Glucose catabolism

Active Figure 29.7 MECHANISM The 10-step glycolysis pathway for catabolizing glucose to two molecules of pyruvate. Individual steps are described in the text. Sign in at www.thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

The synthesis of some enzymes is referred to as constitutive, implying that the enzyme is formed no matter what the environmental conditions of the cell. For example, many bacteria synthesize the enzymes required to catabolize glucose under all conditions of growth. Other enzymes, known as inducible, are often produced only in small amounts. However, if... 

In fast white fibers, glycolysis catabolizes glucose. The relative lack of mitochondria in these fibers causes the white appearance. The rapid breakdown of glucose by anaerobic metabolism means that ATP is made rapidly. These muscles are used in rapid, short-duration movement and exhibit a fast twitch when electrically stimulated. The flight muscles of birds are of this type—remember that you find the white meat of a chicken on the breast. 

The ten-step glycolysis pathway for catabolizing glucose to pyruvate. The individual steps are described in more detail in the text. 

The PPP handles pentoses and is important for nucleotide (ribose-5-phosphate) and fatty acid biosynthesis (NADPH2). The Entner-Doudoroff pathway catabolizes glucose into pyruvate and glyceraldehyde-3-phosphate. It is important primarily in Gram negative prokaryotes. ... 

Epinephrine Is particularly Important In mediating the body s response to stress, such as fright or heavy exercise, when all tissues have an Increased need to catabolize glucose and fatty acids to produce ATP. These principal metabolic fuels can be supplied to the blood In seconds by the rapid breakdown of glycogen to glucose In the liver (glycogenolysis) and of tri-acylglycerols to fatty acids In adipose cells (lipolysis). 

In class VI are ADP-Glc PPases from anaerobic bacteria Rhodospirillum, capable of growing in either hetero-trophic conditions in the dark or autotrophic conditions in the light under anoxygenic photosynthesis (Table 1). These organisms cannot catabolize glucose but grow very well on pyruvate and tricarboxylic acid cycle (TCA) intermediates. ADP-Glc PPases from class VI are specifically regulated by pyruvate (Table... 

Lactic acid bacteria and muscle tissue also catabolize glucose by the BMP pathway but regenerate NAD- by reducing pyruvic acid to lactic acid using the enzyme lactate dehydrogenase ... 

C. It is secreted along with noradrenaline by the adrenal medulla, from which it may be obtained. It may be synthesized from catechol. It is used as the acid tartrate in the treatment of allergic reactions and circulatory collapse. It is included in some local anaesthetic injections in order to constrict blood vessels locally and slow the disappearance of anaesthetic from the site of injection. Ultimately it induces cellular activation of phosphorylase which promotes catabolism of glycogen to glucose. 

Whereas catabolism is fundamentally an oxidative process, anabolism is, by its contrasting nature, reductive. The biosynthesis of the complex constituents of the cell begins at the level of intermediates derived from the degradative pathways of catabolism or, less commonly, biosynthesis begins with oxidized substances available in the inanimate environment, such as carbon dioxide. When the hydrocarbon chains of fatty acids are assembled from acetyl-CoA units, activated hydrogens are needed to reduce the carbonyl (C=0) carbon of acetyl-CoA into a —CHg— at every other position along the chain. When glucose is... 

Vnother pathway of glucose catabolism, the pentose phosphate pathway, is the primary source of N/ E)PH, the reduced coenzyme essential to most reductive biosynthetic processes. For example, N/VDPH is crucial to the biosynthesis of... 

Animal cells obtain much of their energy from the breakdown (catabolism) of the six-carbon sugar glucose (C(,H, 0 ). The overall reaction for the catabolism of glucose is ... 

The first segment of glucose catabolism is called glycolysis. This process begins when glucose is transported into a cell. In a series of reactions within the cell, each of which requires a specific enzyme, a single six-carbon glucose molecule is converted to... 

The next steps of glucose catabolism are called the citric acid cycle. The pyruvic acid formed in glycolysis is transported into the mitochondria, which arc subcellular organelles with double (inner and outer) membranes. They are referred to as the powerhous-... 

Pyruvate, produced by catabolism of glucose (and by degradation of several amino acids), can undergo several further transformations depending on the conditions and on the organism. In the absence of oxygen, pyruvate can be either reduced by NADH to yield lactate [CHjCHfOHjCO - or, in yeast,... 

Lactate, a product of glucose catabolism in oxygen-starved muscles, can be converted into pyruvate by oxidation. What coenzyme do you think is needed Write the equation in the normal biochemical format using a curved arrow. 

One of the steps in the pentose phosphate pathway for glucose catabolism is the reaction of sedoheptulose 7-phosphate with glyceraldehyde 3-pho phate in the presence of a transaldolase to yield erythrose 4-phosphate and fructose 6-phosphate. 

---