Notes on Hormones

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Water-Soluble Hormones:

• Transmit signals within cells using second messenger systems and protein kinases.

• Protein kinases: phosphorylates other proteins.

Activation by Hormone Events:

• Hormone binds receptor (cAMP or PIP2 transmembrane system).

• G protein activated.

• Enzyme (adenylate cyclase or phospholipase).

• Second messenger (cAMP of IP3/DAG, etc.).

• Protein kinase (A, C, or G).

• Protein phosphorylation and gene expression.

First Messenger (?) G Protein:

• Located in membrane.

• Three parts: alpha, beta, and gamma.

• When activated by hormone, GDP on alpha subunit is replaced by GTP, and alpha subunit separates.

• Activated alpha subunit alters the activity of adenylate. (alpha-s activates; alpha-i inhibits).

Second Messengers:

• cAMP and PIP2.

• 7-helix membrane-spanning domains.

Second messenger:

• cGMP.

• Deals with ANF and NO.

Tyrosin kinase:

• Insulin receptor, a tyrosine kinase.

Ras Activation Steps:

• Insulin directly activates the tyrosine kinase receptor without the aid of second messengers.

• Autophosphorylation.

• IRS binds receptor and is phosphorylated on tyrosine residues.

• SH-2 domain proteins bind phosphotyrosing residues on IRS.

In the end:

• PI-3 increases GLUT-4.

• p21 ras G protein activated.

Insulin vs Glucagon:

• Oppose each other.


• Favors phosphorylation.


• Favors dephosphorylation.

ADP-Ribosylation by Bacterial Toxins:

• Activate G proteins and subunits.

• Increased cAMP.

• Cause problems like diarrhea.

Lipid-Soluble Hormones:

• Diffuse through cell membrane.

• Bind receptors that have DNA binding sites (usually Zn-fingers).

• Response elements include enhancers or silencers.

• Eg., workings of PEPCK gene.

Additional Notes:

• Tyrosine: formed by dopamine and noradrenaline.

Additional Readings:

Basic Biochemistry

1. Nucleic Acid Structure and Organization
2. DNA Replication and Repair
3. Transcription and RNA Processing
4. Genetic Code, Mutations, and Translation
5. Genetic Regulation
6. Recombinant DNA
7. Amino Acids, Proteins, Enzymes
8. Hormones
9. Vitamins
10. Energy Metabolism
11. Glycolysis and Pyruvate Dehydrogenase
12. Citric Acid Cycle and Oxidative Phosphorylation
13. Glycogen, Gluconeogenesis, and Hexose Monophosphate Shunt
14. Lipid Synthesis and Storage
15. Lipid Mobilization and Catabolism
16. Amino Acid Metabolism Disorders
17. Purine and Pyrimidine Metabolism
18. Electron Transport
19. Citric Acid Cycle and Glyoxylate Cycle
20. Glycolysis
21. Pyruvate Metabolism
22. Mitochondrial ATP formation
23. Gluconeogenesis
24. Glycogen Metabolism
25. Nitrogen Fixation (Metabolism) reactions, and Heme Metabolism
26. Amino Acid Metabolism
27. What is Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD)?

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