BIO 360 - Exam 1 - Chapter 5 Review Questions

Question 1

List the four functions of membrane proteins, and give an example of each.

Answer 1

Structural proteins (link cell to matrix), transporter proteins (water channels), receptors (hormone receptors), and enzymes (intestinal digestive enzymes)

Question 2

Distinguish between active transport and passive transport.

Answer 2

Active: requires direct or indirect use of energy. Passive: uses energy stored in a concentration gradient.

Question 3

Which of the following processes are examples of active transport, and which are examples of passive transport? Simplediffusion, phagocytosis, facilitated diffusion, exocytosis, osmosis, endocytosis.

Answer 3

Passive: simple and facilitated diffusion, osmosis. Active: phagocytosis, exocytosis, and endocytosis.

Question 4

List four factors that increase the rate of diffusion in air.

Answer 4

greater concentration gradient, smaller distance, higher temperature, and smaller molecular size

Question 5

List the three physical methods by which materials enter cells.

Answer 5

simple diffusion, protein-mediated transport, or vesicular transport

Question 6

A cotransporter is a protein that moves more than one molecule at a time. If the molecules are moved in the same direction, the transporters are called ______carriers; if the molecules are transported in opposite directions, the transporters are called ______carriers. A transport protein that moves only one substrate is called a(n) ______ carrier.

Answer 6

symport; antiport; uniport

Question 7

The two types of active transport are ______, which derives energy directly from ATP, and ______, which couples the kinetic energy of one molecule moving down its concentration gradient to the movement of another molecule against its concentration gradient.

Answer 7

primary (direct) and secondary (indirect)

Question 8

A molecule that moves freely between the intracellular and extracellular compartments is said to be a(n) ______ solute. A molecule that is not able to enter cells is called a(n) ______ solute.

Answer 8

penetrating; nonpenetrating

Question 9

Rank the following individuals in order of how much body water they contain as a percentage of their body weight, from highest to lowest: (a) a 25-year-old, 74-kg male; (b) a 25-year-old, 50-kg female; (c) a 65-year-old, 50-kg female; and (d) a 1-year-old, 11-kg male toddler.

Answer 9

(d), (a), (b), (c)

Question 10

What determines the osmolarity of a solution? In what units is body osmolarity usually expressed?

Answer 10

Osmolarity: concentration of osmotically active particles, expressed as osmol/L or milliosmoles per liter

Question 11

What does it mean if we say that a solution is hypotonic to a cell? Hypertonic to the same cell? What determines the tonicity of a solution relative to a cell?

Answer 11

Hypotonic: net influx of water into the cell at equilibrium. Hypertonic: net water loss at equilibrium. Tonicity is determined by relative concentrations of nonpenetrating solutes in cell versus solution.

Question 12

Match the membrane channels with the appropriate descriptions. Answers may be used once, more than once, or not at all.

(a) chemically gated channel
(b) open pore
(c) voltage-gated channel
(d) mechanically gated channel

(1) channel that spends most of its time in the open state
(2) channel that spends most of its time in a closed state
(3) channel that opens when resting membrane potential changes
(4) channel that opens when a ligand binds to it
(5) channel that opens in response to membrane stretch
(6) channel through which water can pass

Answer 12

(a) 2, 4, 6; (b) 1, 6; (c) 2, 3, 6; (d) 2, 5, 6

Question 13

In your own words, state the four principles of electricity important in physiology.

Answer 13

(1) Like charges repel; opposite charges attract.
(2) Every positive ion has a matching negative ion.
(3) Energy must be used to separate ions or electrons and protons.
(4) Conductors allow ions to move through them; insulators keep ions separated.

Question 14

Match each of the following items with its primary role in cellular activity.

(a) NA+ K+ ATPase
(b) protein
(c) unit of measurement for membrane potential
(d) K+
(e) Cl-
(f) ATP

(1) ion channel
(2) extracellular cation
(3) source of energy
(4) intracellular anion
(5) intracellular cation
(6) millivolts
(7) electrogenic pump
(8) extracellular anion
(9) milliosmoles

Answer 14

(a) 7; (b) 1, 7; (c) 6; (d) 5; (e) 8; (f) 3; (g) 2

Question 15

The membrane potential at which the electrical gradient exactly opposes the concentration gradient for an ion is known as the ion’s ______.

Answer 15

equilibrium potential

Question 16

A material that allows free movement of electrical charges is called a(n) ______, whereas one that prevents this movement is called a(n) ______.

Answer 16

conductor; insulator

Question 17

Create a map of transport across cell membranes using the following terms. You may add additional terms if you wish.

Answer 17

Use Figs. 5.5, 5.8, 5.10, and 5.19 to create your map.

Question 18

Draw a large rectangle to represent the total body volume. Using the information in Figure 5.1b, divide the box proportionately into compartments to represent the different body compartments. Use the information in Figure 5.1d and add solutes to the compartments. Use large letters for solutes with higher concentrations and small letters for solutes with low concentrations. Label the cell membranes and the endothelial membrane.

Answer 18

See Fig. 5.1C and d.

Question 19

What factors influence the rate of diffusion across a membrane? Briefly explain each one.

Answer 19

Lipid solubility, so that a molecule can pass through the lipid core of the membrane. Diffusion is slower for larger or heavier molecules and faster when there is more membrane surface area.

Question 20

Define the following terms and explain how they differ from one another: specificity, competition, saturation. Apply these terms in a short explanation of facilitated diffusion of glucose.

Answer 20

Specificity: Enzyme or transporter works on one molecule or class of molecules. Competition: Similar substrates can compete for the protein binding site. Saturation: Rate reaches a maximum when all binding sites are filled. GLUT is specific for hexose sugars. If glucose and fructose are both present, they compete for GLUT binding sites. If enough sugar is present, transport saturates.

Question 21

Red blood cells are suspended in a solution of NaCl. The cells have an osmolarity of 300 mOsM, and the solution has an osmolarity of 250 mOsM. (a) The solution is (hypertonic, isotonic, or hypotonic) to the cells. (b) Water would move (into the cells, out of the cells, or not at all).

Answer 21

(a) hypotonic, (b) into the cells

Question 22

Two compartments are separated by a membrane that is permeable to glucose but not water. Each compartment is filled with 1 M glucose. After six hours, compartment A contains 1.5 M glucose and compartment B contains 0.5 M glucose. What kind of transport occurred? Explain.

Answer 22

Active transport. Must use energy to go from a state of equilibrium to one of disequilibrium.

Question 23

A 2 M NaCl solution is placed in compartment A and a 2 M glucose solution is placed in compartment B. The compartments are separated by a membrane that is permeable to water but not to NaCl or glucose. Complete the following statements. Defend your answers.
(1) The salt solution is ______ osmotic to the glucose solution.
(2) True or false? Water will move from one compartment to another. If water moves, it will move from compartment to compartment .

Answer 23

(a) hyperosmotic (convert molarity to osmolarity), (b) True. Water moves from B to A.

Question 24

Explain the differences between a chemical gradient, an electrical gradient, and an electrochemical gradient.

Answer 24

Chemical gradient = concentration gradient. Electrical gradient = separation of electrical charge. Electrochemical gradient includes both concentration and electrical gradients.

Question 25

Sweat glands secrete into their lumen a fluid that is identical to interstitial fluid. As the fluid moves through the lumen on its way to the surface of the skin, the cells of the sweat gland’s epithelium make the fluid hypotonic by removing Na+
and leaving water behind. Design an epithelial cell that will reabsorb Na+ but not water. You may place water pores, Na+
leak channels, K+ leak channels, and the Na+-K+-ATPase in the apical membrane, basolateral membrane, or both.

Answer 25

Apical side: Na+ leak channels but no water pores. Basolateral side: Na+-K+-ATPase and K+ leak channels. May also have water channels.

Question 26

Insulin is a hormone that promotes the movement of glucose into many types of cells, thereby lowering blood glucose concentration. Propose a mechanism that explains how this occurs, using your knowledge of cell membrane transport.

Answer 26

Insulin could increase the number or affinity of GLUT proteins or could act on cell metabolism to keep the intracellular glucose concentration low.

Question 27

The following terms have been applied to membrane carriers: specificity, competition, saturation. Why can these terms also be applied to enzymes? What is the major difference in how enzymes and carriers carry out their work?

Answer 27

Both enzymes and transporters are proteins that bind ligands at a specific binding site. Enzymes alter their substrates. Transporters move substrates unchanged across a membrane.

Question 28

Integral membrane glycoproteins have sugars added as the proteins pass through the lumen of the endoplasmic reticulum and Golgi complex(p. 115). Based on this information, where would you predict finding the sugar “tails” of the proteins: on the cytoplasmic side of the membrane, the extracellular side, or both? Explain your reasoning.

Answer 28

Sugars are added to proteins inside the organelle/vesicle, therefore will face the ECF after being inserted into the membrane.

Question 29

NaCl is a nonpenetrating solute and urea is a penetrating solute for cells. Red blood cells (RBCs) are placed in each of the solutionsbelow. The RBC intracellular concentration of nonpenetrating solute is 300 mOsM. What will happen to the cell volume in each solution? Label the solutions with all the terms that apply: hypertonic, isotonic, hypotonic, hyperosmotic, hyposmotic, isosmotic. Watch units! Assume
for simplicity.

(a) 150 mM NaCl plus 150 mM urea
(b) 100 mM NaCl plus 50 mM urea
(c) 100 mM NaCl plus 100 mM urea
(d) 150 mM NaCl plus 100 mM urea
(e) 100 mM NaCl plus 150 mM urea

Answer 29

Must convert units from mM to mOsM. (a) hyperosmotic, isotonic; (b) hyposmotic, hypotonic; (c) isosmotic, hypotonic; (d) hyperosmotic, isotonic; (e) hyperosmotic, hypotonic

Question 30

The addition of dissolved solutes to water lowers the freezing point of water. A 1 OsM solution depresses the freezing point of water by 1.86 °C. If a patient’s plasma shows a freezing-point depression of 0.55 °C, what is her plasma osmolarity? (Assume that 1kg water = 1L.)

Answer 30

296 mOsM

Question 31

The patient in the previous question is found to have total body water volume of 42 L, ECF volume of 12.5 L, and plasma volume of 2.7 L.
(a) What is her intracellular fluid (ICF) volume? Her interstitial fluid volume?
(b) How much solute (osmoles) exists in her whole body? ECF? ICF? plasma?
(Hint:concentration = solute amount / volume of solution)

Answer 31

(a) ICF=29.5 L; interstitium=9.8 L. (b) Total solute = 12.432 osmoles; ECF=3.7 osmoles; ICF=8.732 osmoles; plasma=0.799 osmoles.

Question 32

What is the osmolarity of half-normal saline (0.45% NaCl)?
[p. 43] Assume that all NaCl molecules dissociate into two ions.

Answer 32

154 mOsM

Question 33

If you give 1 L of half-normal saline (see question 32) to the patient in question 31, what happens to each of the following at equilibrium? (Hint: NaCl is a nonpenetrating solute.)
(a) Her total body volume
(b) Her total body osmolarity
(c) Her ECF and ICF volumes
(d) Her ECF and ICF osmolarities

Answer 33

(a) increases, (b) decreases, (c) increase, (d) decrease

Question 34

The following graph shows the results of an experiment in which a cell was placed in a solution of glucose. The cell had no glucose in it at the beginning, and its membrane can transport glucose. Which of the following processes is/are illustrated by this experiment?
(a) diffusion
(b) saturation
(c) competition
(d) active transport

Answer 34

Diffusion (a). Cannot be active transport because concentration in never exceeds concentration out.