Glycolysis/TCA Flashcards
Lec 23 - 28 (26 cards)
Where does the following process take place in a prokaryotic cell?
1) Glycolysis
2) TCA
3) ETC
4) Fermenation
1) Cytoplasm
2) Cytoplasm
3) Cell membrane
4) Cytoplasm
Where does the following process take place in a eukaryotic cell?
1) Glycolysis
2) TCA
3) ETC
4) Fermenation
1) Cytoplasm
2) Mitochondria
3) Mitochondrial membrane
4) Cytoplasm
What does the TCA cycle produce and release?
Produces - 3 NADH, 1FADH2, 1 A(G)TP
Releases - 4CO2
Which enzyme catalyzes the committed step of glycolysis?
A. Hexokinase
B. Glucokinase
C. Phosphoglucose isomerase
D. Phosphofructokinase
D
Which of the following best explains why glucose-6-phosphate cannot exit the cell?
A. It is too large
B. It is neutral and uncharged
C. It binds to membrane proteins
D. It is charged and hydrophilic, and cannot cross the lipid bilayer
D
Phosphoenolpyruvate (PEP) to pyruvate conversion is energetically favorable because:
A. It generates NADH
B. It uses ATP
C. It involves hydrolysis of phosphate with a large negative ∆G
D. It transfers a high-energy phosphate to ADP, producing ATP
D
Which of the following is true about metabolic pathways?
A. All steps are reversible
B. They operate near equilibrium
C. They often contain irreversible steps with large negative ∆G values
D. They do not require energy input
C
Which of the following is a product of glycolysis?
A. FADH₂
B. GTP
C. Pyruvate
D. Acetyl-CoA
C
Which cofactor is commonly used by hexokinase?
A. Ca²⁺
B. Zn²⁺
C. Mg²⁺
D. Mn²⁺
C
What enzyme catalyzes the conversion of glucose to glucose-6-phosphate?
Hexokinase (or glucokinase in the liver)
Why is glucose phosphorylation important for metabolism?
It traps glucose inside the cell and commits it to metabolism
Which step in glycolysis uses phosphofructokinase and why is it significant?
Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate; it is the committed and regulated step
What is the role of pyruvate kinase in glycolysis?
Catalyzes the final step of glycolysis; converts PEP to pyruvate, generating ATP
Which steps in glycolysis are considered irreversible?
Steps catalyzed by hexokinase, phosphofructokinase, and pyruvate kinase
What is the overall ∆G°′ of oxidative metabolism per mole of glucose?
-2834 kJ/mol
What does a large negative ∆G indicate about a metabolic reaction?
The reaction is highly exergonic and irreversible under cellular conditions
What is the thermodynamic significance of the ∆G°′ being highly negative in the pyruvate kinase-catalyzed step of glycolysis?
A: It indicates the reaction is essentially irreversible and drives glycolysis forward toward ATP production.
Q: Which glycolytic intermediates are triose sugars, and how are they interconverted?
A: Dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P); they are interconverted by triose phosphate isomerase.
Q: Explain why ATP hydrolysis is commonly coupled to unfavorable reactions in metabolism.
A: ATP hydrolysis releases a large amount of free energy, which can drive endergonic reactions forward when coupled.
Q: Why is phosphofructokinase considered the key regulatory enzyme in glycolysis?
A: It catalyzes the rate-limiting step and is allosterically regulated by ATP, AMP, and citrate, adjusting glycolytic flux based on energy status.
Q: Describe how glucose uptake and trapping inside the cell is achieved.
A: Glucose enters via GLUT transporters (facilitated diffusion); once inside, it is phosphorylated to glucose-6-phosphate, which is charged and cannot cross the membrane.
Q: What role does NAD⁺ play in glycolysis, and at which step is it involved?
A: NAD⁺ is reduced to NADH during the conversion of G3P to 1,3-bisphosphoglycerate by glyceraldehyde-3-phosphate dehydrogenase.
Q: How is metabolic irreversibility ensured in key steps of glycolysis?
A: Enzymes catalyzing steps with large negative ∆G values make the reactions essentially irreversible, enforcing directional flow.
Q: Why is the conversion of PEP to pyruvate used to drive ATP synthesis?
A: PEP has a high phosphoryl transfer potential; its conversion to pyruvate releases energy sufficient to phosphorylate ADP to ATP.
