GENETICS
Genetics - Gene-> Dna-> MRna->protein - >cell structure->cell enzymes ->cell function.
Enzymes , Hormones, Rna, Golgi, Mitochondria circulation , atp - cell growth . Synthesis of a biochemical product requires a series of reactions catalyzed by special proteins, hormone formation , enzymes, the synthetic process often is controlled by sequence of genes located in series of the same chromosome ,dna strand, this area is known as the Operon.
Genes responsible for enzymes are called structurel genes ,three such genes show on operon which control three enzymes a segment on DNA known as Promoter consisting of nucleotides with specific affinity for RNA Polymerase which binds this promoter before travelling along DNA strand to synthesize RNA therefore the promoter is useful in activating operon for transcription of Genetic code .
An operon is frequently controlled by a regulatory gene located elsewhere in the genetic complex of the nucleous, the regulatory gene causes formation of a regulatory protein that in turn acts either as an activator or as a repressor substance . proteins breaks its bond with the operator is called activator substance because it activates the transcription process by removing protein in nucleated cells .
To control the operon, another operator called activator operator lies adjacent but ahead of the promoter. when a regulatory activating protein binds to this operator ,it helps to attract the RNA Plolymerase to the promoter activating the operon .
An addition band of nucleotides lying middle of the Promoter called Repressor Protein ,because a Regulatory inhibitory Protein is bind here and prevent attachment of RNA polymerase to the Promoter , blocking transcription of genes of this operon , such a regulator protein called Repressor inhibitory Protein. Various non protein substances as cell metabolites or toxins can bind with the repressor proteins to change its state. A substance which causes it to change so that it binds with the operator and stops transcription called repressor proteins,
when within each chromosome the DNA is wound around by histones proteins held compactly it cannot function to form RNA the operon is known as closed operon.
The transcription of genetic code is transmitted to other cells adjacent where the genetic transcription continues to more cells bringing metabolism to stop in surrounding cell while closing operon on adjacent cells , using up the remaining stored nutrients in cells surrounding leading to death of cells the deterioration overall dries up and depletes hyalurinic acid chondriotin sulphate , arachidonic acid etc which are important ingredients interchangeable molecules existing , for stability condition of skin moisture and cell growth , are depleted as cells are dried up and lack of growth of new cells , substituting the dead cells above, lack of nutrients and moisture for skin as vit e, vitc, vit d 3etc elasticity of skin decreases and skin is depleted . when there is open wound with number of bacteria and lack of immunity and wbc , pus infection starts from the limb to the bone leading to amputation as there is no medicine to cure .
no new cell and cell division appears unless repaire and, activation of operon , DNA , RNA and Golgi in Mitochondria with growth of RNA for release of enzymes from the cell structures , and pinocytosis for metabolism and energy formation continues .
Each regulatory protein exists In two allosteric forms one that binds with operator and repress the transcription .one that is straight and one that bends in the middle .only one of this forms can repress the operator . The transcription of genetic code is transmitted to other cells adjacent where the genetic transcription continues to more cells bringing metabolism to stop in surrounding cell while closing operon. of adjacent cells , meanwhile using up the remaining stored nutrients in cells surrounding , and as the wounds infected by staphylococci pyogenes eating of tixxue , leading to death of cells .
Dna is located in the nucleous of cell and most functions in the cell are carried out in the cytoplasm by RNA the formation of which is also controlled by DNA of the nucleous which passes through the nuclear pores into the cytoplasmic compartment for protein synthesis . four nucleotides adenine ,guanine, cytosine, uracil, form RNA and activated by RNA Polymerase by adding to each nucleotide- 2 extra phosphate radicals to form triphosphates , by the 2RNA nucleotides to the far right during RNA chain formation. Thease last 2 bonds are combined with nucleotides by high energy phosphate bonds derived from ATP of the cell there by large quantity of high energy are available for each nucleotide to promote chemical reaction that add each nucleotide to the end of RNA chain .
Each gene which is a nucleic acid called Deoxy Ribonucleic acid automatically controls formation of Ribonucleic acid which spreads through out the cell to control formation of specific protein. as there are I lakh genes in each cell they form a large number of different proteins, some of the cellular proteins are structurel proteins, which in association with various lipids and carbohydrate form the structure of various intracellular organelles, most of the proteins are mostly enzymes , that catalyse different chemical reactions in the body. enzymes promote all the oxidative reactions that supply energy to the cell and they promote synthesis of all the cell chemicals such as lipids glycogen and ATP.
Body hormones can activate specific chromosomal areas and specific transcription controlling the chemical machinery for function of cell ,some chemical substances formed inside the cell have direct feed back effects in inhibiting them , cyclic AMP is formed as breakdown product of ATP, which activates glycogen splitting enzyme phosphorylase liberating glucose molecules which are rapidly metabolized and energy used for ATP stores occur in purines pyrimidines depends on the mechanism of genetic regulation ,enzyme regulation , Hormone activation or inhibhition .
Hormones monitor cell biochemical composition and growth at the time of mitosis there is active proof reading of the dna strands wherever inappropriate DNA nucleotides have been matched up with the nucleotides of the original template strand . special enzymes cut out defective areas and replace thease with appropriate complementary nucleotides this is acheived by the same dna polymerase and dna ligase in replication. Because of repair and proof reading the transcription process only rarely makes a mistake hence wound cure is as original (called mutation), which then forms abnormal protein leading to abnormal cellular function and cell death. most of the Hormones in the Body are Polypeptides and Proteins.
Aminoacids < 100 number are peptides , and Aminoacids with >100 number arePolypeptides.
Hormones are degraded at target cells by enzymatic process that causes endocytosis of the cell membrane hormone receptor complex ,and the hormone metabolized in the cell cytoplasm and the receptor recycled to cell membrane. .absence of enzyme, receptor, golgi, rises to decrease in tissue function of cell their presence activate enzymes in the cell , activates protein kinase which promotes phophorelation of severel substances inside cells as insulin on cell,
When the hormone binds with special trans membrane receptor to become adenylcyclase enzyme ,catalyzes forming CAMP which has multitude of effects inside the cell for its life and cell activity.
Specially steroid hormones bind with protein receptors inside cells , activate hormone receptor complex , activates specific portions of DNA strands of the nucleus which in turn initiates transcription of specific genes, to form MRNA . eg thyroxine triiodothyronine Therefore after the hormone enters the cell initial action onset will be hrs to 20 days newly formed proteins appear in the cells and become controller of a number of increased cellular functions , the CAMP in turn causes subsequent intracellular effects of the hormone ,when ca ions , products of membrane phopholipid breakdown ,also activate intracellular effects .binding of the hormones with the receptor allows coupling of the receptor to a G protein . if the G protein stimulates adenyl cyclase CAMP system it is called Gs protein which stimulates adenyl cycase membrane bound enzyme which catalyses conversion of ATP to CAMP inside the cells which activates CAMP dependent protein kinase which phosphorelates specific proteins inside the cells trigerring biochemical Reactions that ultimately lead to cells response to hormone
once CAMP is formed inside the cells it activates cascade of enzymes first enzyme activates second and third and soon, initiates powerful cascading activation of cell binding of hormone to its receptor, some hormones activate transmembrane receptors that activate enzyme phospholipase inside receptors resulting in breakdown of phospholipids in cell membrane , as ip3 , phophotidyl inositol biphosphate which cleaves into inositol tri phosphate and diaceyl glycerol DAG . IP3 mobilizes ca ions from mitochondria and the endoplasmic reticulum gives cell secretion, DAG activates protein kinase which phophorelates large number of proteins leading to cell response . the lipid portion of DAG is archidonic acid which forms the precursor for the prostaglandins and other local hormones that cause multiple effects in tissues
Five special ingredients Endoplasmic reticulum, Golgi apparatus ,Mitochondria, Lysosomes, Peroxisomes, Ribosomes , are found on the surface of Granular Endoplasmic Reticulum which are composed of proteins and important in synthesis of new protein molecules . The agranular endoplasmic reticulum responsible for synthesis of lipid and enzymatic process inside cell are responsible for cell synthesis growth and during Absence of endoplasmic reticulum , golgi bodies , phospholipids , cholesterol , synthesis of essential enzymes , absence of glycogen breakdown for energy and absence of essential enzymes for detoxification of drugs damage cells by process of coagulation hydrolysis exists.
Growth hormone somotropin ,contains 191 amino acids mw 220005 causes growth of almost cell tissue of the body in size and mitosin increased rate of protein in most cells , mobilization of fatty acids from adipose tissue to increase free fatty acids in the blood to form lipids and growth of cells and increased use of fatty acids to form energy and RNA translation causing protein synthesis by ribosomes stimulates transcription DNA in the nucleus to MRNA to form more protein if sufficient energy, amino acids, vitamins, for growth are available ,catecholamines dopamine, serotonin all increase growth hormone secretion. Top layer of the skin is the epidermis , keratinocyte activation, neutraphils terminates inflammation, regulates keratinocyte and endothelial cell growth , inhibits proteases, activates leukocytes , stimulates nerve growth
Lipids =fatty acids ,glycerol storage form of energy to meet long term demands and to form structurel components of membranes are formed .
Aminoacids
Collagen has an unusual amino acid composition and sequence: Glycine (Gly) is found at almost every third residue, Proline (Pro) makes up about 17% of collagen .Collagen contains two uncommon derivative amino acids not directly inserted during translation These amino acids are found at specific locations relative to glycine and are modified post-translationally by different enzymes, both of which require vitamin c as a cofactor.
Hydroxyproline (Hyp), derived from proline. Hydroxylsine (Hyl), derived from lysine (Lys). Depending on the type of collagen, varying numbers of hydroxylysines are glycosylated mostly having disaccharides attached .
Synthesisofcollagen
The synthesis of collagen occurs inside and outside of the cell. Meshwork collagen, which is often involved in the formation of filtration systems is the other form of collagen. It should be noted that all types of collagens are triple helixes, and the differences lie in the make-up of the alpha peptides created in step2.
Transcription of mRNA: There are approximately 34 genes associated with collagen formation, each coding for a specific mRNA sequence, . The beginning of collagen synthesis begins with turning on genes which are associated with the formation of a particular alpha peptide (typically alpha 1, 2 or 3).
Pre-pro-peptide Formation: Once the final mRNA exits from the cell nucleus and enters into the cytoplasm it links with the ribosomal subunits and the process of translation occurs. The early/first part of the new peptide is known as the signal sequence. The signal sequence on the N-terminal of the peptide is recognized by a signal recognition particle , on the endoplasmic reticulum, which will be responsible for directing the pre-pro-peptide into the endoplasmic reticulum. Therefore, once the synthesis of new peptide is finished, it goes directly into the endoplasmic reticulum for post-translational processing..
Alpha Peptide to Procollagen: Three modifications of the pre-pro-peptide occurs leading to the formation of the alpha peptide. Secondly, the triple helix known as procollagen is formed before being transported in a transport vesicle to the golgi apparatus. 1) The signal peptide on the N-terminal is dissolved, and the molecule is now known as propeptide .
2) Hydroxylation of lysines and prolines on pro peptide by the enzymes prolyl hydroxylase and lysyl hydroxylase (to produce hydroxyproline and hydroxylysine) occurs to aid cross linking of the alpha peptides. It is this enzymatic step that requires vitamin C as a cofactor. In scurvy, the lack of hydroxylation of prolines and lysines causes a looser triple helix (which is formed by 3 alpha peptides).
3) Glycosylation occurs by adding either glucose or galactose monomers onto the hydroxy groups that were placed onto lysines, but not on prolines. From here the hydroxylated and glycosylated propeptide twists towards the left very tightly and then three propeptides will form a triple helix. It is important to remember that this molecule, now known as procollagen is composed of a twisted portion (center) and two loose ends on either end. At this point the procollagen is packaged into a transfer vesicle destined for the golgi apparatus.
Golgi Apparatus Modification: In the golgi apparatus, the procollagen goes through one last post-translational modification before being secreted out of the cell. In this step oligosaccharides (not monosaccharides like in step 3) are added, and then the alpha peptide is packaged into a secretory vesicle destined for the extracellular space.
Formation of Tropocollagen: Once outside the cell, membrane bound enzymes known as collagen peptidases, remove the "loose ends" of the procollagen molecule. What is left is known as tropocollagen. Defect in this step produces one of the many collagenopathies known as ehlers –danlos syndrome .This step is absent when synthesizing type IV or meshwork collagen.
Formation of the Collagen Fibril: Lysyl oxidase and extracellular enzyme produces the final step in the collagen synthesis pathway. This enzyme acts on lysines and hydroxylysines producing aldehyde groups, which will eventually undergo covalent bonding between tropocollagen molecules. This polymer of tropocollogen is known as a collagen fibril.
Collagen I formation Most collagen forms in a similar manner, but the following process is typical for type I: Inside the cell , Two types of peptide chains are formed during translation on ribosomes along the rough endoplasmic reticulam (RER): alpha-1 and alpha-2 chains. These peptide chains (known as preprocollagen) have registration peptides on each end and a signal peptide. Polypeptide chains are released into the lumen of the RER. Signal peptides are cleaved inside the RER and the chains are now known as pro-alpha chains. Hydroxylation of lysine and proline amino acids occurs inside the lumen. This process is dependent on ascorbic acid (Vitamin C) as a cofactor. Glycosylation of specific hydroxylysine residues occurs. Triple helical structure is formed inside the endoplasmic reticulum from each two alpha1 chains and one alpha-2 chain. Procollagen is shipped to the golgi apparatus, where it is packaged and secreted,byexocytosis.
Enzymes , Hormones, Rna, Golgi, Mitochondria circulation , atp - cell growth . Synthesis of a biochemical product requires a series of reactions catalyzed by special proteins, hormone formation , enzymes, the synthetic process often is controlled by sequence of genes located in series of the same chromosome ,dna strand, this area is known as the Operon.
Genes responsible for enzymes are called structurel genes ,three such genes show on operon which control three enzymes a segment on DNA known as Promoter consisting of nucleotides with specific affinity for RNA Polymerase which binds this promoter before travelling along DNA strand to synthesize RNA therefore the promoter is useful in activating operon for transcription of Genetic code .
An operon is frequently controlled by a regulatory gene located elsewhere in the genetic complex of the nucleous, the regulatory gene causes formation of a regulatory protein that in turn acts either as an activator or as a repressor substance . proteins breaks its bond with the operator is called activator substance because it activates the transcription process by removing protein in nucleated cells .
To control the operon, another operator called activator operator lies adjacent but ahead of the promoter. when a regulatory activating protein binds to this operator ,it helps to attract the RNA Plolymerase to the promoter activating the operon .
An addition band of nucleotides lying middle of the Promoter called Repressor Protein ,because a Regulatory inhibitory Protein is bind here and prevent attachment of RNA polymerase to the Promoter , blocking transcription of genes of this operon , such a regulator protein called Repressor inhibitory Protein. Various non protein substances as cell metabolites or toxins can bind with the repressor proteins to change its state. A substance which causes it to change so that it binds with the operator and stops transcription called repressor proteins,
when within each chromosome the DNA is wound around by histones proteins held compactly it cannot function to form RNA the operon is known as closed operon.
The transcription of genetic code is transmitted to other cells adjacent where the genetic transcription continues to more cells bringing metabolism to stop in surrounding cell while closing operon on adjacent cells , using up the remaining stored nutrients in cells surrounding leading to death of cells the deterioration overall dries up and depletes hyalurinic acid chondriotin sulphate , arachidonic acid etc which are important ingredients interchangeable molecules existing , for stability condition of skin moisture and cell growth , are depleted as cells are dried up and lack of growth of new cells , substituting the dead cells above, lack of nutrients and moisture for skin as vit e, vitc, vit d 3etc elasticity of skin decreases and skin is depleted . when there is open wound with number of bacteria and lack of immunity and wbc , pus infection starts from the limb to the bone leading to amputation as there is no medicine to cure .
no new cell and cell division appears unless repaire and, activation of operon , DNA , RNA and Golgi in Mitochondria with growth of RNA for release of enzymes from the cell structures , and pinocytosis for metabolism and energy formation continues .
Each regulatory protein exists In two allosteric forms one that binds with operator and repress the transcription .one that is straight and one that bends in the middle .only one of this forms can repress the operator . The transcription of genetic code is transmitted to other cells adjacent where the genetic transcription continues to more cells bringing metabolism to stop in surrounding cell while closing operon. of adjacent cells , meanwhile using up the remaining stored nutrients in cells surrounding , and as the wounds infected by staphylococci pyogenes eating of tixxue , leading to death of cells .
Dna is located in the nucleous of cell and most functions in the cell are carried out in the cytoplasm by RNA the formation of which is also controlled by DNA of the nucleous which passes through the nuclear pores into the cytoplasmic compartment for protein synthesis . four nucleotides adenine ,guanine, cytosine, uracil, form RNA and activated by RNA Polymerase by adding to each nucleotide- 2 extra phosphate radicals to form triphosphates , by the 2RNA nucleotides to the far right during RNA chain formation. Thease last 2 bonds are combined with nucleotides by high energy phosphate bonds derived from ATP of the cell there by large quantity of high energy are available for each nucleotide to promote chemical reaction that add each nucleotide to the end of RNA chain .
Each gene which is a nucleic acid called Deoxy Ribonucleic acid automatically controls formation of Ribonucleic acid which spreads through out the cell to control formation of specific protein. as there are I lakh genes in each cell they form a large number of different proteins, some of the cellular proteins are structurel proteins, which in association with various lipids and carbohydrate form the structure of various intracellular organelles, most of the proteins are mostly enzymes , that catalyse different chemical reactions in the body. enzymes promote all the oxidative reactions that supply energy to the cell and they promote synthesis of all the cell chemicals such as lipids glycogen and ATP.
Body hormones can activate specific chromosomal areas and specific transcription controlling the chemical machinery for function of cell ,some chemical substances formed inside the cell have direct feed back effects in inhibiting them , cyclic AMP is formed as breakdown product of ATP, which activates glycogen splitting enzyme phosphorylase liberating glucose molecules which are rapidly metabolized and energy used for ATP stores occur in purines pyrimidines depends on the mechanism of genetic regulation ,enzyme regulation , Hormone activation or inhibhition .
Hormones monitor cell biochemical composition and growth at the time of mitosis there is active proof reading of the dna strands wherever inappropriate DNA nucleotides have been matched up with the nucleotides of the original template strand . special enzymes cut out defective areas and replace thease with appropriate complementary nucleotides this is acheived by the same dna polymerase and dna ligase in replication. Because of repair and proof reading the transcription process only rarely makes a mistake hence wound cure is as original (called mutation), which then forms abnormal protein leading to abnormal cellular function and cell death. most of the Hormones in the Body are Polypeptides and Proteins.
Aminoacids < 100 number are peptides , and Aminoacids with >100 number arePolypeptides.
Hormones are degraded at target cells by enzymatic process that causes endocytosis of the cell membrane hormone receptor complex ,and the hormone metabolized in the cell cytoplasm and the receptor recycled to cell membrane. .absence of enzyme, receptor, golgi, rises to decrease in tissue function of cell their presence activate enzymes in the cell , activates protein kinase which promotes phophorelation of severel substances inside cells as insulin on cell,
When the hormone binds with special trans membrane receptor to become adenylcyclase enzyme ,catalyzes forming CAMP which has multitude of effects inside the cell for its life and cell activity.
Specially steroid hormones bind with protein receptors inside cells , activate hormone receptor complex , activates specific portions of DNA strands of the nucleus which in turn initiates transcription of specific genes, to form MRNA . eg thyroxine triiodothyronine Therefore after the hormone enters the cell initial action onset will be hrs to 20 days newly formed proteins appear in the cells and become controller of a number of increased cellular functions , the CAMP in turn causes subsequent intracellular effects of the hormone ,when ca ions , products of membrane phopholipid breakdown ,also activate intracellular effects .binding of the hormones with the receptor allows coupling of the receptor to a G protein . if the G protein stimulates adenyl cyclase CAMP system it is called Gs protein which stimulates adenyl cycase membrane bound enzyme which catalyses conversion of ATP to CAMP inside the cells which activates CAMP dependent protein kinase which phosphorelates specific proteins inside the cells trigerring biochemical Reactions that ultimately lead to cells response to hormone
once CAMP is formed inside the cells it activates cascade of enzymes first enzyme activates second and third and soon, initiates powerful cascading activation of cell binding of hormone to its receptor, some hormones activate transmembrane receptors that activate enzyme phospholipase inside receptors resulting in breakdown of phospholipids in cell membrane , as ip3 , phophotidyl inositol biphosphate which cleaves into inositol tri phosphate and diaceyl glycerol DAG . IP3 mobilizes ca ions from mitochondria and the endoplasmic reticulum gives cell secretion, DAG activates protein kinase which phophorelates large number of proteins leading to cell response . the lipid portion of DAG is archidonic acid which forms the precursor for the prostaglandins and other local hormones that cause multiple effects in tissues
Five special ingredients Endoplasmic reticulum, Golgi apparatus ,Mitochondria, Lysosomes, Peroxisomes, Ribosomes , are found on the surface of Granular Endoplasmic Reticulum which are composed of proteins and important in synthesis of new protein molecules . The agranular endoplasmic reticulum responsible for synthesis of lipid and enzymatic process inside cell are responsible for cell synthesis growth and during Absence of endoplasmic reticulum , golgi bodies , phospholipids , cholesterol , synthesis of essential enzymes , absence of glycogen breakdown for energy and absence of essential enzymes for detoxification of drugs damage cells by process of coagulation hydrolysis exists.
Growth hormone somotropin ,contains 191 amino acids mw 220005 causes growth of almost cell tissue of the body in size and mitosin increased rate of protein in most cells , mobilization of fatty acids from adipose tissue to increase free fatty acids in the blood to form lipids and growth of cells and increased use of fatty acids to form energy and RNA translation causing protein synthesis by ribosomes stimulates transcription DNA in the nucleus to MRNA to form more protein if sufficient energy, amino acids, vitamins, for growth are available ,catecholamines dopamine, serotonin all increase growth hormone secretion. Top layer of the skin is the epidermis , keratinocyte activation, neutraphils terminates inflammation, regulates keratinocyte and endothelial cell growth , inhibits proteases, activates leukocytes , stimulates nerve growth
Lipids =fatty acids ,glycerol storage form of energy to meet long term demands and to form structurel components of membranes are formed .
Aminoacids
Collagen has an unusual amino acid composition and sequence: Glycine (Gly) is found at almost every third residue, Proline (Pro) makes up about 17% of collagen .Collagen contains two uncommon derivative amino acids not directly inserted during translation These amino acids are found at specific locations relative to glycine and are modified post-translationally by different enzymes, both of which require vitamin c as a cofactor.
Hydroxyproline (Hyp), derived from proline. Hydroxylsine (Hyl), derived from lysine (Lys). Depending on the type of collagen, varying numbers of hydroxylysines are glycosylated mostly having disaccharides attached .
Synthesisofcollagen
The synthesis of collagen occurs inside and outside of the cell. Meshwork collagen, which is often involved in the formation of filtration systems is the other form of collagen. It should be noted that all types of collagens are triple helixes, and the differences lie in the make-up of the alpha peptides created in step2.
Transcription of mRNA: There are approximately 34 genes associated with collagen formation, each coding for a specific mRNA sequence, . The beginning of collagen synthesis begins with turning on genes which are associated with the formation of a particular alpha peptide (typically alpha 1, 2 or 3).
Pre-pro-peptide Formation: Once the final mRNA exits from the cell nucleus and enters into the cytoplasm it links with the ribosomal subunits and the process of translation occurs. The early/first part of the new peptide is known as the signal sequence. The signal sequence on the N-terminal of the peptide is recognized by a signal recognition particle , on the endoplasmic reticulum, which will be responsible for directing the pre-pro-peptide into the endoplasmic reticulum. Therefore, once the synthesis of new peptide is finished, it goes directly into the endoplasmic reticulum for post-translational processing..
Alpha Peptide to Procollagen: Three modifications of the pre-pro-peptide occurs leading to the formation of the alpha peptide. Secondly, the triple helix known as procollagen is formed before being transported in a transport vesicle to the golgi apparatus. 1) The signal peptide on the N-terminal is dissolved, and the molecule is now known as propeptide .
2) Hydroxylation of lysines and prolines on pro peptide by the enzymes prolyl hydroxylase and lysyl hydroxylase (to produce hydroxyproline and hydroxylysine) occurs to aid cross linking of the alpha peptides. It is this enzymatic step that requires vitamin C as a cofactor. In scurvy, the lack of hydroxylation of prolines and lysines causes a looser triple helix (which is formed by 3 alpha peptides).
3) Glycosylation occurs by adding either glucose or galactose monomers onto the hydroxy groups that were placed onto lysines, but not on prolines. From here the hydroxylated and glycosylated propeptide twists towards the left very tightly and then three propeptides will form a triple helix. It is important to remember that this molecule, now known as procollagen is composed of a twisted portion (center) and two loose ends on either end. At this point the procollagen is packaged into a transfer vesicle destined for the golgi apparatus.
Golgi Apparatus Modification: In the golgi apparatus, the procollagen goes through one last post-translational modification before being secreted out of the cell. In this step oligosaccharides (not monosaccharides like in step 3) are added, and then the alpha peptide is packaged into a secretory vesicle destined for the extracellular space.
Formation of Tropocollagen: Once outside the cell, membrane bound enzymes known as collagen peptidases, remove the "loose ends" of the procollagen molecule. What is left is known as tropocollagen. Defect in this step produces one of the many collagenopathies known as ehlers –danlos syndrome .This step is absent when synthesizing type IV or meshwork collagen.
Formation of the Collagen Fibril: Lysyl oxidase and extracellular enzyme produces the final step in the collagen synthesis pathway. This enzyme acts on lysines and hydroxylysines producing aldehyde groups, which will eventually undergo covalent bonding between tropocollagen molecules. This polymer of tropocollogen is known as a collagen fibril.
Collagen I formation Most collagen forms in a similar manner, but the following process is typical for type I: Inside the cell , Two types of peptide chains are formed during translation on ribosomes along the rough endoplasmic reticulam (RER): alpha-1 and alpha-2 chains. These peptide chains (known as preprocollagen) have registration peptides on each end and a signal peptide. Polypeptide chains are released into the lumen of the RER. Signal peptides are cleaved inside the RER and the chains are now known as pro-alpha chains. Hydroxylation of lysine and proline amino acids occurs inside the lumen. This process is dependent on ascorbic acid (Vitamin C) as a cofactor. Glycosylation of specific hydroxylysine residues occurs. Triple helical structure is formed inside the endoplasmic reticulum from each two alpha1 chains and one alpha-2 chain. Procollagen is shipped to the golgi apparatus, where it is packaged and secreted,byexocytosis.