Chapter 16 Notes Flashcards
The citric acid cycle produces __ ATP by substrate level phosphorylation.
2
Glucose is oxidized to produce what?
2 molecules of pyruvate, ATP, and NADH
The electron transport chain produces __ ATP by oxidative phosphorylation.
34
What are the 3 routes to oxidize pyruvate?
Anaerobic fermentation (2 different products), and aerobic metabolism
What are the products of anaerobic fermentation?
Ethanol and lactate
What are the products of aerobic metabolism?
CO2 + H2O
How many ATP molecules does glycolysis make? How?
2 by substrate level phosphorylation
What is stage one of glycolysis referred to as?
The Set Up Phase
What occurs in stage one of glycolysis?
Conversion of glucose to fructose-1,6-bisphosphate
How much ATP does stage 1 use?
2
Why is the first step in glycolysis so important?
Glucose enters the cell through transporters and is phosphorylated to glucose-6-phosphate which cannot pass through the membrane because it is not a substrate for the transporters. The addition of the phosphoryl group by ATP destabilizes the glucose, and allows further metabolism
Kinases?
Enzymes that catalyze the transfer of phosphoryl groups from ATP to an acceptor
How and why is fructose-1,6-bisphosphate generated from glucose-6-phosphate?
Through isomerization by conversion of an aldose to a ketose.
Because the fructose molecule is symmetric, whereas glucose is not. Then you can use it to get two 3-carbon compounds that are the same and use the same pathway to metabolize them (GAP and DHAP).
What is stage 2 of glycolysis referred to as?
The cleavage phase
What occurs in the cleavage phase?
Production of 2 molecules of glyceraldehyde-3-phosphate
Two enzymes convert the 6-carbon compound into a 3-carbon compound that can be isomerized to form another 3-Caron compound
What is stage 3 of glycolysis referred to as?
The Payoff Phase
What occurs in the Payoff Phase?
Production of 2ATP, 2NADH, and 2 pyruvate by further oxidation
5 enzymes involved using substrate level phosphorylation
This pathway occurs twice: once for each 3-carbon compound (DHAP and GAP)
For every glucose that enters glycolysis, two ___ sugars are produced.
Triose phosphate sugars
What type of enzyme is aldose?
Catalytic
What are the percentages of DHAP and GAP as they are produced in glycolysis? Why?
96% DHAP and 4% GAP because the subsequent reactions of glycolysis remove this product
What is an example of classic coupling of reactions?
DHAP and GAP
Which group is isomerized from DHAP and GAP?
Ketone to aldose
The Payoff Phase produces what?
4 ATP and 2 NADH
How is ATP in the Payoff Phase produced?
Substrate-level phosphorylation
Glycolysis produces a net __ ATP and __ NADH
2,2
Energy is stored in what two steps of the Payoff Phase?
1) GAP to 1,3-bisphosphoglycerate
2)
Isomerization vs mutate
Molecular formula is similar but the groups that get changed differ (change ligation of carbon=isomerization; mutase doesn’t change functional groups or arrangement around carbon-carbons coordinated with the same carbons); mutase catalyzes intramolecular shifts of chemical groups such as phosphoryl groups
Enolase?
Enol group formation
Why does phosphoenolyruvate have such a high phosphoryl-transfer potential?
The phosphoryl group traps the molecule in its unstable enol form. When the phosphoryl group is donated to ATP, the enol is converted to a ketone (more stable)
RxN type of hexokinase?
Phosphoryl transfer
RxN type of phosphoglucose isomerase?
Isomerization
RxN type of phosphofructokinase?
Phosphoryl transfer
RxN type of aldolase?
Aldol cleavage
RxN type of triose phosphate isomerase?
Isomerization
RxN type of glyceraldehyde 3-phosphate dehydrogenase?
Phosphorylation coupled to oxidation
RxN type of phosphoglycerate kinase?
Phosphoryl transfer
RxN type of phosphoglycerate mutase?
Phosphoryl shift
RxN type of enolase?
Dehydration
RxN type of pyruvate kinase?
Phosphoryl transfer
What are the three irreversible steps in glycolysis?
1) hexokinase
2) phosphofructokinase (PFK)
3) pyruvate kinase phosphoryl transfer
What is the most important control point in glycolysis? Why?
PFK because it is the committed step in glycolysis
During glycolysis, NADH is produced. Why does it need to be reoxidized in lactic a I’d fermentation?
To sustain glycolysis or else energy metabolism stops
What is the energy output of lactic acid fermentation compared to respiration?
Poor
When does lactic acid fermentation occur? Give an example.
When oxygen is limiting. During a burst of intense muscle activity such as a sprint
What conditions does ethanolic fermentation occur under? What occurs? Give an example.
Anaerobic conditions where NADH is recycled by the dual action of pyruvate decarboxylase and alcohol dehydrogenase. Ex. Beer and yeast fermentation
For pyruvate oxidation, the first step is catalyzed by what enzyme?
Pyruvate dehydrogenase complex
Where is energy stored in the pyruvate dehydrogenase complex?
NADH (in the high energy electrons)
Which reaction catalyzes the oxidative decarboxylation of pyruvate?
Pyruvate to acetyl CoA
The reaction of pyruvate to acetyl CoA is highly exergonic or endergonic? What two forms is energy stored in for this reaction?
Exergonic
1) reducing power as NADH
2) high energy thioester acetyl CoA
Describe the structure of phosphofructokinase.
It is similar to hemoglobin where oxygen is the only binding site but in PFK there are four catalytic binding sites and four allosteric binding sites. Once the catalytic sites of PFK are bound by ATP, then the allosteric sites will be bound by ATP
How do ATP concentrations affect affinity?
A high level of ATP inhibits the enzyme by decreasing it’s affinity for fructose-6-phosphate. AMP diminishes and citrate enhances the inhibitory effect of ATP.this makes the curve appear sigmoidal
How is glycolysis stimulated?
By energy charge
What is the key regulatory point in glycolysis?
Energy charge
What are the positive and negative regulators of PFK when glycolysis is inhibited?
Negative: ATP
Positive: AMP, ADP
What is PFK in the muscle regulated by?
Energy charge
What is PFK regulated by in the liver?
pH
How does glycolysis differ in the muscle when it is inhibited or stimulated?
Inhibited: there is a negative feedback of glucose-6-phosphate on hexokinase which inhibits the production of more glucose-6-phosphate; the high energy charge of excess ATP also inhibits PFK and pyruvate kinase
