PPP, glycogen, gluconeogenesis - chapter 13

PHR 3200

PPP (pentose phosphate pathway)

• produce NADPH for biosynthesis (fatty acid) and antioxidant defense (ROS or protecting cells from damage)

• produce ribose - 5 - phosphate for nucleotide synthesis

• RNA/DNA building blocks

1 GAP to PPP

makes 1 ribulose- 5 - phosphate

2 NADPH

1 CO2

PPP and ATP

does not directly produce ATP

Glycogen Synthesis

• contains branches and chains

  • alpha (1→ 4) connects chains

  • alpha (1→ 6) connects branches

glycogen synthase

builds glycogen by adding glucose from UDP - glucose

Glycogen Phosphorylase

breaks down glycogen using inorganic phosphate (Pi) releasing glucose - 1 - phosphate

energy requires for glycogen synthesis

• 1 GAP needs 1 ATP equivalent

• 1 free glucose needs 2 ATP equivalent

liver glycogen

release glucose into blood to maintain blood sugar

muscle glycogen

• uses glycogen for its own energy ATP

• muscle lacks GAP so it cannot release free glucose like the liver

gluconeogenesis

• happens when body lack glucose

• requires bypass reaction

• 3 irreversible steps of glycolysis

• different enzymes are needed for bypass steps

pyruvate to PEP

step 1. pyruvate to oxaloacetates

• uses ATP and CO2

step 2. oxaloacetates to PEP

• uses GTP and release CO2

2 pyruvate to 1 glucose

• needs 4 ATP, 2 GTP, and 2 NADH

• 4 ATP + 2 GTP = 6 ATP equivalence

fructose -2.6- bisphosphate (F2,6BP) to glucose in the liver

• activates PFK - 1

• inhibits FBPase- 1

• higher F2,6BP

• lower F2,6BP

Activating PFK- 1

increase glycolysis

breaks down glucose

inhibits FBPase - 1

decrease gluconeogenesis

makes glucose

increase F2,6BP

increase glycolysis

breaks down glucose

decrease F2,6BP

increase gluconeogenesis

makes glucose

glycolysis

• break down glucose

• makes ATP

• produce energy

gluconeogenesis

• makes glucose

• uses ATP

• requires energy

glycogen

• stored glucose molecule

• is a form of glucose