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71 Cards in this Set
- Front
- Back
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In the body, these proteins help refold newly synthesized proteins and older proteins that have been misfolded
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cis-trans-prolyl isomerases
& Protein disulfide isomerases |
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heat absorbers in eukaryotes that help refold proteins after excessive heat has misfolded them
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HSP 60 and HSP 10
which are equivalent to bacteria GROEL and GROES |
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Hsp 60 adn Hsp 10 forms a cavity which binds to exposed ________ patches of misfolded proteins
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hydrophobic
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What powers the Hsp complex to unfold and refold misfolded proteins?
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ATP
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What is Cotranslational?
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proteins are modified as they are being translated
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What is posttranslational?
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Proteins are modified after they have been translated
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Name the 5 types of posttranslational modification and what happens in each modification
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1. glycosylation: adding carbs
2. hydroxylation: adding of OH 3. methylation: adding of methyl group 4. phosphorylation: adding of phosphates Proteolysis: cleaving of the protein chain |
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During which pathway does glycosylation occur?
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secretory pathway
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how are proteins passed out of the cell?
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proteins are passed out of the cell during the secretory pathway
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what are the steps of secretory pathway?
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1. cytosolic ribosome synthesize an N-terminal peptide sequence
2. signal recognition particle (SRP) recognizes a seq. of a.a and binds to it which halts translation. 3. ribosome moves to ER where the SRP binds to docking protein 4. ribosome is transferred to translocon and translation resumes with the protein inside the ER. 5. protein is modified and passed to the Golgi Apparatus and is excreted from the cell |
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N-linked glycosylation
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Occurs cotranslationally so it can affect protein folding
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O-linked glycosylation
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Occurs later in the Golgi Apparatus (posttranslationally after the protein has already been folded)
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O-linked glycosylation occurs on 3 a.a which is
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Ser= serine= S
and Thr= threonine= T Also know that hydroxylation can introduce an O into Lys= Lysine+l which can then be O-linked glycosylated |
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What are glycosyltransferases?
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enzymes that transfer sugars.
The sugar that finds to the tissues are dependent upon which glycosyltransferases are present in that cell type. When many glycosyltransferases are present, the compete to ad sugars so that the quantity present will determine the frequency that a particular sugar is added. .:. the oligosaccaride that results is very heterogenous |
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What does posttranslational modification determine?
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Determines where protein goes, and what the protein does
ex. glycosyltransderases add N-acetylglucosamine phosphate (GlcNAc-P) to high mannose-type oligosaccharides on proteins which are destined to g to the lysosomes. A glycosidase removes the GlcNAc forming a mannose-6-phosphate which signals for that protein to be transported into the lysosomes |
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Where is preproinsulin produced? And what results when preproinsulin undergoes proteolysis?
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in the pancreatic islet cells and it undergoes proteolysis in the ER to remove the beginning 24 a.a at the N-terminal signal peptide
This results in protein cutting of the M and starting with F and the protein is now called PROINSULIN |
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what happens when proinsulin reaches the golgi apparatus?
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once proinsulin reaches the golgi apparatus, it is packaged into a vesicle and ready for export.
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What cleaves Proinsulin at T-30 and R31 and also at R65-G66 releasing the connected peptide (C-peptide)?
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Carboxypeptidase E
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The cleavage of proinsulin results in insulin with the two a.a chains of what?
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A chain of insulin- begins Gly=glycine= G
and B chain of insulin which begins with Phe=Phenylalanine=F |
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if the disulfide bonds which holds the A and B chain of insulin are reduced at this point, what will happen?
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the two chains, A & B will be seperated and insulin will not be easilly reformed
*some proteins cannot be properly folded after some modification have been performed |
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fibrous protein
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is a family of collagen which provides the framework that gives tissues their form and stregnth
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procollagens contains
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cotranslational hydroxylation of proline to form 4-hydroxyproline and 3 hydroxyproline
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What happens when cotranslation hydroxylation of lysine happens?
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forms 5-hydroxylysine which becomes the sight of O-linked glycosylation of procollagens
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what are procollagens?
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glycoproteins
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Procollagens contains the repeating tripeptide sequence of what a.a?
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Gly-Pro_T
and Gly-X-Hyp repeated hundreds of times The Pro or Hyp at every 3 a.a forms a polyproline type II helix where the peptide carbonyl points towards the neighboring chains and this allows for strong H-bonds to form the GLy at every 3 a.a forms an apolar edge attracting the chains together and being small allows for contact btw the chains |
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how are procollagen secreted?
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secreted from the cell via a vesicle. The procollagen is cleaved on both termini by proteases
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what is the importance of lysyl enzymes?
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lysyl enzymes cross-links the lysine side chains which adds strength and stab
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What is the finals step of collagen formation?
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cross-linking. which involves the formation of an aldehyde derivative of lysine (allysine)
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two allysine can react to form
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aldol cross-link
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allysine can react with lysine to form
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lysinonorleucine cross-link
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what are fibrous protein, elastin? How is it form and what cross link does it form?
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3 allylysine + 1 lysine
and forms a desmosine cross-link |
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how is protein half-life determined?
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by their N-terminal a.a
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what are the enzyme ubiquitin-protein ligase (E3)?
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ubuiquitin protein ligase (E3) identifies a protein to be condemned and binds to it, which tags the protein for intracellular digestion
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steps for ATP and ubuiquitin protein degradation
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E3, Ubuiquitin protein ligase attracts Ubiquitin (UB) to bind to the condemned protein
1. Ubuiquitin activating enzyme (E1) and ATP as it forms a thioester bond to UB's C terminus 2. UB is transferred to Cys on one of a family called ubuiquitin conjugating enzymes (E2) 3. Ubuiquitin protein ligase, E3, transfers the activated UB to the condemned protein which forms an isopeptide bond to a Lys 3. after many UBs are linked (polyubiquination) either to protein or to the orginal UB, the condemned protein is delivered to and degraded by proteosome. *So, to condemn a protein for degradation by proteases, you will need to use E3, UB, E1,E2, in order to attack the protein and carry it to be degraded. ATP is require to start the process of polyubiquination |
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Where are polyubiquinated proteins lysed?
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inside the hollow core of the proteosome.
*Ubuiquitin and a.a are released and recycled** |
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Take home message for proteins
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proteins are changing even when their concentration remains constant.
you are constantly synthesizing new proteins and breaking down old proteins. You can alter the rate of either one of your protein |
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what happens when you 1st ingest food?
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when you ingest food, you will 1st homogenize (grind the food) which will give you more surface area
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amylase
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an enzyme that catalyzes the breakdown of carbs
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glycogen
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animal polysaccharides similar to starch but with more branched points
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starch
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plant polysaccharides
straight chain-linked glu 1,4 alpha (amylose) branched glc alpha 1,6 (amylopectin) |
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Pepsin
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is released from cells in the inactive form, pepsinogen
-has optimal pH of 2 |
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what cells secrete the inactive proenzyme (a zymogen) pepsinogen?
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gastric chief cells
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at what ph is pepsinogen autoactivated by intramolecular rxn?
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pH less than 5
once activated pepsin cleaves residues 46 & 47 of other pepsinogen molecules to activate them at an exponential rate |
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what is the importance of the small fragments of a.a cleaved by pepsins?
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the small fragments are important for the activation of the pancreas.
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how does gastric parietal cells lower pH?
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use K+/H+ exchanging ATPase (gastric proton pump) to lower pH.
Cl- and K+ enter the stomach via the channels Bicarbonate is exchanged for Cl- in the blood |
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Omeprazole (Prilosec)
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Is a proton pump inhibitor use to treat peptic ulcer disease and GI reflux
-under acidic conditions, omeprazole converts to a sulfenaminde which binds to Cys of H+/K+ exchanging ATPase. This inhibits the proton ferom producing HCL which takes away the pain from GI reflux |
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what organ initiates protein and lipid hydrolysis which simulates liver and pancreas output?
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stomach
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what peptide stimulates the gallbladder to contract and secrete pancreatic enzymes?
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CCK
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Secretin
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is released when the pH is less than 5.
Secretin stimulates secretion of pancreatic juice which is rich in NaHCO3( sodium bicarbonate) which brings the pH to 7 |
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CCK
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CCK is used to trigger intestinal epithelial cells to release the enzyme enteropeptidase. Enteropeptidase is active and will convert inactive trypsinogen to active trypsin Once activated, trypsin can go back & activate other trypsinogen. The pancreas contains a lot of sodium bicarbs which neutralizes the acids that is released by the pancreas
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CCK and Secretin
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CCK and secretin goes on to release pancreatic aclnar cells which releases trpsinogen
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From the luminal side, where are the a.a transported?
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into the enterocyte via a transporter.
*di and tripeptides are transported via a different transporter* ***ONLY FREE A.A ARE TRANSPORTED INTO THE BLOODSTEAM*** |
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what is the major enzyme for lipid hydrolysis?
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pancreatic lipase aided by colipase
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What are the 3 types of carbs
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GLucose, fructose, galactalose
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Where those pancreatic lipase hydrolyze esters?
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alpha position of 1 or 3 TG.
the products are free fatty acids and monoacylglycerols |
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what is the main function on bile?
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to form micelles which promote dietary fat processing
*80% of bile acids are conjugates of cholic acids |
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what happens to acid in the intestines when the pH is at 7?
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the acid is deprotonated to the anionic form cholate
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What does micelles transport?
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cholesterol and lipid soluble vitamins like K,A, D, E,
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long fatty acid uptake is enhanced by what transporter?
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FATP4
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A fatty acid has less than 10 Carbons, how will that go through the enterocyte membrane?
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less than 10 fatty acid carbon is uptake via DIFFUSION through the enterocyte membrane
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What does Apolipoproteins form?
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forms Chylomicrons which are passed out into the lymphatic sys and from there they go into the capillaries and out into the rest of the body
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What happens when there is less than 10 carbon fatty acid
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it is passed directly into the bloodstream
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What happens when you have a long fatty acid chain?
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long fatty acids are transported to the ER where they are converted to TG
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Nucleobases
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planar, aromatic, nitrogenous, heterocyclic, unprimed numbering
Ex. Purines and Pyrimidines |
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Pyrimidine
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CUT
cytosine uracil Thymine Have 6 member ring ends with -DINE |
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Purine
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Adenine
Guanine have additional 5 member rings ends with -SINE |
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Nucleoside
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Base+sugar
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Nucleotide
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Bse+sugar+phosphate
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Beta-N-Glycosidic linkage
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Purines bond to N9 of C1
Pyrimidine bond to N1 of C1 |
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oligonucleotides
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less than 50 nucleotide nucleic acids
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polynucleotides
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more than 40 nucleotide nucleic acid
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