Exam 3 Review:  Chapter 23:  Liver Function

carbohydrate metabolism - The diverse set of biochemical reactions which occur within cells that (1) convert ingested sugars into larger carbohydrates (glycogenesis = synthesis of starch) or (2) add sugars to other large polymers such as lipids and proteins (glycosylation) or (3) create new sugar molecules from non-carbohydrate precursors (gluconeogenesis) or (4) breakdown starch (glycogenolysis) into glucose molecules or (5) breakdown glucose and other simple sugars in oxidative pathways (glycolysis, the citric acid cycle, oxidative phosphorylation) to produce useful chemical energy (ATP) and waste products (CO₂ and H₂O) or (6) in fermentation pathways (lactic acid production) to produce useful chemical energy (ATP); processes 1, 2 and 3 above are anabolic while processes 4, 5, and 6 are catabolic.

lipid metabolism - The diverse set of biochemical reactions which occur within cells that (1) convert ingested lipid subunits (glycerol, fatty acids, cholesterol, etc.) into larger lipids (lipogenesis = synthesis of neutral fats, di- and tri-glycerides) or (2) add lipid subunits to other large polymers such as carbohydrates and proteins or (3) create new lipid molecules from non-lipid precursors or (4) breakdown lipids (lipolysis) into lipid subunits (glycerol, fatty acids, cholesterol, etc.) or (5) breakdown lipid subunits (glycerol, fatty acids, cholesterol, etc.) in oxidative pathways (beta oxidation, glycolysis, the citric acid cycle, oxidative phosphorylation) to produce useful chemical energy (ATP) and waste products (CO₂ and H₂O); processes 1, 2 and 3 above are anabolic while processes 4, and 5 are catabolic.

beta oxidation - The catabolic process by which fatty acids are degraded, involving oxidation of the beta carbons and removal of successive two-carbon fragments from the fatty acid to form molecules of acetyl co-enzyme A;  acetyl co-enzyme A can transfer the two-carbon acetyl groups to the the citric acid cycle in mitochondria for further oxidation to produce useful chemical energy (ATP) and waste products (CO₂ and H₂O).

protein metabolism - The diverse set of biochemical reactions which occur within cells that (1) convert ingested protein subunits (amino acids) into larger proteins (proteine synthesis = transcription + translation) or (2) add protein subunits (amino acids) to other large polymers such as carbohydrates and lipids or (3) create new lipid molecules from non-lipid precursors or (4) breakdown lipids (lipolysis) into protein subunits (amino acids) (transamination) or (5) breakdown protein subunits (amino acids) in oxidative pathways (deamination, glycolysis, the citric acid cycle, oxidative phosphorylation) to produce useful chemical energy (ATP) and waste products (CO₂, H₂O and ammonia → urea); processes 1, 2 and 3 above are anabolic while processes 4, and 5 are catabolic.

transamination - The enzyme-catalyzed transfer of an amino group (-NH₂) from one compound to another; an important function of the liver hepatocytes and carried out in lesser amounts by many other cell types.

deamination - The enzyme-catalyzed removal of an amino group (-NH₂) from an organic compound; an important function of the liver hepatocytes and carried out in lesser amounts by renal tubular cells and a few other cell types.

ammonia - A colorless, pungent, strongly basic, irritating volatile gas, NH₃, extensively used to manufacture fertilizers and a wide variety of nitrogen-containing organic and inorganic chemicals; it is very soluble in water; it is a by-product of protein catabolism in cells, but is highly toxic and must be rapidly excreted or else converted into less toxic nitrogenous wastes, e.g., urea.

urea - A highly water-soluble, non-toxic compound, CO(NH₂)₂, formed from the addition of two amino groups (-NH₂) to a molecule of carbon dioxide (CO₂) in the liver, which is the major nitrogenous waste product of protein catabolism and is the chief nitrogenous waste component of the urine.

16.  the functions of the liver.

          (1)  carbohydrate metabolism (storage, glycogenesis, glycogenolysis, gluconeogenesis, contribute to regulation of blood glucose levels, etc.)
          (2)  lipid metabolism (storage, cholesterol synthesis and degradation, synthesize and process lipoproteins, etc.)
          (3)  protein metabolism (amino acid storage, deamination, transamination, etc.)
          (4)  synthesis and secretion of most plasma proteins (albumins, most alpha and beta globulins, a few (non-antibody) gamma globulins)
          (5)  nutrient and mineral storage (starch, some triglycerides, amino acids, oil soluble vitamins (A,D,E, K), minerals, e.g., iron, etc.)
          (6)  deal with toxic materials (breakdown and metabolize toxins, render toxins more water soluble to facilitate urinary excretion, store certain toxins that cannot be metabolized or modified for excretion)
          (7)  synthesize bile salts from "waste" cholesterol and secrete them into bile to act as lipid emulsifiers
          (8)  secrete bile 
          (9)  activate vitamin D (?) 
          (10)  phagocytosis of old, worn RBCs and, potentially, microbes
          (1l)   a site of fetal hematopoiesis