Có 80+ tài liệu thuộc chủ đề "nguyên tắc của hóa sinh"
tailieu.vn Xem trực tuyến Tải xuống
the complete process is diagrammed in Figure 19.1. Although two molecules of ATP come from glycolysis and two more directly out of the TCA cycle, most of the ATP arises from oxidative phosphorylation. Specifically, reducing equivalents released in the oxidative reactions of glycolysis, pyruvate de- carboxylation, and the TCA cycle are captured in the form of NADH and enzyme- bound...
tailieu.vn Xem trực tuyến Tải xuống
In the inactive state of the enzyme, one corner of the cube is va- cant. Fluoroacetate Blocks the TCA Cycle Fluoroacetate is an extremely poisonous agent that blocks the TCA cycle in vivo, although it has no apparent effect on any of the isolated enzymes. FCH 2 COO – FCH 2 C COO. C COO – C COO. of the...
tailieu.vn Xem trực tuyến Tải xuống
One of these alternative models, postulated by Günter Wächtershäuser, involves an archaic version of the TCA cycle running in the reverse (reductive) direction. Reversal of the TCA cycle results in assimilation of CO 2 and fixation of carbon as shown. For each turn of the reversed cycle, two carbons are fixed in the formation of isocitrate and two more are...
tailieu.vn Xem trực tuyến Tải xuống
The outer membrane plays a prominent role in maintaining the shape of the mitochondrion. thus, its density is higher than that of the outer membrane. Species that must cross the mitochon- drial inner membrane—ions, substrates, fatty acids for oxidation, and so on—are carried by specific transport proteins in the membrane. The Mitochondrial Matrix Contains the Enzymes of the TCA Cycle....
tailieu.vn Xem trực tuyến Tải xuống
electrons to UQ, including mitochondrial sn -glycerophosphate dehydrogenase, an inner membrane-bound shuttle enzyme, and the fatty acyl-CoA dehydrogenases, three soluble matrix enzymes involved in fatty acid oxidation (Figure 20.8. The path of electrons from succinate to UQ is shown in Figure 20.7.. In the third complex of the electron-transport chain, reduced coenzyme Q (UQH 2 ) passes its electrons to...
tailieu.vn Xem trực tuyến Tải xuống
In the crystal struc- ture first characterized by John Walker, one of the -subunit ATP sites contains AMP-PNP (a nonhydrolyzable analog of ATP), another contains ADP, and the third site is empty.. Walker and Boyer, whose efforts provided complementary insights into the workings of this molecular motor, shared in the Nobel Prize for Chemistry in 1997.. The elegant studies by...
tailieu.vn Xem trực tuyến Tải xuống
other hand, if these 2 NADH take part in the malate–aspartate shuttle, each yields 2.5 ATP, giving a total (in this case) of 32 ATP formed per glucose oxidized. Most of the ATP—26 out of 30 or 28 out of 32—is produced by oxidative phosphorylation;. Mitochondria not only are the home of the TCA cycle and oxidative phosphoryla- tion but...
tailieu.vn Xem trực tuyến Tải xuống
CO 2 by a series of enzymatic reactions found in the stroma (see Equation 21.3, which follows).. O 2 2 NADPH 2 H x ATP x H 2 O (21.2) describes the process, where nh symbolizes light energy (n is some number of pho- tons of energy h , where h is Planck’s constant and is the frequency of the...
tailieu.vn Xem trực tuyến Tải xuống
An interesting aspect of the system is that no electron transfer occurs through M, even though it has components apparently symmetric to and identical to the L e transfer pathway.. The use of light energy to drive ATP synthesis by the concerted action of these membrane proteins is called photophos- phorylation (Figure 21.15).. Cytochrome c 2 , a periplasmic protein,...
tailieu.vn Xem trực tuyến Tải xuống
In the course of this metabolic sequence, the NADPH and ATP produced in the light reactions are consumed, as indicated earlier in Equation 21.3.. The Calvin cycle of reactions starts with ribulose bisphosphate carboxylase catalyzing formation of 3-phosphoglycerate from CO 2 and RuBP and concludes with ribulose-5- phosphate kinase (also called phosphoribulose kinase), which forms RuBP (Figure 21.24 and Table...
tailieu.vn Xem trực tuyến Tải xuống
esis are the liver and kidneys, which account for about 90% and 10% of the body’s gluconeogenic activity, respectively. Glucose produced by gluconeogenesis in the liver and kidneys is released into the blood and is subsequently absorbed by brain, heart, muscle, and red blood cells to meet their metabolic needs. Somehow the energetics of the process must be augmented so...
tailieu.vn Xem trực tuyến Tải xuống
For instance, in the fasting state, when food (that is, glucose) intake is zero, phosphofructokinase (and therefore glycolysis) is inactive due to the low concentration of fructose-2,6- bisphosphate. In the liver, gluconeogenesis operates to provide glucose for the brain. However, in the fed state, up to 30% of fructose-1,6-bisphosphate formed from phosphofructokinase is recycled back to fructose-6-P (and then to...
tailieu.vn Xem trực tuyến Tải xuống
Among the many physi- ological changes elicited by epinephrine, one is the initiation of the enzyme cas- cade, as in Figure 15.17, which leads to rapid breakdown of glycogen, inhibition of glycogen synthesis, stimulation of glycolysis, and production of energy. The burst of energy produced is the result of a 2000-fold amplification of the rate of glycolysis.. Glucagon is involved...
tailieu.vn Xem trực tuyến Tải xuống
Elevated expression of the appropriate genes sets the stage for lipid biosynthesis in the liver, an important consequence of ingestion of carbohydrates.. In addition to pyruvate and lactate, other noncarbohydrate precursors can be used as substrates for gluconeogenesis in animals, including most of the amino acids, as well as glycerol and all the TCA cycle intermediates. On the other hand,...
tailieu.vn Xem trực tuyến Tải xuống
chain derivatives must first be converted to acylcarnitine derivatives, as shown in Figure 23.8. Carnitine acyltransferase I, associated with the outer mitochondrial membrane, catalyzes the formation of the O -acylcarnitine, which is then trans- ported across the inner membrane by a translocase. At this point, the acylcarni- tine is passed to carnitine acyltransferase II on the matrix side of the...
tailieu.vn Xem trực tuyến Tải xuống
23.4 How Are Unsaturated Fatty Acids Oxidized?. An Isomerase and a Reductase Facilitate the  -Oxidation of Unsaturated Fatty Acids. Unsaturated fatty acids are also catabolized by -oxidation, but two additional mito- chondrial enzymes—an isomerase and a novel reductase—are required to handle the cis double bonds of naturally occurring fatty acids. Is it possible to demonstrate specific effects of catechins...
tailieu.vn Xem trực tuyến Tải xuống
Cells Must Provide Cytosolic Acetyl-CoA and Reducing Power for Fatty Acid Synthesis. Eukaryotic cells face a dilemma in providing suitable amounts of substrate for fatty acid synthesis. Sufficient quantities of acetyl-CoA, malonyl-CoA, and NADPH must be generated in the cytosol for fatty acid synthesis. Malonyl-CoA is made by carboxylation of acetyl-CoA, so the problem reduces to generating suf- ficient acetyl-CoA...
tailieu.vn Xem trực tuyến Tải xuống
C 16 Fatty Acids May Undergo Elongation and Unsaturation. Additional Elongation As seen already, palmitate is the primary product of the fatty acid synthase. Cells synthesize many other fatty acids. Longer chains are made through special elongation reactions, which occur both in the mitochondria and at the surface of the endoplasmic reticulum (ER). The ER re- actions are actually quite...
tailieu.vn Xem trực tuyến Tải xuống
2% to 8% of the lipids in most animal membranes, but breakdown products of PI, in- cluding inositol-1,4,5-trisphosphate and diacylglycerol, are second messengers in a vast array of cellular signaling processes.. These glyceroether phospholipids are synthesized from dihydroxyacetone phosphate (Figure 24.23). HO CH 2 CH 2 R 1 R C O–. R 1 CH 2 CH 2. R 1 CH...
tailieu.vn Xem trực tuyến Tải xuống
In the cholesterol synthesis pathway, subsequent reactions, including HMG- CoA reductase and the following kinase reactions, pull the thiolase-catalyzed con- densation forward. However, in the case of fatty acid synthesis, a succession of eight thiolase condensations would be distinctly unfavorable from an energetic perspec- tive. Given the necessity of repeated reactions in fatty acid synthesis, it makes better energetic sense...