vl Q3. Péclet number – We've seen the Péclet number Pé = as a useful metric to determine if stirring (Pé > 1) is more efficient than diffusion (Pé < 1) for mixing solutions. "Stirring” here can designate any process which applies a force on the molecules, resulting in a velocity v. a) Find the Péclet number for a system of dimension of l = 10 μm. This corresponds to the scale over which most cellular processes occur. b)Find the scale f for which diffusion is just as efficient as electric field for displacing λ-DNA.

vl Q3. Péclet number – We've seen the Péclet number Pé = as a useful metric to determine if stirring (Pé > 1) is more efficient than diffusion (Pé < 1) for mixing solutions. "Stirring” here can designate any process which applies a force on the molecules, resulting in a velocity v. a) Find the Péclet number for a system of dimension of l = 10 μm. This corresponds to the scale over which most cellular processes occur. b)Find the scale f for which diffusion is just as efficient as electric field for displacing λ-DNA.

Biology 2e

2nd Edition

ISBN:9781947172517

Author:Matthew Douglas, Jung Choi, Mary Ann Clark

Publisher:Matthew Douglas, Jung Choi, Mary Ann Clark

Chapter6: Metabolism

Section: Chapter Questions

Problem 10RQ: In each of the three systems, determine the state of entropy (low or high) when comparing the first...

See similar textbooks

Similar questions

Quantitative – diffusion time: Consider a spherical, single-celled organism which needs oxygen tosurvive. a. Assume oxygen needs to diffuse from the outside of the cell to its center. Write an equation thatgives the diffusion time in terms of the cell radius. b. The cell has a 4 micron (m) diameter, and diffusion coefficient of oxygen is 1.8 x 10-5 cm2/s inwater (assume diffusion is the same through the cell membrane). How long does it take for oxygento diffuse to the center of the cell? c. Cells typically need key molecules such as oxygen to survive. Diffusion times of oxygen can limithow big cells can become. If the cell gets too large for oxygen to reach its center, the cell coulddie. Calculate the size of a cell at which oxygen diffusion time becomes too slow and so limits theability of the cell to get that big. Explain your assumptions. How does this compare to typical cellsizes?
Q.1. We are familiar with the semipermeable nature of bio-membrane, then what types of molecules would be able to pass through them and what types of molecule would be failed to pass?
Q1: In what ways is the plasma membrane a barrier, and in what ways is it a gatekeeper? Q2: Why can’t ions (such as Na+) cross the plasma membrane without the help of a transport protein? Q3: If no energy were available to the cell, what forms of transport would not be able to occur? What forms of transport could occur?
Q36. The picture below shows a preparation of isolated thylakoid membranes suspended in a buffer at pH 8. The preparation is in complete darkness. Which of the following is required in order for the thylakoids to generate ATP? A. Addition of ADP and phosphate to the buffer. B. Incubation in the light plus ADP and phosphate. C. Incubation in the light plus addition of ADP, phosphate and NADP+. D. Isolated thylakoid membranes are not able to synthesize ATP.
Q8. Which of the following statements is thought to be the underlying reason for why a typical eukaryotic cell is more complex than a typical aerobic bacterial cell? A. A eukaryotic cell has a greater plasma membrane area / cell volume ratio than a bacterium. B. A eukaryotic cell has a greater number of electron transport chains than a bacterium. C. An aerobic bacterium lacks membranes required for electron transport. D. An aerobic bacterium cannot undergo oxidative phosphorylation.
Q6: A protein that spans the phospholipid bilayer one or more times isO a glycoprotein.O a transmembrane protein.O an extracellular matrix protein.O a peripheral protein.
WHAT IF? Some membrane proteins diffuse faster in the plasma membrane when the cytoskeleton or the extracellular matrix is artificially removed than when cells are unperturbed. Explain why.
Q1: If endocytosis itself is nonspeciﬁc, how does receptor-mediated endocytosis bring only certain molecules into a cell? Q2: What sorts of molecules could be moved by endocytosis or exocytosis, but not by diffusion? Q3: How does the ﬂuid that enters a cell via pinocytosis differ from the ﬂuid that enters by osmosis?
For fusion of a vesicle with its target membrane tooccur, the membranes have to be brought to within 1.5 nmso that the two bilayers can join (Figure Q13–1). Assum-ing that the relevant portions of the two membranes at thefusion site are circular regions 1.5 nm in diameter, calcu-late the number of water molecules that would remainbetween the membranes. (Water is 55.5 M and the volumeof a cylinder is πr2h.) Given that an average phospholipid occupies a membrane surface area of 0.2 nm2, how manyphospholipids would be present in each of the opposingmonolayers at the fusion site? Are there sufficient watermolecules to bind to the hydrophilic head groups of thisnumber of phospholipids? (It is estimated that 10–12 watermolecules are normally associated with each phospho-lipid head group at the exposed surface of a membrane.)
Electrochemical gradients (a) power simple diffusion (b) are established by pinocytosis (c) are necessary for transport by aquaporins (d) are established by concentration gradients (e) are a result of both an electric charge difference and a concentration difference between the two sides of the membrane
MAKE CONNECTIONS Explain why the set of forces driving ionmovement across the plasma membrane of a cell is described as anelectrochemical (electrical and chemical) gradient (see Concept 7.4).
Q8: The primary structural components of the cell membrane areO proteins and cellulose.O glycoproteins and cholesterol.O cholesterol and proteins.O phospholipids and cellulose.O phospholipids and proteins.