Lecture 16 Flashcards
Who are Hans and Buchner?
they saw that adding sucrose, a carbohydrate, to a yeast extract resulted in the process of fermentation that produces ethanol
Which of the following is NOT true concerning the alcohol fermentation of pyruvate?
A) Stimulation of pyruvate decarboxylase would result in the increase formation of acetaldehyde
B) Alcohol dehydrogenase is responsible for the regeneration of NAD+
C) increasing the pH of solution will increase the the formation of ethanol through fermentation
D) carbon dioxide is a product of alcohol fermentation
C
True or false
Reduction of NAD+ results in a decrease in pH and Oxidation of NADH results in an increase in pH
False, reverse is true
What is the net product of alcoholic fermentation?
2 ethanol, 2 ATP, 2 CO2, 2H20
What is the general function of Stage one of glycolysis?
To prime glucose to effectively trap them in the cell. It is meant to commit glucose into the cell and prevent escape out.
What is the net of Stage one of glycolysis?
-2ATP
2 glyceraldehyde-3-phosphate
True or false
Hexokinase IV has a bigger Km than Hexokinase 1
true
true or false
enzymatic reactions using ATP typically have MG2+ as a cofactor to stabilize the negative oxygens on phosphate
True
What is the purpose of hexokinase 1 In glycolysis
– It is the first step that phosphorylates glucose to glucose 6 phosphate. This traps glucose in the cell and destabilizes the glucose so down the line cleave is more favorable
What is the name for different isoforms of a specific enzyme that may exist in different tissues?
isozymes
What is the function of phosphoglucose isomerase? aka Step 2 in Energy Investment Phase
It changes the glucose, an aldose sugar, into a fructose, a ketose sugar. It also creates an alcohol group at the c1 position that is able to be phosphorylated in a subsequent reaction
– also sets up molecule for symmetrical cleavage in reaction 4
What is the function of phosphofructokinase? aka Stage 1, step 3 – phosphorylation
it uses 1 ATP and phosphorylates Fructose 6-phosphate to Fructose 1-6 - bisphosphate in an irreversible manner
What is the function and products of the aldolase enzyme in glycolysis? aka Stage 1, step 4
It cleaves F16BP to dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GAP), two 3 carbon units
True or false. The retro-aldol condensation reaction in glycolysis is considered to be highly endergonic under standard conditions.
true, but because the products are continually used as glycolysis continues, it becomes a slightly exergonic reaction
True or false.
Inhibition of triose phosphate isomerase would inhibit glycolysis from occuring
false. it would just half products in half and result in no net product of ATP
True or false
96% of triose phosphate is in DHAP form under standard conditions because of the strong equilibrium favor to this product
true
What is the net product of Stage 1 of glycolysis?
-2ATP +2GAP
What is the general overview of Stage 2 of glycolysis?
– 2 Glyceraldehyde 3 phosphate are further oxidized and it is joined with orthophosphate to yield an intermediate that will product 1 ATP molecule.
–This product will be rearranged and the water will be removed. Finally, ATP will be generated again as the final pyruvate is created.
What happens in the first reaction of glyceraldehyde 3 phosphate?
– GAP is oxidized and phosphorylated to form 1,3 bisphosphoglycerate (BPG) by the enzyme GAP dehydrogenase. (GAPDH) This forms 1 NADH molecule and 1 H+.
True or false
oxidation of an aldehyde to a carboxylic acid occurs when NADH is produced
True
True or false
Generation of BPG results in the formation of a molecule with a high phosphoryl group (potential) transfer
True
Why is the formation of BPG favorable despite creation of a high energy compound?
- It is coupled to the oxidation of a compound that is very exergonic.
- This is coupled to the addition of a orthophosphate that results in BPG formation, which overall will be favorable.
What enzyme is responsible for the reaction of 13BPG to 3-phosphoglycerate
Phosphoglycerate kinase
Why is the reaction of BPG to 3PG favorable?
– You form ATP from the cleavage of a higher phosphoryl transfer group, BPG, that is very favorable to the synthesis of ATP.
true or false
formation of ATP during glycolysis is known as substrate level phosphorylation?
true
Which enzyme is involved in the reaction between 3PG to 2PG?
phosphoglycerate mutase (PGM)
– simple reaction = involves swap of phosphoryl and hydroxyl groups on C-2 and C-3
– slightly endergonic reaction that proceeds to right bc concentrations of 3PG are higher than 2PG in cell
aka deltaG is negative
Which enzyme is involved in the reaction between 2PG and phosphoenol pyruvate? (PEP)
enolase
– to generate a compound of high phosphoryl-transfer potential, bond linking C2 and C3 needs to be converted from single to double bond via dehydration reaction (releasing water) creating an enol
What is the structure of phosphophenol pyruvate?
it is a three carbon compound that resembles an enol except that the oxygen is attached to a phosphate.
Which enzyme is involved in the reaction of phosphophenol pyruvate to pyruvate?
pyruvate kinase
– catalyzes transfer of phosphoryl group to ADP to form ATP
– reaction clarifies why PEP has high phosphoryl-transfer potential - the phosphoryl group traps the molecule in an unstable enol form
– as soon as phosphoryl group is removed, enol form rapidly converts to more stable keto form, i.e. pyruvate
– an irreversible reaction and highly exergonic, but making ATP in process
What is the structure of pyruvate?
it is a 3 carbon structure that contains a carboxylic acid end, a ketone, and a methyl end.
What is the Net product of glycolysis?
2 pyruvate 2 ATP 2 NADH 2 H+ 2H20
What is the net delta G released during glycolysis?
-102.9kj/mol
true or false
all reactions in glycolysis under biological conditions are either 0 or slightly exergonic
true
Which of the following enzymes do not catalyze irreversible reactions in glycolysis? A) Hexokinase B) phosphofructokinase C) pyruvate kinase D) triose phosphate isomerase
D
How can 1,3-BPG be used to synthesize ATP?
– has very high phosphoryl transfer potential, higher than ATP, thus it can be used to synthesize ATP
What is substrate-level phosphorylation?
– when phosphate donor is a substrate with high phosphoryl-transfer energy potential
Explain the coupling of an exergonic reaction to an endergonic reaction and it’s importance
– aldehyde is oxidized to an acid, then instead of releasing the acid (exergonic aspect), the enzyme incorporates a Pi, creating a high energy acyl-phosphate compound (endergonic aspect)
– the reactions must be coupled otherwise the 2nd would never occur in the cell
T or F, only GAP is on the direct path for glycolysis
True; thus to make full use of original glucose molecule ( and not have a separate pathway for processing) DHAP needs to be converted to GAP
T or F, DHAP isomerization is readily reversible
True; catalyzed by triose phosphate isomerase
What are the two important features of the conversion of GAP to 1,3 - BPG
1.) oxidation of the aldehyde to carboxylic acid by NAD+
– oxidation and joining
