BIOC 212 Lecture Notes - Lecture 50: Glycogen Phosphorylase, Glucagon, Glycogen Synthase
![](https://new-preview-html.oneclass.com/aAyDl2zeo7d4jWY9kl82Q83M69wRbkvx/bg1.png)
Metabolism XII
Mitochondria Generate ATP from NADH Oxidation
• Mitochondria are specialized organelles that have evolved to generate the
electrochemical gradient across the inner membrane by the activity of the
enzymes that oxidize NADH and FADH2 back to NAD+ and FAD
o Double membrane
o Impermeability of inner membrane is important as it is the energetic
reservoir step before production of ATP
o Most of energy produced in glycolysis in mammalian cells is ultimately
stored as this electrochemical gradient
• This is why have so many complex mechanisms for getting metabolites
& proteins across the inner membrane
• Evolutionary requirement for maintaining permeability is so critical for
energetic properties of the cell
• The electrochemical gradient is the ultimate carrier for the chemical energy
released by glucose and fatty acid oxidation before ATP production
• This is why inner membrane impermeability is so important
o Gradient formed is used to make ATP
Excess Glucose Stored in Polysaccharides
• Cells in the body are not always in a state of needing more energy
o Frequently, cells will be able to take up glucose and not actually need it to
generate ATP, own metabolic proteins or lipid substrates at the moment
• Glucose molecules are linked to form glycogen (animals) or starch (plants)
o All organisms have evolved ways to store energy when not needed
o In mammals, glucose mostly stored in the form of glycogen
• When liver cells or muscle cells are able to take up glucose from the
bloodstream but do not need it immediately for their own metabolic
requirements or for export
• Funnel it off of the glycolytic pathway after step 1 as glucose-6-P
• Glucose-6-phosphate (product of step 1 in glycolysis) can be redirected to be
stored in cells with sufficient ATP levels
o Glucose-6-P is then incorporated into a growing glycogen chain
• Stored there ready to go for whenever the cell needs it
• Upon local starvation of the cell or upon signaling from extracellular cues that
tell the cells to release glucose to the bloodstream