11 O Macmillan LearningLipids in a bilayer can diffuse laterally at a relatively fast rate, but "flip-flop" from one leaflet to the other very slowly withoutcatalysis. Three protein families, flippases (or flipases), floppases, and scramblases, catalyze the movement of lipids acrossthe bilayer.Classify each phrase as describing flippases, floppases, or scramblases.Flippasesnot ATP-dependentFloppasesAnswer Banktranslocate phosphatidylserine, preventing apoptosis and engulfment by macrophagesWWWnmove phospholipids across the lipid bilayer down the concentration gradienttranslocate lipids from outer (extracellular) leaflet to inner (cytosolic) leafletmove phospholipids from inner (cytoplasmic) leaflet to outer (extracellular) leafletAttemptABC transporterScramblasesactivation may result in increased membrane lipid symmetry

Flippases, floppases, and scramblases are phospholipid translocators present in the membrane…

Answered: Lipids in a bilayer can diffuse…

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter31: Completing The Protein Life Cycle: Folding, Processing, And Degradation

Section: Chapter Questions

Problem 9P

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Proteins may be bound to the exoplasmic or cytosolic face of the plasma membrane by way of covalently attached lip- ids. What are the three types of lipid anchors responsible for tethering proteins to the plasma membrane bilayer? Which type is used by cell surface proteins that face the external medium? By glycosylated proteoglycans?
Three mechanisms by which membrane-bind-ing proteins bend a membrane are illustrated in FigureQ10–2A, B, and C. As shown, each of these cytosolic mem-brane-bending proteins would induce an invagination ofthe plasma membrane. Could similar kinds of cytosolicproteins induce a protrusion of the plasma membrane(Figure Q10–2D)? Which ones? Explain how they mightwork.
Multipass transmembrane proteins synthesized by ribosomes on the rough endoplasmic reticulum generally have which of the following arrangements of start-transfer and stop-transfer signals? multiple start signals and multiple stop signals (to allow multiple transmembrane regions) multiple start signals, but only one stop signal (to allow only one transmembrane region) only one start signal, but multiple stop signals (to allow only one transmembrane region) only one start signal, and only one stop signal (to allow only one transmembrane region) only one stop signal, and only one start signal (to allow only one transmembrane region)
How many copies of a protein need to be presentin a cell in order for it to be visible as a band on an SDSgel? Assume that you can load 100 μg of cell extract ontoa gel and that you can detect 10 ng in a single band by sil-ver staining the gel. The concentration of protein in cellsis about 200 mg/mL, and a typical mammalian cell has avolume of about 1000 μm3 and a typical bacterium a vol-ume of about 1 μm3. Given these parameters, calculatethe number of copies of a 120-kd protein that would needto be present in a mammalian cell and in a bacterium inorder to give a detectable band on a gel. You might try anorder-of-magnitude guess before you make the calcula-tions.
The movements of single motor-protein moleculescan be analyzed directly. Using polarized laser light, it ispossible to create interference patterns that exert a cen-trally directed force, ranging from zero at the center to afew piconewtons at the periphery (about 200 nm from thecenter). Individual molecules that enter the interferencepattern are rapidly pushed to the center, allowing them tobe captured and moved at the experimenter’s discretion.Using such “optical tweezers,” single kinesin mol-ecules can be positioned on a microtubule that is fixed toa coverslip. Although a single kinesin molecule cannotbe seen optically, it can be tagged with a silica bead andtracked indirectly by following the bead (Figure Q16–3A).In the absence of ATP, the kinesin molecule remains at thecenter of the interference pattern, but with ATP it movestoward the plus end of the microtubule. As kinesin movesalong the microtubule, it encounters the force of the inter-ference pattern, which simulates the load…
Understanding the Relevance of Chaperones in Protein Folding Protein molecules, like all molecules, can be characterized in terms of general properties such as size, shape, charge, solubility/hydrophobicity. Consider the influence of each of these general features on the likelihood of whether folding of a particular protein will require chaperone assistance or not. Be specific regarding just Hsp7O chaperones or Hsp7O chaperones and Hsp60 chaperonins.
Explain how the amphipathic (containing both hydrophobic and hydrophilic sides) protein (shown; left)would be anchored in the phospholipid bilayer (shown; right); which portion do you predict would besticking out towards the water? Which portion would be hiding inside the membrane?
Transmembrane portrudes on both sides. Integral protein is in the width of the bilayer and may portrude on one or both sides of the bilayer. Is Transmembrane Protein semi-similar to Integral Proteins? How can we tell the difference of the two?
journey of c f t r protein shows trafficking to the Golgi apparatus via vesicles, and subsequent transport to the cell membrane by secretary vesicles.
Hydropathy plot analysis of your protein of interest reveals a single, prominent hydrophobic peak. However, you later discover that this protein is soluble and not membrane associated. Explain how the hydropathy plot may have been misleading.
Calculate ΔGinward. Is energy required for transport to happen? The internal pH of a lysosome= 4.0 and the pH of the cytosol is 7.0. For a cell at 25°C with a -40 mV lysosome membrane potential. What is the ΔGinward for the proton gradient into the lysosome?
Describe critical concentration (Cc)• Describe actin/microtubule polymerization• Contrast “T” and “D” forms of actin and microtubule subunits– Which nucleotide is bound to actin monomers in “T” and “D” forms?– Which nucleotide is bound to microtubule dimers in “T” and “D” forms? – Which subunit form, “T” or “D,” has higher affinity for polymerization? What are the implications of this on Cc(T) and Cc(D)?

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