Cellular Respiration: Stages and Regulation, Exams of Biochemistry

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BIOCHEM – CAC| 106 Questions | WITH

COMPLETE SOLUTIONS

what is the product from glycolysis that enters the Citric Acid Cycle (CAC) correct answer: pyruvate pyruvate will ve converted to ____________ in the CAC correct answer: Acetyl CoA when cells consume O2 and produce CO2 correct answer: cellular respiration provides more energy from glucose than glycolysis does correct answer: cellular repsiration 3 major stages of cellular respiration correct answer: acetyl CoA production acetyl CoA oxidation electron transfer + oxidative phosphorylation Respiration: Stage I - Acetyl CoA production generates ______________ correct answer: ATP, NADH, FADH Respiration Stage II - Acetyl CoA oxidation generates ______________ correct answer: NADH, FADH2, and 1 GTP Respiration: Stage III - Oxidative Phosphorylation generates what correct answer: a lot of ATP

in eukaryotes, the CAC occurs where? correct answer: mitochondrial matrix glycolysis occurs where? correct answer: in the cytoplasm oxidative phosphorylation occurs where? correct answer: in the inner membrane succinate dehydrogenase of the CAC occurs where? correct answer: in the mitochondrial inner membrane - only exception conversion of pyruvate to Acetyl CoA is catalyzed by _______________ correct answer: pyruvate dehydrogenase complex pyruvate dehydrogenase requires _______ coenzymes correct answer: 5 TPP, lypoyllysine, FAD, NAD+, + CoA-SH pyruvate decarboxylase enzyme is called _________________ correct answer: pyruvate dehydrogenase E T/F Coenzymes are a permanent part of the enzymes structure correct answer: False, they associate, fulfill a function, and dissociate the function of CoA is ______________ correct answer: to accept and carry acetyl groups

_____________ groups of lipoyllysine are strongly bound to the protein correct answer: prosthetic the lipoid acid is covalently linked to the enzyme via a lysine residue pyruvate dehydrogenase complex is made up of ____________ correct answer: 3 enzymes (all 3 must work) glycolysis runs through the pyruvate dehydrogenase complex how many times in one cycle? correct answer: twice/cycle what are the 3 enzymes that make up pyruvate dehydrogenase complex correct answer: pyruvate dehydrogenase (E1) dihydrolipoyl transacetylase (E2) dihydrolipoyl dehydrogenase (E3) pyruvate dehydrogenase does what correct answer: basically a decarboxylase takes off CO2 and turns pyruvate into an aldehyde oxidation of the aldehyde to a carboxylic acid dihydrolipoyl transacetylase does what correct answer: transfers the acetyl group to form Acetyl CoA technically, the complex should be done here

dehydrolopoyl dehydrogenase does what correct answer: needs to regenerate lipollysine, takes off an H+ so lipollysine can be recycled produces NADH after the pyruvate dehydrogenase complex is finished, what are the products of 1 cycle correct answer: 2 Acetyl CoA 2 NADH what are the advantaged of the multi-enzyme complex of pyruvate dehydrogenase complex? correct answer: there is a short distance between the catalytic sites allowing channeling of substrates from one site to another channeling minimizes side reactions from happening regulation of activity of 1 subunit will affect the entire complex what enters the CAC correct answer: Acetyl-CoA CAC cycle: Step 1 correct answer: C-C bond formation to make citrate CAC cycle: step 2 correct answer: isomerization via dehydration/rehydration CAC cycle:

steps 3-4 correct answer: oxidative decarboxylations to give 2 NADH CAC cycle: step 5 correct answer: substrate level phosphorylation to give GTP what step has substrate level phosphorylation and is the first energy producing step correct answer: step 5 - GTP CAC cycle: step 6 correct answer: dehydrogenation to give reduce FADH CAC cycle: step 7 correct answer: hydration CAC cycle: step 8 correct answer: dehydrogenation to give NADH C-C bond formation in the first step occurs by correct answer: condensation of Acetyl CoA + Oxaloacetate by citrate synthase the only reaction with C-C bond formation correct answer: citrate synthase rate limiting step of CAC correct answer: C-C bond formation from acetyl-coA + oxaloacetate via citrate synthase

citrate synthase largely depends on ______________ correct answer: oxaloacetate citrate synthase is ________________ (favorable, unfavorable, reversible, irreversible) correct answer: favorable + irreversible citrate synthase is regulated by correct answer: substrate availability + product inhibition when oxaloacetate binds to citrate synthase, a conformational change happens. open conformation: ___________________ closed conformation: __________________ correct answer: open - free enzyme does not have binding sites for acetyl CoA closed - binding of OAA creates binding for acetyl CoA elimination of H2O from citrate gives a cis C=C bond correct answer: aconitase tertiary alcohol that is a poor substrate for oxidation correct answer: citrate secondary alcohol that is a good substrate for oxidation correct answer: isocitrate aconitase is _________________(favorable, unfavorable, reversible, irreversible) correct answer: unfavorable + reversible aconitase is regulated by ______________- correct answer: product concentration kept low to pull forward

water removal from citrate and subsequent addition to cis- aconitate are catalyzed by _____________________ correct answer: iron sulfur center what are sensitive to oxidative stress correct answer: iron sulfur center in aconitase oxidative decarboxylation that loses a CO2 and generates NADH correct answer: isocitrate dehydrogenase ketogluterate dehydrogenase requires Mg2+ or Mn2+ to stabilize the intermediate during decarboxylation correct answer: isocitrate dehydrogenase systolic isozyme of isocitrate dehydrogenase uses what as a cofactor correct answer: NADP+ isocitrate dehydrogenase is ________________(favorable, unfavorable, reversible, irreversible) correct answer: favorable irreversible isocitrate dehydrogenase is regulated by _______________ correct answer: product inhibition + ATP the carbon lost as CO2 in isocitrate dehydrogenase is NOT lose from _____________ correct answer: Acetyl-CoA final oxidative decarboxylation correct answer: ketogluterate dehydrogenase complex

what step is the net full oxidation of all carbons of glucose fulfilled after 2 turns of the cycle correct answer: ketogluterate dehydrogenase the carbons lost are not from glucose, but they are from __________________ correct answer: oxaloacetate another high-energy thirster bond correct answer: succinyl-CoA ketogluterate dehydrogenase is __________________(favorable, unfavorable, reversible, irreversible) correct answer: favorable

• irreversible ketoglutrate dehydrogenase is regulated by _______________ correct answer: product inhibition complex similar to pyruvate dehydrogenase -same coenzymes -identical mechanisms correct answer: ketogluterate dehydrogenase substrate level phosphorylation correct answer: succinyl-CoA synthetase the energy of thioester in succcinyl-CoA synthetase allows for incorporation of _________________ correct answer: inorganic phosphate which step of the CAC cycle produces GTP correct answer: Succinyl-CoA syntehtase

sucinnyl CoA synthetase is __________________(favorable, unfavorable, reversible, irreversible) correct answer: slightly favorable/reversible sucinnyl CO-A synthetase is regulated by correct answer: product concentration kept low to pull forward what step includes oxidation of an alkane to an alkene correct answer: succinate dehydrogenase succinate --> fumarate which enzyme is bound to the mitochondrial inner membrane and is also involved in complex II in the ETC correct answer: succinate dehydrogenase succinate dehydrogenase is involved in complex ______ of the ETC correct answer: II ___________ is stereospecific and the addition of water is always trans and forms ____________ correct answer: fumarase forms L-malate whats the uniqueness about fumarase binding with OH correct answer: it cannot distinguish between inner carbons, so either can gain OH- fumarse is _________________(favorable, unfavorable, reversible, irreversible) correct answer: slightly favorable/reversible

fumarase is regulated by _____________ correct answer: product concentration kept low to pull reaction forward which step deals with the oxidation of alcohol to a ketone correct answer: malate dehydrogenase malate --> oxoloacetate what is the final step of the CAC cycle that regenerates oxaloactate for citrate synthase correct answer: malate dehydrogenase malate dehydrogenase is _______________(favorable, unfavorable, reversible, irreversible) correct answer: highly unfavorable/reversible malate dehydrogenase is regulated by correct answer: oxalolacetate concentration is kept VERY low by citrate synthase to pull reaction forward what are the net result of the CAC correct answer: 3 NADH 1 FADH 2 CO 1 GTP pyruvate dehydrogenase complex (pyruvate --> acetyl co-A) is inhibited by correct answer: ATP, acetyl-CoA, NADH, and fatty acids citrate synthase (Acetyl-CoA --> citrate) is inhibited by correct answer: NADH, succinyl-CoA, citrate, ATP

isocitrate dehydrogenase (citrate --> isocitrate --> a- ketogluterate) is inhibited by correct answer: ATP a-ketogluterate dehydrogenase complex (a-ketogluterate --> succinyl CoA) is inhibited by correct answer: succinyl-CoA + NADH pyruvate dehydrogenase is regulated by reversible E1. when is it active and inactive? correct answer: phosphorylation: inactive dephosphorylation: active what are part of the mammalian PDH complex correct answer: PDH kinase + PDH phosphorylase PDH kinase is activated by correct answer: ATP the CAC is regulated by: correct answer: highly thermodynamically favorable/irreversible steps PDH, citrate synthase, IDH, + KDH the main inhibitors of the CAC is correct answer: NADH + ATP the main activators of the CAC is correct answer: NAD+ and AMP _________________ is an important branch point for amino acid metabolism correct answer: a-ketogluterate regulation of isocitrate dehydrogenase controls citrate levels. accumulated citrate will ______________________ correct

answer: leave mitochondria + inhibits phosphofructokinase in glycolysis _______________ is produced at the succinyl CoA step correct answer: porphyrins, heme, chlorophyll heme + porphyrins are produced at what step correct answer: succinyl-CoA ____________ produces fatty acids and sterols correct answer: citrate ____________ produces glutamate --> other AA --> prunes correct answer: a-ketogluterate _________________ produces aspartate (other AA, purines + pyramidines) and glucose correct answer: oxaloacetate _______________ is a group of genetic diseases that result from defects in enzymes of the biosynthetic pathway from glycine --> ______________ correct answer: porphyria porphyrin what are the signs and symptoms of porphyria correct answer: drastic mental shifts muscle pain insomnia seizures

heme --> ______________ correct answer: biliverdin (by heme oxygenase) then biliverdin --> bilirubin (by biliverdin reductase) the green compound seen in a bruise correct answer: biliverdin a yellow compound that travels bound to serum albumin in the bloodstream correct answer: bilirubin in the liver, bilirubin is made into ___________ correct answer: bilirubin diglucouronide it is secreted with the rest of bile into the small intestine bilirubin diglucouronide that is in the bile is broken down into _______________ and some of that is transported to the kidney and converted to ____________ which gives urine its yellow color correct answer: urobilinogen urobilin jaundice is caused by ______________ accumulation correct answer: bilirubin jaundice can result from (3 things) _____________ correct answer: impaired liver (in liver cancer, hepatitis) blocked bile secretion (gallstones, pancreatic cancer) insufficient glucouronyl bilirubin transferase to process bilirubin (occurs in infants)

CAC plays important _____________ roles in the cell correct answer: anabolic