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Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other, nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD + and NADH (H for hydrogen), respectively.
When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, NAD+ is regenerated from NADH by reduction of pyruvate to lactate. [4] Lactate is converted to pyruvate by the enzyme lactate dehydrogenase. [3] The standard free energy change of the reaction is -25.1 kJ/mol. [6]
Glycolysis is the metabolic pathway that converts glucose (C 6 H 12 O 6) into pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). [1]
The cell cycle, or cell-division cycle, is the sequential series of events that take place in a cell that causes it to divide into two daughter cells. These events include the growth of the cell, duplication of its DNA ( DNA replication ) and some of its organelles , and subsequently the partitioning of its cytoplasm, chromosomes and other ...
The glycerol-3-phosphate shuttle is a mechanism used in skeletal muscle and the brain [1] that regenerates NAD + from NADH, a by-product of glycolysis. NADH is a reducing equivalent that stores electrons generated in the cytoplasm during glycolysis. NADH must be transported into the mitochondria to enter the oxidative phosphorylation pathway.
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP [1] [2] or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADPH as a reducing agent ('hydrogen source').
The two substrates of this enzyme are sn-glycerol 3-phosphate and NAD +, whereas its 3 products are glycerone phosphate, NADH, and H +. This enzyme belongs to the family of oxidoreductases , specifically those acting on the CH-OH group of donor with NAD + or NADP + as acceptor.
Simultaneously, NADH is oxidized to NAD+ in the following reaction: GPD1 Reaction Mechanism. As a result, NAD+ is regenerated for further metabolic activity. GPD1 consists of two subunits, [9] and reacts with dihydroxyacetone phosphate and NAD+ though the following interaction: Figure 4. The putative active site.