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Physiology vs. Metabolism

Explore the relationship between physiology and metabolism, and how they are interconnected at cellular and organismal levels. Delve into the processes and systems involved in glucose homeostasis and the insulin/glucagon ratio. Understand the complexity of these biological processes and their significance in maintaining overall health.

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Physiology vs. Metabolism

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  1. Physiology vs. Metabolism The same, part of, different?

  2. History • During the modifications of the development portion of the graph, we split out processes that occurred at a cellular level from those that occurred at a higher level. • Many cellular processes are universally conserved • Eventually all other processes would consist of building blocks of cellular processes

  3. Physiological processes • We decided since the graph was already arranged in this way, we would break physiology into organismal physiology and cellular physiology • Struggled with whether cell growth and or maintenance was equivalent to cell physiology • Struggled with how to fit metabolism into the physiology part of the graph • Is metabolism biochemical physiology?

  4. Physiological process continued • Decided to put metabolism under physiological process. GO:0008105 ; biological process -GO:0007582 ; physiological process ---GO:0008152 ; metabolism -GO:0009987 ; cellular process --GO:0050875 ; cellular physiological process -----GO:0008151 ; cell growth and/or maintenance

  5. Metabolic things are wrong • DNA repair • Transcription • RNA metabolism • Protein folding • Protein targeting • Protein modification • Protein biosynthesis

  6. What do we do with metabolism? • Split it out to the top level of the graph • Put it under cellular process • Keep it under physiological process but have some of its children (DNA metabolism) be cellular • The problem here is where does it begin and end. Some argue that getting the building blocks to make a macromolecule are part of its metabolism. So it includes things like transport of starting materials.

  7. We can’ simply make it cellular:glucose homeostasis Time after lactose intake

  8. Glucose homeostasis is systemic Pancreatic beta cells Hypothalamus

  9. Pancreatic beta cell • Serves as a glucostat for high glucose levels • Glucose transporters bring glucose in • Glukokinase and hexokinase make G6P • When the rate of production of G6P gets high enough the cell depolarises • Calcium channels open • The cell secretes insulin by exocytosis

  10. Hypothalamus • Serves as glucostat for low glucose levels • Actual sensor is unknown • Activates autonomic nervous system • Adrenal medulla->adrenaline and noradrenaline • Pancreatic alpha cells->glucagon • Pituitary gland->ACTH • Adrenal cortex->glucocorticoids

  11. The insulin/glucagon ratio • Glucagon is an antagonist of insulin • It stimulates pathways that put glucose into the blood • Take it out of storage (glycogen) • Make new glucose from amino acids • Insulin is an antagonist of glucagon • Stimulates pathways that put glucose into storage

  12. It is the Insulin/Glucagon ratio that is the key factor lower ratio by reducing insulin or increasing glucagon Bottom line is this is happening on a much higher level than a single cell

  13. The brain uses glucose as its only energy source • Glucose must get through the blood-brain barrier • Blood vessel endothelial cell transporters put glucose into the cerebrospinal fluid • Brain cell plasma membrane trannsporters take glucose into the brain cells • There is also diffusion

  14. So back to the problem with the GO • Is glucose homeostasis a physiological process? • It relies on many different cells and systems to be maintained. • But wouldn’t all of these steps also be thought of a glucose metabolism? • What about the initial digestion of lactose into galactose and glucose?

  15. Conclusion • We define metabolism to be restricted to processes where there is a transformation of the chemical substance. • This means that simple transport is not a part of metabolism.

  16. Do we need Organismal metabolism? • Yes. We still need it for things like protein, and carbohydrate catabolism in higher organisms. • We also need it for things like C4 photosynthesis. • This process is split among three different cells • Metabolites are transported between the cells • In this case, the transport IS part of the metabolic process because of its necessity.

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