Krebs Cycle Flashcards
can pyruvate enter the mitochondria?
Yes
what molecule is pyruvate converted to in the first step of the TCA cycle?
Acetyl CoA
function of pyruvate dehydrogenase
removes hydrogen from pyruvate and gives it to NAD+ to convert it to NADH
- makes carbon weak and falls off
- allows CoA to bind
- gives off co2
Can pyruvate enter the TCA cycle as it is?
no, must be converted to acetyl coa
krebs cycle happens in the
mitochondria
what happens to acetyl coa and oxaloacetate
they fuse together to make citrate
- 2 carbons fuse with 4 carbons coa falls off
citrate has how many carbons
6
function of citrate synthase
fuses oxaloacetate and acetyl coa
what deactivates citrate synthase
lots of ATP NADH succinyl coa
what activates citrate synthase
adp
citrate is converted to
isocitrate
is the conversion of citrate to isocitrate reversible or irreversible?
reversible
what enzyme converts citrate to isocitrate
aconitase
what is fluoroacetate?
it inhibits aconitase - stops production of ATP - rat poison
what is isocitrate converted to?
alpha ketoglutarate
how many carbons are in isocitrate? alpha ketoglutarate?
6 in isocitrate, 5 in alpha keto glutarate
what is the role of isotrate dehydrogenase?
- converts isocitrate to alpha ketoglutarate
- takes a hydrogen and gives it to nad+ to form nadh
- carbon of isocitrate gets weak and falls off
- gives off co2
what deactivates isotrate dehydrogenase?
atp
explanation - high amount of atp mean that we do not need any more in the system so the krebs cycle is not needed to keep going
what activates isotrate dehydrogenase?
ca2+ and adp
explanation - ca2+ works with atp, if ca is signaling it needs atp then the krebs cycle need to work, high amounts of adp mean that we need energy as well
what two molecules work together for muscle contraction
atp and ca2+
where does glycolysis occur
in the cytoplasm
what is alpha ketoglutarate converted to
succinyl coa
how many carbons are in a ketoglutarate? succinyl coa?
5 and 4
function of a ketoglutarate dehydrogenase
- converts a ketoglutarate to succinyl coa
- gives hydrogen to nad+ to form nadh
- carbon fall off to give off co2
- coa binds to carbon
succinyl coenzyme a inhibits what two enzymes via feedback mechanism
citrate synthase and alpha ketoglutarate dehydrogenase
what activates alpha ketoglutarate dehydrogenase?
calcium
what deactivates alpha ketoglutarate dehydrogenase?
NADH and succinyl coa
- accumulation of these means that we have enough energy and do not need to go on with the krebs cycle
what is succinyl coa converted to
succinate (4c)
why does the coa fall off of succinyl coa
- inorganic phosphate attaches to gdp to make gtp
- creates energy to remove coa
two ways to get rid of coa
- fusing with a molecule that doesnt have coa will force it to fall off
- inorganic phosphate fusing with gdp to make gtp forms energy to take off coa
gtp has affinity for… and what happens
adp - gives phosphate to adp to form atp
what enzyme converts succinyl coa to succinate
succinyl coa synthetase
what is succinate converted to
fumarate
what enzyme converts succinate to fumarate
succinyl dehydrogenase
what is the function of succinyl dehydrogenase
- converts succinate to fumarate
- gives two hydrogens at the SAME time to fad to form fadh2
- cannot use nad here because we need a molecule that can take two hydrogens at the same time
fumarate fuses with… to be converted to
water to be converted to malate
oxaloacetate and malate can
talk to each other
can oxaloacetate leave the mitochondria?
no
can malate leave the mitochondria
yes
what enzyme converts malate to oxaloacetate
malate dehydrogenase
function of malate dehydrogenase
- convertse malate to oxaloacetate
- gives hydrogen to nad to form nadh BUT not from the first carbon
what is the transition step
conversion of pyruvate to acetyl coa
connects cytosol to mitochondria
how many molecules of CO2 are made in the kerbs cycle
2
how many molecules of nadh are made in the tca cycle
3
how many molecules of atp are made - tca
1
how many molecules of fadh2 - tca
1
what are the steps of oxidative decarboxylation
- conversion of isocitrate to alpha ketoglutarate using isocitrate dehydrogenase
- conversion of alpha ketoglutarate to succinyl coa using alpha ketoglutarate dehydrogenase
how many molecules of nadh are produced in oxidative decarboxylation
2
how many molecules of co2 are produced in oxidative decarboxylation
2
what other role does alpha ketoglutarate have?
amino acid synthesis (neurotransmitters)
what other role does oxaloacetate have?
amino acid synthesis
what other role does succinyl coa have?
heme synthesis
what other role does malate have?
gluconeogenesis
what two enzymes need vitamin B1 in order to work properly
pyruvate dehydrogenase and alpha ketoglutarate dehydrogenase
what part of the body is involved with Dry beriberi
CNS
what part of the body is involved with wet beriberi
cardiovascular system
what is beriberi
deficiency in vitamin B1 (thiamin) - vitamin that allows tca enzymes to work at full capcity
what two enzymes does arsenic inhibit completely
pyruvate dehydrogenase and alpha ketoglutarate dehydrogenase
symptoms of arsenic poisoning
- memory loss and other neurological conditions such as parkinsons
- brain damage
- apoptosis of cerebral neurons
- brain dna damage leading to brain cell death
