Mitochondria Flashcards
Discuss the mitochondrial activity and inheritance within human germ cells
A human egg has 1000s of mitochondria that are largely inactive within the ovaries; only become active around fertilisation. Nurse cells in ovary follicles provide the metabolic needs of the egg.
Human sperm have hyperactive mitochondria that ensure the propulsion of sperm to the egg.
Sperm mitochondria are discarded at fertilisation - thus all mitochondria are maternally inherited
Mitochondrial genetics have allowed us to track the migrations and selection of regional populations accross the globe over history.
Where and when are mitochondria thought to have developed?
Mitochondria developed from endosymbiotic bateria that were incorporated into eukaryotes 2 billion years ago
Mitochondria have prokaryotic DNA and a double folded membrane suggestive of endocytosis preocesses earlier in human evolutionary history.
In a brief overview, list the functions of mitochondria
- Acetyl CoA Production
* from either pyruvate or fatty acid beta-oxidation - Ketone Body Synthesis
* from acetyl CoA via HMG-CoA as an intermediate - Krebs Cycle
- Oxidative Phosphorylation (electron transport change)
- Initiation of the Urea Cycle
Describe the anabolic fates of citric acid cycle metabolites!
(Throw in images here)
Why are mitochondria known as the powerhouses of animal cells?
Mitochondria are the site of ATP production within cells
Mitochondria use energy extracted from the chemical bonds of nutrients in order to generate a proton gradient across the inner membrane. This proton force drives ATP synthase to synthesise ATP from ADP. This process is described as the chemiosmotic process
Mitochondria recieve yielding intermediates from glycolysis and beta-fatty acid oxidation - both of which feed into the citric acid cycle via Acetyl-CoA production
In additionto Acetyl-CoA, the glycolytic pathway also produces NADH which can be shuttled into the mitochondria via the malate-aspartate shuttle
The Krebs/citric acid/tricarboxylic acid cycle produces 1x ATP/GTP, 3x NADH and 1x FADH2 from a single molecule of Acetly-CoA
**NADH **and **FADH2 **are rich electron carriers that donate their electrons to complexes 1 (NADH) or 2(FADH2). The electrons follow a route through the electron transport chain that, over its course, partitions off energy to to move protons across the inner mitochondrial membrane. This establishes an electrochemical gradient.
The electrochemical gradient drives ATP synthesis through the ATPase (complex 5) to mechanically synthesis ATP.
This entire process is known as oxidative phosphorylation because, eventually, O2 is the electorn sink that receives the electron chain electrons (1/2 O2 +2H+-> H20)
What are the sequential steps in the electron transport chain?
NADH/FADH2 -> Q -> Cyt b -> cyt b -> cyt c1 -> cyt c -> cyt a -> cyt a1
What is the molecule Ubiquinone?
What effect do statins have on
More commonly refered to as coenzyme Q (CoQ10), Ubiquinone is involved in the electorn transport chain. It is anchored in mitochondrial inner membrane, but is able to iffuse laterally within the inner membrane -> carrying electrons between complexes
It is the fully oxidised form of the molecule family:
Ubiquinone (Q) = fully oxidised
Semiquinone radical (.QH)
Ubiquinol (QH2) = fully reduced
STATINS reduce the isoprenoid pathway involving Q production -> complications of reduced Q include cardiac and skeletal muscle dysfunction. Supplements of Q are advised and completely alleviate problems.
How can different types of cytochromes be differentiated?
Cytochromes are coloured haem-proteins of types a, b and c,.
The cytochromes can be differentiated by their spectra of wavelength colour emission
They are contained within the respiratory complexes in various concentrations/make-ups
Discuss the genes responsible for encoding the electron transport chain of mitochondria
There are 90 proteins involved in the electron transport chain; 77 are encoded by nuclear DNA (nDNA); 13 encoded by mitochondrial DNA (mtDNA).
Mitochondrial DNA mutations affect protein synthesis and affect all of the respiratory complexes EXCEPT complex 2 which is completely encoded by nuclear DNA
Explain proton motive force!
How does this lead to the formation ATP?
How does this principle fit in with the chemiosmotic model?
Proton motive force describes the chemical potential of NADH/FADH2 efficiently converted into an electrochemical from -> the seperation of charge across the inner mitochondria membrane due to the establishment of a proton gradient.
The energy provided by NADH to pump protons across membrane:
- 20kJ/mol of H+
- 200 kj/mol of NADH -> One NADH molecule pumps 10H+
The energy to synthesise ATP is provided by the mechanical action of the gamma-subunit of ATPase -> itslef provided energy by the movement of H+ back into the mitochondrial matrix.
(INSERT IMAGE OF CHEMIOSMOTIC MODEL)
How do mitochondria contribute to the formation of reactive oxygen species?
It is possible that electrons may leak out of the electron transport chain prematurely and react with molecules in the matrix - like oxygen and nitrogenous compounds - to create reactive oxygen species (ROS).
For example: electron + O2-> .O2- —(superoxide reductase)—> H202
There are
