In the experimental conditions described below, how many molecules of dextrose do you have to add to the extracellular fluid in order to make it iso-osmotic relative to the intracellular fluid? Intracellular fluid: Number of water molecules = 60 • Number of Dextrose molecules = 7 • Number of Sucrose molecules = 3 ● Extracellular fluid: • Number of water molecules = 160 • Number of dextrose molecule = ???? • Number of Sucrose molecules = 0

In the experimental conditions described below, how many molecules of dextrose do you have to add to the extracellular fluid in order to make it iso-osmotic relative to the intracellular fluid? Intracellular fluid: Number of water molecules = 60 • Number of Dextrose molecules = 7 • Number of Sucrose molecules = 3 ● Extracellular fluid: • Number of water molecules = 160 • Number of dextrose molecule = ???? • Number of Sucrose molecules = 0

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter3: The Plasma Membrane And Membrane Potential

Section: Chapter Questions

Problem 6RE

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Calculate the number of cells in the body of an average 68-kg (150-lb) adult. (This will only be accurate to about 1 part in 10 but should give you an idea how scientists estimate this commonly quoted number.) Assume all cells are spheres 20 m in diameter. The volume of a sphere can be determined by the equation v=4/33. (Hint: We know that about two thirds of the water in the body is intracellular and the density of cells is nearly 1 g/mL. The proportion of the mass made up of water is about 60%.)
A characteristic of carrier molecules in a primary active transport pump is that: a. they cannot transport a substance and also hydrolyze ATP. b. they retain their same shape as they perform different roles. c. their primary role is to move negatively charged ions across membrances. d. they move Na+ into a neural cell and K+ out of the same cell. e. they act to establish an electrochemical gradient.
Water molecules tend to diffuse in response to their own concentration gradient. How can water be more or less concentrated?
Test Your Understanding 7.In cotransport (indirect active transport) (a) a uniporter moves a solute across a membrane against its concentration gradient (b) the move of one solute down its concentration gradient provides energy for transport of some other solute up its concentration gradient (c) a channel protein moves ions by facilitated diffusion (d) osmosis powers the movement of ions against their concentration gradient (e) sodium is directly transported in one direction, and potassium is indirectly transported in the same direction
Using the answer code on the right, indicate which membrane component is responsible for the function in question: 1. channel formation____________________________________ (a) lipid bilayer 2. barrier to passage of water- __________________ (b) proteins soluble substances ____________________________________ (c) carbohydrates 3. receptor sites 4. membrane fluidity 5. recognition of self 6. membrane-bound enzymes 7. structural boundary 8. carriers
Which of the following methods of transport is being used to transfer the substance into the cell in the accompanying graph? a. diffusion down a concentration gradient b. osmosis c. facilitated diffusion d. active transport e. vesicular transport f. It is impossible to tell with the information provided.
Discuss why the following affect the rate of diffusion: molecular size, temperature, solution density, and the distance that must be traveled
Assume that a membrane permeable to Na+ but not to Cl- separates two solutions. The concentration of sodium chloride on side 1 is higher than on side 2. Which of the following ionic movements would occur? a. Na+ would move until its concentration gradient is dissipated (until the concentration of Na+ on side 2 is the same as the concentration of Na+ on side 1). b. Cl- would move down its concentration gradient from side 1 to side 2. c. A membrane potential, negative on side 1, would develop. d. A membrane potential, positive on side 1, would develop. e. None of the preceding is correct.
One of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?
Figure 6.14 The hydrolysis of one ATP molecule releases 7.3 kcal/mol of energy (?G = -7.3 kcal/mol of energy). If it takes 2.1 kcal/mol of energy to move one Na+ across the membrane (?G = +2.1 kcal/mol of energy), how many sodium ions could be moved by the hydrolysis of one ATP molecule?
Figure 5.19 If the pH outside the cell decreases, would you expect the amount of amino acids transported into the cell to increase or decrease?
Consider a pendulum swinging. Which type(s) of energy is/are associated with the pendulum in the following instances: i. the moment at which it completes one cycle, just before it begins to fall back towards the other end, ii. the moment that it is in the middle between the two ends, and iii. just before it reaches the end of one cycle (just before instant i.). i. potential and kinetic, ii. potential and kinetic, iii. kinetic i. potential, ii. potential and kinetic, iii. potential and kinetic i. potential, ii. kinetic, iii. potential and kinetic i. potential and kinetic, ii. kinetic iii. kinetic