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Cover Biochemistry and Molecular Biology

Mechanisms of metabolic control and their applications to metabolic integration  

This chapter highlights metabolic pathways that must be regulated to avoid futile substrate cycling. It determines how enzyme activities may be controlled by changing the amount of enzyme or by changing the rate of catalysis of enzymes. Control points in metabolic pathways usually occur at irreversible steps in which the forward and backward reactions can be separately controlled. The chapter cites allosteric control, which is a powerful concept essential for cells to exist. Allosteric enzymes are multisub-unit proteins which contain allosteric sites to which molecules attach and affect the activity. The chapter notes the effect of substrate concentration on reaction rates which is sigmoidal rather than hyperbolic.

Chapter

Cover Thrive in Biochemistry and Molecular Biology

Integration of mammalian metabolism  

This chapter explores the integration of mammalian metabolism. All metabolic pathways are coordinated to meet the needs of the whole body as they vary with changes in exercise and nutrition. The chapter then looks at the key organs, metabolites, and hormones in metabolic integration. It also considers the key aspects of fuel utilization. Finally, the chapter highlights the principles of hormone signalling in metabolism. There are two main classes of receptors: G-protein-coupled receptors (GPCR) and receptor tyrosine kinases (RTKs). Receptor activation stimulates production of second messengers — diffusible molecules inside the cell which transmit the signal to intracellular components. Often a cascade of protein kinases amplifies the effect of a few activated receptor molecules by phosphorylating downstream target proteins.

Chapter

Cover Thrive in Biochemistry and Molecular Biology

Mammalian metabolic pathways  

This chapter addresses the mammalian metabolic pathways. It begins by explaining catabolism and anabolism. Catabolism is the breakdown of organic molecules to release energy in a usable form of ATP. ATP acts as an energy 'currency' in the cell and it is not stored in the cell. Meanwhile, anabolism is the biosynthesis of complex molecules using energy, usually in form of ATP. The chapter then looks at glucose breakdown and synthesis; the tricarboxylic acid (TCA) cycle; and oxidative phosphorylation. It also considers the breakdown and synthesis of glycogen, lipid, ketone body, and amino acid. Finally, the chapter examines the pentose phosphate pathway, as well as lactate and ethanol metabolism.

Chapter

Cover Molecular Biology of Cancer

Reprogrammed metabolism and diet  

This chapter highlights the role of diet in cancer prevention and causation. It explores our understanding that some food constituents exert their cancer-relevant effects by their ability to regulate gene expression: a paradigm of how environmental factors work together with genes, rather than the concept of environment versus genes. The chapter also describes the new therapeutic approaches that exploit our knowledge of reprogrammed metabolism and the molecular mechanisms of food constituents. The chapter then shifts to demonstrate the preventative factors of diet and causative factors of diet. It also investigates the link between nutrients, cancer, and hormone action. Next, the chapter addresses the drug strategies that target metabolic pathways. It also considers “enhanced” foods and dietary supplements for chemoprevention.