Cell components, protein release from

There are several steps in the absorption of vitamin B. In the stomach and lumen of the small intestine it is hydrolysed from its (peptide) links with the proteins of which it is a component. It then attaches to gastric intrinsic factor, which is a glycoprotein of molecular mass about 50 000 kDa, to form a complex. This protects the vitamin from being damaged by acid in the stomach. The complex is carried into the ileum, where it binds to a receptor on the surface of the absorptive cells and is released from the intrinsic factor within the absorptive cell, hi the portal venous blood, it is transported to the liver bound to the vitamin B 12-binding protein, which also protects the vitamin. 

FIGURE 1.25 The virus life cycle. Viruses are mobile bits of genetic iuformatiou encapsulated in a protein coat. The genetic material can be either DNA or RNA. Once this genetic material gains entry to its host cell, it takes over the host machinery for macromolecular synthesis and subverts it to the synthesis of viral-specific nucleic acids and proteins. These virus components are then assembled into mature virus particles that are released from the cell. Often, this parasitic cycle of virus infection leads to cell death and disease. 

There may be several mechanisms for these metabolic effects. Unsaturated fatty acids have been shown to directly activate specific enzymes and to induce DNA synthesis and cytokine release from lymphocytes (Karsten et al., 1994). The induction of specific protein synthesis may produce the reduction in glutamine metabolism. The increase in the robustness of the fatty acid-grown hybridomas in agitated cultures could be explained by a high incorporation of the available fatty acids into the cellular phospholipids fraction, which is a major structural component of the outer membrane of the cell (Butler et al., 1999). 

---