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19 Cards in this Set
- Front
- Back
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What is the basic structure of mitochondria?
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1. outer membrane: contains porins
2. inner membrane: contains electron transport chain and ATP synthase 3. intermembrane space: folds into vaginiations 4. matrix: contains enzymes for TCA cycle and fatty acid oxidation 5. cristae: "lamellar" # and length proportional to energy demand bc has electron transport chain |
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What is the relationship to number of mitochondria and energy use.
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The number of mitochondria (varies in shape also) is proportional to the energy requirement of a cell
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How is mitochondria inherited?
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mitochondria DNA inherited from the mother
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Why does mitochondria have a high mutation rate?
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because there is no DNA repair mechanism. Also, mitochondrial diseases worsen over time because there is a natural tendency for mitochondria to mutate and die
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Describe the organization of the mitochondrial genome.
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circular DNA of ~1700 bp (not the same as nuclear genome). the mtDNA is replicated and transcribed in the region called the D loop
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What does mtDNA transcribe?
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2 long RNAs:
1 RNA is process into 2 mt-rRNAs, 14 mt-tRNA, and a plycistronic mRNA and codes 12 proteins the other RNA is processed into 8 mt-tRNA and 1 mRNA |
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What are the main elements of the presequence pathway
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1. Tom and tim
2. Presequence 3. Internal sequence 4. Heat shock proteins 5. Matrix processing peptidase |
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What does matrix processing peptidase do?
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Cleaves off the presequence of the protein when it enters into the matrix so it is able to fold properly
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What is the role of heat shock proteins in mitochondia?
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Hsp keep the protein in a stable string form so it is able to pass through Tom and Tim. The hsp 70 chaperone proteins are in the cytoplasm help through the membrane and the other hsp 70 are in the matrix and assist with proper folding. they are ATP dependent
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What is the significance of an internal sequence in proteins?
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Some proteins have a hydrophobic internal sequence so when it passes through the membranes, the hydrophobic sequences are sensed and insert into the membrane.
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What are the major steps in the presequence pathway?
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1. The presequence of a protein binds to TOM and passes through the outer membrane then passes through TIM. The presequence is cleaved off in the matrix by Matrix processing peptidase. Hsp helps throughout this entire processes and folds the protein at the end
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Describe the most common process to which proteins from outside of the mitochondria are destined to be outer mitochondria membrane proteins.
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They pass through TOM just like other proteins, but in the intermembrane space Tiny Tims shuttle the protein to the SAM Sorting and Assembly Machinery complex to which it inserts the protein as a beta barrel called Porins (VDAC)
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Describe the electrochemical gradient and the pumps that maintain this gradient within the mitochondria?
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The intermembrane space side of the inner membrane is + and the matrix side of the inner membrane is -. THere are 4 pumps:
1. Adenin Nucleotid Tanslocase (ANT): 1 ADP in matrix in exchange for 1 ATP 2. Pi symporter: Pi +H+ into matrix 3. pyruvate symporter: pyruvate + H+ into matrix 4. Ca++ Uniporter: Ca++ into matrix |
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What are VDACs?
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Porins or Voltage-Dependent Anion Channels are beta barrel proteins on the outer membrane and facilitate nonspecific transport of hydrophillic molecules
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What are mitochondrial permeability transition pores (MPTP)?
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Pores that form between the inner and outer membrane of the mitochondria where 2 transporters become associated under certain physiological conditions: ANT and cyclophilin D on the inner and VDAC on the outer. MPTP causes under oxidative dress due to ROS, increase in Ca++ in matrix and depletion of ATP
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Describe the endosymbiotic theory.
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Mitochondrial DNA if from aerobic bacteria (both circular DNA).
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What is the structure of peroxisomes?
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single membrane that contain ~50 enzymes. contain electron dense cystalloids composed of urate oxidase
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What is the function of peroxisomes?
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Organelles in the cytoplasm that:
1. get rid of peroxide by catalase and turns it into water and oxygen. 2. synthesize lipids 3.synthesize bile acids in liver 4. synthesize plasmalogen (specialized phospholipids for cell membranes) |
