Section 5 Flashcards
What is metabolism, and what are its two main types of reactions?
Metabolism describes the sum of all chemical reactions in organisms, including the synthesis, degradation, and transport of substances. The two main types of reactions are anabolic (leading to the synthesis of larger molecules) and catabolic (involving the breakdown of larger molecules).
Define anabolic reactions and provide examples of their purpose.
Anabolic reactions, or anabolism, lead to the synthesis of larger organic macromolecules from smaller molecular subunits. They are used for repair, growth, and the storage of excess ingested nutrients.
Define catabolic reactions and explain their processes.
Catabolic reactions, or catabolism, involve the breakdown of larger organic macromolecules through hydrolysis into smaller molecules or the oxidation of smaller molecules (such as glucose) to yield ATP.
How is excess glucose stored in the body?
Excess glucose is stored in the liver and skeletal muscle as glycogen. Once glycogen stores are full, additional glucose is converted into free fatty acids and glycerol for the synthesis of triglycerides, mainly occurring in adipose tissue.
How are excess fatty acids stored in the body?
Excess fatty acids are stored as triglycerides.
What happens to excess amino acids in the body?
Excess amino acids not needed for protein synthesis are either used for structural proteins or converted to glucose and fatty acids for eventual storage as triglycerides.
Define triglycerides and explain their role in the body.
Triglycerides are a major form of fat storage in the body. They are formed by combining glycerol and three fatty acids and are stored in adipose tissue.
What are the two functional metabolic states of the body, and what characterizes each state?
The two metabolic states are the absorptive state and the postabsorptive state. In the absorptive state, anabolism dominates as ingested food is digested and absorbed, while in the postabsorptive state, catabolism dominates, utilizing stored energy sources.
What is lipolysis, and when does it occur?
Lipolysis is the breakdown of lipids involving the hydrolysis of triglycerides into glycerol and free fatty acids. It occurs during the postabsorptive state when glycogen stores are insufficient to meet the body’s energy needs.
How can glycerol be utilized as an energy source in the body?
Glycerol, derived from the backbone of triglycerides during breakdown, can be converted to glucose by the liver.
What is lactic acid, and how can it be utilized as an energy source?
Lactic acid, produced by glycolysis, can be converted to glucose by the liver.
What are ketone bodies, how are they produced, and in what situations can they serve as an energy source?
Ketone bodies are compounds produced in the liver during times of glucose shortages. When the liver uses free fatty acids as an energy source, they are oxidized to acetyl CoA, which is then converted to ketone bodies. In times of starvation, the brain can use ketone bodies as an alternative energy source instead of glucose.
What are the major types of cells found in the islets of Langerhans in the pancreas? And what do they produce/secrete?
α (alpha) cells: Produce and secrete glucagon.
P P cells: Secrete pancreatic polypeptide, which may play a role in reducing appetite.
β (beta) cells: Produce and secrete insulin.
δ (delta) cells: Produce and secrete somatostatin.
What is the role of somatostatin, and where is it produced?
Role: Somatostatin is released in response to circulating glucose and amino acids after a meal. Its effect is to slow down the digestive system, inhibiting digestion and absorption of nutrients.
Production: Produced in the δ (delta) cells of the pancreas, cells lining the digestive tract (acting as a paracrine hormone to inhibit digestion), and released by the hypothalamus to inhibit the secretion of growth hormone and TSH.
What is insulin, and what are its primary effects in the body?
Insulin: Insulin is a small peptide hormone produced by beta cells of the pancreatic islets.
Primary Effects: It is the dominant hormone in the absorptive state and plays a major role in anabolism. While primarily associated with the regulation of blood sugar, it also has effects on fats and proteins.
