Lecture 19 Flashcards
What is the Pentose Phosphate Pathway ?
– primarily an anabolic pathway, but it involves the catabolism of glucose and occurs in cytosol
T or F, PPP converts glucose to NADPH and ribose 5-phosphate
True
T or F, NADPH used as reducing power for biosynthesis
True
T or F, ribose-5-phosphate and its derivatives are the building blocks for synthesis of RNA, DNA, ATP, NADH, and other important molecules
True
What are the two ways plants make NADH?
– PPP
– photosynthesis
– organisms w/o photosynthesis use only PPP
What is the net product of NADPH CO2 and F6P and GAP from 3 molecules of glucose?
6 NADPH
2F6P
1 GAP
3 CO2
What is the main enzyme involved in the oxidative phase of PPP?
glucose 6 phosphate dehydrogenase
phosphogluconate dehydrogenase
What conditions favor product of NADPH?
- fatty acid synthesis
- oxidative stress
- synthesis of XNA, ATP, and NADH
Which enzyme in the oxidative portion of PPP is responsible for decarboxylation?
6- phosphogluconate dehydrogenase
What is the starting product and ending product of the oxidative portion of PPP
- Glucose 6 phosphate –> NADP+ is reduced to NADPH in the process
- ribulose-5-phosphate
True or false
PPP pathway can continue with only 1 glucose for only stage 1
trye
Which enzyme is responsible for the conversion of ribulose to ribose in PPP pathway?
phosphopentose isomerase
Which enzymes are used in the non-oxidative stage of PPP
- transketolase
- - transaldolase
What is the stoichiometric representation of reactants needed to create the typical amount of products of the last stage of PPP?
3C5 —> 2C6 + C3
Which of the following is the correct order of enzyme activity in the second stage of PPP?
A) transketolase X3
B) transketolase-transketolase-transaldolase
C) transketolase-transaldolase-transketolase
D) none of the above
C
Which of the following is NOT true of the transketolase and transaldolase reaction?
A)
Transketolase transfers a 2 carbon unit from ketose donor to aldose acceptor
B) both involve the participation of a ketose donor and acceptor
C) Transaldolase involves the transfer of a 4 unit carbon unit from ketose donor to an aldose acceptor
D) all of the above are true
C; that’s transketolase
Which products from PPP can enter glycolysis?
– F6P and glyceraldehyde-3-phosphate
summarize phase 1 and phase 2 of PPP
– Phase 1 - oxidative - glucose 6-P converted to ribulose 5-P with NADPH as a byproduct
– Phase 2 - nonoxidative – ribulose 5-P converted to glyceraldehyde 3-P and fructose 6-P
T or F, decisions on where glucose is directed are based on the metabolic needs of cell
True
Which enzyme is the RDS of PPP pathway?
g6p dehydrogenase
True or false.
NADP+/NADPH are competitive substrates of glucose 6 phosphate dehydrogenase
true
Which of the following is NOT true concerning the shifts between PPP and glycolysis?
A) A person with high oxidative stress levels would benefit from a allosteric activator of 6- phosphogluconate dehydrogenase
B) RBC breakdown due to the dysfunction of Peroxisome, an organelle involved in eliminating reactive oxygen species, would be aided by an increase shift in PPP pathway
C) a body in need of both lipid synthesis and energy would see an increase in both PPP and glycolysis
D) a cell with normal ATP levels and high need for reducing agents would see increases PPP as well as increase glycolysis
D
T or F, when NADPH is adequate, glycolysis is favored
true
T or F, interplay between the pentose phosphate pathway and glycolysis depends on metabolic state of cell
True
Which of the following shifts would be appropriate for a cell undergoing the S phase of the cell replication with normal oxidative needs?
A) completion of priming and trapping of glucose
B) increased activity of G6P dehydrogenase and 6-phosphogluconate dehydrogenase
C) decreased activity the first stage of glycolysis
D) increased activity of G6Pase
A
How many molecules of glucose would be needed to create 6 molecules of ribose-5-phosphate under high dna need and normal NADPH? A) 2 molecules of glucose B) 3 molecules of glucose C) 6 molecules of glucose D) 5 molecules of glucose
D
true or false
when NADPH and ribose 5 phosphate levels are balanced there is a preference to build NADPH and undergo the regular oxidative phase of PPP
true
Which of the following is NOT true when NADPH cellular needs is high?
A) decrease activity of F16BPase
B) increased activity of glycolytic aldolase
C) increase activity of phosphoglucoisomerase
D) recycle of PPP non-oxidative products
A
How many NADPH can be made from one molecule of glucose-6-phosphate when NADPH need is high?
12 NADPH
What is the net output per glucose molecule when in need of high levels of NADPH?
12 NADPH
12H+
6Co2
1 Pi
True or false
One would expect an upregulation of PPP and a downregulation of glycolysis when there is a high need for ATP and NADPH.
false. both upregulated
How many molecules would be needed to create at least 6 NADPH molecules and 6 F6P molecules under regular conditions? A) 3 glucose molecules B) 5 glucose molecules C) 7 glucose molecules D) 9 glucose molecules
D
Which conditions are correct for the product of ONLY 12 molecules of ribose when?
A) high NADPH and 12 molecules of glucose
B) cell undering rapid synthesis and 10 molecules of glucose
C) a resting cell with equal NADPH/ribose needs and 10 molecules of glucose
D) none of the above are correct
B
Which of the following would be true if a competitive inhibitor of triose phosphate isomerase was present in the cell?
A) it would take more molecules of glucose to get the same amount of ribose when under the cell is undergoing synthesis
B) the maximum speed of the conversion of glucose molecules under high synthesis needs would be reduced
C) the km of DHAP to the enzyme will decrease
D) none of the above are correct
A
Given your knowledge of the PPP, how many NADPH can be made from the full oxidation of 10 glucose molecules? A) 95 B) 20 C) 25 D) 120
D
What is the condition and the solution for PPP?
condition: cells require NADPH and ATP
solution: make NADPH via oxidative phase of PPP and make ATP by sending ribose 5-phosphate to the glycolytic pathway
What is the TCA?
– the citric acid cycle –> produces reduced electron carriers and some ATP
T or F, high- energy electrons are used to reduce O2 to water and this powers a proton gradient that is used to generate ATP
true
T or F, glucose, fatty acids, and amino acids can go into the citric acid cycle
True
T or F, these energy harvesting reactions occur in mitochondria
True
What is the overview of the TCA?
– 2-carbon units (from Acetyl Co-A) enter CAC cycle and are joined to oxoacetate
- resulting 6-carbon molecule is then sequentially oxidized to 2 molecules of CO2 and a 4-carbon unit
- -> generates high-energy electrons that are stored as NADH
- resulting 6-carbon molecule is then sequentially oxidized to 2 molecules of CO2 and a 4-carbon unit
– Ocaloacetate is then regenerated. This produces more reducing power (NADH, FADH2) and an ATP
– then cycle starts over again
How do we generate Acetyl CoA from pyruvate?
– produced by glycolysis in cytoplasm
– is then transported into mitochondria, where it is oxidatively decarboxylated to form Acetyl CoA
What is the end product of generating Acetyl CoA from Pyruvate?
– Acetyl Coenzyme A
– transferring a 2-carbon molecule to CoA (Coenzyme A)
Why is Acetyl CoA an activated carrier?
– oxygen esters are stabilized by resonance structures not available to thioesters
– hydrolysis is highly exergonic due to thioester linkage
What enzyme catalyzes the generation of Acetyl CoA from Pyruvate?
– pyruvate dehydrogenase
T or F, the pyruvate dehydrogenase reaction is a massive complex composed of 3 distinct enzymatic activities and 5 coenzymes
- TPP
- Lipoamide
- FAD
- NAD+
- CoA
