Lecture 6 Flashcards
Do all eukaryotic cells contain mitochondria?
No, most.
How do eukaryotic cells without mitochondria obtain ATP?
Glycolytic fermentation.
How many mitochondria do most cells contain?
How many mitochondria do liver cells contain?
Most cells several hundred.
Liver cells about 2,500.
What are the two parts of a mitochondrial membrane?
Inner and outer membrane.
What is the inner membrane of the mitochondrial folded into?
Cristae.
What are the two compartments in the mitochondria?
The matrix inside the inner membrane,
Intermembrinal space.
What moves mitochondria around the cells and whereabouts are they usually found in the cell?
Microtubules of the cytoskeleton.
Regions of high ATP consumption, e.g. myofibrils of muscle cells.
What protein comprises the majority of the outer membrane of mitochondria and what does it form?
Porin.
Large non-specific aqueous channels through the outer membrane.
What benefit do cristae offer the mitochondria?
Increases surface area.
What is the inner membrane of the mitochondria?
Energy transducing membrane.
What is the inner membrane of the mitochondria impermeable to and why?
Impermeable to most small ions due to cardiolipin.
Three types of membrane complex found in the inner membrane of the mitochondria?
Components of the electron transport chain,
ATP synthase,
Specific transporters moving metabolites between mitochondrial matrix.
Which cell type has the greatest variety of metabolite transporters and why?
Liver mitochondria.
Involved in the initial reactions of several anabolic pathways.
What does the mitochondrial matrix contain?
Enzymes that catalyse the Krebs cycle and fatty acid oxidation. Also contains ribosomes and mitochondrial DNA.
Where does glycolysis take place?
How much energy is released, and how?
What product is formed?
Cell cytosol.
About a quarter of the energy of glucose, through substrate level phosphorylation.
Pyruvate.
After glycolysis what happens to pyruvate?
Enters mitochondria and converted to acetyl CoA with the loss of CO2.
What electron carriers carry electrons from the Krebs cycle?
Also where do they transport them to?
NAD and FAD.
Electron transport chain on the inner membrane of the mitochondria.
What does the election transport chain do?
Pumps H+ ions across the inner membrane creating an ion gradient used by ATP synthase to generate ATP.
Where does the Krebs cycle take place?
In mitochondrial matrix.
What is the majority of the energy in the Krebs cycle proceed from?
Transfer of electrons to NAD and FAD.
Only a small amount of ATP generated due to substrate level phosphorylation.
How does the ETC generate energy?
Via redox reactions.
What does the ETC consist of?
Collection of molecules (mostly proteins with prosthetic groups) embedded in the inner membrane of the mitochondria.
What is the first molecule in the electron transport chain and why has it been given its name?
Flavoprotien.
Because prosthetic group = flavin mononucleotide.
What does the last cytochrome in the ETC pass its electrons onto? What does this molecule do?
Oxygen.
Picks up a pair of H+ ions forming water.
What is the name for the indirect generation of ATP from the electron transport chain?
Chemiosmosis.
What is the overall energy drop from NADH to O2?
53 kcal/mol.
What is the ion gradient which drives ATP synthesis?
H+ gradient.
Why is cyanide the fastest poison?
Prevents the passage of electrons from one of the cytochromes, halting the electron transport chain.
What does DNP do?
Makes the inner membrane leaky to hydrogen ions so a gradient cannot be generated. ETC still works, but just releases energy as heat instead of ATP.
What is brown fat, and what is the function of the mitochondria in brown fat?
Specialised type of adipose tissue in many mammals.
Produce heat.
In what type of human is brown fat found in large quantities? And why?
New-born babies, important to generate heat to maintain body temperature.
What is unique about the structure of mitochondria in brown fat, and what does it mean?
Have a special protein on their inner membrane functioning as an H+ channel through the membrane (thermogenin).
Means H+ ions pumped across membrane by ETC leak back without passing through ATP synthase molecule, so doesn’t generate ATP.
Is brown fat present in healthy human adults?
Yes.
What type of technique has just been conceived to prevent passing on faulty mitochondria?
IVF technique.
What is MERRF? And what is it caused by?
Myoclonic epilepsy and ragged-red fiber disease.
Caused by mutation in mitochondrially encoded tRNA Lys gene.
What type of disease is MERRF?
Multisystem, affecting mainly muscles but also causing epilepsy and general weakness.
