Mitochondria Flashcards
Function of mitochondria
Oxidative phosphorylation (production of ATP through use of oxygen), Calcium sequestration, cell death, generate heat, organ-specific functions (urea cycle in the liver)
Structure of mitchondria
Double lipid bilayer, innermembrane - convoluted structures - cristae, matrix (w/ ribosomes), outermembrane
Inner membrane contains:
cristae, contains proteins for electron-transport, ATP synthase, transport proteins, but is impermeable to protein diffusion, because of large amounts of cardiolipin
Matrix contains:
enzymes (TCA cycle), DNA, RNA, Ca++ granules, ribosomes
Outer membrane contains:
Channel-forming protein (porin), is semipermiable, lipid synthesis enzymes
Intermembrane space contains:
Enzymes that use ATP to phosphorylate nucleotides
Staining of mitchondria
show up as striations, can use immunohistochemistry, enzyme histochemistry
Oxidative phosphorylation definition
Oxidative because using oxygen as reactant to phosphorylate ADP to ATP
Oxidative phosphorylation steps
- Pyruvate/FAs are transported into mitochondria from glycolysis and converted to acetyl CoA
- Acetyl CoA goes through the citric acid cycle in the matrix and produces NADH and CO2
- NADH is converted to NAD+ and e-
- e- move down electron transport chain the inner mitochondrial membrane with oxygen as the final e- acceptor becoming water, that simultaneously pushed H+ into the intermembrane space
- H+ flowing down its electrochemical gradient drives the production of ADP to ATP by ATP synthase
Electron transport chain
Electron passed between different complexes in inner membrane
Which has higher pH: inner membrane space or matrix?
Matrix because electron transport chain pumps H+ out
Why do brown fat cells produce heat?
They uncouple ATPase and use H+ for lipid metabolism to make heat
Metabolite transport
Carrier proteins that need energy, symporters driven by pH gradient and antiporters driven by voltage gradient
Proteins targeted for matrix
TOM and TIM23, cleavable presequence
Proteins targeted for inner membrane
TOM and TIM23, cleavable presequence AND ‘stop transfer’ sequence
Proteins targeted for intermembrane space
TOM and TIM23, cleavable presequence AND inner membrane peptidase cleavage sequence
What do chaperones do for proteins destined for the mitochondria
Keeps polypeptide in unfolded position until it gets to its final location
Proteins w/out presequence
Some proteins lack presequence, but instead have noncleavable signals such as b-barrel proteins (porins), metabolite carrier proteins
SAM complex
Important for proteins that need to stay in the outermembrane, such as porins, that go through TOM first and then are folded and then goes through SAM and into membrane
TIM22 complex
Important for proteins that stay in the innermembrane, but that DONT have a cleavable presequence, that go through TOM first and then are folded and then goes through TIM22 and into membrane
Chaperones use what form of energy
ATP and electrochemical gradient
OXA translocase
Used for proteins synthesized in the mitochondria, presequence is not cleaved and protein is destined for inner membrane
Ways to die when no ATP
Necrosis, causes inflammation
Ways to die when ATP is available
Apoptosis, no inflammation
