Skills to Develop
- explain reasons for the strongly exergonic hydrolysis of carboxylic acid anhydrides, phosphoric acid anhydrides, mixed anhydrides, and analogous structures and give approximate values for the ΔG0 of hydrolysis of them;
- identify from Lewis structures molecules whose hydrolytic cleavage are strongly exergonic;
- explain how the exergonic cleavage of phophoanhydride bonds in ATP can be coupled to the endergonic synthesis of macromolecules like proteins;
- draw mechanisms to show how oxidation and phosphorylation reactions are coupled in anaerobic metabolism through the productions of a mixed anhydride catalyzed by the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase;
- explain how arsenate can double oxidation and phosphorlyation reactions in glycolysis
- explain how NAD+ can be regenerated from NADH in anaeroboic condition to allow glycolysis to continue;
- explain the general flow of electrons from NADH to dioxgen through a series of mobile and membrane protein bound electron acceptors in electron transport in the mitochondria inner member.
- explain with picture diagrams how oxidation and phosphorylation reactions (to produce ATP) are coupled in aerobic metabolism through the generation and collapse of a proton gradient in the mitochondria;
- draw pictures diagrams explaining the structure of F1F0ATPase in the inner mitochondria member and explain using the picture how ATP synthesis is coupled to protein gradient collapse
- write an equation for the electrochemical potential and use it to calculate the available ΔG0 for ATP production on proton gradient collapse, given typical values for ΔpH and ΔE across the membrane
Biological oxidation reactions serve two functions:
- Oxidation of organic molecules can produce new molecules with different properties (e.g., an increase in solubility is observed on hydroxylation of aromatic substrates by cytochrome P450) and Likewise, amino acids can be oxidized to produce neurotransmitters.
- Most biological oxidation reactions occur, however, to produce energy to drive thermodynamically unfavored biological processes such as protein and nucleic acid synthesis, or motility.
Chemical potential energy is not just released in biological oxidation reactions. Rather, it is transduced into a more useful form of chemical energy in the molecule ATP (adenosine triphosphate). This chapter will discuss the properties that make ATP so useful biologically, and how exergonic biological oxidation reactions are coupled to the synthesis of ATP.
- C1. ATP
- Biological oxidation reactions serve two functions. Oxidation of organic molecules can produce new molecules with different properties. For example, increases in solubility is observed on hydroxylation of aromatic substrates by cytochrome P450. Likewise, amino acids can by oxidized to produce neurotransmitters. Most biological oxidation reactions occur, however, to produce energy to drive thermodynamically unfavored biological processes such as protein and nucleic acid synthesis, or motility.
- C6. Complex III
- Complex III is a complicated, multisubunit protein. The subunits involved in electron transfer are cytochrome b, cytochrome c1 and the Rieske iron sulfur protein (ISP). Cytochrome b has two hemes.
- C13. PPARs and the Regulation of Metabolism
- In the well fed state (high levels of carbohydrates and lipids), glycogen, triacylglycerides, and fatty acids synthesis should be activated, while glycogen breakdown (glycogenolysis), mobilization of triglycerides reserves, and fatty acid oxidation should be minimized. In the fasting state, the opposite pathways should be activated. The regulatory control of these opposing processes is complicated but PPARs (peroxisome proliferator-activated receptors) have been shown to have a major role.