Name: Chem 464 Bichemistry Third Hur Exam Multiple chice (5 pints apiece): 1. Which f the fllwing statements cncerning fatty acids is crrect? A) One is the precursr f prstaglandins. B) Phsphatidic acid is a cmmn ne. C) They all cntain ne r mre duble bnds. D) They are a cnstituent f sterls. E) They are strngly hydrphilic. 2. Sphingsine is nt a cmpnent f: A) cardilipin. B) ceramide. C) cerebrsides. D) ganglisides. E) sphingmyelin. 3. Identify the mlecule(s) derived frm sterls. A) Arachidnic acid B) Ganglisides C) Phsphatidylglycerl D) Prstaglandins E) Vitamin D 4. Which f these statements abut the cmpsitin f membranes is true? A) All bilgical membranes cntain chlesterl. B) Free fatty acids are majr cmpnents f all membranes. C) The inner and uter membranes f mitchndria have different prtein cmpsitins. D) The lipid cmpsitin f all membranes f eukarytic cells is essentially the same. E) The lipid:prtein rati varies frm abut 1:4 t 4:1 5. The type f mtin least cmmn in bilgical membranes is: A) flip-flp diffusin f phsphlipid frm ne mnlayer t the ther. B) lateral diffusin f individual lipid mlecules within the plane f each mnlayer. C) lateral diffusin f membrane prteins in the bilayer. D) lateral diffusin f prtein mlecules in the lipid bilayer E) randm mtin f the fatty acyl side chains in the interir f the phsphlipid bilayer.
6. Which f these statements abut facilitated diffusin acrss a membrane is true? A) A specific membrane prtein lwers the activatin energy fr mvement f the slute thrugh the membrane. B) It can increase the size f a transmembrane cncentratin gradient f the diffusing slute. C) It is impeded by the slubility f the transprted slute in the nnplar interir f the lipid bilayer. D) It is respnsible fr the transprt f gases such as O 2, N 2, and CH 4 acrss bilgical membranes. E) The rate is nt saturable by the transprted substrate Lnger questins (10 pints each) 5,8,11 7. Draw the structure f a fatty acid designated 20:3(Ä ) 8. One f the lipids that was difficult t place in ur lipid structural rganizatin was Sphingmyelin. Describe the structure f sphinmyelin and tell why this structure has characteristics f a cuple f different membrane lipids. Sphingmyelin has a sphingsine backbne with a fatty acid attached by an amide linkage and either a phsphchline r a phsphethanlamine charged plar head grup. The phsphchline r phsphethanlamine makes this a phsphlipid. Yet mst f the sphinglipids have sugars as the charged head grup, s there is a tendency t want t put this in the class f glyclipids.
9. Define the fllwing terms F-type ATPase While it is classed as an ATPase because it will hydrlyze ATP t pump prtns acrss a membrane, the actual activity f this enzyme in a cell is t allw prtns t cme int a cell r rganelle dwn a gradient, and synthezie ATP frm ADP and Pi symprt A transprt mechanism where 2 different mlecules are transprted by the same enzyme either int r ut f the cell at the same time. Aquaprin A pre prtein that is used t allw water mlecules t enter r leave the cell. Bilayer The lipid membrane arund a cell r rganelle. It is called a bilayer because it is cmpsed f tw layers f membrane lipids. inphre A mlecule that wraps itself arund an in t give it a hydrphbic exterir that allws the in-inphre cmplex t easily crss the lipid bilayer. 10. Describe hw K Channel wrks The prtein furnishes a passage thrugh the membrane that is just big enugh fr a nn-hydrated K ins t pass. The carbnyl grups f the plypeptide backbne lining this passage prvide the in with enugh plar interactins t replace the interactins the in usually has with its hydrating water mlecules. A nn-hydrated Na in is t small t prperly interact with these carbnyl grups, s it desn t pass, and a hydrated Na in is t large t enter the channel. The prtein als has several negatively charged residues at bth ends f the pre t repel any negative ins that might try t pass and, presumably, t attract psitively charged K ins t the prtein t find the pre. 11. What is the difference between a G prtein cupled receptr signal system and a receptr guanylyl cyclase receptr signal system? In a G prtein cupled receptr the primary message binds t a specific receptr prtein n the cell membrane. This prtein then displaces a GDP frm a stimulatry G prtein and it is replaced with a GTP. The stimulatry G prtein then activates a secnd membrane bund prtein t create a secnd messenger inside the cell, ften camp. In a guanylyl cyclase receptr system when the primary message binds t the receptr prtein, the receptr prtein itself cnverts GTP t the secnd messenger cgmp.
12. Next semester we will examine the enzyme that cnverts fructse 6-phsphate t glucse 6- phsphate. A. If this reactin has an equilibrium cnstant f 1.97 at 25 C, what is the ÄG fr this reactin? ÄG = -RTlnK = -8.314(298)ln(1.97) = -2477(.678) = -1680 Jule = -1.68 kj B. What is the ÄG fr this reactin if the cncentratin f fructse 6-phsphate is adjusted t 1.5M and the cncentratin f glucse 6-phsphate is adjusted t.1m? ÄG=ÄG -RTlnQ = -1680 8.314(298)ln(0.1/1.5) = -1680 2477(-2.71) = -1680-6710 = -8390 J = -8.39 kj 13. In class we discussed three different cmpunds that cntain phsphate grups with a higher energy than the phsphate grup in ATP. What were these three high energy cmpunds and what is it abut their structure that make them high energy cmpunds? Phsphenl pyruvate (PEP) cnverted t pyruvate and a phsphate grup. The enl intermediate that is btained when the phsphate is remved is very high energy because it needs t cnvert t the lwer energy ket frm. The cnversin f the high energy phsphenl t the lw energy ketne is what drives this reactin. The prducts are als favred because negative charges in the PEP have been separated and a single reactant has been split int tw prducts
1,3-Bisphsphglycerate cnverted t phsphglycerate and a phsphate grup The mixed phsph-carbxyl anhydride releases lts f energy when is it cleaved because the resulting free carbxylic acid is resnance stabilized s it has a much lwer energy. The prducts are als favred because 2 f negative charges in the phsphglycerate have been separated and frm the mlecule a single reactant has been split int tw prducts Phsphcreatine cnverted t creatine and a phsphate. Phsphcreatine is high energy when cmpared t the creatine prduct because the creatine prduct is very lw energy due t the resance stabilizatin f the prduct. Entrpy als favrs the separatin f phsphcreatine int phphate and creatine.
1A 2A 3E 4 4C 5A 6A