Purine and Pyrimidine Metabolism
39 Purine and Pyrimidine Metabolism Purines and pyrimidines are required for synthesizing nucleotides and nucleic acids. These molecules can be synthesized either from scratch, de novo, or salvaged from existing…
Cellular Bioenergetics: Adenosine Triphosphate and O2
20 Cellular Bioenergetics: Adenosine Triphosphate and O2 Bioenergetics refers to cellular energy transformations. The Adenosine Triphosphate–Adenosine Diphosphate (ATP–ADP) Cycle. In cells, the available free energy of fuels is transformed into…
Basic Concepts in the Regulation of Fuel Metabolism by Insulin, Glucagon, and Other Hormones
19 Basic Concepts in the Regulation of Fuel Metabolism by Insulin, Glucagon, and Other Hormones All cells use adenosine triphosphate (ATP) continuously and require a constant supply of fuels to…
Enzymes as Catalysts
8 Enzymes as Catalysts Enzymes are proteins that act as catalysts, which are compounds that increase the rate of chemical reactions (Fig. 8.1). Enzyme catalysts bind reactants (substrates), convert them…
Oxygen Toxicity and Free-Radical Injury
25 Oxygen Toxicity and Free-Radical Injury O2 is both essential to human life and toxic. We are dependent on O2 for oxidation reactions in the pathways of adenosine triphosphate (ATP)…
Tetrahydrofolate, Vitamin B12, and S-Adenosylmethionine
38 Tetrahydrofolate, Vitamin B12, and S-Adenosylmethionine Groups that contain a single-carbon atom can be transferred from one compound to another. These carbon atoms may be in a number of different…
The Extracellular Matrix and Connective Tissue
47 The Extracellular Matrix and Connective Tissue Many of the cells in tissues are embedded in an extracellular matrix that fills the spaces between cells and binds cells and tissue…
Translation: Synthesis of Proteins
14 Translation: Synthesis of Proteins Proteins are produced by the process of translation, which occurs on ribosomes and is directed by messenger RNA (mRNA). The genetic message encoded in DNA…
Gluconeogenesis and Maintenance of Blood Glucose Levels
28 Gluconeogenesis and Maintenance of Blood Glucose Levels During fasting, many of the reactions of glycolysis are reversed as the liver produces glucose to maintain blood glucose levels. This process…
Metabolism of Ethanol
33 Metabolism of Ethanol Ethanol is a dietary fuel that is metabolized to acetate principally in the liver, with the generation of reduced nicotinamide adenine dinucleotide (NADH). The principal route…
