Guide To Learn
Protein synthesis inhibitors serve two major purposes (Figure 6.25) (Table 6.1). First, they have been very useful scientifically in elucidating the biochemical mechanisms of protein synthesis. Second, some of these inhibitors affect prokaryotic but not eukaryotic protein synthesis and thus are medically important antibiotics. Streptomycin Streptomycin is an aminoglycoside antibiotic that affects the function of […]
Some proteins such as low-density lipoprotein (LDL), the iron-carrying protein transferrin, peptide hormones and circulating proteins, which are destined to be degraded, are imported into certain cells from the surrounding medium. These proteins bind to receptors on the outer face of the plasma membrane. These receptors are concentrated in the invaginations of the membrane called […]
The nucleus is separated from the cytoplasm by two membranes which form the ‘nuclear envelope’. The nuclear membrane acts as barrier that prevent the free passage of molecules between the nucleus and the cytoplasm. The transport of macromolecules including mRNA, tRNAs and ribosomal subunits out of the nucleus and the transport of all nuclear proteins […]
Besides being bound by two membranes, both mitochondria and chloroplasts also contain similar type of electrotransport proteins and use an F-class ATPase to synthesize ATP. The growth and division of mitochondria and chloroplasts are not coupled to nuclear division. Proteins encoded by the mitochondrial and chloroplast DNA are synthesized on the ribosomes within the organelles […]
Membrane and soluble secretory proteins that are synthesized on the rough ER undergo four principal modifications before they reach their final destination. Protein Glycosylation One or more carbohydrate chains are added to vast majority of proteins that are synthesized on the rough ER; indeed glycosylation is the principal chemical modification to most of these proteins. […]
The same secretory pathway is used by all eukaryotic cells for synthesizing and sorting secreted proteins and soluble luminal proteins in the ER, Golgi apparatus and lysosomes. These proteins are collectively referred to as ‘secretory proteins’. Although all cells secrete a variety of proteins (e.g., extracellular matrix proteins), certain types of cells are specialized for […]
Signal sequences are the sequences that help in targeting proteins to their proper cellular destinations. These sequences are present in the synthesized protein itself. They are about 20–50 amino acids in length. These signal sequences or uptake-targeting sequences are bound by receptor proteins. These govern the specificity of targeting. After binding with the receptor, the […]
There are 10,000 different kinds of proteins in a mammalian cell. Most of these proteins are synthesized by cytosolic ribosomes and they remain within the cytosol. However, many of the proteins produced in a cell are delivered either to a particular cell membrane or to the cell surface for secretion. For example, many hormone receptor […]