Microbial Biochemistry [STH 301] Second Lecture
Fructose as a source of carbohydrate is converted to fructose-1-phosphate in the present of the enzyme fructokinase where fructose-1-phosphate enter glycolytic pathway where it is split into Dihydroxyacetone phosphate (DHAP) and Glycyaldehyde.
lactose or milk product is converted to glucose and galactose in the present of the enzyme lactase. Glucose is converted to Glucose-6-phosphate and enter glycolysis, while galactose is converted to galactose-1-phosphate in the present of the enzyme galactokinase. Galactose-1-phosphate is converted to glucose-1-phosphate in the present of the enzyme transferases and UDP-glucose (uridine di-phosphate glucose).
fig 1.4 Gluconeogenesis pathway.
Energetics of Glycolysis
Equation:
Fig 1.0 image of the energetics of glycolysis.
Glycolytic pathway can be sum up in the equation below
i.e. D-Glucose + 2ADP + 2Pi + 2NAD+ will give 2 pyruvate + 2ATP + 2NADH+ +H+
D-Glucose
It should be noted that two moles of ATP were used in stage one of glycolysis while 4 ATP was produced in stage 2 of glycolysis, and the net ATP produced during glycolysis is 2ATP
Net = 4ATP - 2 ATP = 2ATP.
In addition 2 mole of NADH is also produced.
The entry point of other Sugars into Glycolysis
1. Fructose: Dietary sources of glucose includes, fruit, honey, sucrose (table sugar), beverages and high fructose corn syrup.
2. Lactose: (gotten from milk) (Glucose + Galactose)
Fates of pyruvate
When oxygen is available (left), in aerobic organisms, pyruvate is completely oxidized to give CO2 and H20 (carbon dioxide and water). This process normally occur in the TCA (Tricarboxylic acid cycle) and ETC (electron transmission chain) in the absence of oxygen, pyruvate can be converted to several types of reduced molecules. In some cells for example yeast (saccharomyces cereviases) ethanol and CO2 (Carbon dioxide) are produced (middle) and the process is called alcoholic fermentation. However in other cells e.g. muscle cells, homolactic fermentation occurs in which lactase acid is produced.
GLUCONEOGENESIS
Glycerol, Pyruvate, Amino acids, Non-carbohydrate, fats to give = Glucose.
Whats is gluconeogenesis? Gluconeogenesis is the formation of a new glucose from non-cabohydrate sources such as lactase, pyruvate, Glycerol and amino acids, this process normally occur in the lever, this process normally occur when lever glycogen is depleted. Gluconeogenesis provide the body with adequate glucose. Gluconeogenesis also occurs in all animals plants, fungi and microorganisms.
Pathway of Gluconeogenesis
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