The lactose permease is an example of an enzyme-like transporter that couples import of a specific sugar, lactose, with theimport of an H+ ion. Lactose can bind the protein from either the outside of the cell or from the cytoplasm. The site(s) forthis binding aredifferent, only the outside site show specificity for lactose.the same central site with high specificity. The protein controls access to the site by physically blocking entry from oneside or the other.different, only the cytoplasmic site show specificity for lactose.different, both sites show specificity for lactose.the same central site with high specificity. The protein controls access to the site using potential barriers that changewith the lactose needss of the cell.

Lactose is a disaccharide, which is broken down into two monosaccharides glucose and galactose by…

Answered: The lactose permease is an example of…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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A bacterial lactose transporter, which is highly specific for lactose, contains a Cys residue that is essential to its transport activity. Covalent reaction of N-ethylmaleimide (NEM) with this Cys residue irreversibly inactivates the transporter. A high concentration of lactose in the medium prevents inactivation by NEM, presumably by sterically protecting the Cys residue, which is in or near the lactose-binding site. You know nothing else about the transporter protein. Suggest an experiment that might allow you to determine the Mr of this Cys-containing transporter polypeptide.
The K+ channel is an example of a transmembrane protein (a protein that spans the phospholipid bilayer of the plasma membrane). What types of amino acids are likely to be found (a) lining the channel through which K+ passes, (b) in contact with the hydrophobic core of the phospholipid bilayer con- taining fatty acyl groups, (c) in the cytosolic domain of the protein, and (d) in the extracellular domain of the protein?
The amino acid sequence Leu-His-Arg-Leu-Asp-Ala-Gln-SerLys-Leu-Ser-Ser is a signal sequence that directs proteinstowards the endoplasmic reticulum, say if it is true or false if it is false justify it.
Imagine a protein which functions in ER but requires modification in the Golgi apparatus before it can achieve that function. Describe the protein’s path through the cell starting with protein in ER, with the help of diagram.
In eukaryotic cells secreted proteins are targeted first to the endoplasmic reticulum and then pass through the Golgi, before being released from secretory vesicles into the extracellular space. A much simpler route would be for ribosomes synthesising secretory proteins to be targeted to a translocon in the plasma membrane, with the protein being secreted directly as it is translated. List three potential advantages of the former, more circuitous, route for protein secretion over the simpler, more direct, alternative route suggested.
Signal transduction pathway. Sketch a G protein in the active and inactive stages, and label its parts.
Please draw or trace a pathway of any protein from translation to the plasma membrane. Name the protein (make sure it is a transemembrane protein). The protein in question must also have seceral protein modifications including, but not limited to, N-linked glycosylation, cysteine disulfide bonds, lipid modifications, and 3-D folding
Describe the structure of SRP in eukaryotes, and outline its role intargeting proteins to the ER membrane.
Select the correct statement regarding electrochemical gradients. Thermodynamically, electrochemical gradients will maintain their relative concentrations across both sides of the membrane. The cytoplasmic side of the cell membrane has a net positive charge relative to the extracellular side. Ions can freely pass through the cell membrane. Electrochemical gradients are sources of potential energy due to the differences in concentrationsand charge across both sides of the cell membrane. Select the correct statement(s) about transfer RNAs. Codon recognition occurs through specific base-pairing by the anticodon arm. Amino acids are linked to the T-loop. They are transcribed by RNA Polymerase III. There is strict matching requirements at the third position, else the tRNA cannot interact with the codon.
Acidification is achieved by an H+ pump in the endosomal membrane, which also contains Cl– channels. if the channels do not function properly (e.g., because of a mutation in the genes encoding the channel proteins), acidification is also impaired. Can you explain how Cl– channels might help acidification? According to your explanation, would the Cl– channels be absolutely required to lower the pH inside the endosome?
The following are steps that occur when a protein is targeted for synthesis on the endoplasmic reticulum (ER). Which of the following indicates the correct sequence for the signal mechanism that targets proteins for the ER? The SRP leaves and polypeptide synthesis resumes, with simultaneous translocation across the membrane. Polypeptide synthesis begins on a free ribosome in the cytosol. An SRP binds to the signal peptide, halting synthesis momentarily. The rest of the completed polypeptide leaves the ribosome and folds into its final conformation. The SRP binds to a receptor protein in the ER membrane that is part of a protein complex that forms a pore. The signal peptide is cleaved by an enzyme in the receptor protein complex. A. 2, 3, 5, 1, 6, 4 B. 2 ,3, 5, 6, 1, 4 C. 3, 1, 6, 5, 2, 4 D. 3, 2, 1, 5, 6, 4
Proteins that possess a signal sequence of substantially non-polar amino acids, but do not possess a signal sequence of several positively-charged amino acids, are destined for which cellular location? the peroxisome the endoplasmic reticulum the chloroplast the mitochondrion the cytosol

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