Biochem Test 4/24
Terms in this set (99)
Glc to G6P
G6P to F6P
F6P to 1,6 FBP
1,6 FBP to DHAP/G3P
DHAP to G3P
triose phosphate isomerase
G3P to 1,3-BPG
1,3 BPG to 3PG
-named for reverse
3PG to 2PG
2PG to PEP
PEP to pyr
-named for reverse
enzyme that removes the 3rd phosphate from a nucleoside triphosphate (ATP or GTP) and attaches that phosphate to the organic metabolite (metabolic intermediate)
several types of hexoses
phosphoglycerate kinase substrate
pyruvate kinase substrate
enzyme that rearranges the positions of atoms within a molecule
---there is no net addition to the substrate, and nothing is subtracted
subclass of isomerase, they move an entire functional group from one location to another within the same molecule
removes 2 Hs from the substrate, equivalent to removal of 2 protons and 2 electrons
-1 proton is release to solution as H+
-the other proton and 2 electrons make a hydride (H- ion) and they are transferred to NAD+ to make NADH
What are the 2 jobs of glycolysis step 6?
-removes a hydrogen from GAP
-phosphorylates the product (phosphate taken from solution)
What happens in glycolysis step 9?
dehydration reaction, the atoms of water are removed
-2 electrons are left behind to form a double bond
-makes: phosphorylated enol (double bond with phosphorylated OH group)
DHAP is converted to
GAP (G3P) to make the pathway more efficient
Glycolysis begins by....
spending 2 ATPs to:
-trap the sugar
-to make F6P more symmetric so 1,6 FBP can be split more evenly (DHAP and GAP)
Net gain of glycolysis in payoff stage:
2 ATP and 2 NADH
Each NADH processed by the ETC produces
Which steps of glycolysis are strongly downhill?
1, 3 and 10
If the steps in glycolysis are not downhill then...
their delta G values are ~0
The 3 downhill steps serve as...
sites of regulation
3 factors that effect favorability:
1- enol---keto tautomerization
2- separation of charges
3- formation of "happy" Pi
1st reaction in glycolysis:
conversion of glucose into glucose-6-phosphate
-unfavorable, which is why we use 1 ATP
Steps 6 and 7 of glycolysis result in...
the production of 2 high energy products, ATP and NADH
The chemical basis for the products of steps 6 and 7 is...
the conversion of a aldehyde to a carboxylic acid
-inserting O converts non polar bonds to make stable polar bonds
-formation of new ionizable group, a carboxylic acid (looses proton to water)
typical carboxyl pKa value:
~5, less then the physiological pH of 7 which is why the COO- deprotonated form is favored in the body, resulting in increase solubility in water
The 10th step of glycolysis couples...
PEP hydrolysis to ATP synthesis
----important to have "super high-energy" PEP to drive ATP synthesis
PEP gets converted to....
Pi + pyruvate (largely favorable)
small molecules regulate the enzymes catalyzing steps 1, 3 and 10 of glycolysis by...
binding at a regulatory site (R) which is separate from the catalytic site (C)
-binding causes conformational change
Hydrolysis of ATP produces the by-products:
ADP, AMP, and PPi
In terms of regulation ADP, AMP, PPi indicate....
low cellular energy
-which is why they function as activators in glycolysis catabolism
Step 1 product/inhibitor:
Step 3 substrate/activator
Step 10 substrate/activator
The long range product Ac-CoA functions as a _____ of glycolysis
Step 3 is inhibited by....
PEP is a product of...
step 9 of glycolysis
Step 10 is activated by...
1,6-FBP the product of step 3
Several different hexoses and disaccharides of hexoses are processed by the payoff stage of glycolysis, they are converted into...
a common point of convergence, which immediately proceeds to step 3 of glycolysis
Step 3 is catalyzed by...
High ATP concentrations inhibit _____ giving the graph a complicated shape
the phosphate group of G6P is simply cut off glucose and released into solution as Pi
What makes Bypass 3 favorable
-increased resonance of stabilized Pi
What enzyme catalyzes Bypass 3
phosphate simply cut off carbohydrate molecule (like Bypass 3)
What enzyme catalyzes Bypass 2?
Bypass 1 step 1/3
HCO3- is added (in the form of a new carboxyl group) to the methyl end of pyruvic acid, using the energy of 1 ATP to provide the energy for organizing HCO3- and pyruvate into a larger molecule (oxaloacetate)
Bypass 1 step 2/3
the energy of 1 GTP and the favorable entropy effect of releasing a CO2 gas molecule are used to convert oxaloacetate into the super-high-energy molecule, phosphoenolpyruvate
Bypass 1 step 3/3
the gamma phosphate group on ATP is transferred to GDP, because phosphate is put on another di-phosphate group (delta G ~0)
-enzyme= nucleoside diphosphate kinase
How to make bypass 1 favorable:
spending 2 ATP
How is it possible that both glycolysis and gluconeogenesis are exergonic in both directions? negative delta G values
Overall gluconeogenesis reaction:
2 pyr + 6 ATP + 2NADH ----> glucose
----extra 4 ATP compared to glycolysis
AMP allosteric regulation glycolysis vs. gluconeogensis
-activator of phosphofructokinase (glycolysis step 3 enzyme)
-inhibitor of fructose-1,6-biphosphate (Bypass 2)
acetyl-CoA regulation glycolysis vs. gluconeogensis
-inhibits pyruvate kinase (glycolysis step 10)
-activates pyruvate carboxylase (Bypass 1 step 1/3)
when G6P is converted into a ribose (a pentose) by oxidizing the aldehyde ending into a carboxylic acid group, which is then released as CO2
---also produces energy which can be stored in a high-molecular form
The energy produced from the pentose-phosphate shunt creates...
-negative phosphate distinctive from NADH
What are the 2 phases of the pentose phosphate shunt?
oxidative and non-oxidative phase
What happens to excess ribose
they are converted back into glycolysis intermediates
ex: 3 ribose to 2 F6P and 1 G3P (15C total)
Examples of water soluble hormones (cannot enter membrane)
-small proteins such as glucagon and insulin
Adrenalin effects involve
a G protein and adenylate cyclase
Adrenalin causes ATP to get converted into____ which then....
cAMP, which then causes other events to occur inside the cell, such as protein kinases
Glucagon and insulin are synthesized in...
95% of the pancreas is....
secreting hormones to the (outside) digestive tract
precursors such as trypsinogen and chymotrypsin
pancreatic duct to small intestine
5% of the pancreas is...
secretes into the blood (insulin and glucagon)
pancreatic vein to portal vein to liver
cyclic nucleotide phosphodiesterase
constantly breaking down cAMP in the cell
-inhibited by caffeine
Insulin triggers a...
glucagon and adrenalin both trigger a...
muscle cells have no receptors for....
muscle cells do not express the gene for...
-the enzyme which catalyzes Bypass 3, which reverses glucose ionization
step 10 of glycolysis is regulated by...
phosphorylation/ dephospho rylation
When adrenalin is released the liver and the muscles have opposite reactions in regards to...
The liver and muscles can have a different response to adrenalin because...
of 2 different isozymes of pyruvate kinase
-1 gets inhibited (liver) by adrenalin and the other does not
muscle hexokinase and liver glucokinase have different...
affinities for glucose
-shown in their Ks and Km values
"substrate-level control" in the liver
the velocity of step 1 is directly proportional to the concentration of the substrate (glucose)
V-init = S-init
Since the Km of muscle cells is much less then the physiological concentration of glucose...
the cells can be viewed as being fully saturated with glucose at all times
muscle hexokinase, but not liver glucokinase, is....
allosterically inhibited by its own product G6P
When insulin arrives in muscles cells...
it causes vesicles filled with the GLUT4 transporter to fuse with the outer plasma membrane (exocytosis) where they can then bind glucose in the bloodstream
---vesicles reform when insulin blood concentration falls
Why do we need lactic acid?
to reform NAD+, which we can only get from NADH
-when no oxygen present, H pasted back on pyruvate
After pyruvate is resynthesizes from lactate in the liver, the liver...
processes pyruvate all the way to glucose by gluconeogenesis (Bypass 1,2,3)
The Cori Cycle as a "futile cycle" but not really
some ATP is spent to make the glycolysis and gluconeogensis segments both favorable
--net cost of 4 ATPs per glucose, made up by aerobic oxidation recycled lactate (now glucose)