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DrVirgo
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13. Eukaryotic proteins that exist as a nonmembrane-associated, glycosylated, disulfide-linked dimer in the mature form are generally found in which of the following?
A) Cytoplasm
B) Extracellular space
C) Mitochondrial matrix
D) Nuclear matrix
E) Nuclear pore
14. Which of the following enzymes acting on phosphatidylcholine will directly generate diacylglycerol?
A) Hormone-sensitive lipase
B) Lipoprotein lipase
C) Pancreatic lipase
D) Phospholipase C
E) Sphingomyelinase
26. A 3-week-old infant has milk intolerance due to a defect in the enzymes that digest lactose. This enzyme is located at which of the following sites in enterocytes?
A) At the apical surfaces
B) At the basolateral surfaces
C) Within the Golgi complex
D) Within lysosomes
E) Within peroxisomes
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| sarika
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extracellular space
phospholipase C
Apical surface
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| nadiabarati
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same as sarika
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| DrVirgo
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What is: proteins that exist as a nonmembrane-associated, glycosylated, disulfide-linked dimer in the mature form describing?
-defect in enzyme that digests lactose -which enzyme? how do you know its at the apical surface?
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| sarika
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13.the protein they r talking abt is probably an immunoglobulin (disulfide linked dimer)
26.The enterocytes possess microvilli on their apical surface which are coated with glycocalyx that contains enzymes e.g lactase, sucrase, enterokinase.
LActase is the one that digest lactose.
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| DrVirgo
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ok. thanks. I thought it was probably immunoglobulin too but I got thrown off when they said dimer... because Ig is two heavy and two light... But i guess thats the only thing that makes sense.
You are right about lactase too..
Thanks again for the explanation.
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| nadiabarati
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I got another idea from Lehninger, it says glycosylated proteins usually are exposed to extracellular space and/or in the extracellular space, by this idea in my mind I went for answer B, Q13...I didn't think about Ig!!
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| DrVirgo
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Here's what happens:
Proteins are either made on Free Ribosomes or on Ribosomes associated with the Endoplasmic reticulum: RER.
Proteins made on Free ribosomes are targeted to the cytoplasm, and mitochondria.
Proteins that are made in the RER undergo post-translational modification and get glycosylated in the RER as well as the Golgi and go to:
1. Extracellular space (get secretd out of the cell)
2. Become a membrane protein (within the membrane like a channel, etc.)
3. Lysosomes (eg. Lysosomal enzymes)
* (Lysosomal enzymes will only go to Lysosomes if there is phosphorylation of mannose residues on the enzyme that takes place in the Golgi!) -If NO phospyorylation of mannose residues, then that enzyme gets secreted out of the cell! (I-Cell Disease)
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| docswapna
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DrVirgo wrote:
Here's what happens:
Proteins are either made on Free Ribosomes or on Ribosomes associated with the Endoplasmic reticulum: RER.
Proteins made on Free ribosomes are targeted to the cytoplasm, and mitochondria.
Proteins that are made in the RER undergo post-translational modification and get glycosylated in the RER as well as the Golgi and go to:
1. Extracellular space (get secretd out of the cell)
2. Become a membrane protein (within the membrane like a channel, etc.)
3. Lysosomes (eg. Lysosomal enzymes)
* (Lysosomal enzymes will only go to Lysosomes if there is phosphorylation of mannose residues on the enzyme that takes place in the Golgi!) -If NO phospyorylation of mannose residues, then that enzyme gets secreted out of the cell! (I-Cell Disease)
If phosphorylation of mannose does not occur in golgi, then where are these enzymes found?
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| drbin
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serum
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