Module 1: Carbohydrates III Part 1 Flashcards
Physical Characteristics: Outer Membrane (semipermeable)
– 50% lipid, 50% protein
– Porin (transmembrane channel protein)
– Permeability < 5,000 – 10,000 MW
– 6% of total mitochondrial protein
Physical Characteristics: Intermembrane space
– 6% of total mitochondrial protein
Physical Characteristics: Inner membrane (impermeable)
- 24% lipid, 76% protein (highest proportion of protein than other cellular membranes)
- Cardiolipin
- Cristae
- 21% of total mitochondrial protein
- ANT, ATP synthase, respiratory chain enzymes, transport proteins
Physical Characteristics: Matrix
– Hundreds of enzymes, mtDNA, ribosomes, tRNAs
– 67% of total mitochondrial protein
What is located in the Matrix?
- TCA cycle enzymes
- Fatty-acid oxidation
- mtDNA replication
- mtDNA transcription/translation
- Fe-S biogenesis
- Protein folding and degradation
- Urea cycle enzymes (liver & small intestines)
- Gluconeogenic enzymes (liver & kidney)
What is located in the Inner Membrane?
- Oxidative phosphorylation
- Metabolic transport
- Protein import (TIM)
- Protein assembly
- Protein degradation
What is located in the Intermembrane Space?
- Electron transfer (cytochrome c)
- Cristae remodeling (Opa 1)
- Redox enzymes
- Protein imports (s TIMs)
- Apoptosis factors (e.g., cytochrome c, Smac/Diablo)
What is located in the Outer Membrane?
- Protein imports (TOM & SAM)
- Metabolite influx/efflux
- Fission, fusion, & distribution
- Apoptosis factors (e.g., Bcl-2, Bax)
- Signaling molecules
What do mitochondria do?
-Generate 90% of energy needs via mitochondrial oxidative phosphorylation (they make ATP)
-Aerobic metabolism
Ca2+ signaling (buffering) **
Re-generate NADH for glycolysis **
Urea Cycle
Biosynthesis of amino acids, heme, steroid hormones
“Gatekeepers” for apoptotic signaling (cytochrome c) **
-Make heat (esp. brown adipose tissue)
-Generate free radicals for cell-signaling **
How are mitochondria related to circulation and respiration?
- Aerobic metabolism
- Systematically extract energy from nutrient (substrate) molecules
- Constantly remove of excess electrons through the reduction of water
- The respiratory and circulatory system’s primary purpose is to deliver oxygen and substrates to the mitochondria (and to eliminate carbon dioxide)
Pi Transport
- Phosphate carrier, an electroneutral Pi-
- H+ symport driven by delta pH
- Maintaining high concentration of Pi for
- ATP synthesis
Ca2+ Transport
- Influx driven by membrane potential, (negative inside)
- Efflux driven by Na+ gradient, in exchange for Na+, an antiport
NADH Transport
- Transport of NADH formed by glycolysis
- NADH goes cytoplasm -> mitochondria matrix via electron shuttle systems that accept electrons from cytoplasmic NADH
- Reducing equivalents enter mitochondria, and give up the electrons to electron acceptors in the mitochondrial matrix
Glycerol phosphate shuttle
- Functions in mammalian skeletal muscle and brain, very energy-demanding tissues (insect flight muscles)
- NADH produced by glycolysis enters the electron transport chain via FADH2, which is less energy efficient.
- For every NADH you get 3 ATP
- For every FADH2 you get 2 ATP
ETC Complex I
- NADH-CoQ oxidoreductase, AKA NADH dehydrogenase
- Entry site for NADH
- Transfers e- from NADH to Coenzyme Q
- Proton pump
- e- transfer leads to a net flux of 4 protons to the intermembrane space/P side
- ATP is produced
ETC Complex II
- Succinate-CoQ reductase
- Entry site for FADH2
- Transfers e-‘s from succinate to Coenzyme Q (accept electrons from Complex I and II)
- The transfer produces very little free energy, cannot contribute to the formation of the proton gradient (not a proton pump)
- No ATP is produced
ETC Complex III
-CoQH2:Cytc oxidoreductase
-Electron transfer from reduced Q, a 2e- carrier, to cytochrome c, single e- carrier
-Two steps, Q Cycle—radical state of Q is formed, semiubiquinone
-2e- transferred to Cyt c and 4 net H+ are pumped into the intermembrane space (two half Q cycles of 2 H+ each)
Pumps protons outside the matrix to the intermembrane space
-ATP produced
ETC Complex IV
- Cytochrome c oxidase
- Electron transfer from Cytochrome c to molecular oxygen
- Two protons (per e- pair) are pumped across the membrane
- ATP is produced
What are the 4 Complexes of the ETC?
- Complex I: NADH-CoQ oxidoreductase, AKA NADH dehydrogenase
- Complex II: Succinate-CoQ reductase
- Complex III: CoQH2:Cytc oxidoreductase
- Complex IV: Cytochrome c oxidase
Summarize the Electron Transport Chain
- The e-‘s from NADH and FADH2 formed during glycolysis, beta-oxidation and the TCA cycle, are transferred to molecular O2, to generate H2O
- Electron transfer occurs through electron transport chain, complexes of electron carriers, in the inner mitochondrial membrane
- For every molecule of NADH that is oxidized, 10 protons are pumped into the intermembrane space of the mitochondria (4 protons from Complex I, 4 protons from Complex III and 2 from Complex IV)
- These protons form a concentration gradient across the membrane (higher concentration in the intermembrane space than in the mitochondrial matrix)
