Module 4 contin
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Questions and Answers

What is the number of transmembrane segments in a major facilitator superfamily integral membrane protein?

12

What is the structural arrangement of the α-helices in the glucose transporter?

4-5 amphipathic α-helices are packed to form a hydrophilic channel

What is the mechanism by which glucose transport occurs in GLUT1?

Gated Pore Mechanism

How many GLUT family members exist in the human genome?

<p>12</p> Signup and view all the answers

What is the primary function of GLUT1 in erythrocytes?

<p>Transporting glucose into erythrocytes</p> Signup and view all the answers

What is the superfamily of sugar transporters that GLUTs belong to?

<p>Major Facilitator (MF) superfamily</p> Signup and view all the answers

What is the main function of GLUT1?

<p>basal uptake of glucose to the blood brain barrier and erythrocytes, defective in De Vivo disease</p> Signup and view all the answers

In cases of defective GLUT1, why do patients present with brain-related symptoms?

<p>Due to impaired glucose transport into the brain</p> Signup and view all the answers

Explain why a ketogenic diet is standard care for patients with defective GLUT1.

<p>ketone bodies derived from lipids metabolism is used as an alternative energy source to glucose</p> Signup and view all the answers

What is the role of GLUT2 in the liver and kidney?

<p>Transport glucose into liver and kidney when blood glucose is high</p> Signup and view all the answers

How does GLUT4 respond to high blood glucose levels in adipocytes?

<p>By triggering the exocytosis of GLUT4 to the cell membrane</p> Signup and view all the answers

What happens to GLUT4 transporters when insulin levels decrease?

<p>They are removed from the cell membrane by endocytosis</p> Signup and view all the answers

What is the main function of SERCA pumps?

<p>Transporting Ca+2 from the cytoplasm to the sarcoplasmic reticulum</p> Signup and view all the answers

How does the E1 conformation of SERCA differ from E2?

<p>E1 exposes the Ca+2 binding sites on the cytoplasmic side, while E2 exposes the Ca+2 binding site on the lumenal side of the membrane. E1 has higher affinity towards Ca2+ than E2</p> Signup and view all the answers

What is the role of Plasma membrane Ca+2-ATPase? (PMCA)

<p>Pumping Ca+2 out of the cell</p> Signup and view all the answers

How does Na+K+ ATPase of the plasma membrane move ions across the membrane?

<p>By coupling the phosphorylation-dephosphorylation of Asp to the movement of 3 Na+ out and 2 K+ in, against their electrochemical gradient.</p> Signup and view all the answers

What can inhibit the Na+K+ ATPase of the plasma membrane?

<p>Ouabain and digitoxigenin (foxglove)</p> Signup and view all the answers

How much of the energy (ATP) used by cells goes towards the function of the Na+K+ ATPase?

<p>Up to 30%, and in nerve cells, it can be up to 70%.</p> Signup and view all the answers

How does Digitoxigenin, an inhibitor of Na+/K+ ATPase, stimulate cardiac contraction?

<p>Digitoxigenin increases cardiac contraction by inhibiting the Na+/K+ ATPase, leading to an increase in intracellular sodium and calcium, which results in increased contraction force.</p> Signup and view all the answers

What is the main function of V-Type ATPases?

<p>involved in acidifying of compartments such as vacuoles, lysosomes, endosomes, and secretory vesicles.</p> Signup and view all the answers

What is the difference between F0 and F1 in F-type ATPases?

<p>F0 is the integral proton channel, while F1 is the peripheral ATP-binding site with ATPase activity.</p> Signup and view all the answers

What is the role of ABC ATPases?

<p>ABC ATPases are involved in the transport of various molecules across membranes using ATP energy.</p> Signup and view all the answers

What is the function of F-type ATPases in mitochondria and chloroplasts?

<p>F-type ATPases synthesize ATP in mitochondria and chloroplasts using the energy from the proton gradient.</p> Signup and view all the answers

What is the common feature of ABC ATPases?

<p>2 NBD (ATP binding site- conserved) and 2 TMD (each with 6 helices)</p> Signup and view all the answers

What is the main difference between primary active transport and secondary active transport?

<p>Primary active transport creates a gradient of one solute, whereas secondary active transport uses the exergonic downhill movement of one solute to drive the endergonic movement of another solute up its concentration gradient.</p> Signup and view all the answers

What is the role of P-type ATPases in primary active transport?

<p>They are cation transporters that use ATP to pump ions across the membrane, undergoing phosphorylation and conformational change in the process.</p> Signup and view all the answers

What is the source of energy for primary active transport?

<p>Energy can be derived from absorption of sunlight, oxidation reactions, hydrolysis of ATP, or simultaneous flow of another chemical species down its electrochemical gradient.</p> Signup and view all the answers

What is the significance of maintaining low cytoplasmic Ca+2 levels?

<p>Maintaining low cytoplasmic Ca+2 levels is important for cell signaling.</p> Signup and view all the answers

What is the common structural feature of all P-type ATPases?

<p>integral protein with 8-10 TM sections in a single polypeptide, conserved Asp region that undergoes phosphorylation, sensitive to inhibition by vanadate .</p> Signup and view all the answers

What is the physiological role of the erythrocyte Anion Exchange Protein (AE1)?

<p>Shuttling CO2 from tissues to lungs via the blood</p> Signup and view all the answers

What type of exchange does the Band 3 Transporter (AEP) perform?

<p>The Band 3 Transporter (antiport) performs one-for-one exchange of Cl- for HCO3-, making it electro-neutral.</p> Signup and view all the answers

Why is the coupling of Cl- and HCO3- considered obligatory in the AE system?

<p>AE is a co-transport system. In the absence of Cl-, HCO3- transport cannot be carried out</p> Signup and view all the answers

Where is the enzyme that converts CO2 to HCO3- located in the red blood cell?

<p>In the cytosol</p> Signup and view all the answers

How many times does the AEP span the membrane?

<p>14 times</p> Signup and view all the answers

what does ABCB1 (gene) encode for?

<p>Encodes for MDR1 P-glycoprotein</p> Signup and view all the answers

Which ABC transporter is known as P-glycoprotein 1 and plays a role in multidrug resistance in humans?

<p>ABCB1</p> Signup and view all the answers

What is the function of the ABCG2 transporter?

<p>Overexpressed in breast cancer cells major exporter of anticancer drugs</p> Signup and view all the answers

Which ABC transporter is known as the cystic fibrosis transmembrane conductance regulator protein?

<p>ABCC7</p> Signup and view all the answers

What is the significance of Multidrug transporter (MDR1), also known as ABCB1, in human organisms?

<p>In placental membranes and BBB it removes toxic compounds and is responsible for resistance of tumors to anti cancer drugs</p> Signup and view all the answers

How does the Cystic Fibrosis Transmembrane conductance Regulator Protein (CFTR) transport ions?

<p>Transports Cl- across plasma membrane when both NBDs have ATP bound</p> Signup and view all the answers

what is the enzyme that converts co2 to HCO3- called

<p>carbonic anhydrase</p> Signup and view all the answers

which ABC gene is defective/mutated in tangier disease

<p>ABCA1</p> Signup and view all the answers

what is the role of ABCA1

<p>use in reverse cholesterol transport</p> Signup and view all the answers

What is the target for treatment of diabetes that Gliflozins inhibit in the kidney?

<p>SGLT2</p> Signup and view all the answers

What type of channels are K+-channels in mammals?

<p>Voltage-gated</p> Signup and view all the answers

Where are bacterial porins typically found?

<p>Outer membrane of Gram-negative bacteria</p> Signup and view all the answers

What is the minimum number of β-strands required to form a barrel in bacterial porins?

<p>8</p> Signup and view all the answers

What is the structural basis for voltage-gating in K+-channels?

<p>S4 helix with Arg residues</p> Signup and view all the answers

What is the general role of SGLT2 inhibitors in the treatment of type 2 diabetes?

<p>Lower blood glucose</p> Signup and view all the answers

What is the quaternary structure of the ligand-gated Acetylcholine-receptor ion channel?

<p>5 subunits, alpha2-beta-gamma-delta (α2βγδ)</p> Signup and view all the answers

What is the mechanism by which Na+ selectivity is dictated in ligand-gated ion channels?

<p>Rings of negative side chains at top and bottom entrance to the channel</p> Signup and view all the answers

What are the competitive antagonists that block the ligand-gating of Acetylcholine-receptor ion channels?

<p>curare (poison arrows), bungarotoxin (snake venom)</p> Signup and view all the answers

Which neurotransmitters trigger the opening of cation channels in ligand-gated ion channels?

<p>Acetylcholine &amp; other neurotransmitters</p> Signup and view all the answers

What is the essential principal subunit in mammalian channels and how many homologous domains does it have?

<p>alpha subunit, with 4 homologous domains</p> Signup and view all the answers

What drives the co-transport of lactose in E. coli's lactose permease (LacY) transporter?

<p>H+ gradient</p> Signup and view all the answers

What happens to the transport function of LacY if cytochrome oxidase of the electron transport chain is inhibited by CN-?

<p>LacY acts as a passive transporter</p> Signup and view all the answers

In eukaryotic cells, what ion gradient generated by the sodium-potassium ATPase drives the sodium-glucose symporter?

<p>Na+ gradient</p> Signup and view all the answers

What provides the energy needed for the transport of glucose into eukaryotic cells by the sodium-glucose symporter?

<p>Na+ flow</p> Signup and view all the answers

What is the role of the Na+-glucose symporter located on the apical surface of animals' intestines?

<p>Takes up glucose</p> Signup and view all the answers

What is the main function of the glucose uniporter GLUT2 located on the basal surface of certain cells?

<p>Transport glucose out</p> Signup and view all the answers

Which aquaporin is predominantly found in the lens and has low water permeability?

<p>AQP0</p> Signup and view all the answers

In which tissue is AQP7 predominantly found with high permeability to water, glycerol, and urea?

<p>Adipose tissue</p> Signup and view all the answers

Where is AQP3 predominantly located with high permeability to water, glycerol, and moderate permeability to urea?

<p>Basolateral plasma membrane</p> Signup and view all the answers

Which aquaporin is mainly distributed in the salivary gland, lacrimal gland, sweat gland, and has high water permeability?

<p>AQP5</p> Signup and view all the answers

Where can AQP10 be found with low water permeability and high permeability to glycerol and urea?

<p>Small intestine</p> Signup and view all the answers

Which aquaporin is primarily located in the kidney, testis, liver, and pancreas, with high water permeability?

<p>AQP8</p> Signup and view all the answers

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