4. Insulin and Glucagon Flashcards
Endocrine control of fuel metabolism [3]
- metabolism - chemical reactions in cells - ie degradation, synthesis and transformation of proteins, carbs and fats
- Nutrient molecules are broken down through digestion into smaller absorbable molecules
- proteins - amino acids
- carbohydrates - monosaccharides (mainly glucose)
- dietary fats (triglycerides) - monoglycerides and free fatty acids
Anabolism
- buildup or synthesis of larger organic macro-molecules from small organic sub-units
- reactions usually require ATP energy
- Reactions result in manufacture of materials needed by the cell and storage of excess ingested nutrients not immediately needed for energy production or cellular building blocks
Catabolism
- breakdown or degradation of large, energy rich organic molecules within cells
- 2 levels
- hydrolysis of large cellular molecules into smaller subunits
- oxidation of smaller subunits to yield energy from ATP production
Summary of Reactions in Fuel Metabolism
Digestion to ATP example
Stored Metabolic fuel in the body
Comparison of Absorptive and Post absorptive states
Role of Key tissues in metabolic states
Liver
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Liver
- Primary role in maintaining normal blood glucose levels
- principal site for metabolic interconversions - e.g. gluconeogenesis
Role of Key Tissues in metabolic states
Adipose Tissue
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Adipose tissue
- primary energy storage site
- Important in regulating fatty acids levels in the blood
Role of Key Tissues in metabolic states
Muscle
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Muscle
- Primary site of amino acid storage
- major energy user
Role of Key Tissues in metabolic states
Brain
-
Brain
- Normally can only use glucose as energy source
- doesn’t store glycogen
- Mandatory blood glucose levels be maintained
Role of Key Tissues in metabolic states
Pancreas
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Pancreas
- endocrine cells - islets of Langerhans
- B (beta) cells - site of insulin synthesis and secretion
- A (alpha) cells - produce glucagon
- D (delta) cells - pancreatic site of somatostatin synthesis
- PP cells - least common islet cells
- secrete pancreatic polypeptide
- endocrine cells - islets of Langerhans
- Insulin and glucagon are most important in regulating fuel metabolism
The endocrine pancreas
Islets of Langerhans Part 1
- compose 1-2% of pancreatic mass
- Approximately 1 million islets of Langerhans per pancreatic mass
Islets of Langerhans Part 2
Islets of Langerhans Part 3
Insulin
- anabolic hormone
- promotes cellular uptake of glucose, fatty acids, amino acids - enhances their conversion into glycogen, triglycerides and proteins, respectively
- lowers blood concentration of these small organic molecules
- Secretion is increased during absorptive state
- primary stimulus for secretion is increase in blood glucose concentration
Factors increasing or decreasing blood glucose - part 1
Factors increasing or decreasing blood glucose - part 2
Neural Stimulation of Insulin Release
Actions of Insulin in a diagram
Fed state, insulin dominates
How does insulin get into the cell?
What happens when you eat?
Glycogenesis
Glucose > glycogen
= lower blood glucose
Glycogenolysis
Glycogen > glucose
= increase in blood glucose
Gluconeogenesis
Amino acids > glucose
= increase in blood glucose
Protein Synthesis
Amino acids > protein
= decrease in amino acids
Protein Degradation
Protein > Amino acids
= increase in amino acids
Fat synthesis (lipogenesis or triglyceride synthesis)
fatty acids + glycerol > triglycerides
= decrease in fatty acids
Fat breakdown (lipolysis or triglyceride degradation)
Triglycerides > fatty acids + glycerol
= increase in fatty acids
