52-Peptide Hormones, Growth Factors, and Cytokines:
Covers metabolism as the sum of anabolic and catabolic reactions, how pathways are coordinated across organs to match nutrient supply and energy demand, and the main regulators: hormones, enzymes and substrate levels. It gives fasting, feeding and exercise examples, then classifies hormones into peptide, steroid and amino acid-derived types with a comparison table of synthesis, storage, solubility, receptors and effects. Endocrine, paracrine and autocrine action and feedback control are described, followed by the intracellular receptor mechanism of steroid hormones and four multiple-choice questions with answers.
Topic 52 of 70 in the MU Sofia syllabus for Biochemistry (Medicine, Year 2). The free AceMed note covers it in 18 sections, about 496 words (5 min of reading), with 10 flashcards.
In this note
Integrated Regulation of Metabolism at the Organism Level
Metabolism Overview
Coordination of Metabolic Pathways
Key Players in Metabolic Regulation
Example:
Examples of Integrated Metabolic Regulation:
Hormones - Classification
Definition of Hormones
Classification of Hormones
Mechanisms of Hormonal Action
Regulation of Hormone Secretion
Molecular Mechanisms of Steroid Hormones
Mechanism of Action
Mechanism of action:
Examples of Steroid Hormones
Regulation of Steroid Hormone Production
MCQs ☺
Answers
Metabolism Overview
Metabolism refers to the sum of all chemical reactions occurring within an organism to maintain life.
It includes anabolism (building molecules) and catabolism (breaking down molecules).
Coordination of Metabolic Pathways
Metabolic pathways are tightly regulated to ensure energy balance and homeostasis.
Integration involves the coordination of various organs, tissues, and cells to respond to nutrient availability and energy demands.
Key Players in Metabolic Regulation
Hormones: Chemical messengers that regulate metabolism by signalling between organs and tissues.
Enzymes: Catalytic proteins that control the rate of metabolic reactions.
Substrate availability: Nutrient levels in the bloodstream influence metabolic pathways.
Examples of Integrated Metabolic Regulation:
Fasting vs. Feeding States:
Fasting: Body switches to catabolic pathways to generate energy (lipolysis).
Feeding: Anabolic pathways are activated to store excess nutrients (lipogenesis).
Exercise:
Increased energy demand triggers catabolic pathways to release energy (glycolysis, \beta-oxidation).
Definition of Hormones
Hormones are signalling molecules secreted by glands into the bloodstream to regulate physiological processes in distant target cells.
Classification of Hormones
Peptide/Protein Hormones :
Composed of amino acids.
Examples: Insulin, Growth hormone, Glucagon.
Steroid Hormones :
Derived from cholesterol.
Examples: Estrogen, Testosterone, Cortisol.
Amino Acid-Derived Hormones :
Derived from amino acids.
Examples: Thyroxine (derived from tyrosine), Epinephrine (derived from phenylalanine).
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