Metabolism + Bioenergetics

Question 1

Metabolic pathways that lead to biosynthesis are ___ while pathways that lead to degradation of complex metabolites are ___

Answer 1

Anabolic, catabolic

Question 2

Metabolism equation

Answer 2

Metabolism = anabolism + catabolism

Question 3

Phosphoanhydride bonds

Answer 3

Join the 3 phosphate groups on a nucleotide - cleaving these bonds releases energy due to instability caused by neighbouring negatively charged P groups

Question 4

Metabolites

Answer 4

Intermediates in metabolic pathways

Question 5

Glycolysis

Answer 5

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)

Question 6

TCA cycle

Answer 6

Further oxidation of pyruvate into CO2 occurs during this - inside mitochondria of eukaryotes

Question 7

What does transport of pyruvate into mitochondria occur via?

Answer 7

Pyruvate translocase

Question 8

Exergonic vs endergonic

Answer 8

If delta G prime < 0 it’s exergonic and if > 0 it’s endergonic

Question 9

Oxidizing agent vs reducing agent

Answer 9

Oxidizer receives electrons while reducer donates electrons

Question 10

Oxidative phosphorylation

Answer 10

Produces further ATP from NADH produced during complete CO2 oxidation from pyruvate in aerobic metabolism

Question 11

Two stages of glycolysis pathway

Answer 11

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

Question 12

Ethanolic fermentation

Answer 12

• 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+

Question 13

Lactic acid fermentation

Answer 13

NADH is regenerated in anaerobic metabolism by this - pyruvate converted into lactic acid

Question 14

Homolactic fermentation

Answer 14

Pyruvate converted to lactic acid - catalyzed by lactase dehydrogenase

Question 15

Heterolactic fermentation

Answer 15

Occurs via pentose phosphate pathway - 1 molecule glucose converted into 1 molecule lactate+ 1 molecule ethanol + 1 molecule CO2

Question 16

Acetyl-CoA

Answer 16

• 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

Question 17

Where is citric acid cycle in prokaryotes? What about in eukaryotes? What about glycolysis in eukaryotes?

Answer 17

Cytosol; mitochondria; cytosol

Question 18

Where are citric acid enzymes found in eukaryotes?

Answer 18

Mitochondrial matrix

Question 19

Symport

Answer 19

Process by which pyruvate is transported together w/H+ ion by pyruvate translocate - requires energy

Question 20

Protonmotive force

Answer 20

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

Question 21

Oxidative phosphorylation

Answer 21

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

Question 22

Steps of oxidative phosphorylation

Answer 22

1. 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
2. Phosphorylation of ADP to form ATP via ATP synthase which uses proton motive force to perform phosphorylation via chemiosmosis

Question 23

Electron transport chain

Answer 23

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

Question 24

Intermembrane space

Answer 24

H+ ions are concentrated in this area of mitochondria - found between inner + outer mitochondrial membrane

Question 25

Cristae

Answer 25

Invaginations on inner mitochondrial membrane - more of these lead to higher cell respiratory activity

Question 26

Shuttle systems

Answer 26

On inner mitochondrial membrane + allow for passage of pyruvate, NADH + other molecules required for citric acid cycle

Question 27

Anaerobic respiration

Answer 27

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

Question 28

Flavin mononucleotide

Answer 28

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

Question 29

Iron-sulfur clusters

Answer 29

Prosthetic group found in mitochondrial electron transport chain protein complexes - only accept/donate 1 electron

Question 30

Cytochrome proteins

Answer 30

• 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

Question 31

Coenzyme Q

Answer 31

• 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

Question 32

Cytochrome C

Answer 32

• 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

Question 33

Redox loop mechanism

Answer 33

Used to transport 4H+ ions by coenzyme Q + 2H+ ions by Complex IV

Question 34

Proton pump mechanism

Answer 34

Used to transport 4H+ ions by coenzyme Q + 2H+ ions by Complex IV

Question 35

Proton pumps

Answer 35

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

Question 36

Chemiosmosis

Answer 36

H+ electrochemical gradient used to drive endergonic rxns - coupling between electron transport chain + ATP synthesis via creation/use of electrochemical gradient

Question 37

2 domains of ATP synthase

Answer 37

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

Question 38

What makes the conformation of the beta subunit fluctuate?

Answer 38

1. Presence of loose binding site binding ADP and Pi
2. Conformational change to create tight binding site that catalyzes formation of ATP
3. Conformational change to create open binding site releasing ATP