Metabolism + Bioenergetics Flashcards
Metabolic pathways that lead to biosynthesis are ___ while pathways that lead to degradation of complex metabolites are ___
Anabolic, catabolic
Metabolism equation
Metabolism = anabolism + catabolism
Phosphoanhydride bonds
Join the 3 phosphate groups on a nucleotide - cleaving these bonds releases energy due to instability caused by neighbouring negatively charged P groups
Metabolites
Intermediates in metabolic pathways
Glycolysis
Leads to breakdown of glucose into 2 pyruvate molecules (oxidation of glucose to pyruvate is coupled to reduction of NAD+ into NADH + to production of 2 ATP)
TCA cycle
Further oxidation of pyruvate into CO2 occurs during this - inside mitochondria of eukaryotes
What does transport of pyruvate into mitochondria occur via?
Pyruvate translocase
Exergonic vs endergonic
If delta G prime < 0 it’s exergonic and if > 0 it’s endergonic
Oxidizing agent vs reducing agent
Oxidizer receives electrons while reducer donates electrons
Oxidative phosphorylation
Produces further ATP from NADH produced during complete CO2 oxidation from pyruvate in aerobic metabolism
Two stages of glycolysis pathway
1) Preparatory stage to create 2 molecules of glyceraldehyde-3-phosphate - requires investment of 2 ATP
2) Energy production stored as ATP - GAP and DHAP are further phosphorylated using P to create 2 molecules of 1,3-biphosphoglycerate which have higher free energy than glucose + are converted to pyruvate to release energy. Rxns coupled w/production of 2 ATP per 1,3-biphosphoglycerate for total of 4 ATP
Ethanolic fermentation
- NADH is regenerated in anaerobic metabolism by this - allows regeneration of NAD+ needed for further glycolysis rxns
- 1st is decarboxylation of pyruvate to produce acetaldehyde + CO2
- 2nd is reduction of acetaldehyde to ethanol allowing for oxidation of NADH into NAD+
Lactic acid fermentation
NADH is regenerated in anaerobic metabolism by this - pyruvate converted into lactic acid
Homolactic fermentation
Pyruvate converted to lactic acid - catalyzed by lactase dehydrogenase
Heterolactic fermentation
Occurs via pentose phosphate pathway - 1 molecule glucose converted into 1 molecule lactate+ 1 molecule ethanol + 1 molecule CO2
Acetyl-CoA
- Condenses w/oxaloacetate to form citrate + closes cycle - acetyl groups enter citric acid cycle via this
- Obtained via decarboxylation of pyruvate + then acetyl group condensed w/oxaloacetate to yield citrate - regenerates free CoA
- Citrate undergoes oxidation rxns releasing 2 CO2 molecules to end cycle
Where is citric acid cycle in prokaryotes? What about in eukaryotes? What about glycolysis in eukaryotes?
Cytosol; mitochondria; cytosol
Where are citric acid enzymes found in eukaryotes?
Mitochondrial matrix
Symport
Process by which pyruvate is transported together w/H+ ion by pyruvate translocate - requires energy
Protonmotive force
Electrochemical gradient obtained during electron transfer to O2 from NADH and FADH2 that receive electrons and H+ from glucose - used by ATP synthase via chemiosmosis
Oxidative phosphorylation
Electron transport chain proteins + ATP synthase are coupled to oxidation of glucose to production of ATP from ADP by creating/releasing H+ gradient across membrane
Steps of oxidative phosphorylation
- Oxidation of NADH and FADH2 in electron transport chain - redox rxns that occur in the chain are coupled to transport of H+ across membrane which leads to protonmotive force
- Phosphorylation of ADP to form ATP via ATP synthase which uses proton motive force to perform phosphorylation via chemiosmosis
Electron transport chain
Sequence of integral proteins that electron pairs are passed on to which were stored in NADH and FADH2 - as proteins undergo redox rxns the free energy is coupled to passage of H+ from 1 membrane side to other by chain proteins to form proton motive force
Intermembrane space
H+ ions are concentrated in this area of mitochondria - found between inner + outer mitochondrial membrane
Cristae
Invaginations on inner mitochondrial membrane - more of these lead to higher cell respiratory activity
Shuttle systems
On inner mitochondrial membrane + allow for passage of pyruvate, NADH + other molecules required for citric acid cycle
Anaerobic respiration
Coupled redox rxns used to create proton motive force across cytoplasmic membrane followed by use of force to drive ATP synthesis via ATP synthase - final electron acceptor is anything but oxygen
Flavin mononucleotide
Organic molecule that is like FAD but no AMP group - can donate/accept 2 electrons + is found in prosthetic group of mitochondrial electron transport chain protein complexes
Iron-sulfur clusters
Prosthetic group found in mitochondrial electron transport chain protein complexes - only accept/donate 1 electron
Cytochrome proteins
- Present in everything but obligatory anaerobes - membrane-bound + contain many heme groups w/central iron ion that can undergo reduction
- Heme groups similar to hemoglobin heme group but dif functional groups attached - only accept/donate 1 electron
Coenzyme Q
- Can move w/in membrane + shuttles electrons between between protein complexes of electron transport chain - hydrophobic ring that donates/accepts 1/2 electrons
- Soluble in lipid bilayer + can accept 2 electrons from Complex I + diffuse through membrane + donate 2 electrons to Complex III
Cytochrome C
- Involved in transfer of electrons between protein complexes of electron transport chain - peripheral + loosely attached to mitochondrial outer membrane
- Shuttle between Complex III and Complex IV
Redox loop mechanism
Used to transport 4H+ ions by coenzyme Q + 2H+ ions by Complex IV
Proton pump mechanism
Used to transport 4H+ ions by coenzyme Q + 2H+ ions by Complex IV
Proton pumps
Complex I and IV proteins that cause protonation/deprotonation of certain amino acids leading to transfer of H+ ions across membrane via protonation/deprotonation of amino acids inside protein
Chemiosmosis
H+ electrochemical gradient used to drive endergonic rxns - coupling between electron transport chain + ATP synthesis via creation/use of electrochemical gradient
2 domains of ATP synthase
F1 domain catalyzes ATP synthesis + F0 transmembrane domain translocates proteins across membrane - contains a c-ring that rotates while contacting a subunit + as each c-subunit surpasses an a the c subunit takes proton from outer membrane leading to conformation change leading to exit of c subunit from a subunit
- Continues + when same c subunit enters a again a channel in a allows exit of proton - c can take new proton as it continues to rotate
- Cts process leads to cts rotation of c-ring of ATP synthase leading to force on gamma + beta subunits
What makes the conformation of the beta subunit fluctuate?
- Presence of loose binding site binding ADP and Pi
- Conformational change to create tight binding site that catalyzes formation of ATP
- Conformational change to create open binding site releasing ATP
