1. Describe a. the biochemical steps of gluconeogenesis. b. one example of a regulatory mechanism used to control glucose metabolism. C. two commercial uses of ethanol production in yeast. a. Gluconeogenesis is the synthesis of glucose from carbohydrate precursors such as pyruvate and related three- and four-carbon compounds. Glucogenic pathways share may intermediates with the glycolytic pathway but the two pathways are distinct. Many of the steps are catalysed by the same enzymes used in glycolysis-reversible reactions. There are three main steps of gluconeogenesis. The first step involves the formation of phosphoenolpyruvate (PEP) from pyruvate by way of oxaloacetate. The next step is the formation of fructose-6-phosphate by hydrolysis of fructose-1,6-bis-phosphate. The last main step of gluconeogenesis is the formation of glucose by hydrolysis of glucose -6-phosphate.There are five main metabolites that feed into the pathway: pyruvate (or related three-carbon compounds e.g. lactate), gluconic amino acids, triacylglycerol (converted to G3P), CO2 (plants and photosynthetic bacteria), fatty acids (plants and some bacteria). b. Metabolic pathway need to be controlled. Glycolysis and gluconeogenesis are reciprocally regulated to prevent wasteful operation of both pathways at the same time. The first point of regulation involves pyruvate allosteric regulation. The same molecule has different effect on different enzymes. Acetyl-CoA is a positive allosteric modulator of pyruvate carboxylase and a negative modulator of pyruvate dehydrogenase. High acetyl-CoA concentrations indicates that the cell's energetic needs are being met. Excess pyruvate is converted to glucose. Low levels of acetyl-CoA results in the stimulation of PDH (pyruvate dehydrogenase) and pyruvate is converted into acetyl-CoA for the TCA cycle.The second point of regulation involves fructose 6-phoshate and fructose 1,6-bisphosphate. When energy levels are low, concentrations of ADP and AMP increase. Amp stimulates PFK-1 and inhibits FB-Pase-1, ADP stimulates PFK-1 which leads to carbohydrate catabolismoglycolysis). c. In beer brewing, the fermentation of carbohydrates in cereal grains (seeds) such as barley is carried out by yeast glycolytic enzymes. The beer brewing process comprises of a number of steps: malting, milling, infusion mashing, wort boiling, fermentation, filtration and pasteurisation. Malting involves germinating barely seeds under controlled conditions. This allows endogenous amylases to begin the breakdown of starch to fermentable carbohydrates. The product is called malt. Milling involves the crushing of the germinated seeds (malt) to a grist. Infusion mashing involves sparing the grist with how water to produce the nutrient medium required for fermentation by yeast cells. This is then allowed to incubate. The enzymes formed in the malting process act on the cereal polysaccharides to form maltose and glucose which are soluble in the aqueous medium. The product is called wort. In boiling the wort, hops are added which results in the characteristic flavour of beer. Yeast is then added to the mixture and fermented under controlled conditions. The fermentation of alcohol is a two-step process. It involves an aerobic stage and an anaerobic stage. In the aerobic wort, the yeast grows and reproduces very rapidly using energy obtained from available sugars. No ethanol is formed during this stage because the yeast