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62 Cards in this Set
- Front
- Back
How does trypsinogen become trypsin?
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enteropeptidase activity
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HCL is created in the gut lumen by what cells?
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parietal
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How does pepsinogen become pepsin?
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autocatalytic (cleaves itself) in the acidic gut lumen
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Where does pepsin cleave proteins?
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endopeptidase (cleaves in the AA chain, not on the ends), tends to find aromatic or acidic amino acids
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Why does the pancreas secrete bicarbonate into the small intestine?
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to raise the pH after coming out of the stomach, allows intestinal/pancreatic enzymes to function
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Why is it important that the active pancreatic enzymes are all activated within a short time span?
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they have the ability to digest each other if given enough time
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Why is trypsin said to have a central role in digestion?
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it can directly cleave peptides, as well as activate many other digestive enzymes
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How does chymotrypsinogen become chymotrypsin?
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activated by trypsin
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How does proelastase become elastase?
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activated by trypsin
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How does procarboxypeptidase become carboxypeptidase?
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activated by trypsin
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What type of protease are trypsin, chymotrypsin and elastase?
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serine proteases
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Where does trypsin cleave peptides?
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where carbonyl group is attached to lysine or arginine
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Where does chymotrypsin cleave peptides?
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hydrophobic amino acids
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Where does elastase cleave peptides?
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amino acids with small side chains (alanine, glycine, serine), and elastin
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What causes Kwashiorkor?
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protein deficit in 3rd world countries due to malnutrition.
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What occurs in children with Kwashiorkor?
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muscle wasting due to lack of protein intake, drop of albumin = edema
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Why do children with Kwashiorkor have muscle wasting?
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they are malnourished and cannot create albumin due to protein deficit. also canot create digestive enzymes and cannot digest proteins that they make intake
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What is α-1-antitrypsin?
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a protease inhibitor made by liver
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What occurs in patients with α-1-antitrypsin deficits?
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since there is less inhibition of proteases, elastases can cleave elastin with little regulation. in the lungs, they lose their recoil ability = emphysema
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What is nephelometry?
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measuring α-1-antitrypsin levels in blood sample. use light scattering techniques
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Once peptides have been broken down by pancreatic enzymes (trypsin, chymotrypsin, elastase), what are these smaller peptides attacked by?
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exopeptidases, cleave AAs off the ends of the peptide
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Where does carboxypeptidase cleave peptides?
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it is an exopeptidase so it cleaves the AAs on the end of the peptide
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Carboxypeptidase A works to cleave which Amino acids?
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hydrophobic ones
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Carboxypeptidase B works to cleave which Amino acids?
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lysine, arginine (basic amino acids)
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Where do Trypsin, chymotrypsin, elastase, and carboxypeptidase come from?
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pancreas
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Where do aminopeptidase enzymes come from?
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the brush border cells of the intestines
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Where do aminopeptidases cleave peptides?
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exopeptidases, cleave one AA at a time from the end of the peptide
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Once a peptide is broken into AAs, how does it enter the cells of the intestines?
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passive co-transport with Na+ (gradient in the cell is created by Na/K pump)
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How does an amino acid get from the intestine cell into the blood stream?
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facilitated transport down gradient into portal vein
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What is inspissation in the pancreatic duct?
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drying and thickening of the pancreatic secretions (seen in cystic fibrosis). leads to duct obstruction
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Why is it important that the pancreas also create and store a trypsin inhibitory protein?
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to prevent accidental trypsin activation. that would lead to all the digestive enzymes accidentally activating and can lead to pancreatitis
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Why/when would amino acid transport on the serosal side of the intestines (into the blood) reverse direction?
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during starvation, when proteins are not entering the cell on the apical side (from the intestine), they must take AA from the blood
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How would a polypeptide end up in the blood?
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by passing through the intestinal epithelium (via pinocytosis) or by slipping between the intestinal cells. normally peptides need to be broken down into AAs then the AAs are absorbed through the intestinal cells into the blood
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Why might is be a problem if peptides are present in the blood of an infant?
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immune system can react to them and lead to allergies to the food they eat. normally peptides need to be broken down into AAs then the AAs are absorbed through the intestinal cells into the blood
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What is Hartnup disease's pattern of inheritance?
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autosomal recessive
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What causes Hartnup disease?
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defect in transport of AA across intestinal and renal cells
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What causes the symptoms of Hartnup's disease?
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lack of essential AA in the blood, since they cannot be reabsorbed into the blood from intestines or kidneys
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What is cystinuria?
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high levels of cystine in the urine; can lead to kidney stones
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What levels of amino acids would we expect to see in a Hartnup's patient's blood?
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low levels, AA cannot enter the blood form intestines or kidneys
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Why might a patient with Hartnup's disease be at high risk for kidney stones?
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Since they cannot reabsorb AA from the urine into the blood, the Amino acids can collect in the ducts. they can form stones over time, specifically cystine
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Why are muscles degraded during period of starvation?
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the amino acids can be used for gluconeogenesis
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What happens to excess dietary protein in the body?
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it is stored as glycogen and triacylglycerol for storage
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Life span of an RBC
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120 days
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In patients with cystinuria, why is there not usually hypoaminoacidemia (low AA in the blood)?
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cystinuria mean cystine is not re-entering the blood from urine, so we expect low levels in the blood. but cystine is made by the body. Cystine levels in the blood can remain normal
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What is a nonessential amino acid?
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one that can be made by the body
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Why does cystinuria increase the risk of kidney stones?
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cystine is insoluble and if here are high levels in the urine it precipitates and can collect
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What is renal colic?
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genitourinary bleeding and pain, e.g. kidney stones
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2 mechanisms for enzyme degradation
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lysosomal protein turnover and ubiquitin-proteosome pathway
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What happens to the AAs after the lysosomal degradation of peptides?
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they enter the cell's cytoplasm from the lysosome
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What family of proteases degrade the proteins in the lysosome during lysosomal protein turnover?
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cathepsin family of proteases
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What is the primary process of degradation in the lysosomal protein turnover pathway of protein degradation?
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autophagy within a cell
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Describe the process of autophagy within a cell.
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cytoplasm is sequestered in the cells and the new vesicles (with protein in them) fuse with the lysosome. the lysosome uses cathepsin proteases to degrade the protein into AAs. the AAs leave the lysosome and enter the cytosol
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What triggers the lysomal protein turnover pathway?
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starvation. we want more AA monomers in the cell cytosol so it can enter the blood
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Ubiquitin binds to which AA?
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lysine (amino group)
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What is polyubiquitinylation?
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the process of marking the proteins for degradation by adding a chain of ubiquitin on the target protein
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Why is ATP needed for the ubiquitin-proteosome pathway?
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to unfold the target protein and bring it into the proteosome active site
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What is the function of cap proteins in the ubiquitin-proteosome pathway?
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cap protein complexes bind the target protein and bring it to the proteosome; needs ATP
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What happens to ubiquitin after the target protein is destroyed?
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it is released and recycled
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What is a PEST sequence?
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region of a protein rich in Proline, Glutamine, Serine, Threonine; typically hydrolyzed by ubiquitin pathway
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What causes pellagra?
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lack of niacin or tryptophan, leads to less NAD/NADP.
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Glutathione serves what purpose in cells?
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prevent against oxidative damage
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How is glutathione syntehsized?
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from glutamate, via the γ-glutamyl cycle
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