Download Cellular Energetics

Cellular Energetics
1.
Carbon dioxide is passed into a solution of bromthymol blue indicator until the acid
solution turns yellow. A sprig of elodea is then placed into this yellow solution. After a
few hours in the sunlight, the yellow solution turns blue. The purpose of this experiment
is to show that
a. oxygen is given off during photosynthesis
b. carbon dioxide is used during photosynthesis
c. carbon dioxide is given off as a by-product of photosynthesis
d. bromthymol blue changes to bromthymol yellow under acid conditions
e. chlorophyll acting as a photocatalyst is necessary for photosynthesis
2.
Which of the following statements concerning respiration is correct?
a. Aerobic respiration is probably more ancient in an evolutionary sense than is
anaerobic respiration.
b. When oxygen is present, fermentation proceeds without the participation of
enzymes.
c. Each NADH + H+ generated in the Krebs cycle contains sufficient energy for the
production of 3 ATP molecules.
d. Unlike pyruvic acid, fatty acids break up into 3-carbon units during respiration.
e. In one turn of the citric acid cycle, 8 molecules of CO2 are formed.
3.
When a person exercises strenuously, all of the following occur EXCEPT:
a. Glucose decreases.
b. ADP increases.
c. Lactic acid increases.
d. Glycogen increases.
e. CO2 increases.
4.
A substrate molecule may be bound to the active site of an enzyme by all of the
following EXCEPT:
a. hydrogen bonds
b. peptide bonds
c. ionic bonds
d. van der Waals interactions
e. hydrophobic interactions
5.
The end products of the light-dependent reactions of photosynthesis are
a. ADP, H2O, NADPH2
b. ADP, PGAL, RuBP (RuDP)
c. ATP, CO2, H2O
d. ATP, NADPH2, O2
e. CO2, H+, PGAL
6.
Which of the following enzymes is responsible for CO2 fixation in C3 plants?
a. Succinate dehydrogenase
b. RuBP (RuDP) carboxylase
c. Hexokinase
d. Amylase
e. DNA polymerase
7.
All of the following statements concerning cellular respiration are true EXCEPT
a. In the citric acid cycle, two molecules of CO2 and one molecule of FADH2 are
produced.
b. ATP is converted to ADP during two of the reaction of glycolysis.
c. When aerobes respire anaerobically, they may build up an oxygen debt that may be
paid eventually by intake of oxygen.
d. The metabolic breakdown of glucose yields more energy during fermentation than
during aerobic respiration.
e. The conversion of glucose to pyruvic acid can occur in the absence of oxygen.
8.
Dichlorophenolindophenol (DPIP) is a blue dye that is decolorized when it is reduced.
After being mixed with DPIP, which of the following would show the greatest change in
color?
a. Isolated chloroplasts in the light
b. Isolated chloroplasts in the dark
c. Chlorophyll extract in the dark
d. Boiled chloroplasts in the light
e. Boiled chloroplasts in the dark
Questions 9-11 refer to a laboratory experiment using spectrophotometry, in which an
enzyme is combined with its substrate at time zero. The absorbance of the resulting
solution is measured at time zero and at five-minute intervals. In this procedure, an
increase in absorbance is related to the amount of product formed during the reaction. The
experiment is conducted using the three preparations shown in the table below.
Absorbance
Enzyme Preparation
0 min 5 min 10 min
15 min
20 min
I. 3 mL of enzyme preparation
2 mL of substrate
pH 5.0
9.
0.0
0.22
0.33
0.38
0.37
II. 3 mL of boiled enzyme preparation
2 mL of substrate
pH 5.0
0.0
0.06
0.04
0.03
0.04
III. 3 mL of enzyme preparation
2 mL of substrate
pH 6.0
0.0
0.32
0.37
0.36
0.38
The most likely reason for the failure of the absorbance to increase significantly after
10 minutes in preparation III is that
a. the reaction is thermodynamically impossible at pH 6.0
b. the enzyme is not active at this pH
c. a pH of 6.0 prevents color development beyond an absorbance of 0.38
d. the enzyme is degraded more rapidly at pH 6.0 than it is at pH 5.0
e. most of the substrate was digested during the first 10 minutes
10. Which of the following statements is best supported by the data?
a. Increasing the pH to 7.0 would yield an absorbance higher than 0.30 after 5
minutes.
b. The enzyme demonstrates more activity at pH 6.0 than at pH 5.0
c. The enzyme has no activity at pH 6.0.
d. A pH of 5.0 is the optimum for the activity of the enzyme.
e. The enzymatic activity is independent of pH.
11. Which of the following can best be concluded from a comparison of the results of
preparation II with those of preparation I?
a. Heating the enzyme is required to increase the absorbance.
b. Boiling does not break down the substrate.
c. Most of the increase in the amount of product in preparation I was due to
enzymatic degradation of the substrate.
d. Enzymatic reactions proceed at a faster rate after boiling the enzyme.
e. Products resulting from the breakdown of the enzyme are responsible for the
absorbance increase in preparation II.
For questions 12-13, refer to the information below:
Frogs of three different species are weighed and the amount of oxygen consumed by
each species is determined by placing them in a respirometer for 1 hour. The results of
this experiment are below:
Species
1
2
3
Average
Weight in Grams
15
11
21
Total Cubic Centimeters of Oxygen
Consumed in 1 Hour
0.75
0.55
1.05
12. From the information in the table, it is most reasonable to conclude that
a. since all frogs respire through their skin, smaller frogs with small surface areas will
consume less oxygen per gram of body weight than larger frogs with larger surface
areas
b. frogs placed in a warm environment will respire more rapidly than frogs placed in a
colder environment
c. each species of frog has its own unique rate of respiration
d. the amount of oxygen consumed per gram of body weight for each species is the
same
e. the amount of oxygen consumed per gram of body weight by the largest frog is
almost twice that by the smallest frog
13. If each frog doubles its rate of oxygen consumption in 1 hour after an injection of
thyroxine, it would be most reasonable to conclude that thyroxine
a. acts a general stimulus to respiratory metabolism
b. stimulates the release of hormone from the pituitary
c. doubles the amount of hormone released by the thyroid gland in each species
d. doubles the rate of breathing by doubling the rate of contraction of the diaphragm
muscle
e. increases the permeability of the mitochondrial membrane to oxygen
A + B + energy
AB
14. Which of the following best characterizes the reaction represented above?
a. Hydrolysis
b. Catabolism
c. Oxidation-reduction
d. Exergonic reaction
e. Endergonic reaction
15. Oxygen consumption can be used as a measure of metabolic rate because oxygen is
a. necessary for ATP synthesis by oxidative phosphorylation
b. necessary to replenish glycogen levels
c. necessary for fermentation to take place
d. required by all living organisms
e. required to break down the ethanol that is produced in muscles
16. In a mesophyll cell of a leaf, the synthesis of ATP occurs in which of the following?
I. Ribosomes
II. Mitochondria
III. Chloroplasts
a. I only
b. II only
c. III only
d. II and III only
e. I, II, and III
17. During respiration, most ATP is formed as a direct result of the net movement of
a. potassium against a concentration gradient
b. protons down a concentration gradient
c. electrons against a concentration gradient
d. electrons through a channel
e. sodium ions into the cell
18. Which of the following processes is carried out more efficiently by a C4 plant than by a
C3 plant?
a. Light absorption
b. Chemiosmotic coupling
c. Photolysis
d. Fixation of CO2
e. Transport of sugars
Essay Questions
RESPIRATION
1977:
Explain how the molecular reactions of cellular respiration transform
the chemical bond energy of Krebs cycle substrates into the more
readily available bond energy of ATP.
Include in your discussion the structure of the mitochondrion and
show how it is important to the reactions of the Krebs cycle and the
electron transport chain.
1982:
Describe the similarities and differences between the biochemical
pathways of aerobic respiration and photosynthesis in eukaryotic cells.
Include in your discussion the major reactions, the end products, and
energy transfers.
1989:
Explain what occurs during the Krebs (citric acid) cycle and electron
transport by describing the following:
a. The location of the Krebs cycle and electron transport chain
in the mitochondria.
b. The cyclic nature of the reactions in the Krebs cycle.
c. The production of ATP and reduced coenzymes during the
cycle.
d. The chemiosmotic production of ATP during electron
transport.
1990:
The results below are measurements of cumulative oxygen consumption
by germinating and dry seeds. Gas volume measurements were corrected
for changes in temperature and pressure.
Cumulative Oxygen Consumed (mL)
______________________________________________
Time (minutes)
0
10
20
______________________________________________
22o C Germinating Seeds 0.0
8.8
16.0
Dry Seeds
0.0
0.2
0.1
______________________________________________
10o C Germinating Seeds 0.0
2.9
6.2
Dry Seeds
0.0
0.0
0.2
______________________________________________
30
40
23.7
0.0
32.0
0.1
9.4
0.1
12.5
0.2
a. Using the graph paper provided, plot the results for the
germinating seeds at 22o C and 0o C.
b. Calculate the rate of oxygen consumption for the germinating
seeds at 22o C, using the time interval between 10 and 20 minutes.
c. Account for the differences in oxygen consumption observed
between:
1) germinating seeds at 22o C and at 10o C;
2) germinating seeds and dry seeds.
d. Describe the essential features of an experimental apparatus
that could be used to measure oxygen consumption by a small organism.
Explain why each of these features is necessary.
1993:
Membranes are important structural features of cells.
(a)
Describe
materials across
(b)
Describe
either cellular
how membrane structure is related to the transport of
a membrane.
the role of membranes in the synthesis of ATP in
respiration or photosynthesis.
1995:
Energy transfer occurs in all cellular activities. For 3 of the
following 5 processes involving energy transfer, explain how each
functions in the cell and give an example. Explain how ATP is involved
in each example you choose.
Cellular movement
Active transport
Synthesis of molecules
Chemiosmosis
Fermentation
PHOTOSYNTHESIS
1971:
The process of photosynthesis consists of two phases, the light
reactions and the dark reactions. Discuss each of these groups of
reactions and their interrelationships.
1978:
Explain how the molecular reactions of photosynthesis transform
light energy into chemical bond energy. Include in your discussion the
relationship between chloroplast structure and light and dark
reactions.
1979:
In relation to plants, describe in detail one way of:
a.
measuring the rate of transpiration
b.
measuring the rate of photosynthesis
c.
separating pigments
1982:
Describe the similarities and differences between the biochemical
pathways
of aerobic respiration and photosynthesis in eukaryotic
cells. Include in your discussion the major reactions, the end
products, and energy transfers.
1983:
Relate the structure of an angiosperm leaf to each of the
following.
a.
Adaptations for photosynthesis and food storage.
b.
Adaptations for food translocation and water transport.
c.
Specialized adaptations to a desert environment.
1986:
Describe the light reactions of photosynthesis and, for both a C3
and a C4 plant,
trace the path of a carbon dioxide molecule from the
point at which it enters a
plant to its incorporation into a glucose
molecule. Include leaf anatomy and biochemical pathways in your
discussion of each type of plant.
1993:
Membranes are important structural features of cells.
(a)
Describe how membrane structure is related to the transport
of materials across a membrane.
(b)
Describe the role of membranes in the synthesis of ATP in
either cellular respiration or photosynthesis.