The list of intracellular enzymes present in the cytoplasm is never-ending. It is because the cytoplasm is the main metabolic centre of each cell.
The majority of the cellular metabolic reactions occur within the cytoplasm. Other than the ones participating in the metabolic process mentioned above, following cytoplasmic enzymes are also important. Mitochondria is also a site of a large number of metabolic reactions within the cells. Therefore, it also contains a large population of enzymes.
It is said that mitochondria contain a battery of enzymes that extract energy from various molecules and provides it to the cell in the form of ATP. A brief detail of important metabolic processes along with the intracellular enzymes needed for them is given below. It is the final pathway for the oxidative metabolites of carbohydrates, fatty acids, and amino acids. During this cycle, pyruvate, and other carboxylic acids, obtained from various sources are oxidized to simple carbon dioxide molecules and the energy is released.
The enzymes involved in this cycle are as follows. Before starting the tricarboxylic acid cycle, pyruvate is converted to acetic acid by an intracellular enzyme complex called pyruvate dehydrogenase. It is also located within the mitochondria. The enzymes needed for these reactions are as follows. Some reactions of the urea cycle also occur in mitochondria. These include the synthesis of carbamoyl phosphate and its transfer to ornithine to form citrulline.
The enzymes involved in these reactions are:. In addition to the above-mentioned reaction, several other anabolic and catabolic reactions also occur in mitochondria, catalysed by intracellular enzymes. Because of keeping the writing simple, all those reactions cannot be discussed here. The nucleus not only contains the genetic material of a cell but also contains certain enzymes. These enzymes are useful in the metabolic process taking place within the nucleus such as transcription, DNA duplication, mitosis, etc.
These enzymes are also sometimes called nuclear proteins. They are made in the cytoplasm and enter the nucleus via nuclear pores. Lysosomes are the membrane-bound organelles found in animal cells. They contain a collection of enzymes for intracellular digestion and detoxification of phagocytosed molecules.
They are involved in the breakdown of various large-sized molecules. Ribosomes are the protein-making machinery of the cell. They contain enzymes needed for the translation of mRNA to make proteins. Following intracellular enzymes are present within the ribosomes. As the name indicates, extracellular enzymes are present in the extracellular fluid. They catalyse chemical reactions taking place outside the cells.
They may be present in tissue spaces, in body fluids like saliva and blood, and cavities of organs like the stomach, intestine, etc. Like intracellular enzymes, the extracellular ones are also synthesized by ribosomes in the process of translation.
Once synthesized, they are transferred to the Golgi apparatus from the rough endoplasmic reticulum. Here, the enzymes are packed into membrane-bound vesicles and are directed towards the cell membrane.
The Golgi vesicles fuse with the cell membrane and dump the enzymes into the extracellular space. The extracellular enzymes either work in these spaces between the cells or are transported via specialized ducts into different body organs for their function as seen in the case of pancreatic enzymes. Saliva is a watery fluid produced by salivary glands and released into the oral cavity via salivary ducts.
It contains important enzymes that are necessary for the digestion of food. Digestion begins in the oral cavity and is initiated by extracellular enzymes present in the saliva.
Salivary enzymes are mixed with food in the oral cavity. They continue to perform their action as the food bolus moves from the oral cavity to the stomach via the oesophagus. Pepsin is an extracellular enzyme released by chief cells of the stomach into gastric juice. This enzyme is released in an inactive form called pepsinogen. The inactive variant is converted to an active enzyme by abundant hydrochloric acid present in the stomach. The activated enzyme causes partial digestion of proteins.
It is a protease enzyme that digests protein particles present in food to form simpler polypeptides. These polypeptides are later digested by another enzyme to generate simpler products. Pepsin is released in an inactive form to protect cells from its proteolytic action. It can only be activated in the presence of an acidic environment that is provided by the HCL in the stomach antrum. It is another enzyme involved in protein digestion.
Like pepsin, it is released in an inactive form called trypsinogen. It is produced by the pancreas and released in the duodenum along with other enzymes in pancreatic juice. Once in the duodenum, it is activated by another enzyme called enterokinase. Enterokinase is released by the cells of the duodenum. It cleaves a peptide from the amino terminal of trypsinogen to form trypsin. Trypsin acts on polypeptides and converts them into simpler peptides.
They are further acted upon by other enzymes to be converted into simpler products. Trypsin also causes activation of other enzymes in the pancreatic juice such as chymotrypsinogen and proelastase etc. It is a pancreatic enzyme released in an inactive chymotrypsinogen form.
Trypsin from the pancreas causes activation of this enzyme. It is also involved in protein digestion within the small intestine. These are proteolytic extracellular enzymes released by the pancreas into the small intestine. They act upon elastin and collagen fibres present in the food particles. These extracellular enzymes cause complete digestion of protein fibres into the constituent amino acids.
It is another extracellular enzyme released by the pancreas. It is an enzyme involved in carbohydrate digestion. Just like salivary amylase, it causes hydrolysis of starch present in food. It converts starch into simpler sugars like disaccharides and trisaccharides. Pancreas also releases extracellular enzymes for the digestion of lipid particles present in food.
The enzymes and their actions are listed below. Nuclease acts upon long strands of nucleic acids and releases individual nucleotides by cleaving phosphodiester bonds. Nucleosidase then acts upon individual nucleotides and cause their breakdown into nitrogenous base and sugar.
It should be kept in mind that all the pancreatic enzymes are made by pancreatic parenchymal cells. They are then released out of the cell into the pancreatic duct. The pancreatic enzyme along with water and other components together make the pancreatic juice that is then released into the duodenum. All these enzymes act extracellularly in the lumen of the small intestine and cause the digestion of various food particles. In addition to the digestive enzymes mentioned above, intestinal cells also make and release some enzymes that complete the process of digestion.
These are extracellular enzymes released by the cells lining the intestines into the intestinal lumen. Some important enzymes are as follows. Intracellular and Extracellular Enzymes. Furthermore, decomposers play a key role in ecosystems, recycling nutrients. In addition, these organisms can absorb nutrients, which are the products of the extracellular digestion through their cell wall.
Other organisms such as plants can also absorb these nutrients from their roots. Intracellular enzymes refer to the enzymes which act inside the cell while extracellular enzymes refer to the enzymes made by the cell but, work in the outside of the cell. Intracellular enzymes are also known as endoenzymes while extracellular enzymes are known as exoenzymes. Moreover, intracellular enzymes account for the majority of enzymes while the minority is extracellular enzymes.
While itracellular enzymes breakdown large polymers into smaller chains of monomers, extracellular enzymes act on the end of the polymer to breakdown its monomers one at a time. Furthermore, intracellular enzymes undergo intracellular digestion while extracellular enzymes undergo extracellular digestion. Intracellular enzymes are responsible for the digestion of food particles inside the cytoplasm of unicellular organisms while extracellular enzymes are responsible for the digestion of food inside the alimentary canal of higher animals and the extracellular digestion in decomposers such as fungi and bacteria.
Intracellular enzymes are the enzymes that function inside the cell. Most enzymes are intracellular enzymes, breaking down large polymers into small chains of monomers.
Generally, intracellular enzymes occur in unicellular organisms that undergo intracellular digestion of food particles. On the other hand, extracellular enzymes are the minor group of enzymes, functioning outside the cell. In contrast, they breakdown large polymers into monomers starting from the ends. In addition, extracellular enzymes released by decomposers to the external environment are responsible for the digestion of decomposing organic material.
In addition, decomposers play a key role in ecosystems by recycling nutrients. In addition, these organisms can absorb nutrients that are products of extracellular digestion through their cell walls. Other organisms such as plants can also absorb these nutrients from their roots.
Intracellular enzymes refer to the enzymes that work inside the cell, while extracellular enzymes refer to the enzymes produced by the cell but which work outside the cell. Intracellular enzymes are also called endoenzymes, while extracellular enzymes are called exoenzymes.
While itracellular enzymes break down large polymers into smaller monomer chains, extracellular enzymes work at the end of the polymer to break down its monomers individually. In addition, intracellular enzymes undergo intracellular digestion while extracellular enzymes undergo extracellular digestion. Intracellular enzymes are responsible for the digestion of food particles in the cytoplasm of unicellular organisms, while extracellular enzymes are responsible for the digestion of food in the alimentary canal of higher animals and the extracellular digestion in decomposers such as fungi and bacteria.
Intracellular enzymes are the enzymes that work inside the cell. Most enzymes are intracellular enzymes that break down large polymers into small chains of monomers. In general, intracellular enzymes occur in unicellular organisms that undergo intracellular digestion of food particles. Extracellular enzymes, on the other hand, are the subgroup of enzymes that function outside of the cell.
In contrast, they break large polymers down into monomers from the ends. In principle, extracellular enzymes are responsible for digestion in the alimentary canal in higher animals and for extracellular digestion in decomposers such as fungi and bacteria. Therefore, the main difference between intracellular and extracellular enzymes is where they act and what they mean.
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