Chapter 4-2. Glycolysis
Recommended Post: 【Biology】 Chapter 4. Cell and Energy Metabolism
1. Overview
Figure 1. Glycolysis whole process
1. Overview
⑴ Phosphorylation of the substrate level: Glycolysis
⑵ Chemical osmotic phosphorylation
① Photophosphorylation
② Oxidative phosphorylation
⑶ Hormones and glycolysis
① Insulin: Promotes the glycolysis.
② Glucagon: Inhibits the glycolysis.
2. Step 1 out of 10 Steps
Figure 2. Glycolysis Step 1 Mechanism
⑴ Overview: Investment phase, Irreversible·voluntary(ΔG < 0) reaction → Active allosteric regulation for reaction rate
⑵ Glucose + ATP → g-6-ⓟ + ADP
① Glucose is the least oxidized form of alcohol.
⑶ Enzyme: Hexokinase (Gene Name: HK2)
① Feature: Isozyme
② Located in cytoplasm.
③ g-6-ⓟ promotes the reverse reaction by inhibiting hexokinase.
⑷ Reverse reaction enzyme: glucose-6-phophatase
⑸ The significance of this step
① Prevents glucose from being released out of the cell.
② Mechanism for maintaining the glucose concentration gradient.
③ Increase the energy level of the reactants for glycolysis.
⑹ Reactions involving g-6-ⓟ
① Example 1. Glycolysis
② Example 2. Generating glycogen via g-1-ⓟ
③ Example 3. Pentose phosphate pathway
3. Step 2 out of 10 Steps
Figure 3. Glycolysis Step 2 Mechanism
⑴ Overview: Investment phase
⑵ g-6-ⓟ ⇄ F-6-ⓟ
⑶ Enzyme: glucose-6-phosphate isomerase (= phophoglucoisomerase, Gene Name: GPI)
4. Step 3 out of 10 Steps
Figure 4. Glycolysis Step 3 Mechanism
⑴ Overview: Investment phase, irreversible·voluntary(ΔG < 0) reaction → Active allosteric regulation for reaction rate
⑵ F-6-ⓟ + ATP → F-1,6-bisphosphate + ADP
⑶ Enzyme: PFK-1 (Gene Name: PFK1)
① Allosteric enzyme
② Active site: F-6-ⓟ and ATP as substrate.
③ Positive regulation site: AMP, ADP, NAD+, Ca2+ (muscle), F-2,6-bisphosphate
④ Negative regulation site: ATP, Citric acid, NADH
⑤ Located in cytoplasm.
⑷ Reverse reaction enzyme: FBPase Ⅰ (fructose-1,6-bisphophatase)
⑸ PFK-1 activation - ATP experiment: Bell-shaped curve
⑹ F-2,6-bisphosphate
① F-6-ⓟ + … ⇄ F-2,6-bisphosphate + … (Enzyme: PFK-2)
② F-2,6-bisphosphate + … ⇄ F-6-ⓟ + … (Enzyme: FBPase Ⅱ)
③ The formation of F-2,6-bisphosphate indicates that there is a high concentration of F-6-ⓟ. Therefore, to promote glycolysis, PFK-1 is activated.
④ F-2,6-bisphosphate is allosteric inhibitor for FBPase Ⅰ.
5. Step 4 out of 10 Steps
Figure 5. Glycolysis Step 4 Mechanism
⑴ Overview: Investment phase
⑵ F-1,6-bisphosphate ⇄ DHAP (ketose) + G3P (aldehyde)
⑶ G3P(glyceraldehyde-3-phosphate) is aldyhyde, so G3P is reactive to be oxidized to carboxylic acid.
⑷ Enzyme: aldolase (Gene Name: ALDOA)
6. Step 5 out of 10 Steps
Figure 6. Glycolysis Step 5 Mechanism
⑴ Overview: Investment phase
⑵ DHAP(dihydroxyacetate phosphate) ⇄ G3P
⑶ The reaction rate can be regulated by controlling the equilibrium between DHAP and G3P.
⑷ Enzyme: Triose phosphate isomerase
7. Step 6 out of 10 Steps
Figure 7. Glycolysis Step 6 Mechanism
⑴ Overview: Retrieval phase
⑵ G3P + NAD+ + pi ⇄ 1,3-BPGA + NADH
⑶ Because the process of NAD+ reduction is very important, if PFK-1 is not functioning, pentose phosphate pathway operates to produce G3P.
⑷ 1,3-BPGA: 1,3-bisphosphoglycerate
⑸ Enzyme: Glyceraldehyde-3-phosphate dehydrogenase (Gene Name: GAPDH)
8. Step 7 out of 10 Steps
Figure 8. Glycolysis Step 7 Mechanism
⑴ Overview: Retrieval phase, Irreversible·voluntary(ΔG < 0) reaction → Active allosteric regulation for reaction rate
⑵ 1,3-BPG + ADP + pi ⇄ 3PGA + ATP
⑶ 1,3-BPG ⇄ 2,3-BPG ⇄ 3PGA
① 1,3-BPG ⇄ 2,3-BPG (Enzyme: BPG mutase)
② 2,3-BPG ⇄ 3PGA (Enzyme: 2,3-BPG phosphatase)
③ Loss in energy yield due to the absence of ATP production.
⑷ 3PGA: 3-phosphoglycerate
⑸ Enzyme: Phosphoglycerate kinase (Gene Name: PGK1)
① 2,3-BPG ⇄ 3PGA reaction is limited when there is a lack of pyruvatee kinase, i.e. when the glycolysis is active.
② The amount of 2,3-BPG increases when the glycolysis is active (mainly in tissue cells).
③ Bohr effect: Increaseing the amount of 2,3-BPG promotes the release of oxygen from oxy-hemoglobin.
9. Step 8 out of 10 Steps
Figure 9. Glycolysis Step 8 Mechanism
⑴ Overview: Retrieval phase
⑵ 3PGA (a.k.a 3PG) → 2PGA (a.k.a 2PG)
⑶ 2PGA: 2-phosphoglycerate (= 2PG)
⑷ Enzyme: phosphoglycerate mutase (Gene Name: PGAM1)
10. Step 9 out of 10 Steps
Figure 10. Glycolysis Step 9 Mechanism
⑴ Overview: Retrieval phase
⑵ 2PGA → PEP
⑶ PEP: Phosphoenolpyruvate
⑷ Enzyme: Enolase (Gene Name: ENO)
11. Step 10 out of 10 Steps
Figure 11. Glycolysis Step 10 Mechanism
⑴ Overview: Retrieval phase, irreversible·voluntary(ΔG < 0) reaction → Active allosteric regulation for reaction rate
⑵ PEP + ADP → pyruvate + ATP
① Pyruvate is carboxylic acid, so it is the most oxidized form.
⑶ Enzyme: Pyruvate kinase (Gene Name: PKM)
① Insulin: Makes glycolysis more preferred to lower the blood glucose level.
② Glucagon: Makes glycolysis less preferred to higher the blood glucose level.
③ Located in cytoplasm.
Input: 2019.01.15 19:25
Revised: 2024.07.22 00:21