Chapter 16: Glycolysis
What enzyme is used to catalyze reaction 1 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
the enzyme hexokinase will catalyze reaction one. this will phosphorylate glucose Glucose-6-phophate is formed and can not exit the cell This reaction is not reversible because it would require a high concentration of ADP
What is the fate of glucose 1-phosphate
It can be converted to glucose-6-phosphate and used in the glycolytic pathway
How does pyruvate regulation in the liver operate?
It is regulated by energy charge regulated allosterically, same way as in muscle It is also regulated by covalent modification low blood glucose leads to the phospohorylation and inhibition of liver pyruvate kinase
Why must the NADH be re- oxidized to to NAD+? What reaction does this occur in? What does this reaction look like?
NADH generated in glycolytic reaction 6 must be re-oxidized to NAD+ with out the regeneration of NAD+ the ratio of NAD+/NADH increases, creating an imbalance in cellular redox state
What does reaction 7 start with and go to
Starts with 1,3-bisphosphoglycerate and is converted to 3-phosphoglycerate
What does reaction 4 start with and go to
Starts with fructose-2,6 bisphosphate and goes to glyceraldehyde-3-phosphate and dihydroxyacetone-phosphate.
What does reaction 3 start with and go to and why does it start with this?
Starts with fructose-6-phosphate and goes to fructose-1,6-bisphosphate
What does reaction 1 start with and go to and why does it start with this?
Starts with glucose because its more like to be pushed through a biological membrane this will go to glucose-6-phosphate (its phosphoylated so that it is trapped outside of the cell.
What does reaction 2 start with and go to and why does it start with this?
Starts with glucose-6-phosphate and goes to fructose-6-phosphate.
What does reaction 10 start with and go to
Starts with phosphoenol-pyruvate and goes to pyruvate
At this point what has has been done in the glycolytic path way?
Step 1 has been completed of the glycolytic pathway. the glucose been made to be involved in a redox reaction there are two 3 carbon glyceraldehye 3 phosphate molecules (GAP) ready to be converted to pyruvate.
How do we know that energy charge regulates glycolysis in muscle? Looking specifically at phosphofructokinase -1 (PFK-1)
When there is low energy (low ATP and high AMP) The reaction will be sped up. When there is high energy (high ATP and low AMP) the reaction of fructose 6 phophate will be slow.
Why is glycolysis considered an energy conversion pathway?
it converts one glucose to 2 pyruvates and 2 ATP (Net conversion)
Why is glucose such a prominent fuel?
it forms under prebiotic conditions and its the most stable hexose.
Why is the regulation of glycolysis different in the liver in the muscle?
it is more complex because the liver is responsible for maintaining blood glucose in physiological range.
What does reaction 5 start with and go to
it starts with dihydroxyacetone-phosphate and is converted to glyceraldehyde 3- phosphate.
What is the purpose of glycolysis and what does it do?
purpose is to make ATP. It converts one glucose to 2 pyruvates.
What does reaction 9 start with and go to
starts with 2-phosphoglycerate and is converted to phosphoenol-pyruvate
What is reaction three in the galactose - glucose conversion pathway What does this reaction look like and why is it important?
the UDP-galactose is converted to UDP glucose by the enzyme UDP- glactose 4- epimerase This reaction will regenerate the UDP-glucose so the reaction can be repeated.
What enzyme is used to catalyze reaction 9 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
the enzyme enolase is used. enolase will convert 2-phosphoglycerate (2-PG) into phosphoenolpyruvate (PEP) Phosphoenolpyruvate has a high phosphoryl transfer potential because phophate traps compound in unstable enol tautomer its high energy reversible
What two stages can glycolysis be thought be thought as?
1.) glucose becomes trapped in a cell and modified so that it can be cleaved into a pair of phophorylated 3-carbon compounds one six carbon molecule to two carbon molecules 2.) oxidation of the 3- carbon compounds to pyruvate and generation of pyruvate
What is the 2 enzymes that are used to convert pyruvate to ethanol? What does the reaction look like?
1.) pyruvate decarboxylase 2.) alcohol dehydrogenase
What is the net effects of glycolysis? Where in the pathway are things converted?
2 molecules of ATP produced 2 molecules of NAD+ reduced to 2 molecules of NADH
What does reaction 8 start with and go to
3- phophoglycerate is convereted to 2-phosphoglycerate
Why is glycolysis an energy conversion pathway
Because 2 ATP molecules are formed in the conversion into pyruvate.
Why are people lactose intolerant?
Because they lack the enzyme lactase that is necessary for break down of lactose to galactose and glucose This is called hypolactasia
What is the summary of phosphofructokinase-1 regulation in the liver?
F-2,6, bisphosphate is an activator of PFK-1 Atp is a substrate and allosterically inhibitor of PFK-1 AMP allosterically activates PFK-1 by relieving the ATP inhibition
what is the first step in the galactose - glucose conversion pathway What does this look like?
Galactose is phosphorylated to galactose 6- phosphate
Why does glucose 6 phosphate have a pivotal role in the liver?
Glucose 6 phosphate can be used for several different pathways
What is the summary of pyruvate utilization?
In aerobic conditions, it is oxidized to acetyl CoA which enters the citric acid cycle for further oxidation. under anaerobic conditions (Ethanol): conversion to ethanol under anaerobic in muscles: pyruvate is converted to lactic acid
How does the glyceraldehyde 3 phosphate dehydrogenase (DAPDH) accomplish the conversion of GAP to 1,3 bisphosphoglycerate What do these reaction look like?
It preforms 2 reactions. oxidation and acyl phosphate formation the thiol linage allows oxidation but prevents a drop in free energy so that phosphoryl group can be added covalent linage between substrate and enzyme accounts for drop in free energy
What does reaction 6 start with and go to
It starts with glyceraldehyde 3- phosphate and is converted to 1,3- bisphosphoglycerate (will have an increase in phosphoryl transfer potential.
What does fermentation allow for?
It will allow for the usable energy in the absence of oxygen. Muscles can function anaerobically using lactic acid fermentation but this can only be used for a short period of time because of the build up lactic acid in the muscles.
What other reaction does lactate dehydrogenase catalyze and what does this allow? What does this look like?
It will catalyze the reaction to oxidize NADH to NAD+. The conversion of glucose into 2 molecules of lactate is called lactic acid fermentation.
How is is the redox balance restored?
NADH generated by glycerldhehyde 3- phosphate dehydrogenate (glycolysis) is oxidized by alcohol dehydrogenase (fermentation) thus regenerating NAD+
What is the conclusion about PFK-1 relating to energy charge?
PFK-1 is allosterically inhibited by ATP and allosterically stimulated by AMP PFK -1 is a key regulator of metabolism
What enzyme is used to catalyze reaction 8 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme in this reaction is phosphoglycerate mutase This enzyme converts 3-phosphoglycerate to 2-phosphoglycerate. this is reversible
What enzyme is used to catalyze reaction 10 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme pyruvate kinase (PK) is used pyruvate kinase (PK) will convert phosphoenolpyruvate (PEP) into pyruvate ADP is phosphorylated at the expense of PEP generating ATP and pyruvate This reaction is irreversible
What enzyme is used to catalyze reaction 7 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme used in this reaction is phosphoglycerate kinase (PGK) this enzyme is used to convert 1,3 bisphosphoglycerate to 3-phosphoglycerate. Energy that was traped in the oxidation of 1,3 bisphophoglycerate is used to form ATP. The 1,3 bisphosphoglycerate has a higher phosphoryl transfer potential than ATP and will power the synthesis of ATP from ADP. This produces 3-phosphoglycerate this reaction is unique because it involves a kinase but it is still reversible (other kinases are not reversible)
What enzyme is used to catalyze reaction 2 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme used is glucose 6 phosphate isomerase. This catalyzes the conversion of glucose 6-phosphate (G6P) to fructose- 6- phosphate (F6P) This reaction is easily reversible.
What enzyme is used to catalyze reaction 6 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme used is glyceraldehyde 3- phosphate dehydrogenase (DAPDH) The compound glyceraldehyde 3- phosphate (GAP) is converted to 1,3 bisphosphoglycerate and has a high phosphoryl transfer potential the glyceraldehyde 3- phosphate (GAP) has been oxidized Reaction is reversible
What enzyme is used to catalyze reaction 4 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme used to catalyze the reaction Fructose 1,6 bisphosphate (F 1,6 BP) to dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3- phosphate (GAP) This reaction begins with cleavage of frucose 1,6 bisphosphate (F 1,6 BP) by aldose
What enzyme is used to catalyze reaction 3 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
The enzyme used to catalyze the reaction Fructose 6 phosphate (F6P) to Fructose 1,6 bisphosphate (F1,6BP) is phosphofructokinase (PFK-1) This enzyme traps the carbohydrate in the fructose form by the addition of a second phosphate to form fructose 1,6-bisphosphate (F1,6BP). this reaction is irreversible
What does the reaction mechanism of regulation by low blood glucose look like?
The phosphoryltion that occurs at low blood glucose level will lead to a less active pyruvate kinase.
How do the regulatory methods change when the muscle goes from resting to contracting (active state)?
There will not be negative feed back of the glucose-6-phosphate intermediate because the concentration will be low. This will allow for hexokinase to phosphorylate glucose There will also be a low energy charge (positive because lack of ATP have a lot of AMP) This will drive the enzyme PFK and pyruvate kinase to function normally.
What are fermentation reactions?
They are a way of oxidizing NADH to NAD+ to restore redox balance
How can sugars similar to glucose be converted to glucose to be used in the glycolytic pathway?
They are epimers of each other so a series of reaction must be done to swap they hydroxyl group. Galactose is phosphorylated to Galactose 6 phosphate UDP: Glc: GA1-pp Uridylyltransferase is used to exchange the galactose for glucose. the enzyme UDP-gal epimerase will then regenerate the UDP galactose Glucose 1- phosphate will continue to the glycolysis pathway it will then be converted to glucose - 6 - phosphate by phosphoglycomutase
How do rapidly growing tumors get ATP what transcription factor allows this and what other people have this transcription factor.
They get ATP metabolizing glucose to lactic acid even in the presence of oxygen This is called aerobic glycolysis The transcription factor HIF-1 facilitates aerobic glycolysis HIF-1 also activates the glycolytic pathway in muscles in people who exercise
What do fermenting bacteria use at their final electron acceptor?
They use organic compounds Fermentations are ATP generating pathway that transfers electrons between 2 organic compounds. Formation of ethanol from pyruvate requires 2 enzymes
Why is magnesium used during ATP binding?
This is because ATP will bind to 2 magnesium because of opposite charge attractions this allows for better binding to enzyme active site
Which reactions in the glycolytic pathway are controlled/ regulated and how are they? When does this regulation occur? What does the flow chart of this process look like?
This process occurs when the skeletal muscles are at rest. They are regulated in two ways: When intermediates in glycolytic pathway are at a high concentration, feedback inhibition will take place When energy charge is high; inhibition will occur When glucose - 6 phosphate is at a high concentration is will have negative feedback inhibition on the enzyme hexokinase. (the rest of the intermediates are still at high concentration tho) when the charge get svery high (more negative from the ATP) the high charge will inhibit phosphofructokinase (PFK) to form fructose 1,6 bisphosphate (F 1,6 BP) from fructose 6 phosphate (F6P) and also inhibit the enzyme pyruvate kinase from converting phophoenolpyruvate to form pyruvate
What is the last reaction in the galactose - glucose conversion pathway?
This reaction does not have to be the last. it could be the third. This converts the glucose 1 phosphate to glucose 6 phosphate with the enzyme phosphoglucomutase
What enzyme is used to catalyze reaction 5 of the glycolytic pathway. what does this reaction entail? Is this reaction reversible?
This reactions uses the enzyme triose phosphate isomerase (TPI) The glyceradlehyde 3- phosphate (GAP) can be processed to pyruvate, but the dihydroxyacetone phosphate (DHAP) can not. The triose phosphate isomerase (TPI) will convert the dihydroxyacetone phosphate into glyceraldehyde 3 phosphate (GAP) so that dihydroxyacetone phosphate can be converted to pyruvate
What is the effect of fructose 2,6 bisphosphate and ATP on the catalytic rate of liver phosphofructo kinase 1?
as the concentration of fructose 2,6 bisphosphate increases the rate of the catalytic turnover of fructose 6 phosphate to fructose 1,6 phosphate ATP at low concentration will stimulate the enzyme phosphofructokinase as was seen in normal muscle.
How is galactose converted into glucose - 6- phosphate
by the galactose - glucose conversion pathway.
What is reaction 2 in the galactose - glucose conversion pathway
galactose 1- phosphate reacts with UDP glucose (uridine group is on this molecule. This reaction is catalyzed by galactose 1- phosphate uridyl transferase. This yields UDP-galactose (uridine group is on his molecule now) and glucose 1-phosphate
What if the transferase is missing in the galactose - glucose conversion pathway What does the toxic reaction look like?
galactose will become very toxic called classic galactosemia This is when the galactose 1- phosphate uridyl tansferase is deficient or missing can lead to enlarged liver, or cataract formation the galactose is converted to galactitol by the enzyme aldose reductase
How is Phosphrofuctokinase activated in the liver?
the intermediate fructose 2,6 bisphosphate is needed in order to active phosphofructose kinase-1 this will allow the reaction of Fructose - 6 - phosphate to fructose 1,6 bisphosphate
