Asymmetric carbons (C-1 in the glucose) that are created by cyclisation at the carbon bound to oxygen in hemiacetals formation are anomeric in nature. A ring structure is formed between the carbonyl group and the alcoholic group. This ring formation produces an anomeric carbon at C-1 in aldose and C-2 in ketose sugars.
In 1929, Haworth proposed a six-membered ring structure for sugar called pyranose, because pyran contains a ring of five carbons and one oxygen. Haworth projection formulae are shown in Figure 2.5. Haworth also called sugars containing a five-membered ring as furanose, because furan contains a ring of four carbons and one oxygen. Only 1% of monosaccharides contain…
Amino Acid Metabolism A number of glycogenic amino acids enters the TCA cycle via transamination reactions. Glutamate α-KetoglutarateAspartate OxaloacetateAlanine Pyruvate
In acidic conditions, aldehydes combine with one or two of the hydroxyl groups of an alcohol, resulting in the formation of a hemiacetal or an acetal. A ring structure is formed when hemiacetals are cyclic in nature, as shown in Figure 2.4.
The word ‘amphi’ means both—the anabolic and catabolic reactions occur in the same pathway or cycle and hence TCA cycle is regarded as ‘amphibolic’.
Asymmetric carbon atoms confer optical activity to the sugars. When a polarised light passes through a solution showing optical activity, the plane of the light is rotated to the right or the left. If it is rotated towards the right the sugar (compound) is called dextrorotatory (denoted as d or +), and if it is…
TCA cycle is called amphibolic pathway as explained in Figure 8.8 because both catabolic and anabolic processes are involved in this pathway. Figure 8.8 Tricarboxylic Acid Cycle or Citric Acid Cycle Catabolic process: The cycle helps in the degradation of acetyl residues, which are derived from carbohydrates, fats, proteins, and so on. Anabolic process: The intermediates of TCA cycle are…
Tricarboxylic acid (TCA) cycle takes place in most of the tissues, but liver is the only tissue where it occurs to a significant extent. The enzymes of the citric acid cycle are located in the mitochondrial matrix, either free or attached to the inner mitochondrial membrane and the crista membrane, where the enzymes of the…
INTRODUCTION The citric acid cycle, Krebs cycle, or tricarboxylic acid cycle is the pathway that occurs in mitochondria that oxidises acetyl-CoA and reduces the coenzymes NADH+ and FADH2 reoxidised through the electron transport chain. The third phase of metabolism is the citric acid cycle. The carbohydrate, lipid and protein finally meet in this pathway, because glucose, fatty…
Inhibition can occur during two reactions in glycolysis. Glyceraldehydes 3-phosphate + H3Po4 → 1,3-diphosphoglyceric acid + NADH + H+ Figure 8.7 Graphical Representation of Allosteric Inhibition of Phosphofructokinase with Respect to ATP Concentration This reaction may be inhibited by iodoacetate; arsenate can also interfere with this reaction, not by inhibition, but by competing with phosphate in the…