BISC 220 - Glycolysis

What is Glycolysis?

Is a metabolic pathway driven by a series of cytosolic enzymes with the ability to catabolize/breakdown glucose (a 6 carbon compound) into two pyruvate molecules (3 carbon compounds)

Where does glycolysis occur?

In the cytosol (the fluid part) of the cytoplasm

What are the two phases of Glycolysis?

1. Energy Investment Phase

2. Energy Payoff Phase (**occurs TWICE per glucose molecule)

In the energy investment phase explain what transpires

Kinases use ATP to phosphorylate glucose and some of the products of glucose catabolism

1. Hexokinase (an enzyme) phosphorylates glucose using the 1st ATP

2. Once phosphorylated, the rearrangement of molecule’s structure by  phosphoglucose Isomerase (PGI) produces Fructose 6-Phosphate (F6P)

3. A second molecule of ATP phosphorylates F6P (which is catalyzed by enzyme phosphofructokinase (PFK)) and converts it to Fructose-1,6-bisphosphate (F1,6BP)

   • This is a more reactive state

4. Aldolase (an enzyme) splits the F1,6BP into two molecules: Dihydroxyacetone phosphate (DHAP) and Glyceraldehyde 3-phosphate (G3P)

5. G3P goes onto the second phase of glycolysis and Isomerase can convert DHAP into G3P to make glycolysis more efficient

How many molecules of ATP are used in glycolysis

2 ATP molecules

In the energy payoff phase explain what transpires

1. Energy from the broken C-H bonds of glucose are converted into ATP and NADH₂

2. G3P is converted to 1,3-bisphosphoglycerate (1,3-BPG) and 1 NADH molecules is produced

3. 1,3-BPG eventually becomes phoshpoenolpyruvate (PEP)

4. PEP becomes 2 pyruvate molecules via pyruvate kinase and 2 ATPs are formed

5. Occurs twice for per glucose molecule so results are: 2 NADH and 4 ATP

What are the products of Glycolysis (both phases)

2 ATP, 2NADH, and 2 pyruvate molecules

The transfer of a phosphate group from a substrate to ADP, as seen in the energy payoff phase of glycolysis is known as?

substrate-level phosphorylation