glycolysis notes

step 1 and hexokinase notes

• G→ G6P

• makes glucose more polar and traps the glucose inside the cell

• negatively charged phosphate added onto carbon 6 of glucose destabilizes the structure and increases its energy

• hexokinase catalyzes the reaction:

- class: transferase (kinase)- transfers phosphate from ATP to glucose

- metabolically irreversible (highly spontaneous) and traps glucose in the cell

- HK depends on the presence of a divalent metal atom (MG+2)

- pushes out H₂O when it binds to glucose with ATP and experiences an induced fit/ conformational change

- inhibited G6P and subject to allosteric regulation from ADP to ATP

step 2 notes

• G6P → F6P (reversible)

• converts aldose to ketose

• phosphoglucose isomerase catalyzes this reaction

steps 3 and PFK notes

• F6P→ F16BP

• this step uses ATP to transfer a phosphate to ADP

• commits cell to glycolysis

• phosphofructo kinase catalyzes this reaction

- rate-limiting step and highly regulated (no other fate than to make F16BP)

- naturally in T state

- At high levels of ATP, V_max of PFK will decrease due to ATP acting as an allosteric inhibitor when it binds to regulatory site and reduces enzyme activity

• metabolically irreversible (highly spontaneous)

• inhibited by ATP and citrate (in the liver), activated by AMP/ADP

step 4 notes

• F16BP→ DHAP + GAP (reversible)

• isomerization of F16BP into 3-carbon molecules

• aldose (lyase) catalyzes this reaction

• DHAP has to be transformed into GAP. If not, it will not be used in glycolysis and can. not be used to form ATP molecules

Step 5 notes

• DHAP → GAP (reversible)

• Triose phosphate isomerase catalyzes this reaction

- catalyzes the conversion of ketose (DHAP) to aldose (GAP) via redox reaction

step 6 notes

• GAP → 1,3-BPG

• uses NAD⁺ to make NADH; adds inorganic phosphate to GAP

• step occurs twice= 2 NADH produced in total

• GAP dehydrogenase catalyzes this reaction

- class: oxidoreductase

- catalyzes the transfer of a hydride group from one molecule to another

fermentation

• the continuation of glycolysis when their is a lack of oxygen present.

• occurs in the cytoplasm and does not use mitochondria

• regenerates NAD⁺ from NADH through Lactate dehydrogenase reaction (w/o this step, cells would run out of NAD⁺ and energy production would stop under anaerobic conditions)

• lactic acid is recycled from this reaction during the cori cycle

step 7 notes

• 1,3-BPG → 3-PG (reversible)

• phosphoryl transfer to ADP to make ATP

• substrate level phosphorylation: when a molecule uses a high phosphoryl potential transfer molecule to make ATP (1,3-BPG)

• Phosphoglycerate kinase catalyzes this reaction

• 2 ATPs made in this step

step 8 notes

• 3-PG → 2-PG (reversible)

• Phosphoglycerate mutase (isomerase) catalyzes the shifting of a functional group from one position to another using the same molecule.

- PGM-His-Pi contains an active site with His side chain and Pi. His donates and accepts a phosphate

Reaction:

• PGM-His-Pi + 3-PG → PGM-His + 2,3-BPG

• PGM-His + 2,3-BPG → PGM-His-Pi + 2-PG

- His donates a phosphate, then accepts a different phosphate

- 2,3-BPG is used to keep his in its phosphorylated state, acts as a transient intermediate, and carries oxygen to red blood cells.

Step 9 notes

• 2-PG → PEP (phosphoenol pyruvate)

• Mg⁺² dependent= stabilizes enolate intermediate

• Enolase (lyase) catalyzes this dehydration reaction to destabilize the sugar and create a high phosphoryl donor potential molecule than ATP

• creates H₂O

step 10 and PK notes

• PEP → Pyruvate + ATP (metabolically irreversible)

• Pyruvate Kinase (transferase) catalyzes this reaction by removing the Pi from PEP ti create a tautomer that settles into Pyruvate

• highly spontaneous in the forward direction

• allosterically regulated by ATP and alanine

• F16BP activates it= once we committed to glycolysis in step 3, we committed to making pyruvate

• PK: pertains to ATP

• PKL: liver PK, inhibited by phosphorylation

• PKM: muscle PK

when the concentration of glucose in the blood is high in the liver, the pancreas secreted insulin will have:

• more GLUTS

• more copies of glucokinase

• more F26BP and PFK activity

• more liver PK in active form

when the concentration of glucose in the blood is low in the liver, the pancreas secreted glucagon will have:

• less GLUTS

• less copies of glucokinase

• less F26BP and PFK activity

• less liver PK in active form

• more glucose phosphatase