ENZYMES PHOTOSYNTHESIS AND CELL RESPIRATION MEGA HW
AP BIOLOGY
DR WEINER
Multiple Choice
1. The energy needed to form ATP by electron transport phosphorylation comes from the net
movement of
a. Glucose into the cell by facilitated diffusion
b. Water molecules diffusing into an intracellular hypertonic environment
c. Oxygen diffusing out of the cell
d. Protons diffusion across the membrane with the concentration gradient
2. What is the function of O2 in aerobic metabolism?
a. Oxidizes glucose making it more soluble in water
b. Reduces enzymes, limiting glucose synthesis
c. Activates enzymes in the citric acid (Kreb’s) cycle
d. Accepts electrons through the electron transport chain
3. CO2 production can be used as a measure of metabolic rate because
a. The heat from metabolism increases its partial pressure
b. CO2 is a waste product of the metabolism of glucose
c. A decreased cellular pH liberates gaseous CO2
d. Plants need CO2 to complete photosynthesis
4. From the evolutionary perspective, the most primitive process in cellular energetics is most
likely
a. Fermentation
b. The citric acid (Kreb’s) cycle
c. The dark reactions of photosynthesis
d. CAM reactions in photosynthesis
5. During complete aerobic cellular respiration, each molecule of glucose broken down in the
mitochondria can yield 36 molecules of ATP. What conditions might lead to a decrease in the
amount of ATP produced in a given system?
a. An increase in the amount of glucose added to the system
b. A decrease in the amount of light the system is exposed to
c. A decease in the amount of oxygen available in the system
d. A decease in the amount of carbon dioxide available in the system
6. Competitive inhibitors of enzymes can be reversed by
a. Increasing the pH above the enzyme’s optimal range
b. Increasing the concentration of substrate
c. Adding noncompetitive inhibitors
d. Lowering the temperature below the enzyme’s optimal range
7. If a reaction results in a ΔG = -625 kcal/mol, one can conclude that
a. Free energy was absorbed
b. The system is closed
c. The system is in equilibrium
d. The reaction is exergonic
8. Aerobic respiration produced much more ATP per glucose molecule than fermentation because
a. Respiration uses glycolysis to oxidize glucose
b. Oxygen is necessary to release energy stored in pyruvate
c. Fermentation used NAD+ as the oxidizing agent in glycolysis
d. Respiration produces 2ATP via glycolysis
9. The tradeoff between water loss and CO2 uptake has resulted in the evolution of what
adaptation in may plants that experience a hot, dry environment?
a. C4 and CAM photosynthesis
b. C3 and CAM photosynthesis
c. C3 and C4 photosynthesis
d. Photorespiration that generates ATP
Questions 10 and 11 are based on the following experiment:
You are conducting an experiment to determine the effect of different wavelengths of light on the
absorption of carbon dioxide as an indicator of the rate of photosynthesis in aquatic ecosystems. If the
rate of photosynthesis increases, the amount of carbon dioxide in the environment decreases and vice
versa. You’ve added an indicator to each solution. When the carbon dioxide concentration decreases,
the color of the indicator solution also changes. Small aquatic plants are placed in containers of water
mixed with carbon dioxide and indicator solution. Container A is placed under normal sunlight, B
under green light, and C under red light. The containers are observed for a 24 h period.
10. Based on your knowledge of the process of photosynthesis, the plant under the red light would
probably
a. Absorb no CO2
b. Absorb the same amount of CO2 as the plant under both the green and the normal light
c. Absorb less CO2 than the plant under the green light
d. Absorb more CO2 than the plant under the green light
11. Carbon dioxide absorption is an appropriate indicator of photosynthesis because
a. CO2 is needed to produce sugars in the Calvin cycle
b. CO2 is needed to complete the light reactions
c. Plants produce oxygen gas by splitting CO2
d. The energy in CO2 is used to produce ATP and NADPH
12. The movement of H+ ions down the concentration gradient along the inner mitochondrial
membrane during chemiosmosis of cellular respiration, is an example of which type of
transport?
a. Active transport
b. Facilitated diffusion
c. Osmosis
d. Cotransport
13. A scientist wanted to measure the metabolic activity of normal cells compared to the metabolic
activity of cancer cells. Which of the following would give the best data set for this question?
a. CO2 consumed by the cell
b. O2 consumed by the cell
c. Water consumed by the cell
d. Glucose produced by the cell
Questions 14-16 are based on the following graphs:
The rate of reaction for three enzymes was calculated at different temperatures, and the rate of reaction
for two additional enzymes was calculated at different pH levels. The results are shown in the
following graphs. Assume the y-axes share the same scale.
14. Which of these enzymes is the most efficient- that is, has the highest rate of reaction?
a. 1
b. 2
c. 4
d. 5
15. How many times more acidic is the optimal environment for enzyme 4 than the optimal
environment for enzyme 5?
a. 6
b. 60
c. 106
d. 108
16. In enzymes 1, 2, and 3 why does the curve of the rate of reaction line for each enzyme drop
sharply after the optimal temperature is reached?
a. The increasing thermal energy of the solution denatures the enzyme, rapidly decresing
the rate of reaction
b. The substrate is completely converted at the optimal temperature, and without substrate
the rate of reaction decreases sharply
c. The optimal point of conversions by the enzyme results in a decreasing number of
enzyme molecules due to molecular fatigue resulting in a rapidly decreasing rate of
reaction
d. The final product of the enzyme conversions is a competitive inhibitor interfering with
the active site of the enzyme resulting in a rapidly decreasing rate of reaction
17. Which of the following is the best reason the curve for the absorbency of light by chlorophyll a
does not perfectly match the rate of photosynthesis?
a. The rate of photosynthesis is always fractionally slower than the rate of absorbency by
chlorophyll a
b. The rate of photosynthesis is always fractionally faster than the rate of absorbency by
chlorophyll a
c. There are fewer chlorophyll a molecules in the cell than the other molecules involved in
photosynthesis so chlorophyll a is the rate limiting reagent
d. Chlorophyll a is not the only photosynthetically important pigment in chloroplasts
18. The graph below shows the absorption spectrum for an unknown pigment molecule. Ehat color
would this pigment appear?
a. Red
b. Yellow
c. Green
d. Blue
19. This graph shows the rate of photosynthesis for two plants under experimental conditions.
From this graph, what is the best conclusion about the mechanism of photosynthesis in the two
plants?
a.
b.
c.
d.
A is a C3 plant and B is a C4 plant
A is a C4 plant and B is a C3 plant
A is a CAM plant and B is a C4 plant
A and B are both CAM plants
20. There are two types of enzyme inhibition: competitive and noncompetitive. Competitive
inhibitors compete with the substrate for the active site, while noncompetitive inhibitors bind to
another part of the enzyme and alter its shape. Malonate is an inhibitor of the respiratory
enzyme succinate dehydrogenase in the following reaction
Succinate dehydrogenase
(enzyme)
succinate
Malonate
fumarate
(inhibitor)
Which of the following choices best describes the best way to determine whether malonate is a
competitive or an noncompetitive inhibitor of succinate dehydrogenase?
a. In the presence of malonate, increase the concentration of succinate, the substrate. If the rate of
reaction increases then malonate is a competitive inhibitor
b. In the presence of malonate, increase the concentration of succinate, the substrate. If the rate of
reaction increases then malonate is a noncompetitive inhibitor
c. Malonate can alternate between a competitive and noncompetitive inhibitor depending on what
is required
d. A coenzyme must be affecting the rate of reaction
21. Here is a graph showing the rate of photosynthesis in a green plant plotted against light
intensity. Which of the following accurately accounts for the shape of the graph?
a. The rate of photosynthesis stops slows as chlorophyll molecules, which are proteins,
denature
b. The rate of photosynthesis stops increasing because chlorophyll molecules begin to
decompose due to increased heat not light
c. Photosynthesis ceases when protons are no longer released by the photolysis of water
d. The rate of photosynthesis increases until the light harvesting apparatus in the thylakoid
membranes become saturated and cannot make use of any additional light
22. Here is a simplified equation for photosynthesis
6CO2 + 6 H20 →C6H12O6 +6O2
Which of the following choices correctly traces the atom identified with an arrow?
Intact chloroplasts are isolated from dark green leaves by low speed centrifugation and are
placed in 6 tubes containing cold buffer. A blue dye, DPIP, which turns clear when reduced, is
also added to all tubes. Then each tube is exposed to different wavelengths of light. A
measurement of the amount of decolorization is made, and the data are plotted on a graph.
Although the wavelengths of light vary, the light intensity stays the same.
23. Which statement below describes the results of the experiment?
a. The lower the wavelength of light the greater the rate of photosynthesis
b. The highest wavelengths of light provide the fastest rate of photosynthesis
c. The highest rate of photosynthesis results from exposure to two different wavelengths
of light
d. The greatest reduction of DPIP occurs at 550 nm
24. What is the best explanation for the results in the above question?
a. 650 and 700 nm of light have the greatest penetrating power
b. The photosynthetic pigments in the experiment do not absorb light in the 650 and 700
nm range
c. Only wavelengths of 650 and 700 nm are reflected by chlorophyll
d. The chloroplasts have two photosystems that absorb light in different wavelengths
25. Which of the following processes is carried out more efficiently by a C4 plant than a C3 plant?
a. Light absorption
b. Chemiosmotic coupling
c. Photolysis
d. Fixation of CO2
26. All of the following could reduce the yield of photosynthetic products EXCEPT
a. a lower concentration of carbon dioxide in the atmosphere
b. increased photorespiration
c. reduced carbon dioxide concentrations in the air spaces of the leaf
d. increased frequency of stomata opening
27. All of the following are common to C3 and C4 photosynthesis EXCEPT
a. Photolysis
b. Initial step of CO2 fixation
c. Cyclic photophosphorylation
d. Noncyclic photophosphorylation
28. In the following branched metabolic pathway, the dotted arrows indicate inhibition of a
metabolic step
Q
P
L
M
N
O
R
S
Which reaction would prevail if both Q and S are present in the cell in high concentrations?
a.
b.
c.
d.
e.
L→M
M→O
L→N
O→P
R→S
29. Which of the following is true about the following reactions?
A → B ΔG = -7.3 kcal
C → D ΔG = 4.0 kcal
a. A →B is most likely anabolic
b. A →B supplies the energy to run C →D.
c. the overall energy change for the coupled reaction is endergonic
d. C → D is exergonic
30. The reaction below is exergonic. Which of the following will slow the rate of reaction from left
to right?
w+x↔y+z
a. increase the concentration of x
b. decrease the concentration of x
c. raise the temperature of x and w
d. increase the energy of activation of x and w
Questions 31-33:
Students do an experiment to explore the effects of pH on enzyme activity. They use the enzyme
catalase, which is found in all aerobic cells. The function of catalase is to break down the harmful
waste product of cellular respiration hydrogen peroxide into water and oxygen:
2H2O2 → 2 H2O + O2
The students set up 10 test tubes each containing 5 mls of peroxide. They adjusted the pH of each test
tube as shown below. To test tubes 1-5 they added 3 ml of catalase. To test tubes 6-10 they added 3 ml
of water. Immediately some of the tubes began to bubble. The students used a glowing splint to test for
the presence of oxygen and to prove that the bubbles were oxygen gas. Their data is shown below.
Test tube
1
2
3
4
5
6
7
8
9
10
pH
1
3
5
7
9
1
3
5
7
9
contents
3 ml catalase
3 ml catalase
3 ml catalase
3 ml catalase
3 ml catalase
3 ml water
3 ml water
3 ml water
3 ml water
3 ml water
Amount of bubbling
none
+
+++
++++
+
none
none
none
none
none
31. According to the data shown, the catalase is most effective under which of the following
conditions?
a. In any acid medium
b. At pH 1
c. At pH 7
d. At pH 9
32. This experiment lends support to the idea that cellular enzymes
a. function within a narrow pH range
b. function best at high pH
c. function best at pH 6-7, which is the pH of the average cell
d. denature at high temperatures
33. What is the reason for adding water to test tubes 6-10?
a. The water is necessary to adjust the pH
b. The water replaces the enzyme in those tubes
c. Water enhances the reactivity of catalase
d. Water is necessary to limit wide temperature changes
Questions 34-36 refer to the following experiment:
Four test tubes are required for this experiment. All the tubes contain pond water and the pH indicator
bromothymol blue, which turns yellow when acidic and blue in the neutral or basic pH range. Carbon
dioxide is bubbled into all 4 test tubes, causing the solutions to turn yellow. Sprigs of the plant elodea
are placed into test tubes I and III. Test tubes I and II are kept in the light; test tubes III and IV are kept
in the dark. After 24 hours, all tubes are examined and the observations are recorded in the table
below.
Test tube
I
II
III
IV
Color at time zero
Yellow
Yellow
Yellow
yellow
Color after 24 hours
Blue
Yellow
Yellow
Yellow
34. after 24 hrs, tube I turned blue because the
a.
b.
c.
d.
plant excreted carbon dioxide as a result of carrying out cellular respiration
plant excreted oxygen as a result of carrying out cellular respiration
plant excreted oxygen as a result of carrying out photosynthesis
plant absorbed carbon dioxide to use in photosynthesis
35. which of the following is correct?
a. The independent variable is Ph
b. The independent variable is time
c. Test tube III is a control for test tube I
d. The dependent variable is the presence of oxygen
36. When carbon dioxide is bubbled into water containing bromothymol blue,
a. The pH increases
b. The pH decreases
c. The water turns blue
d. There is no change in pH because carbon dioxide is a buffer
37. When electrons flow along the ETC of mitochondria, which of the following changes occurs?
a. The pH of the matrix increases
b. ATP synthase pumps protons by active transport
c. The electrons gain free energy
d. The cytochromes of the chain phosphorylated ADP to ATP
Questions 38-41 refer to the following graph. The solid curve and the dashed curve represent
alternative pathways for the same reaction. One pathway is enzyme catalyzed.
B
A
C
E
D
38. Represents the activation energy of the enzyme-catalyzed reaction.
39. Represents the net energy change of the reaction
40. Represents the energy state of the products of the enzyme-catalyzed pathway.
41. Represents the energy state of the products of the pathway that is not enzyme-catalyzed.
Essay Questions (10 pts)
1. Yeast cells are placed in an apparatus with a solution of sugar (a major nutrient of yeast
metabolism). The apparatus detects bubbles of gas released by yeast cells. The rate of respiration
varies with the surrounding temperature as indicated by the data below.
Temperature (C)
0
10
20
30
40
50
60
70
Number of gas bubbles
produced per minute
0
3
7
12
7
4
1
0
a. Graph the results on the axes provided. Determine the optimum temperature for respiration in the
yeast.
b. Respiration is a series of enzyme-catalyzed reactions. Using your knowledge of enzymes and the
data above, analyze and explain the results of this experiment.
c. Design an experiment to test the effect of varying pH of the sugar solution on the rate of
respiration. Include a predication of the expected results.
2. A controlled experiment was conducted to analyze the effects of darkness and boiling on the
photosynthetic rate of incubated chloroplast suspensions. The dye reduction technique was used. Each
chloroplast suspension was mixed with DPIP, an electron acceptor that changes from Blue to clear
when it is reduced. Each sample was placed individually in a spectrophotometer and the percent
transmittance was recorded. The three samples used were prepared as follows.
 Sample 1 – chloroplast suspension + DPIP
 Sample 2 – chloroplast suspension surrounded by foil to provide a dark environment + DPIP
 Sample 3 – boiled chloroplast suspension + DPIP\
Percent Transmittance in three Samples
Time (Min)
0
5
10
15
20
Light, unboiled
chloroplasts
28.8
48.7
57.8
62.5
66.7
% Transmittance
Dark, unboiled
chloroplasts
29.2
30.1
31.2
32.4
31.8
Light, boiled
chloroplasts
28.8
29.2
29.4
28.7
28.5
a. On the axes provided, construct and label a graph showing the results for the three samples.
b. Identify and explain the control or controls of this experiment.
c. The differences in the curves of the graphed data indicate that there were differences in the number
of electrons produced in the three samples during the experiment. Discuss how electrons are
generated during photosynthesis and why the three samples gave different transmittance results.