mitochondria
why are the superoxide radicals bad for the cell?
-they are capable of reacting with macromolecules present in the cell. people have speculated that aging is due to damage from reactive oxygen
was the theory on superoxide dismutase being linked to aging proven to be right or wrong?
-proven to be most likely wrong via an experiment with c elegans
-we took c elegans and knocked out all their isoforms of superoxide dismutase. after that, we still observed a normal lifespan, suggesting that maybe superoxide isnt that important to determine lifespan of organisms
what does superoxide dismutase detoxify free radicals into?
into peroxide (H2O2)
when did the complete sequence of human genome happen?
1981
true or false, the mitochondria has its own genetic code
true
true or false mitochondria from different groups of organisms have the same genome
false
what important part of small genomes explains the wide variety of mitochondrial genomes?
small genomes tend to diverge
what are mitochondrial complexes built of?
combination of mitochondrial and nuclear proteins
what does complex 5 do?
actually synthesizes ATP (last step of ETC)
which complex is only composed of nuclear proteins?
complex II
why are some proteins of the ETC complexes coded in the nucleus, and some are coded in the mitochondria?
-over time, most proteins in the matrix, the DNA coding for them got transferred to the nucleus, and they are translated in the cytoplasm
-for the very hydrophobic ones, genes stay in mitochondria, and translation continues there too, as they are so hydrophobic that if they were in the cytoplasm, they’d fold automatically, and we wouldnt be able to unfold them in order to put them into the mitochondria
