AP Bio Unit 3

Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a coenzyme. A zinc ion binds to the ALAD active site, where it forms favorable interactions with the side chains of three amino acids. Researchers have found that substituting a lead ion for a zinc ion in the ALAD active site causes inhibition of ALAD.

A.) It changes the shape and charge of the substrate so that it becomes more compatible with ALAD's active site.

B.)It changes the amino acid sequence of the ALAD protein so that the enzyme catalyzes a different reaction.

C.) It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate.

D.)It changes the enzyme-substrate complex so that the transition state is more stable and the reaction proceeds at a faster rate.

C.) It changes the three-dimensional structure of the active site so that ALAD is no longer compatible with its substrate.

The substitution of a lead ion for a zinc ion most likely changes the three-dimensional structure of the ALAD active site. The three-dimensional structure of the active site plays an important role in the compatibility between an enzyme and its substrate. Changing the structure of the active site will likely interfere with enzyme function by disrupting the enzyme-substrate interaction.

Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of acetylcholine to acetate and choline. When the concentration of AChE in an aqueous solution is held constant, the rate of the reaction catalyzed by AChE increases with increasing concentrations of substrate. At low concentrations of acetylcholine, a small increase in the substrate concentration results in a large increase in the reaction rate. At high concentrations of acetylcholine, however, a large increase in the substrate concentration results in only a small increase in the reaction rate.

Which of the following statements correctly explains the observed effect of the acetylcholine concentration on the rate of the enzyme-catalyzed reaction?

A.) The active site of AChEAChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time.

B.) AChEAChE begins converting product into substrate as the acetylcholine concentration changes from low to high.

C.)The AChEAChE protein becomes denatured as the acetylcholine concentration changes from low to high.

D.) The substrate specificity of AChEAChE changes as the acetylcholine concentration changes from low to high.

A.) The active site of AChEAChE is specific for acetylcholine, and only one substrate molecule can occupy the active site at a time.

Acetylcholine is the substrate for AChEAChE, and since the shape and charge of the active site is specific for acetylcholine, only one substrate molecule can occupy the active site at a time. Therefore, at high concentrations of acetylcholine, AChEAChE becomes saturated with substrate. When an enzyme is saturated with substrate, adding more substrate to the solution will not lead to an observable increase in the reaction rate.

A researcher proposes a model to explain how enzyme-substrate interactions determine enzyme specificity. The model is based on the idea that substrate molecules form favorable interactions with the amino acid side chains in an enzyme's active site.

Based on the model, which of the following statements best explains an enzyme's specificity for a particular substrate molecule?

A.) A hydrophilic molecule interacts with nonpolar side chains in the enzyme's active site

B.) A hydrophobic molecule interacts with polar side chains in the enzyme's active site.

C.) A molecule with positive charges interacts with positively charged side chains in the enzyme's active site.

D.) A molecule with negative charges interacts with positively charged side chains in the enzyme's active site.

D.) A molecule with negative charges interacts with positively charged side chains in the enzyme's active site.

Because opposite charges attract, a molecule with negative charges will form favorable interactions with positively charged side chains in an enzyme's active site. Based on the model, the favorable interactions helps explain the enzyme's specificity for the molecule as a substrate.

Catalase is an enzyme found in yeast cells that facilitates the chemical breakdown of hydrogen peroxide to water and oxygen gas. An experiment was conducted to determine the effect of pH on catalase function. Five buffer solutions of varying pH (2, 4, 6, 8, and 10) were prepared and added to separate test tubes. Hydrogen peroxide (H2O2) was added to each test tube. Yeast was added, and the reactions were timed. After 1 minute the amount of oxygen gas released was determined by measuring the foam layer produced in each test tube. Figure 1 illustrates the experimental setup

A set of five additional test tubes were prepared and used as controls. Which of the following best describes the contents expected to be contained in one of the five control test tubes?

A.) pH 4 buffer solution and hydrogen peroxide only

B.) All five pH buffer solutions combined and hydrogen peroxide only

C.) Water, hydrogen peroxide, and yeast

D.) Water and yeast only

A.) pH 4 buffer solution and hydrogen peroxide only

Since the experiment is studying the effect of pH on catalase in yeast, the control set should determine what would happen without yeast present. Each test tube in the control set should contain hydrogen peroxide and one of the pH solutions.

Researchers investigated the effect of urea on the three-dimensional structure of a certain enzyme. The researchers dissolved the enzyme in an aqueous buffer solution and added urea to the solution. The enzyme did not appear to have a secondary or tertiary structure. The researchers carefully removed the urea from the solution and determined that the enzyme had the original secondary and tertiary structure again.

Based on the results of the experiment, which of the following statements best predicts the effect of urea on the enzyme's function?

A.) Function will be disrupted by adding the urea and regained by removing the urea.

B.) Function will be disrupted by adding the urea, but it will not be regained by removing the urea.

C.) Function will be gained by adding the urea and disrupted by removing the urea.

D.) Function will be unaffected by the addition and removal of the urea.

A.) Function will be disrupted by adding the urea and regained by removing the urea.

Based on the information, adding the urea denatures the enzyme, which will disrupt the enzyme's function by disrupting the active site. In contrast, removing the urea causes the enzyme to refold, which will restore the active site and the enzyme's function.

A researcher claims that the incorporation of carbon dioxide into organic molecules during photosynthesis does not violate the second law of thermodynamics.

Which of the following statements best helps justify the researcher's claim?

A.) Organisms contain enzymes that lower the activation energies of specific chemical reactions.

B.) An ecosystem is formed by the interaction of a community of organisms with their surrounding environment.

C.) Photosynthetic organisms use the organic molecules produced during photosynthesis for growth and repair.

D.) The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

D.) The total system that includes photosynthetic organisms and the Sun becomes less ordered over time.

Because the total system that includes photosynthetic organisms and the Sun becomes less ordered over time, the incorporation of carbon dioxide molecules into organic molecules that occurs during photosynthesis does not violate the second law of thermodynamics.

A researcher claims that genetic variation provides organisms with the ability to survive and reproduce in different environments. To support the claim, the researcher makes the following observation: bacteria that contain plasmids (small DNA molecules) are resistant to a wider range of antibiotics than are bacteria that contain no plasmids.

Which of the following statements best establishes a connection between the observation and the researcher's claim?

A.) Some antibiotics inhibit the synthesis of bacterial cell walls.

B.) Some antibiotics inhibit protein synthesis in bacteria cells.

C.) Some plasmids cannot exist in a bacterial cell with certain other plasmids.

D.) Some plasmids contain antibiotic resistance genes.

D.) Some plasmids contain antibiotic resistance genes.

Because some plasmids contain antibiotic resistance genes, bacteria that contain plasmids are more likely to be resistant to antibiotics than are bacteria that do not contain plasmids. The observation is evidence that genetic variation in the form of plasmids provides bacteria with the ability to survive and reproduce in different environments.

Phycobiliproteins are a complex of accessory pigments and proteins found in cyanobacteria but not in green algae. A researcher claims that the phycobiliprotein pigments in cyanobacteria allow the cyanobacteria to survive in certain aquatic niches better than green algae can.

Which of the following statements best justifies the researcher's claim?

A.) The additional pigments allow the cyanobacteria to store light energy so that it can be used at night to continue photosynthesis.

B.) The additional pigments block light and prevent it from reaching photosynthetic organisms at greater depths, so no photosynthetic organisms can live below the surface waters containing cyanobacteria.

C.) The additional pigments require energy and cellular resources to produce, so they can be used as an energy source during times of insufficient light.

D.) The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.

D.) The additional pigments absorb light at wavelengths that green algae cannot absorb; this may allow cyanobacteria to capture more light energy for photosynthesis than green algae can in certain areas.

Since the phycobiliprotein pigments absorb light wavelengths not absorbed by green algae, cyanobacteria are able to better perform photosynthesis and survive in areas where there is insufficient light at the needed frequencies for green algae to survive.

A researcher claims that budding yeast are able to survive in different environments because they produce enzymes that allow them to use different molecules as sources of matter and energy.

Which of the following statements best helps justify the researcher's claim by providing a relevant example?

A.) Yeast cells produce protein kinases, which are enzymes that catalyze the transfer of phosphate groups from ATPATP to protein substrates

B.) Yeast cells produce DNADNA polymerases, which are enzymes that catalyze the conversion of free nucleotides into strands of DNADNA.

C.) Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.

D.) Yeast cells produce catalase, which is an enzyme that catalyzes the conversion of hydrogen peroxide into water and oxygen gas.

C.) Yeast cells produce invertase, which is an enzyme that catalyzes the conversion of the disaccharide sucrose into glucose and fructose.

The disaccharide sucrose is not transported efficiently into yeast cells. By producing the enzyme invertase, budding yeast can use the sucrose, glucose, and fructose in the surrounding environment as sources of matter and energy. As such, the production of invertase by budding yeast is a relevant example that will help justify the researcher's claim.

ATP can be termed the universal energy currency in life because it:

A.) enables cells to disobey the first law of thermodynamics

B.) enables cells to disobey the second law of thermodynamics

C.) releases energy as heat when it undergoes hydrolysis

D.) traps energy released from the oxidation of different classes of food molecules

D.) traps energy released from the oxidation of different classes of food molecules

Which of the following statements correctly describes the entropy of the universe, as captured by the second law of thermodynamics?

A.) the total entropy of the universe fluxuates between being high and low

B.) the total entropy of the universe remains constant

C.) the total entropy of the universe is continually decreasing

D.) the total entropy of the universe is continually increasing

D.) the total entropy of the universe is continually increasing

Which statement is not true about catabolic processes?

A.) they break down larger molecules into smaller ones

B.) they decompose carbohydrates, lipids, and proteins

C.) water molecules separate bonds, resulting in smaller molecules

D.) dehydration synthesis is involved in catabolic processes

D.) dehydration synthesis is involved in catabolic processes

Enzymes function in chemical reactions to __________?

A.) lower the energy of activation needed to start the reaction

B.) acts as substrate molecules

C.) prevent the development of metabolic pathways

D.) keep reactants from interacting

A.) lower the energy of activation needed to start the reaction

In an endergonic reaction,

A.) the reactants contain less free energy than the products

B.) the reactants contain more free energy than the products

C.) no activation energy is required

D.) catalysis cannot occur

E.) substrates outnumber enzymes

A.) the reactants contain less free energy than the products

Energy in biological systems is primarily

A.) electrical

B.) chemical

C.) radiant

D.) kinetic

B.) chemical

Metabolism is considered the "total chemical reactions occuring within an organism". These chemical reactions may be linked into "pathways". Which of the following statements best characterizes anabolic and catabolic pathways?

A.) anabolic pathways break down molecules while catabolic pathways synthesize molecules

B.) anabolic pathways synthesise molecules while catabolic pathways break down molecules

C.) both pathways synthesize molecules but do so in different ways

D.) both pathways break down molecules but do so in a different way

B.) anabolic pathways synthesise molecules while catabolic pathways break down molecules

Energy possesed by a body due to its position is called

A.) heat energy

B.) kinetic energy

C.) potential energy

D.) chemical energy

C.) potential energy

Which of the following occurs when one rides a bicycle?

A.) the bicycle had kinetic energy by virtue of its motion

B.) the kinetic energy is obtained fro the conversion of chemical energy stored int he rider's muscles

C.) the energy for riding the bicycle was originally generated in nuclear reactions in the sun

D. All of the above

D. All of the above

Which of the following terms describes a reaction in which there is a net transfer of energy from a system to its surroundings - that is, where more energy is released by bond formation than is consumed by bond cleavage?

A.) exothermic

B.) endothermic

C.) kinetic

D. exchange

A.) exothermic

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

A.) the energy content of an organism is constant

B.) the organism ultimately must obtain all necessary energy for life from its environment

C.) the entropy of an organism decreases with time as the organism grows in complexity

D.) organisms grow by converting energy into organic matter

E.) life does not obey the first law of thermodynamics

B.) the organism ultimately must obtain all necessary energy for life from its environment

Which of the following types of reactions would decrease the entropy within a cell?

A.) anabolic reactions

B.) hydrolysis

C.) respiration

D.) digestion

E.) catabolic reactions

A.) anabolic reactions

which of the following is an example of potential rather than kinetic energy?

A.) the muscle contractions of a person mowing grass

B.) water rushing over Niagara Falls

C.) light flashes emitted by a firefly

D.) a molecule of glucose

E.) the flight of an insect foraging for food

D.) a molecule of glucose

Which of the following is true concerning catabolic pathways?

A.) They combine molecules into more energy-rich molecules

B.) they supply energy, primarily in the form of ATP, for the cell's work

C.) they are endergonic

D. they are spontaneous and do not need enzyme catalysis

E.) thay build up complex molecules such as protein from simpler compunds

B.) they supply energy, primarily in the form of ATP, for the cell's work

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

A.) the starch solution has less free energy than the sugar solution

B.) the hydrolysis of starch into sugar is endergonic

C. the activation energy barrier for this reaction cannot easily be surmounted at room temperature

D.) starch cannot by hydrolyzed in the presence of so much water

E.) starch hydrolysis is nonspontaneous

C. the activation energy barrier for this reaction cannot easily be surmounted at room temperature

During a lab experiment, you discover that an enzyme-catalyzed reaction has a delta G of -20 kcal/mol. If you double the amount of enzyme in that reaction, what will the delta G for the new reaction?

A. -40

B.) -20

C.) 0

D.) 20

E.) 40

B.) -20

mutations that result in single amino acid substitutions in an enzyme

A.) cannot affect the activity or properties of the enzyme

B.) will almost always destroy the activity of the enzyme

C.) will often change the substrate specificity of the enzyme

D.) may change the enzyme's optimal temperature or optimal pH

E.) may, in rare cases, cause the enzyme to run reactions in reverse

D.) may change the enzyme's optimal temperature or optimal pH

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

A.) denaturation of the enzyme

B.) allosteric regulation

C.) competitive inhibition

D. saturation of the enzyme activity

E.) insufficient cofactors

C.) competitive inhibition

The enzymes of the transition reaction and Citric Acid cycle are located in the

A.) cytosol

B.) matrix

C.) thylakoid

D.) cristae

B.) matrix

The general term used for the anaerobic degradation of glucose to obtain energy is

A.) anabolism

B.) oxidation

C.) fermentation

D.) metabolism

C.) fermentation

glycolysis converts

A.) glucose into pyruvate

B.) glucose into phosphoenolpyruvate

C.) fructose into pyruvate

D.) fructose into phosphoenolpyruvate

A.) glucose into pyruvate

during aerobic cellular respiration, which molecule originates from the digestive system?

A. oxygen

B.) Carbon Dioxide

C. ATP

D.) water

E.) glucose

E.) glucose

during chemiosmosis in aerobic respiration, protons are pumped

A.) out of the cell

B.) out of the mitochondria into the cytoplasm

C.) out of the mitochondrial matrix into the outer compartment of the mitochondria

D.) out of the cell cytoplasm and into the matrix of the mitochondria

E.) out of the nucleus and into the mitochondria

C.) out of the mitochondrial matrix into the outer compartment of the mitochondria

the electrons that enter the electron transport system are carried there by ________

A.) NADH

B.) FADH2

C.) ATP

D.) both A and B

D.) both A and B

you are growing animal cells in culture and notice that the cells do not look very healthy. After some checking, you discover that there is a lot of lactic acid in the culture fluid. What is probably wrong with this culture?

A.) too much sugar is in the medium

B.) Ethyl alcohol is being produced in excess

C.) The cells do not have enough oxygen

D.) the cells have too much oxygen

C.) The cells do not have enough oxygen

pyruvic acid in alcoholic fermentation reduced to acetaldehyde which further reduces into

A.) CO2

B.) methanol

C.) ethanol

D.) methane

C.) ethanol

in any oxidation-reduction reaction, the total number of electrons gained is

A.) equal to the total number of electrons lost

B.) less than the total number of electrons lost

C.) greater than the total n umber of electrons lost

D.) unrelated to the total number of electrons lost

A.) equal to the total number of electrons lost

an example of anaerbic fermentation would be

A.) production of sulfates from H2S

B.) production of methane by methanogens

C.) glycolysis by purple bacteria

D.) catabolism

B.) production of methane by methanogens

What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

catabolic pathways

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O)

the ATP made during glycolysis is generated by

substrate-level phosphorylation

How many oxygen molecules (O2) are required each time a molecule of glucose (C6H12O6) is completely oxidized to carbon dioxide and water via aerobic respiration?

6 O2

substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by glycolysis?

100%

in glycolysis, for each molecule of glucose oxidized to pyruvate

two molecules of ATP are used, and four molecules of ATP are produced

Which kind of metabolic poison would most directly interfere with glycolysis?

an agent that closely mimics the structure of glucose but it is not metabolized

A young dog had never had much energy. He is brought to a vet who discovers that the dog's mitochondria can use only fatty acids and amino acids for respiration, and his cells produce more lactate than normal. What is the dog's condition?

his mitochondria lack the transport protein that moves pyruvate across the outer mitochondrial membrane

where are the proteins of the ETC located?

mitochondrial inner membrane

Inside an active mitochondrion, most electrons follow which pathway?

Citric Acid Cycle -> NADH -> ETC -> O2

In chemiosmosis, what is the most direct source of energy that is used to convert ADP + Pi to ATP?

energy released from movement of protons through ATP synthase, down their electrochemical gradient

the synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient is an example of

an endergonic reaction coupled to an exergonic reaction

If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately how many ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to carbon dioxide and water?

14

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?

it increases the surface for oxidative phosphorylation

Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport of protons across the membrane. What will occur in the brown fat cells when they produce thermogenin?

ATP synthesis will decrease, and heat generation will increase

in a mitochondrion, if the matrix ATP concentration is high, and the intermembrane space proton concentration is too low to generate sufficient proton-motive force, then

ATP synthase will hydrolyze ATP and pump protons into the intermembrane space

In vertebrate animals, brown fat tissue's color is due to abundant blood vessels and capillaries. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue?

to regulate temperature by converting most of the energy from NADH oxidation to heat

What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?

glucose

One function of both alcohol fermentation and lactic acid fermentation is to

oxidize NADH to NAD+

An organism is discovered that thrives both in the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism

is an anaerobic organism

which statement best supports the hypothesis that glycolysis is an ancient metabolic pathwaythat originated before the last universal common ancestor of life on Earth?

glycolysis is widespread and found in the domains Bacteria, Archaea, and Eukarya

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

it does not involve organelles or specialized structures, does not require O2, and is present in most organisms

A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells?

the mutant yeast will be unable to grow anaerobically

You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body?

it was released as CO2 and H2O

Starting with one molecule of isocitrate and ending with fumarate, what is the maximum number of ATP molecules that could be made through substrate-level phosphorylation?
A) 1
B) 2
C) 11
D) 12
E) 24

A.) 1

Carbon skeletons for amino acid biosynthesis are supplied by intermediates of the citric acid cycle. Which intermediate would supply the carbon skeleton for synthesis of a five-carbon amino acid?
A) succinate
B) malate
C) citrate
D) α-ketoglutarate
E) isocitrate

D) α-ketoglutarate

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown in the accompanying figure?

oxaloacetate will accumulate and citric acid will decrease

For the following questions: Graphs I-IV depict the effect of pH on the activity of four different hydrolytic enzymes.
Enzymes with their highest activity at an alkaline (basic) pH are represented by which of the following graphs?
A
I only
B
II only
C
III only
D
I and III only
E
I and IV only

B
II only

For the following questions: Graphs I-IV depict the effect of pH on the activity of four different hydrolytic enzymes.
Graphs representing enzymes sensitive to changes in pH include which of the following?
A
I only
B
IV only
C
II and III only
D
III and IV only
E
I, II, and III only

E
I, II, and III only

The diagram below shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction.
Which of the following questions can best be answered by the diagram?
A
Does the addition of an enzyme reduce the activation energy required for a reaction?
B
Does the addition of an enzyme result in the formation of covalent bonds?
C
Does the addition of an enzyme produce a greater amount of products?
D
Does the addition of an enzyme change the pathway for the reaction?

A
Does the addition of an enzyme reduce the activation energy required for a reaction?

A scientist determined the rate of an enzyme-catalyzed reaction by measuring the amount of product formed over time. The following curve was generated from the data collected.
During which time interval is the reaction rate lowest?
A
0-1 minute
B
1-2 minutes
C
2-3 minutes
D
3-4 minutes
E
4-5 minutes

E
4-5 minutes

For following group of questions first study the description of the data and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
To study the actions of the enzyme catalase on hydrogen peroxide, students performed the following experiment. Catalase was extracted from potatoes by blending raw potatoes in a blender with cold distilled water. The filtrate was stored on ice. The following hydrogen peroxide solutions were made: 1 percent, 5 percent, 10 percent, and 15 percent. Filter paper disks were soaked in the catalase filtrate and dropped into beakers containing the various solutions. The activity of the enzyme was measured by the amount of time it took for the disks to float to the surface of the solution on the bubbles produced by the reaction. The following data were obtained.

Which of the following best describes why the disks rose to the surface faster in the more concentrated hydrogen peroxide solutions?
A
There was more enzyme present in the more concentrated solutions.
B
A greater amount of heat was generated in the more concentrated solutions.
C
The more concentrated solutions lowered the activation energy of the reaction.
D
The higher substrate concentrations in the more concentrated solutions speeded the reaction.
E
The density of the water was lower in the more concentrated solutions.

D
The higher substrate concentrations in the more concentrated solutions speeded the reaction.

For following group of questions first study the description of the data and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
To study the actions of the enzyme catalase on hydrogen peroxide, students performed the following experiment. Catalase was extracted from potatoes by blending raw potatoes in a blender with cold distilled water. The filtrate was stored on ice. The following hydrogen peroxide solutions were made: 1 percent, 5 percent, 10 percent, and 15 percent. Filter paper disks were soaked in the catalase filtrate and dropped into beakers containing the various solutions. The activity of the enzyme was measured by the amount of time it took for the disks to float to the surface of the solution on the bubbles produced by the reaction. The following data were obtained.

Which of the following experimental designs should the students use as a control for the experiment?
A
Place a catalase-soaked disk in a beaker of water.
B
Drop the disks from different heights into the solution.
C
Poke the floating disks back down to the bottom of the beaker and retime the rise of the disks.
D
Shake the beakers during the time the disks are rising.
E
Dip the disks in the 5% solution before putting them in any other solution.

A
Place a catalase-soaked disk in a beaker of water.

For following group of questions first study the description of the data and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
To study the actions of the enzyme catalase on hydrogen peroxide, students performed the following experiment. Catalase was extracted from potatoes by blending raw potatoes in a blender with cold distilled water. The filtrate was stored on ice. The following hydrogen peroxide solutions were made: 1 percent, 5 percent, 10 percent, and 15 percent. Filter paper disks were soaked in the catalase filtrate and dropped into beakers containing the various solutions. The activity of the enzyme was measured by the amount of time it took for the disks to float to the surface of the solution on the bubbles produced by the reaction. The following data were obtained.

Which of the following best describes why ice was used during this experiment?
A
To increase the activity of the enzyme
B
To retard the breakdown of the catalase
C
To purge the solution of excess air trapped during blending
D
To slow the catalase molecules to increase the probability of contact with the hydrogen peroxide molecules
E
To increase the size of the active site on the enzyme

B
To retard the breakdown of the catalase

The following questions refer to an experiment that is set up to determine the relative volume of O2 consumed by germinating and nongerminating (dry) pea seeds at two different temperatures. The change in volume is detected by using a respirometer over a given period of time. The data are given below.
The rate of oxygen consumption in germinating pea seeds at 26ºC is
A
0.05 mL / min
B
0.25 mL / min
C
0.50 mL / min
D
0.75 mL / min
E
1.00 mL / min

A
0.05 mL / min

A student placed 20 tobacco seeds of the same species on moist paper towels in each of two petri dishes. Dish A was wrapped completely in an opaque cover to exclude all light. Dish B was not wrapped. The dishes were placed equidistant from a light source set to a cycle of 14 hours of light and 10 hours of dark. All other conditions were the same for both dishes. The dishes were examined after 7 days, and the opaque cover was permanently removed from dish A. Both dishes were returned to the light and examined again at 14 days. The following data were obtained.

Additional observations were made on day 21, and no yellow-leaved seedlings were found alive in either dish. This is most likely because
A
yellow-leaved seedlings were unable to absorb water from the paper towels
B
taller green-leaved seedlings blocked the light and prevented photosynthesis
C
yellow-leaved seedlings were unable to convert light energy to chemical energy
D
a higher rate of respiration in yellow-leaved seedlings depleted their stored nutrients
Related Content & Skills

C
yellow-leaved seedlings were unable to convert light energy to chemical energy

For following group of questions first study the description of the situation and diagrams and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below.

The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device.

Based on the data shown, changes in the light intensity resulted in changes in the rate of which of the following processes?
A
Excretion
B
Photosynthesis
C
Respiration
D
Translation
E
Transcription

B
Photosynthesis

For following group of questions first study the description of the situation and diagrams and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.
A student studied the effects of light intensity on oxygen production in green algae. The algae were suspended in water inside a sealed glass jar, and the jar was placed into a constant-temperature, lightproof box containing a light source. A probe was inserted into the jar to record the concentration of oxygen. The probe was connected to a recording device. The setup is shown below.

The student decreased the intensity of the light hourly and recorded the corresponding changes in oxygen concentration. The graph below shows the results from the recording device.

The rate of oxygen production equaled the rate of oxygen consumption during which of the following time periods?
A
G to H
B
H to I
C
I to J
D
J to K
E
G to K

D
J to K

Which of the following questions will best direct an investigation of the mechanism of ATP synthase?
A
What is the source of the inorganic phosphate that is used to generate ATP from ADP?
B
Is the phosphorylation of ADP by ATP synthase dependent on the formation of a proton gradient?
C
Can ATP synthase use the energy released by phosphorylation of ADP to pump protons against a concentration gradient?
D
Can oxidative phosphorylation be uncoupled from the electron transport chain?

B
Is the phosphorylation of ADP by ATP synthase dependent on the formation of a proton gradient?

The figure above shows an organelle typically found in eukaryotic cells. Which of the following best describes the function of the double membrane system of this organelle?
A
The outer membrane allows the transport of all molecules into the intermembrane space, while the inner membrane serves as the regulatory boundary.
B
The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix.
C
The outer membrane contains transport proteins that establish a sodium ion concentration gradient used for ATP production, while the inner membrane contains transport proteins that establish a hydrogen ion concentration gradient used for glucose production.
D
The toxins and wastes entering a cell cross the outer membrane and are detoxified by digestive enzymes stored within the intermembrane space.

B
The inner membrane has specialized proteins that create a hydrogen ion concentration gradient between the intermembrane space and the matrix.

What most likely causes the trends in oxygen concentration shown in the graph above?
A
The water becomes colder at night and thus holds more oxygen.
B
Respiration in most organisms increases at night.
C
More organisms are respiring at night than during the day.
D
Photosynthesis produces more oxygen than is consumed by respiration during the day.

D
Photosynthesis produces more oxygen than is consumed by respiration during the day.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it.
The following questions refer to the following information and graph.
The data presented in the figure below are measurements of the rate of oxygen consumption at differing body masses in a species of fish. Each point represents measurements from a different fish. Measurements were taken at different temperatures. (○= 10°C,●= 15°C, □= 20°C, ■= 25°C.)




The fact that each line on the graph rises from left to right means that
A
higher temperatures produce higher rates of metabolism
B
there were more large fish in the samples taken at high temperatures
C
larger fish consume more oxygen than smaller fish at all four temperatures
D
when measurements are taken for larger fish late in the day, observed values are higher
E
larger fish prefer to live at higher temperatures than do smaller fish

C
larger fish consume more oxygen than smaller fish at all four temperatures

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it.



A tissue culture of vertebrate muscle was provided with a constant excess supply of glucose under anaerobic conditions starting at time zero and the amounts of pyruvic acid and ATP produced were measured. The solid line in the graph above represents the pyruvic acid produced in moles per liter per minute. ATP levels were also found to be highest at points A and C, lowest at B and D. A second culture was set up under the same conditions, except that substance X was added, and the results are indicated by the dotted line.
Which of the following best accounts for the shape of the solid line between points A and D?
A
After ten minutes the cellular enzymes became ineffective.
B
Respiration became uncontrolled.
C
ATP acted as an allosteric inhibitor on one or more of the enzymes.
D
The measurements of pyruvic acid were unreliable.
E
The cells required more glucose than was being provided.
Related Content & Skills
Topic3.3
SkillSkill 4.B

C
ATP acted as an allosteric inhibitor on one or more of the enzymes.

Directions: Each group of questions below concerns an experimental or laboratory situation or data. In each case, first study the description of the situation or data. Then choose the one best answer to each question following it.



A tissue culture of vertebrate muscle was provided with a constant excess supply of glucose under anaerobic conditions starting at time zero and the amounts of pyruvic acid and ATP produced were measured. The solid line in the graph above represents the pyruvic acid produced in moles per liter per minute. ATP levels were also found to be highest at points A and C, lowest at B and D. A second culture was set up under the same conditions, except that substance X was added, and the results are indicated by the dotted line.
It is most reasonable to hypothesize that, in the breakdown of glucose, substance X is
A
an activator
B
an inhibitor
C
a substrate
D
a coenzyme
E
a cofactor

B
an inhibitor

The chemical reaction for photosynthesis is
6 CO2 + 12 H2O + light energy → C6H12O6 + 6 O2 + 6 H2O
If the input water is labeled with a radioactive isotope of oxygen, 18O, then the oxygen gas released as the reaction proceeds is also labeled with 18O. Which of the following is the most likely explanation?
A
During the light reactions of photosynthesis, water is split, the hydrogen atoms combine with the CO2, and oxygen gas is released.
B
During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.
C
During the Calvin cycle, water is split, regenerating NADPH from NADP+, and oxygen gas is released.
D
During the Calvin cycle, water is split, the hydrogen atoms are added to intermediates of sugar synthesis, and oxygen gas is released.

B
During the light reactions of photosynthesis, water is split, removing electrons and protons, and oxygen gas is released.

An experiment to measure the rate of respiration in crickets and mice at 10o C and 25o C was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O2 consumed per gram of organism over several five-minute trials, and the following data were obtained.

During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following?
A
A substance that removes carbon dioxide gas
B
A plant to produce oxygen
C
A glucose reserve
D
A valve to release excess water

A
A substance that removes carbon dioxide gas

An experiment to measure the rate of respiration in crickets and mice at 10o C and 25o C was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O2 consumed per gram of organism over several five-minute trials, and the following data were obtained.

According to the data, the mice at 10o C demonstrated greater oxygen consumption per gram of tissue than did the mice at 25o C. This is most likely explained by which of the following statements?
A
The mice at 10o C had a higher rate of ATP production than the mice at 25o C.
B
The mice at 10o C had a lower metabolic rate than the mice at 25o C.
C
The mice at 25o C weighed less than the mice at 10o C.
D
The mice at 25o C were more active than the mice at 10o C.

A
The mice at 10o C had a higher rate of ATP production than the mice at 25o C.

An experiment to measure the rate of respiration in crickets and mice at 10oC and 25oC was performed using a respirometer, an apparatus that measures changes in gas volume. Respiration was measured in mL of O2 consumed per gram of organism over several five-minute trials and the following data were obtained.

During aerobic cellular respiration, oxygen gas is consumed at the same rate as carbon dioxide gas is produced. In order to provide accurate volumetric measurements of oxygen gas consumption, the experimental setup should include which of the following?
A
A substance that removes carbon dioxide gas
B
A plant to produce oxygen
C
A glucose reserve
D
A valve to release excess water

A
A substance that removes carbon dioxide gas

A respirometer is a container used to measure the amount of oxygen consumed by an organism. A respirometer was used to determine how environmental temperature affects the uptake of oxygen in one 300-gram rat and one 50-gram mouse. The results of this experiment are shown on the graph below.



Which of the following hypotheses is best supported by the results of this experiment?
A
Metabolic rate per gram of tissue is higher in smaller mammals.
B
Metabolic rate per gram of tissue is not related to body mass.
C
Mice produce less CO2 per gram of tissue than do rats.
D
Rats consume more food per gram of tissue than do mice.
E
Rats lose more heat per gram of tissue than do mice.

A
Metabolic rate per gram of tissue is higher in smaller mammals.

A respirometer is a container used to measure the amount of oxygen consumed by an organism. A respirometer was used to determine how environmental temperature affects the uptake of oxygen in one 300-gram rat and one 50-gram mouse. The results of this experiment are shown on the graph below.
Which of the following would most adversely affect the validity of this experiment?
A
Large variation in metabolic rates between individuals of a species
B
Repeating the experiment several times
C
Using a brown rat and a white mouse
D
Using a thermometer that consistently read 2°C too low
E
Using a scale that consistently indicated 2 grams too much

A
Large variation in metabolic rates between individuals of a species

A scientist determined the rate of an enzyme-catalyzed reaction by measuring the amount of product formed over time. The following curve was generated from the data collected.

The rate of the reaction could also be determined by
A
measuring the change in the amount of enzyme
B
measuring the change in the amount of substrate
C
measuring the change in salt concentration
D
adding more substrate
E
adding more enzyme

B
measuring the change in the amount of substrate

Figure 1. Reaction catalyzed by phosphofructokinase (PFK) during glycolysis
Phosphofructokinase (PFK) is an enzyme that catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate during glycolysis, as represented in Figure 1.
PFK can be allosterically inhibited by ATP at high concentrations. Which of the following is the benefit of regulating glycolysis by the concentration of ATP?
A
Glycolysis proceeds when the intracellular concentration of ATP is low, which provides ATP to drive cellular reactions.
B
Glycolysis proceeds when the intracellular concentration of ATP is high and the cell stores ATP for future use.
C
Glycolysis is inhibited when the intracellular concentration of ATP is low because PFK requires ATP as a substrate for the reaction it catalyzes.
D
Glycolysis is inhibited when the intracellular concentration of ATP is high because ATP will compete with fructose 1,6-bisphosphate for binding to the active site on the enzyme.

A
Glycolysis proceeds when the intracellular concentration of ATP is low, which provides ATP to drive cellular reactions.

Enzymes are often referred to as being "highly specific" (also referred to as enzyme specificity), meaning...

a. Each enzyme found in the body is unique and there are no other enzymes of that kind
b. The enzyme will only work in a specific environment
c. Only a specific substrate will bind to its active site
d. All substrates will bind to its active site except one type of substrate
e. Enzymes are found only in certain parts of the body

C

In what aspect is the "lock and key" model incorrect?

a. It assumed the active site never changed
b. It assumed the active site changes when a substrate entered the active site
c. It assumed that enzymes only accepted one specific substrate
d. It assumed that enzymes accepted many different substrates
e. It assumed that the active site never change and that enzymes accepted many different substrates

D

Hydrolysis and cellular respiration are examples of what types of reactions?

a. Catabolic & Anabolic
b. Exergonic & Endergonic
c. Catabolic & Exergonic
d. Anabolic & Endergonic
e. Catabolic & Endergonic

C

What types of reactions have a net use of energy?

a. Catabolic & Anabolic
b. Exergonic & Endergonic
c. Catabolic & Exergonic
d. Anabolic & Endergonic
e. Catabolic & Endergonic

D

What type of inhibitor binds to the active site?

a. Competitive
b. Non-competitive
c. Active
d. Substrate
e. Protein

A

What type of inhibitor lowers the maximum rate of reaction?

a. Competitive
b. Non-competitive
c. Active
d. Substrate
e. Protein

B

How does ADP turn into ATP?

a. By adding an adenosine
b. By removing an adenosine
c. By adding a phosphate
d. By removing a phosphate
e. By adding an adenosine and removing a phosphate

C

The folded inner membrane in mitochondria increases its __________

a. Outer membrane size
b. Ability to get identified as mitochondria
c. Organelle size
d. Volume
e. Surface Area

E

Why do highly active cells have large amounts of mitochondria?

a. It increases the amount of ATP produced
b. It decreases the amount of ATP produced
c. It increases the amount of nutrients absorbed into the cell
d. It decreases the amount of nutrients absorbed into the cell
e. There is no significance to the large amounts of mitochondria as the same amount of ATP will be produced

A

What is the ultimate source of energy?

a. Thermal energy
b. Radiant energy
c. Electrical energy
d. Solar energy
e. Chemical Energy

D

Where does glycolysis occur?

a. Outer membrane of mitochondria
b. Inner membrane of mitochondria (Cristae)
c. Cytoplasm
d. Cellular membrane
e. Cytoskeleton

C