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WorksheetsAP Biology Unit 3 Practice
Total questions: 81
Worksheet time: 53mins
Which of the following best characterizes the reaction represented below?
A + B + Energy -> AB
Hydrolysis
Catabolism
Oxidation-reduction
Exergonic reaction
Endergonic reaction
Which of the following statements is true concerning catabolic pathways?
They combine molecules into more energy-rich molecules
They supply energy, primarily in the form of ATP, for the cell's work.
They are endergonic
They are spontaneous and do not need enzyme catalysis
They build up complex molecules such as protein from simpler compounds
Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction by making the reaction more exergonic
Enzymes increase the rate of a reaction by lowering the activation energy barrier
Enzymes increase the rate of a reaction by reducing the rate of reverse reactions
Enzymes change the equilibrium point of the reactions they catalyze
Enzymes make the rate of a reaction independent of substrate concentrations
In the series of enzyme reactions shown above, product Z is able to occupy the active site of enzyme E2. Product Z can therefore inhibit the production of
W
E1
X
E2
Y
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
by binding at the active site of the enzyme
by binding to a different part of the enzyme, changing the shape of the enzyme's active site
by changing the free energy change of the reaction
by acting as a coenzyme for the reaction
by decreasing the activation energy of the reaction
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as
metabolic inhibition
feedback inhibition
allosteric inhibition
noncooperative inhibition
reversible inhibition
For the enzyme-catalyzed reaction shown in the figure, which of these treatments will cause the greatest increase in the rate of the reaction, if the initial reactant concentration is 1.0 micromolar?
doubling the activation energy needed
cooling the reaction by 10°C
doubling the concentration of the reactants (substrate) to 2.0 micromolar
doubling the enzyme concentration
increasing the concentration of reactants to 10.0 micromolar, while reducing the concentration of enzyme by 1/2
In the figure, why does the reaction rate plateau at higher reactant concentrations?
Feedback inhibition by product occurs at high reactant concentrations
Most enzyme molecules are occupied by substrate at high reactant concentrations
The reaction nears equilibrium at high reactant concentrations
The activation energy for the reaction increases with reactant concentration
The rate of the reverse reaction increases with reactant concentration
Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?
curves 1 and 4
curves 1 and 5
curves 2 and 4
curves 2 and 5
curves 3 and 4
Which of the following represents the ΔG of the reaction in Figure 8.1?
a
b
c
d
e
Which of the following represents the activation energy required for the enzyme-catalyzed reaction in Figure 8.1?
a
b
c
d
e
According to the data, the absorbance fails to increase significantly after 10 minutes in preparation III. This is most likely explained by which of the following?
The reaction is thermodynamically impossible at pH 6.0
A pH of 6.0 prevents color development beyond an absorbance of 0.38
The enzyme is degraded more rapidly at pH 6.0 than it is at pH 5.0
Most of the substrate was digested during the first 10 minutes
Which of the following statements is best supported by the data?
Increasing the pH to 7.0 would yield an absorbance higher than 0.30 after 5 minutes
The enzyme demonstrates more activity at pH 6.0 than at pH 5.0
A pH of 5.0 is the optimum for the activity of the enzyme
The enzymatic activity is independent of pH
According to the data, which of the following can best be concluded from a comparison of the results of preparation II with those of preparation I?
Heating the enzyme is required to increase the absorbance
Boiling does not break down the substrate
Boiling denatured a majority of the enzymes altering the shape of their active sites
Products resulting from the breakdown of the enzyme are responsible for the absorbance increase in preparation II
Both organic and inorganic chemical reactions can be affected by the addition of a catalyst. Which of the following can be used to determine the rate of enzyme-catalyzed reactions?
Rate of disappearance of the enzyme
Rate of disappearance of the substrate
Rate of disappearance of the product
Increase in activation energy
A molecule becomes oxidized when it _________
changes shape
gains a hydrogen (H+) ion
loses a hydrogen (H+) ion
gains an electron
loses an electron
Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
C6H12O6 is oxidized and O2 is reduced
O2 is oxidized and H2O is reduced
CO2 is reduced and O2 is oxidized
C6H12O6 is reduced and CO2 is oxidized
O2 is reduced and CO2 is oxidized
The function of cellular respiration is to:
reduce CO2
extract CO2 from the atmosphere
extract useable energy from glucose
synthesize macromolecules from monomers
produce carbohydrates
During respiration in a eukaryotic cell, reactions of the citric acid cycle occur _____
In the cytosol
in the matrix of the mitochondria
in the inner membrane of the mitochondria
in the intermediate space of the mitochondria
across the inner membrane of the mitochondria
In the citric acid cycle, for each pyruvate that enters the cycle, 1 ATP, 3 NADH, and 1 FADH2 are produced. For each glucose molecule that enters glycolysis, how many ATP, NADH, and FADH2 are produced in the citric acid cycle?
2 ATP, 6 NADH, 2 FADH2
4 ATP, 6 NADH, 2 FADH2
3 ATP, 3 NADH, 1 FADH2
About 38 ATP
1 ATP, 3 NADH, 1 FADH2
Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?
electron transport
glycolysis
the citric acid cycle
oxidative phosphorylation
chemiosmosis
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of _____.
acetyl CoA
ATP
NADH
CO2
FADH2
The ATP synthase in a human cell obtains energy for making ATP directly from which of the following processes?
The oxidation of NADH and FADH2
The flow of H+ across a membrane through the ATP synthase enzyme
the oxidation of glucose
the movement of electrons through a series of carriers
the reduction of oxygen
During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes?
at the end of glycolysis to oxidize pyruvate
at the end of the citric acid cycle to regenerate citric acid
between glycolysis and the citric acid cycle to split a carbon from pyruvate, producing CO2
as a source of O2 in every reaction that produces CO2
at the end of the electron transport chain to accept electrons and form H2O
Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step _____.
removes poisonous oxygen from the environment
extracts a bit more energy from glucose
enables the cell to recycle NAD+
prevents pyruvate from accumulating
enables the cell to make pyruvate into substances it can use
If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result?
The muscle cells will have more trouble making enough ATP to meet their energy requirements
The cells will convert pyruvate into lactate
The cells will not be able to carry out oxidative phosphorylation
Only the first two answers are correct
The first three answers are correct
Which metabolic process is common to both aerobic cellular respiration and alcoholic fermentation?
Krebs (Citric acid) cycle
Glycolysis
Electron transport chain
Conversion of pyruvic acid to acetyl CoA
Production of a proton gradient
Which of the following directly produces the most ATP per mole of glucose during aerobic cellular respiration?
Glycolysis
Electron transport chain (oxidative phosphorylation and chemiosmosis)
Substrate-level phosphorylation
Kreb's (Citric acid) cycle
Alcoholic fermentation
The organelle that is a major producer of ATP and is found in both heterotrophs and autotrophs is the
chloroplast
nucleus
ribosome
golgi apparatus
mitochondrion
During aerobic respiration, electrons travel downhill in which sequence?
food → citric acid cycle → ATP → NAD+
food → NADH → electron transport chain → oxygen
glucose → pyruvate → ATP → oxygen
glucose → ATP → electron transport chain → NADH
food → glycolysis → citric acid cycle → NADH → ATP
In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + i to ATP?
energy released as electrons flow through the electron transport system
energy released from substrate-level phosphorylation
energy released from movement of protons through ATP synthase, against the electrochemical gradient
energy released from movement of protons through ATP synthase, down the electrochemical gradient
No external source of energy is required because the reaction is exergonic
How does carbon dioxide enter the leaf?
through the chloroplast
through the mesophyll
through the thylakoids
through the stomata
through the vascular system
Chlorophyll molecules are in which part of the chloroplast?
thylakoid
stroma
stomata
plasma membrane
inner membrane space
The photosynthetic event known as the Calvin cycle occurs in the _____
thylakoid membrane
inner thylakoid space
stroma
stomata
matrix
The most important role of pigments in photosynthesis is to _____.
capture light energy
screen out harmful ultraviolet light
store energy in glucose molecules
release energy from glucose molecules
store energy in ATP
Where do the electrons needed by photosystem II originate?
other chlorophyll molecules
ATP
the electron transport chain
light
water
The end products of the light-dependent reactions of photosynthesis are
ADP, H2O, NADPH2
ADP, PGAL, RuBP (RuDP)
ATP, CO2, H2O
ATP, NADPH2, O2
CO2, H+, PGAL
The O2 released during photosynthesis comes from
CO2
H2O
NADPH
RuBP
C6H12O6
Which of the following statements best represents the relationships between the light reactions and the Calvin cycle?
The light reactions provide ATP and NADPH to the Calvin cycle, and the cycle returns ADP, i, and NADP+ to the light reactions
The light reactions provide ATP and NADPH to the carbon fixation step of the Calvin cycle, and the cycle provides water and electrons to the light reactions
The light reactions supply the Calvin cycle with CO2 to produce sugars, and the Calvin cycle supplies the light reactions with sugars to produce ATP
The light reactions provide the Calvin cycle with oxygen for electron flow, and the Calvin cycle provides the light reactions with water to split
There is no relationship between the light reactions and the Calvin cycle
On a sunny day, the closing of stomata in plant leaves results in
a decrease in CO2 intake
a shift from C3 photosynthesis to C4 photosynthesis
an increase in transpiration
an increase in the concentration of CO2 in mesophyll cells
an increase in the rate of production of starch
All of the following statements about a chloroplast and a mitochondrion are true EXCEPT:
Both use proton gradients for energy production
Both capture light energy
Both contain DNA
Both are bound by two unit membranes
Both synthesize ATP
Reactions that require CO2 take place in
the light reactions alone
the Calvin cycle alone
both the light reactions and the Calvin cycle
neither the light reactions nor the Calvin cycle
the chloroplast, but is not part of photosynthesis
Process in which O2 is released as a by‑product of oxidation-reduction reactions
Glycolysis
Krebs cycle (citric acid cycle)
Calvin cycle (light-independent reactions of photosynthesis)
Light-dependent reactions of photosynthesis
Chemiosmosis
Process in which CO2 is released as a byproduct of oxidation-reduction reactions
Glycolysis
Krebs cycle (citric acid cycle)
Calvin cycle (light-independent reactions of photosynthesis)
Light-dependent reactions of photosynthesis
Chemiosmosis
Process in which carbon from CO2 is incorporated into organic molecules
Glycolysis
Krebs cycle (citric acid cycle)
Calvin cycle (light-independent reactions of photosynthesis)
Light-dependent reactions of photosynthesis
Chemiosmosis
Process found in both photosynthesis and cellular respiration
Glycolysis
Krebs cycle (citric acid cycle)
Calvin cycle (light-independent reactions of photosynthesis)
Light-dependent reactions of photosynthesis
Chemiosmosis
Process in which sugar is oxidized to pyruvic acid
Glycolysis
Krebs cycle (citric acid cycle)
Calvin cycle (light-independent reactions of photosynthesis)
Light-dependent reactions of photosynthesis
Chemiosmosis
Where on an enzyme does the substrate bind?
active site
allosteric site
C-terminus
N-terminus
Which environmental conditions can cause denaturation of the enzyme?
slight increase in temperature
extreme increase in temperature
decrease in temperature
extreme increase in temperature and pH changes
Describe the difference between competitive and noncompetitive inhibitors.
noncompetitive binds to active site and competitive binds to other site
competitive binds to active site and noncompetitive binds to other site
competitive is irreversible and noncompetitive is reversible binding
noncompetitive is irreversible and competitive is reversible binding
What is the process of an endergonic reaction being fueled by an exergonic reaction called?
second law of thermodynamics
energy coupling
first law of thermodynamics
endergonic/exergonic switch
Where did photosynthesis first evolve?
prokaryotic organisms
alien organisms
eukaryotic organisms
abiotic processes
What are the products of the light-dependent reactions of photosynthesis?
ATP & NADH
CO2 & H2O
NADPH & ATP
Organic Compounds & O2
Where does the Calvin cycle take place?
thylakoid membrane
cristae
stroma
matrix
Where does the electron transport chain take place?
chloroplasts
prokaryotic plasma membrane
mitochondria
all of the choices
Which process releases energy in glucose to form ATP, NADH, and pyruvate?
Glycolysis
Oxidative Phosphorylation
Krebs Cycle
Fermentation
Which process does NOT require oxygen?
Glycolysis
Oxidative Phosphorylation
Krebs Cycle
Aerobic respiration
Enzymes ___________________ activation energy to speed up chemical reactions.
increase
decrease
What is the relationship between an enzymes active site and its substrate?
The active site has the right polarity to interact with the substrate.
The active site is hydrophobic and interacts with other hydrophobic amino acids on the substrate
The active site has a specific shape that fits the shape of the substrate
The active site uses energy to form covalent bonds with the substrate
What is chemiosmosis?
The diffusion of electrons through the electron transport chain
The breakdown of a glucose molecule
The diffusion of protons down their concentration gradient
The active transport of NADH into the mitochondria
Why is chemiosmosis important to cellular respiration?
It provides the energy needed to catabolize glucose
It is the force that powers ATP synthase
It provides the energy needed to breakdown pyruvate into carbon dioxide
It generates the electrons needed for the electron transport chain
Why is the hydrolysis of ATP important to a cells function?
It provides a source of phosphate for the cell.
It releases energy that can be used to power cellular processes
It absorbs excess hydrogen ions in the cell to regulate the internal pH
It acts as a catalyst for chemical reactions in the cell.
What are the net products of photosynthesis?
6 CO2, 6 H2O, Energy
6 O2 and 6 H2O
C6H12O6 and 6 O2
6 CO2 and C6H12O6
How does a plant obtain the carbon necessary to form glucose?
Through the light reactions
From stored sugars in the roots of the plant
From the catabolic breakdown of water
Through CO2 absorbed from the atmosphere
What are the products of the Krebs Cycle?
Pyruvate, water, ATP, NADH
Acetyl CoA, NADH
NADH, FADH2, carbon dioxide, ATP
ATP, glucose
When will lactic acid build up in animal cells?
When there is excess carbon dioxide
When the cells produce too much ATP
When there is not enough oxygen to fuel the mitochondria
When the cells need to remove excess oxygen to avoid damaging their components.
How are the ATP synthase enzymes in photosynthesis and cellular respiration similar?
They both rely on chemiosmosis of hydrogens down a gradient to power phosphorylation
They are both located in the cytoplasm of the cell
They both use oxygen to create a concentration gradient
They both receive hydrogen ions from FADH2
Based on this graph, which enzyme would function best in a basic environment?
A
B
The reactions of glycolysis occur in the
cytosol
nucleus
matrix of the mitochondrion
membranes of the mitochondrion
stroma of the chloroplast
The O2 released during photosynthesis comes from
H2O
NADPH
RuBP (RuDP)
C6H12O6
CO2
A type of anaerobic respiration that’s purpose is to replenish NAD+ so that glycolysis can be continued. Produces either alcohol or lactic acid as a by product is...
Fermentation
Calvin Cycle
Electron transport chain
Glycolysis
Krebs Cycle
A researcher is looking for a catalase enzyme that has maximal function at 42 degrees Celsius. Catalase is first extracted from three different species of unicellular organism and then used to make sodium alginate spheres. Which of the following actions would provide the most appropriate negative control?
Repeating the experiment with catalase enzyme from a fourth species.
Repeating the experiment at several different temperatures.
Repeating the experiment with denatured catalase.
Repeating the experiment using several different methods for measuring temperature.
The mass of 30 radish seedlings was measured by students over one week. 10 seedlings were left out on the counter in a classroom, 10 were placed under a plant light, and 10 were placed in the dark. Identify the cellular process that caused the plants in the dark to decrease in mass.
Catalysis
Photosynthesis
Cellular Respiration
Metabolism
