Cellular Respiration Flashcards
glycolysis overall equation
C6H12O6 + 2ADP + 2Pi + 2NAD+ –> 2 pyruvate + 2 ATP + 2 NADH + 2H20 + 2H+
3 irreversible steps of glycolysis (enzymes)
glucose –> glucose-6-phosphate (hexokinase)
fructose-6-phosphate –> fructose-1,6-bisphosphate (phosphofructokinase)
phosphoenolpyruvate –> pyruvate (pyruvate kinase)
energy investment phase of glycolysis
ATP required first step with hexokinase and third step with PFK-1
what does hexokinase do that’s important to start glycolysis?
it traps glucose in the cell
how many times does energy payoff phase of glycolysis occur?
twice
once per molecule of glyceraldehyde 3-phosphate
produce two pyruvate at the end
what enzyme is rate-limiting enzyme?
PFK-1
catalyzes formation of fructose-1,6-bisphosphate from fructose-6-phosphate
how many carbons is pyruvate?
three carbons
total glycolysis energy
makes 4 ATP, uses 2 ATP –> NET 2 ATP
2 NADH
overview pyruvate oxidation
2 pyruvate are converted to 2 acetyl CoA
2 carbons are released as CO2
2 NADH are generated
where does pyruvate oxidation occur in eukaryotes and prokaryotes?
eukaryotes: matrix
prokaryotes: cytoplasm
how many steps of the CAC?
8
what are products of one turn of the CAC?
2 CO2
3 NADH
1 FADH2
1 ATP or GTP
how many cycles does a molecule of glucose go through CAC?
twice
1 glucose –> 2 pyruvate –> 2 acetyl-CoA –> 2 turns
what two enzymes of CAC are important to regulate speed of cycle?
isocitrate dehydrogenase and α-ketoglutarate dehydrogenase
*NAD+ –> NADH during both of these steps and a molecule of CO2 is released
is FAD or NAD+ a better electron acceptor?
FAD so it will pull electrons from succinate in the CAC
what is the function of the ETC?
electrons are transferred through the membrane proteins
ENERGY released generates electrochemical gradient
what is the function of chemiosmosis?
energy stored in the gradient is used to make ATP
why is oxygen important in the ETC?
it sits at the end of the ETC and accepts electrons and picks up protons from water
without it, ETC will stop and ATP will not be produced by chemiosmosis
where does ETC gets electrons?
electron carriers (FADH2 and NADH)
how to electrons travel in ETC?
they travel from higher to lower energy levels
release energy
functions of oxidative phosphorylation
- regenerate electron carriers (NAD+ and FAD) that are important for glycolysis and CAC
- proton gradient generated across the inner mitochondrial membrane
high [H+] in intermembrane space
low [H+] in matrix
NADH role in ETC
good at donating electrons (high energy) so energy released at complex I can pump protons from matrix into intermembrane space
FADH2 role in ETC
not as good at donating electrons (low energy) so feeds into ETC through complex II (which does not pump protons across the membrane)
order of complexes of ETC
I –> Q –> III –> cytochrome C –> complex IV
chemiosmosis
any process in which energy stored in a proton gradient is used to do work
ATP synthase role
the flow of H+ protons causes it to turn which catalyzes addition of phosphate to ADP to capture energy as ATP
(protons flow from intermembrane space to matrix)
what happens if ATP synthase not used to synthesize ATP?
energy can be released as heat
uncoupling proteins are channels that allow proteins to pass to matrix –> dissipated as heat
where do parts of cellular respiration occur?
glycolysis: cytosol
pyruvate oxidation: matrix
CAC: matrix
oxidative phosphorylation: intermitochondrial membrane
NAD+ and FAD reduction equations
NAD+ + 2e- + 2H+ –> NADH + H+
FAD + 2e- +2H+ –> FADH2
overall ATP yield
30-32 ATP
glycolysis: 2 ATP, 3-5 ATP (NADH) = 5-7 ATP
pyruvate oxidation: 5 ATP (NADH)
CAC: 2 ATP, 15 ATP (NADH), 3 ATP (FADH2) = 20 ATP
why is there variation of glycolysis NADH ==> ATP conversion?
NADH cannot cross the inner mitochondria membrane to enter ETC so it is converted via a shuttle system where some may be lost
pH of mitochondria parts
intermembrane space (high [H+]) low pH
cytosol
matrix (low [H+]) high pH
two types of fermentation (where)
alcohol in yeast
lactic acid in muscle
what does anaerobic cellular respiration use as final electron acceptor?
sulfate or nitrate
lactic acid fermentation
normal glycolysis
2 pyruvate –> 2 lactate (important for NAD+ regeneration)
lactate –> lactic acid –> back to pyruvate in liver
alcohol fermentation
normal glycolysis
2 pyruvate –> 2 ethanol (important for NAD+ regeneration)
what is gluconeogenesis?
formation of glucose
“almost” reverse of glycolysis
regulation of glycolysis and gluconeogenesis
ATP is negative allosteric inhibitor of glycolysis
AMP is negative allosteric inhibitor of gluconeogenesis
