Q 5: CHO Metabolism: Glycolysis, the Citric Acid Cycle, and Oxidative Phosphorylation Flashcards
What is the primary electron carrier?
NAD+
What is the electron acceptor in glycolysis?
NAD+
Is glycolysis anaerobic or aerobic?
anaerobic
What are the two stages of glycolysis?
preparatory - phosphorylation
payoff - oxidation reduction
What cell types in the body receive their primary source of energy through glycolysis?
erythrocytes (lack mitochondria)
cancer cells
anaerobic bacteria
What two pathways use ~80% of the same enzymes?
glycolysis and gluconeogenesis
What type of rxn does hexokinase initiate on glucose in glycolysis?
transfer rxn (moves phosphate from ATP to glucose)
What is the difference between di and bi phosphate?
Di-means there are two phosphates connected at one location
Bi-means there are two phosphates connected at different locations
Why is the first ATP of glycolysis important?
it keeps glucose in the cell
Where in the cell does glycolysis occur?
in the cytoplasm
What do you yield from the payoff phase in glycolysis?
2 pyruvate
2 ATP
2 NADH + H+
What inhibits glycolysis?
high amounts of citrate (pyruvate –> citrate)
high amounts of ATP
What is the rate limiting enzyme of glycolysis
phospho-fructokinase 1
What is the rate limiting step of the pentose phosphate pathway?
glucose 6-phosphate –> 6-phosphogluconate
What are the other names for the pentose phosphate pathway?
phosphogluconate pathway
hexose monophosphate shunt
What key cells are synthesized in the pentose phosphate pathway?
NADPH
Ribose sugars
- nucleotides
- ATP
- FAD
- Coenzyme A
What inhibits the pentose phosphate pathway?
NADPH (which is produced in the pathway)
Why is NADPH necessary/what is it used for?
creating FA’s (reductive biosynthesis)
free radical protection
it must be maintained within the cell
Why is fermentation important/why do we need it?
we need electron acceptors (it produces 2NAD+)
if you don’t have electron acceptors, glycolysis doesn’t happen
What is the substrate for liver gluconeogenesis?
lactate
What is the electron acceptor of the NADH produced in glycolysis?
lactate
What happens to lactate after its production?
It is shuttled into the blood, taken up by the liver and converted into glucose with ATP within the liver
What rxns occur in the mitochondria?
citric acid cycle (starting with pyruvate –> acetyl CoA –> citric acid cylce)
What organelle has a unique genome inherited through the mother?
mitochondria (which is found in the egg)
What organelle is involved in apoptosis?
mitochondria
What spills out of the mitochondria when it is undergoing apoptosis?
cytochrome C
What does cytochrome C from the mitochondria bind to, after spilling out of the mitochondria, in apoptosis?
ATP, which will induce Apaf-1 to form an apoptosome which eventually leads to cell death/resorption
What enzyme converts pyruvate to acetyl-CoA?
pyruvate dehydrogenase complex
What does the Citric Acid Cycle yield per turn?
3 NADH
2 CO2
1 GTP (ATP)
1 FADH2
How many turns does one glucose provide in the Citric Acid Cycle?
two turns (one glucose is converted into 2 acetyl-CoA)
NADH and FADH2 are electron sources for what pathway?
oxidative phosphorylation
What are the enzymes of the Citric Acid Cycle?
citrate synthase
aconitase
aconitase
isocitrate dehydrogenase
a-ketoglutarate dehydrogenase complex
succinyl-CoA synthetase
succinate dehydrogenase
fumarase
malate dehydrogenase
Which enzyme in the CAC (citric acid cycle) is also part of the ETC (electron transport chain)?
succinate dehydrogenase (electron transport chain complex II)
What enzyme is going to reduce an NAD+?
dehydrogenase enzyme
What steps/enzymes of the CAC produce NADH?
isocitrate–>a-ketoglutarate (isocitrate dehydrogenase)
a-ketoglutarate–>succinyl CoA (a-ketoglutarate dehydrogenase complex)
malate–>oxaloacetate (malate dehydrogenase)
What step/enzyme of the CAC produces FADH2?
succinate–>fumarate (succinate dehydrogenase)
Is the NAD+ you have in the mitochondria shared with the NAD+ in the cytoplasm?
no
Fermentation in the cytoplasm allows for the production of NAD+ for glycolysis, does this occur in the mitochondria to replace depleted NAD+?
no
What substrates/products of the CAC go back and allosterically inhibit/regulate the CAC?
ATP
acetyl-CoA
NADH
FA’s
succinyl-CoA
citrate
What does the CAC help synthesize?
amino acids
nucleic acids
FA’s
gluconeogenesis
neurotransmitters
hemes
What is stage 1 of cellular respiration?
acetyl-CoA production
what is stage 2 of cellular respiration?
acetyl-CoA oxidation
what is stage 3 of cellular respiration?
electron transfer and oxidative phosphorylation
what is stage 3 of cellular respiration?
electron transfer and oxidative phosphorylation
What is the major fx of the electrons in the electron transport chain?
to pump hydrogens from the matrix of the mt into the intermembrane space of the mt
Where does the negative charge reside in the mt?
in the matrix
where does the positive charge reside in the mt?
in the intermembrane space
In what complex of the ETC is oxygen reduced?
complex 4
What are the 3 ways that the ETC generates energy?
1) electrons are moved into the chain through complex 1 and complex 2
2) H+ ions are pumped from the matrix into the intermembrane space
3) due to the high concentration of H+ ions, they are pumped through ATP synthase back into the matrix
What are three common electron carriers transfer electrons BETWEEN/WITHIN the chains and complexes?
ubiquinone (semiquinone, ubiquinol)
cytochromes (a, b, and c….C most prominent)
iron-sulfur proteins
What molecules transfer electrons TO the chains/complexes?
NADH and flavoproteins (FAD, FADH+, FADH2)
At what stage/complex are hydrogens pumped into the intermembrane space?
Complex 1
At what stage/complex is ubiquinone first reduced to semiquinone?
complex 1
At what stage is ubiquinone fully reduced to ubiquinol?
Complex 2
At what stage is ubiquinone fully reduced to ubiquinol?
Complex 2
Where does FA entry into the ETC occur?
complex 2
What is the Q cycle and where does it occur?
occurs at complex 3
involved in the transfer of electrons from ubiquinol to cytochrome c
free electron eventually passed to oxygen to become superoxide
What is complex 4 also know as?
cytochrome oxidase
What happens at complex 4?
final step of ETC
oxygen binds with H+ to make water
4H+ pumped back into intermembrane space
oxygen is the final electron acceptor (this is why we breath, so we have enough oxygen to pump 4H+ back into the intermembrane space)
What does phosphate translocase (symporter) do?
brings Hydrogen phosphate into the matrix (inorganic phosphate for your rxn)
How does ADP get into the mt matrix?
through the adenine nucleotide translocase (antiporter)
How does produced ATP leave the matrix?
pumped out via antiporter
What is the purpose of the Malate-aspartate shuttle?
to get NADH into the matrix of the mt (NADH itself is too big to get into the matrix, so it is shuttled as malate)
In which organs does the malate-aspartate shuttle occur?
liver, kidney, heart
In which organs does the glycerol 3-phosphate shuttle occur?
brain and sk. muscle
What is the purpose of the glycerol 3-phosphate shuttle?
to pass energy via electrons/hydrogens into complex 3
What two conditions favor ROS formation?
mitochondria not making ATP
-lack of 02 in complex 4 and lack of ADP: leads to backup in ETC
excess NADH
What pathway produces the NADPH required to reduce hydrogen peroxide to H2O?
pentose phosphate pathway
What causes the difference of ATP produced in cellular respiration? (30-32 ATP)
The malate-aspartate shuttle produces 32 ATP per molecule of glucose in the liver, kidneys, and heart.
The brain and sk. muscle only generate 30 ATP per molecule of glucose due to the usage of the glycerol 3-phosphate shuttle instead of the malate-aspartate shuttle
What does glucose 6-phosphate inhibit?
hexokinase (glucose –> glucose 6-phosphate
If phoshpofructokinase-1 is inhibited, what happens to glucose 6-phosphate?
it goes to the pentose phosphate pathway (PPP) if it’s needed there
if not needed in PPP it is stored as glycogen
