BIO 360 - Exam 1 - Chapter 5 Review Questions Flashcards
List the four functions of membrane proteins, and give an example of each.
Structural proteins (link cell to matrix), transporter proteins (water channels), receptors (hormone receptors), and enzymes (intestinal digestive enzymes)
Distinguish between active transport and passive transport.
Active: requires direct or indirect use of energy. Passive: uses energy stored in a concentration gradient.
Which of the following processes are examples of active transport, and which are examples of passive transport? Simplediffusion, phagocytosis, facilitated diffusion, exocytosis, osmosis, endocytosis.
Passive: simple and facilitated diffusion, osmosis. Active: phagocytosis, exocytosis, and endocytosis.
List four factors that increase the rate of diffusion in air.
greater concentration gradient, smaller distance, higher temperature, and smaller molecular size
List the three physical methods by which materials enter cells.
simple diffusion, protein-mediated transport, or vesicular transport
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.
symport; antiport; uniport
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.
primary (direct) and secondary (indirect)
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.
penetrating; nonpenetrating
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.
(d), (a), (b), (c)
What determines the osmolarity of a solution? In what units is body osmolarity usually expressed?
Osmolarity: concentration of osmotically active particles, expressed as osmol/L or milliosmoles per liter
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?
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.
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
(a) 2, 4, 6; (b) 1, 6; (c) 2, 3, 6; (d) 2, 5, 6
In your own words, state the four principles of electricity important in physiology.
(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.
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
(a) 7; (b) 1, 7; (c) 6; (d) 5; (e) 8; (f) 3; (g) 2
The membrane potential at which the electrical gradient exactly opposes the concentration gradient for an ion is known as the ion’s ______.
equilibrium potential
A material that allows free movement of electrical charges is called a(n) ______, whereas one that prevents this movement is called a(n) ______.
conductor; insulator
Create a map of transport across cell membranes using the following terms. You may add additional terms if you wish.
Use Figs. 5.5, 5.8, 5.10, and 5.19 to create your map.
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.
See Fig. 5.1C and d.
What factors influence the rate of diffusion across a membrane? Briefly explain each one.
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.
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.
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.
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).
(a) hypotonic, (b) into the cells
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.
Active transport. Must use energy to go from a state of equilibrium to one of disequilibrium.
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 .
(a) hyperosmotic (convert molarity to osmolarity), (b) True. Water moves from B to A.
Explain the differences between a chemical gradient, an electrical gradient, and an electrochemical gradient.
Chemical gradient = concentration gradient. Electrical gradient = separation of electrical charge. Electrochemical gradient includes both concentration and electrical gradients.
