bio membranes-enzymes-practice-problems 2016-10-26 (2)

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Membranes
Membranes, Diffusion
Classwork
1. How does a phospholipid membrane create an isolated internal environment?
2. Draw and label a phospholipid.
3. In what way do the screen on a window and a cell membrane serve a similar
function? What characteristic is used to describe this function?
4. What essential role does a cell membrane play in maintaining homeostasis?
5. If you stir a cube of sugar into a glass of water, which of these materials would be
a solute, and which would be a solvent?
6. If you have a solution consisting of 5 grams of NaCl in 200 mL of water, what is
the molarity of your solution?
7. What characteristic of passive transport makes it ‘passive?’
8. What role does a concentration gradient play in the process of passive transport?
9. Which image below is in a state of equilibrium? Explain your answer.
10. Dialysis tubing contains 0.5 M glucose solution. It is placed in a beaker of 1.0 M
glucose solution. Describe the direction of diffusion.
11. A cell with an O2 concentration of 8 mM and a CO2 concentration of 5 mM is
placed in a solution of 10 mM O2 and 1 mM CO2. Describe the direction of
diffusion of each gas.
Homework
12. Compare a phospholipid membrane to a chain link fence. How are these two
structures similar? What function do they both serve?
13. How do amphiphilic phospholipids prevent their hydrophobic ends from coming
into contact with water?
14. Why is it necessary for cellular health that a cell membrane be selectively
permeable?
15. Make a correction to the following statement to make it true:
A solute has the ability to dissolve a solvent.
16. If you have a solution consisting of 100 grams of C6H12O6 in 1000 mL of water,
what is the molarity of your solution?
17. Suppose you have a solution consisting of 20 grams of carbon dioxide in 750 mL
of water. What is the molarity of your solution?
18. What type of cellular transport would you use to describe a ball rolling down a
hill? Explain your answer.
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19. Suppose you spray air freshener into the corner of a room. Explain how the air
freshener will move throughout the room. Be sure to use the term concentration
gradient in your response. At what point will the air freshener molecules stop
moving through the room?
20. What impact does the state of equilibrium have on the rate of diffusion?
21. Suppose you have a cell that is freely permeable to H2O. There are more H2O
molecules outside of the cell than inside of the cell. In what direction will the net
movement of H2O molecules occur? Why?
22. A cell with an O2 concentration of 2 mM and a CO2 concentration of 10 mM is
placed in a solution of 9 mM O2. Describe the direction of diffusion of each gas.
Osmosis
Classwork
23. Since osmosis is passive transport, in which direction does water move related to
its concentration gradient? What direction does it move in relation to the solution
concentration gradient?
24. If a cell is placed in a hypertonic solution, in which direction will water flow in
relation to the cell?
25. Sometimes, doctors will recommend that patients experiencing a sore throat
should gargle saltwater to relieve their symptoms. Explain, in terms of solute
concentration, how gargling saltwater could help reduce swelling in the throat.
26. Suppose a cell is placed in an unknown solution. After examining the cell under
a microscope, you see that the cell membrane has expanded, like a tight water
balloon. What kind of solution, hypertonic, hypotonic or isotonic, is the unknown
substance? Why did you come to this conclusion?
27. If there is equal concentration of free water molecules inside of a cell compared
to its surrounding solution, what type of environment is the surrounding solution?
28. Suppose you have a houseplant that has begun to wilt. Would it be more
beneficial to water this plant with a solution that was hypertonic or hypotonic
when compared to the plant cells? Explain your answer.
29. A cell with a sucrose concentration of 0.65 M is placed in a 1.2 sucrose solution.
Describe the net flow of water.
Homework
30. Does osmosis require the input of energy? Why or why not?
31. What will happen to a cell that is placed in a hypertonic solution?
32. One way to preserve perishable food, such as meat, is to pack the food in a
heavy concentration of salt. Knowing that bacteria survive well in a moist
environment, explain why this method of food preservation can be effective.
33. If a cell lyses after being submerged in a solution, would you suggest this
solution is hypertonic, hypotonic or isotonic? Why?
34. If a cell membrane were impermeable to water molecules, how would this
change the process of osmosis in our cells?
35. What is the relationship between osmosis and diffusion?
36. A cell with an O2 concentration of 0.4 M and a glucose concentration of 0.1 M is
placed in a 0.5 M glucose solution. Describe the net flow of both solutes and
water.
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Membranes & Enzymes
Plasma Membrane, Transport Through Proteins
Classwork
37. Explain why a cell that requires only passive transport of small molecules may
not require the presence of membrane proteins.
38. What similarities exist between peripheral vision and peripheral proteins? Why is
the same adjective used to describe both of these things?
39. Why might a polar molecule have a difficult time moving across a phospholipid
bilayer, even if it were a small molecule?
40. Explain why the term fluid mosaic is used to describe the structure of a
phospholipid bilayer.
41. Do you think an integral protein or a peripheral protein is more useful for the
transport of molecules across a cell membrane? Justify your answer.
42. Identify one similarity that exists between the processes of active transport and
facilitated diffusion.
43. Suppose you need to determine whether glucose is being transported using
active transport or facilitated diffusion. The only clue you have is that ATP
molecules are required for the movement to occur. Which type of transport do
you suggest is being used? Why?
44. Cl- ions often move across cell membranes through a membrane protein that
does not change shape to accommodate their transport. Is this protein more
likely a channel protein or carrier protein? Justify your response.
45. What type of cell transport is required to move a substance from an area of low
concentration to an area of high concentration?
46. Describe one function that peripheral proteins may provide for the cell.
47. In order for nerve cells to conduct electrical signals appropriately, certain ions
need to be transported against their concentration gradient. What type of cell
transport is necessary for this to occur? Is ATP required for this process to
occur?
Homework
48. Why are membrane proteins necessary for the movement of some larger
molecules across cell membranes?
49. What is the difference between a peripheral membrane protein and an integral
membrane protein?
50. Are the phospholipids and proteins that construct a cell membrane anchored in a
stationary position? What is the term used to describe the arrangement of a
phospholipid bilayer?
51. Why are integral proteins sometimes also called transmembrane proteins?
52. Even though ions are very small, they often require the assistance of a
membrane protein to enter or leave a cell. What characteristic of ions makes this
necessary?
53. Even though they both require the use of membrane proteins, if a molecule
needs to move against a concentration gradient, would active transport or
facilitated diffusion be a more likely method to accomplish this task? Explain
your answer.
54. What do facilitated diffusion and osmosis have in common?
55. Knowing that molecules will naturally move from an area of high concentration to
an area of low concentration, why do you think active transport may require the
input of energy?
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Membranes & Enzymes
56. Suppose a cell needs to move a small, uncharged molecule against its
concentration gradient. What type of transport would be required to accomplish
this task?
57. In what way is active transport similar to pushing a ball up a hill?
Enzymes, Catalytic Cycle
Classwork
58. Explain the impact that an enzyme can have on a chemical reaction.
59. What is the relationship between enzymes and catalysts?
60. Which class of biological macromolecules would contain enzymes?
61. Suppose you are diagnosed with lactose intolerance. What enzyme would you
not find naturally occurring in your body? How would this affect the digestion of
lactose in your body?
62. What is an active site? Why is an active site important for the completion of
chemical reactions?
63. How is an ‘induced fit’ with an enzyme similar to having your shirt tailored?
Explain your answer.
64. How are the reactants altered over the course of a chemical reaction?
65. What is activation energy?
66. How do enzymes affect the amount of activation energy required for a reaction?
Homework
67. Suppose a friend of yours accidentally begins a food fight by flicking a grape off
of your lunch table. Identify the catalyst of the food fight.
68. Identify two ways in which an enzyme impacts a chemical reaction.
69. Explain the ‘lock and key’ relationship between enzymes and substrates.
70. How would activation energy be affected if a reaction occurred in the absence of
an enzyme?
Temperature, pH, Inhibition
Classwork
71. Explain the role that optimal temperature has on enzyme activity?
72. How is an enzyme affected when the environment exceeds its optimal
temperature?
73. If enzymes were a different kind of biological molecule, would temperature and
pH have the same affect on their activity? Explain your answer.
74. What role do cofactors have for enzyme activity?
75. How do competitive inhibitors interact with an enzyme?
76. Would the same solution for negating the impact of a competitive inhibitor work
for a non-competitive inhibitor? Why or why not?
Homework
77. How does increasing temperature affect enzyme activity?
78. Why does denaturing an enzyme impact its ability to influence a chemical
reaction?
79. Draw a graph of enzyme activity for an enzyme that has an optimal pH range of
6-8.
80. What is the relationship between cofactors and inhibitors?
81. Explain one way in which your body may negate the impact of a competitive
inhibitor. Explain why this would work.
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Membranes & Enzymes
82. What affect does non-competitive inhibition have on the active site of an
enzyme?
Allosteric Regulation, Feedback Inhibition
Classwork
83. What is the difference between an allosteric site and an active site?
84. Explain how allosteric inhibitors function through feedback inhibition.
85. Even though allosteric regulation and denaturation both affect the shape of an
enzyme, they are very different processes. Explain the difference between these
two processes.
Homework
86. Explain why allosteric activators and inhibitors may be able to work on the same
enzyme.
87. Explain the process by which an allosteric inhibitor influences an enzyme.
88. Provide a hypothesis for why scientists use the term ‘feedback inhibition.’
89. Compare and contrast an allosteric activator and a coenzyme.
Free Response
1. Below is an illustration of a common lab set-up used to visualize and observe the
process of diffusion. The membrane of the bag is permeable to water and
glucose but is not permeable to starch. Using the illustration, and information
provided, respond to each of the following:
a. Will the starch move out of the bag? If so, why? If not, why not?
b. What reagent would we use to determine if starch moved out of the bag
and into the beaker solution? Explain the test you would use.
c. Will the glucose move into the bag? If so why? If not why not?
d. The beaker solution his composed of 360g of glucose (C6H12O6) in 500
ml of water. What is the molarity of the glucose solution?
Glucose
solution
Starch solution
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Membranes & Enzymes
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Membranes & Enzymes
2. Below is an illustration of the catalytic cycle of an enzyme.
a. Complete the chart below by identifying the items labeled as a,b,c,d and e on
the illustration.
b. Describe the process seen in this illustration. Include the vocabulary specific
to this process in your response.
c
_______e
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3. Feedback is required in order to maintain homeostasis within cells and within
organisms. This feedback may be positive, inducing more production, or
inhibiting, inducing a stop to production.
a. In some processes, the products from one enzyme acts as the substrates
for a second enzyme, and so on. Explain how feedback inhibition can
occur to stop a series of enzyme catalyzed reactions.
b. Explain how feedback inhibition and allosteric inhibition are related.
4. Plasma, or cell, membranes have unique features that have made life possible.
Two of these characteristics are: the presence of transport proteins and a fluid
mosaic structure.
a. Peripheral proteins are located on one side only of the plasma
membrane. Why are integral proteins referred to as “transmembrane”
proteins?
b. Identify the two types of transport proteins
c. Explain how each type of transport protein functions in the process of
transport across the cell membrane. Describe whether the proteins move
molecules with or against the concentration gradient.
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Membranes & Enzymes
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