Biochemistry (Carbohydrate 1)

• The primary structure of a protein is the sequence of amino acids.
• Carbohydrates are polyhydroxylated aldehydes and ketones and substances that yield such compounds upon hydrolysis.
• The functions of carbohydrates include serving as an energy source, part of the structural framework, structural elements in cell walls, part of nucleic acids and some lipids and proteins, and units on cell surfaces for cell-to-cell recognition processes.
• Major classes of carbohydrates include monosaccharides (simple sugars), disaccharides, oligosaccharides, and polysaccharides.
• Monosaccharides are single polyhydroxylated aldehyde or ketone units.
• Disaccharides consist of 2 monosaccharides liked together by a glycosidic bond.
• Oligosaccharides are made up of 3 - 10 monosaccharide units.
• Polysaccharides are long chains of monosaccharide units.
• All monosaccharides (except dihydroxyacetone) are optically active.
• The D - configuration is when the -OH group is at the right.
• The L - configuration is when the -OH group is at the left.
• Regulation of glycolysis ensures that the output of the metabolic pathways meet biological demands and that energy in the form of ATP is not wasted by having opposite pathways run concomitantly in the same cell.
• The second phase of glycolysis involves the conversion of 2 moles of glyceraldehyde-3-phosphate to 2 moles of pyruvate, producing 4 moles of ATP, 2 moles of NADH, and 2 moles of H2O.
• The overall reaction of glycolysis can be summarized as: Glucose + 2 ATP → 2 glyceraldehyde-3-P + 2 ADP.
• Galactosemia is caused by a deficiency in galactose-1-phosphate uridyl transferase, resulting in high concentrations of galactose in the blood.
• Inhibitors of glycolysis include ATP when energy charge is high, which allosterically inhibits PFK-1, preventing glucose from entering glycolysis and causing glucose to be stored as glycogen.
• Galactose, acting as aldose reductase, reduces to galactitol, which accumulates in the eyes and causes galactosemic cataract.
• Activators of glycolysis include ADP/AMP when cellular concentration is high.
• Pyruvate kinase is the third regulatory point in glycolysis, generating two more moles of ATP via substrate level phosphorylation.
• Phosphofructokinase-1 (PFK-1) is the main regulatory point of glycolysis.
• The second phase of glycolysis results in the production of 2 pyruvate, 4 ATP, 2 NADH, and 2 H2O.
• The Phosphogluconate Pathway functions to generate reducing power on the form of NADPH2, generate pentoses from hexoses (D-ribose-5-P), and cover excess pentoses back to hexoses for oxidation via glycolysis.
• NADH enters complex I of the electron transport chain, capable of maximizing ATP yield from NADH produced in glycolysis (2.5 ATPs/ cytosolic NADH).
• Complete oxidation of 1 mol of pyruvate to CO2 and H2O.
• The Phosphogluconate Pathway occurs in the cytosol of the cells in the following issues: Products of PPP.
• NADPH is a phosphorylated NADH but the two are not interconvertible.
• The Oxidative Stage of the Phosphogluconate Pathway involves oxidative generation of NADPH, which is irreversible.
• Glycerol-3-Phosphate (G3P) passes these electrons to mitochondrial FAD to form FADH2.
• FADH2 enters complex II of the electron transport chain, resulting in a lower ATP yield (1.5 ATPs/ cytosolic NADH).
• Ribose-5-P is required in the synthesis of nucleic acids, especially in actively dividing cells.
• Glycolysis-3-Phosphate Shuttle is predominant in the brain and muscle cells, with electrons from cytosolic NADH ultimately accepted by FAD in the mitochondria to form FADH2.
• Glucose-6-Phosphate (G6P) is also called the Hexose Monophosphate Shunt or the Phosphogluconate Pathway.
• Complete oxidation of 1 mol of glucose to CO2 and H2O.
• The first phase of glycolysis involves the cleavage of glucose to give 2 moles of glyceraldehyde-3-phosphate, consuming 2 ATPs.
• Glucose is phosphorylated to form glucose-6-phosphate, increasing the concentration of negative (-) charges in the cytosol.
• Phosphoglucose isomerase, Phosphofructokinase-1 (PFK-1), and Aldolase are committed steps in glycolysis.
• Hexokinase is the first regulatory point of glycolysis.
• Phosphoglycerate kinase generates 2 moles of ATP via substrate level phosphorylation.
• Glucose is trapped inside the cell and is activated for breakdown.
• Phosphoglycerate mutase shifts the phosphate group from C-3 to C-2.