Liver cells mitochondria

Reactions of the type in Eq. (20) were found when a method specially adapted to extract the enzyme from ruptured liver cell mitochondria had been used (Hll). 

In a study of an ethanolic extract of black cohosh administered by gavage to rats in daily doses from 1 to 1000 mg/kg for 21 days, some dose-dependent changes in liver cell mitochondria were observed beginning at the 10 mg/kg dose. At 10 mg/kg, a slight amount of mitochondrial swelling and an enlargement of bile canaliculi was observed. At the 100 or 300 mg/kg dose, more distinct mitochondrial swelling and... 

The De-Ritis ratio is the ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT) in serum. In norn al subjects this is about 1.3. AST is found in both liver cell mitochondria and cytoplasm whereas ALT is found mainly in the cytoplasm. The ratio of the two can therefore give some information on the type of liver damage. For instance in acute hepatitis the ratio is less than 1, whereas high ratios are observed in liver carcinoma. 

An enzyme found in liver cell mitochondria, the measurement of which in the serum can be indicative of hepatocellular disease. 

KBs are generated from acetyl CoA in liver cell mitochondria. The three KBs are acetoacetate, acetone and 3-hydroxybutyrate. They are carried in the blood to tissues that can use them as an energy source. Liver cells are unable to utilize KBs as fuel, as liver cells lack the enzyme 3-ketoacyl CoA transferase that is necessary to regenerate acetyl CoA from the KBs. 

Glutamate too may be produced from oxoglutarate And now that it s been introduced deamination is its fate For inside each mitochondrion of every liver cell Is GDH...(reducing NAD as well). 

Malate is then transported into the mitochondrion where it is reoxidized to oxaloacetate. Mitochondrial NAD is reduced in the process. These electrons are then used in oxidative phosphorylation to produce three ATP per NADH. Thus the energy yield of glycolysis in heart and liver cells is two ATP, produced by substrate level phosphorylation, plus six ATP (three ATP per NADH), produced by oxidative phosphorylation. This gives an energy yield of eight ATP per glucose. 

Reactions of the urea cycle occur in both the mitochondria and cytosol of liver cells. Glutamate dehydrogenase, the citric acid cycle enzymes, carbamoyl phosphate synthetase I, and ornithine transcarbamoylase are localized in the mitochondrion, whereas the rest of the cycle occurs in the cytosol. This means that ornithine must be transported into mitochondria, and citrulline must be exported to the cytosol, in order for the cycle to proceed. 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary. Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 10 . Mammalian cells typically contain several himdred mitochondria and liver cells more than 1000. Mammalian sperm cells may contain... 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary. Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 10 . Mammalian cells typically contain several hundred mitochondria and liver cells more than 1000. Mammalian sperm cells may contain 50-75 mitochondria, but in some organisms only one very large helical mitochondrion, formed by the fusion of many individual mitochondria, wraps aroimd the base of the tail. Typical mitochondria appear to be about the size of cells of E. coU. However, study of ultrathin serial sections of a single yeast cell by electron microscopy has shown that, under some growth conditions, all of the mitochondria are interconnected. In every case a mitochondrion is enclosed by two... 

Now we are in a position to reveal what actually happens to a long-chain fatty acid on the way to total oxidation. If we start with stearic acid, the saturated 18-carbon fatty acid, and assume that it has just been unloaded into, say, a liver cell or a muscle cell, it has to make its way to a mitochondrion because that is where most of the oxidation of fatty acids occurs. 

Fig. 7. Di Ferent types of mitochondria as they form during development of the rat. (A) Some mitochondria with little electron dense matrix and few cristae. Epithel cell of the epidermis (rat embryo, day 17 of gestation). 1 36,000. (B) Mitochondrion with numerous parallel cristae and a matrix of intermediate electron density. Brown fat body. Adult rat. 1 36,000. (C) Typical mitochondrion with tubuh (—>) and cristae and an electron dense matrix. Differentiated liver cell, adult rat. Close spatial relationship with the rough endoplasmic reticulum (X). 1 36,000.

During fasting or in uncontrolled diabetes mellitus, fatty acids enter liver cells and are transported from the cytosol into the mitochondrion (Fig. 33.2). NB The carnitine shuttle is needed to transport fatty acids... 

Mitochondria are intracellular organelles with a double-membrane structure. Both the number and size of mitochondria vary in different cells - for example, a liver cell contains some 800 mitochondria, a renal tubule cell some 300 and a sperm about 20. The outer mitochondrial membrane is permeable to a great many substrates, while the inner membrane provides a barrier to regulate the uptake of substrates and output of products (see, for example, the regulation of palmitoyl CoA uptake into the mitochondrion for oxidation in section 5.5.1). 

The theory has been advanced that there exists in the cell a particulate structure somewhat smaller than the mitochondrion, the lyso-some, that contains certain autolytic enzymes in a latent situation. The lysosome theory55,56 is very largely based upon measurements made in sucrose homogenates of rodent liver. Although the results for a-D-mannosidase in this tissue (see Table IV) are not incompatible with the theory, the results for other tissues do not always conform to it. In particular, the contrast between mouse and rat spleen argues against a universal single particle to which a-D-mannosidase is confined. Apart from the results quoted in Table IV, not much work has been done on the intracellular location of a-D-mannosidase. 

The complex tetrapyrrole ring structure of heme is built up in a stepwise fashion from the very simple precursors sue-cinyl-CoA and glycine (Figure 32-2). The pathway is present in all nucleated cells. From measurements of total bilirubin production, it has been estimated that daily synthesis of heme in humans is 5 to 8mmol/kg body weight. Of this, 70% to 80% occurs in the bone marrow and is used for hemoglobin synthesis. Approximately 15% is synthesized in the liver and is used to produce cytochrome P-450, mitochondrial cytochromes, and other hemoproteins. The pathway is compartmentalized, with some steps occurring in the mitochondrion and others in the cytoplasm. Little is known about the transport of intermediates across the mitochondrial membrane, and no transport defect has yet been reported in the porphyrias. 

Figure 4 Immunogold localization of mannose-terminal glucocerebrosidase in rat liver Kupffer cells 30 minutes after enzyme infusion. Gold particles are concentrated in the lysosomes. Lys = Lysosome M = mitochondrion Nuc = nucleus PM = plasma membrane. Original magnifications (A) x10,000 (B) x33,000. Bars = 1 pm. (From Ref. 24.)...

Although fatty acid synthesis occurs within the cytoplasm of most animal cells, liver is the major site for this process. (Recall, for example, that liver produces VLDL. See p. 349.) Fatty acids are synthesized when the diet is low in fat and/or high in carbohydrate or protein. Most fatty acids are synthesized from dietary glucose. As discussed, glucose is converted to pyruvate in the cytoplasm. After entering the mitochondrion, pyruvate is converted to acetyl-CoA, which condenses with oxaloacetate, a citric acid cycle intermediate, to form citrate. When mitochondrial citrate levels are sufficiently high (i.e., cellular energy requirements are low), citrate enters the cytoplasm, where it is cleaved to form acetyl-CoA and oxaloacetate. The net reaction for the synthesis of palmitic acid from acetyl-CoA is as follows ... 

These substrates are different than those with the carbamoyl phosphate used for urea synthesis. The enzyme for the glutamine-dependent carbamoyl phosphate synthetase (CPS II) is in the cytosol, whereas that for urea synthesis (CPS I) is in the mitochondrion. The glutamine-dependent carbamoyl phosphate synthetase is present in most cells, whereas the mitochondrial carbamoyl phosphate synthetase is present primarily in the liver, kidney, and intestines (Fig. 20.6). 

Borutaite V, Brown GC (1996) Rapid reduction of nitric oxide by mitochondria, and reversible inhibition of mitochondrial respiration by nitric oxide. Biochem J 315 295-299 Boya P, Andreau K, Poncet D, Zamzami N, Perfettini JL, Metivier D, OJcius DM, Jaattela M, Kroemer G (2003a) Lysosomal membrane permeabilization induces cell death in a mitochondrion-dependent fashion. J Exp Med 197 1323-1334 Boya P, Gonzalez-Polo RA, Poncet D, Andreau K, Vieira HLA, Roumier T, Perfettini JL, Kroemer G (2003b) Mitochondrial membrane permeabilization is a critical step of lysosome-initiated apoptosis induced by hydroxychloroquine. Oncogene 22 3927-3936 Bravo JF, Jacobson MP, Mertens BF (1997) Fatty liver and pleural effusion with ibuprofen therapy. Ann Intern Med 87 200-201... 

In mitoehondria such as those of the parenchymal cells of the liver, cristae are relatively scarce and project only part way into the mitochondrial matrix fPalade, 1956 Fawcett, 1966). By contrast, the mitochondria of interscapular brown adipose tissue of certain mammals have many cristae which span completely the distance from one side of the mitochondrion to the other (Napolitano and Fawcett, 1958 Barnard, 1969 Barnard and Lindberg, 1969). The mitochondria of the indirect flight muscles of insects have tightly compacted cristae (Brosemer et al., 19 ). In the blowfly, for example, as many as 34 cristae are packed into 1 /tm of mitochondrial length (Gregory et al., 1967). 

Claude has calculated that a typical liver mitochondrion could contain about one million protein molecules and that in each mitochondrion there may be twenty-five different enzymatic systems. That means that each system could be duplicated 2000 times in each mitochondrion, which certainly lends support to Claude s description of the mitochondria as the power plants of the cell. 

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