BI 218: Cell & Molecular Biology Exam 1 Chapters 1 & 3

Which is the smallest object that can be seen using an electron microscope? -An individual atom -An individual electron -An individual large organelle -An individual molecule -An individual nanometer

Individual Molecule

Which of these cannot be resolved with a conventional light microscope? -Bacterium -Embryonic cell -Mitochondrion -Nucleus -Ribosome

Ribosome

Which is NOT a function of proteins? -To act as molecular motors -To catalyze chemical reactions -To encase certain viruses -To encode genetic information -To provide cells with structural support

To encode genetic information

The breakdown of polymers: is associated with a negative change in free energy. is energetically unfavorable. occurs without the need of enzymes

is associated with a negative change in free energy

Like the differentiated cells in an individual plant or animal, all bacteria have the same DNA. False True

False

One thing all cells have in common is an ability to colonize any environment on Earth. False True

False

Organisms that have inherited their genetic instructions from a common ancestor share the same DNA. -False -True

False

The cytoskeleton is one of the few permanent fixtures in the cell. False True

False

The formation of ATP can be coupled to energetically unfavorable reactions to allow them to proceed. False True

False

One drawback of light microscopy is that it: -can only be used to view samples that are sliced very thinly. -cannot be used to view a whole cell or organism. -cannot be used to view living cells. -cannot be used to view structures smaller than a bacterium. -requires the use of fluorescent probes.

-cannot be used to view structures smaller than a bacterium.

In a chemical reaction, substrate molecule A is broken down to form one molecule of product B and one molecule of product C. The equilibrium constant, K, for this reaction is 0.5. If we start with a mixture containing only substrate A at a concentration of 1 M, what will be the concentration of A when the reaction reaches equilibrium? 0.125 M 0.25 M 0.333 M 0.5 M 0.667 M

0.5 M

For a reaction at 37°C, a 1.42 kcal/mole decrease in ΔG, changes K by a factor of: 10-1. 10. 102. 103.

10

The free-energy change, ΔG, for the chemical reaction A → B is 0 kcal/mole at 37°C when the concentrations of A and B are 10 M and 0.1 M, respectively. What is the free-energy change for the reaction when the concentrations of A and B are 0.01 M and 1 M, respectively? Remember that ΔG° = -1.42 log K. + 2.84 kcal/mole − 2.84 kcal/mole + 4.00 kcal/mole + 5.68 kcal/mole − 5.68 kcal/mole

5.68 kcal/mole

What do eukaryotic cells have that prokaryotes lack? A cell wall A means of generating their own energy A nucleus and other internal organelles Nucleic acids Ribosomes

A nucleus and other internal organelles

When NADH or NADPH transfer electrons to a donor molecule, the donor becomes reduced and the activated carriers are oxidized (to NAD+ or NADP+, respectively). What else happens during this reaction? A molecule of water is released into the solution. A phosphate group is transferred to the donor molecule. A proton is released into the solution. A proton is taken up by the carrier. A proton is taken up by the donor molecule.

A proton is taken up by the donor molecule.

Which of the following is a model plant used by scientists? A. artemisifolia A. thaliana C. elegans H. floresiensis S. cerevisiae

A. thaliana

For some biosynthetic reactions, such as the synthesis of nucleic acids, the energy supplied by the hydrolysis of ATP to ADP and Pi is insufficient to drive the reaction forward. How can such reactions occur inside cells? ATP is hydrolyzed to AMP and Pi in two successive hydrolysis reactions. Nucleic acid synthesis is coupled to nucleic acid breakdown. Nucleic acid synthesis is driven by the hydrolysis of nucleoside monophosphates. They are coupled directly to the breakdown of glucose. They are coupled to the hydrolysis of two molecules of ATP to ADP and Pi.

ATP is hydrolyzed to AMP and Pi in two successive hydrolysis reactions

The ΔG° of the hydrolysis reaction of ATP is −7.3 kcal/mole, but in a cell the actual ΔG is much more negative because: ATP is much higher in concentration than the products ADP and Pi. the concentration of ATP is much lower than the concentrations of its hydrolysis products, ADP and Pi.

ATP is much higher in concentration than the products ADP and Pi.

What is the term for the extra energy boost required to initiate an energetically favorable reaction? Activation energy Free energy Kinetic energy Positive energy Potential energy

Activation Energy

What is the cell theory? -All cells are formed by the growth and division of existing cells. -All cells can be seen using a microscope. -All cells contain DNA. -All cells require a continual input of energy to sustain life. -All cells resemble the chambers occupied by monks.

All cells are formed by the growth and division of existing cells.

DNA contains nucleotide sequences that: (A) are seemingly dispensable. (B) code for functional RNA molecules. (C) code for proteins. (D) regulate gene activity. (E) All of the above.

All of the above

The study of which of these organisms has yielded insights into molecular mechanisms that are relevant to human cancer? (A) Bacteria (B) Mice (C) Worms (D) Yeast (E) All of the above (F) None of the above

All of the above

Which statement about enzymes is NOT true? An enzyme can force an energetically unfavorable reaction to take place inside the cell. Enzymes can help build highly ordered structures. Enzymes can speed up energetically favorable reactions. Enzymes reduce the activation energy required to initiate a spontaneous reaction.

An enzyme can force an energetically unfavorable reaction to take place inside the cell.

Reactions that use energy to drive the synthesis of molecules inside the cell are considered: anabolic. catabolic. diabolic. metabolic. nanobolic.

Anabolic

Which of the following are prokaryotes? Archaea and bacteria Archaea and protozoans Bacteria and fungi Monotremes and prototheria Viruses and microbes

Archaea and bacteria

How long ago is it estimated that the common ancestor for all of life existed? -Between 3.5 and 3.8 billion years ago -Between 3.5 and 3.8 million years ago -Between 3.5 and 3.8 trillion years ago -Between 350 and 380 thousand years ago -Between 3500 and 3800 years ago

Between 3.5 and 3.8 billion years ago

Which is not true of a reaction at chemical equilibrium?

Both the forward and reverse reactions have stopped.

Different molecules diffuse through the cytosol at different speeds. Which series represents the correct order in which molecules will diffuse from the fastest to the slowest? CO2, ribosome, succinate dehydrogenase, tyrosine CO2, tyrosine, succinate dehydrogenase, ribosome Ribosome, succinate dehydrogenase, tyrosine, CO2 Tyrosine, CO2, succinate dehydrogenase, ribosome Tyrosine, succinate dehydrogenase, ribosome, CO2

CO2, tyrosine, succinate dehydrogenase, ribosome

Antibiotics tend to target features that are unique to bacterial cells and absent from eukaryotic cells such as our own. Which of the following would present a safe target for a new antibiotic? The cell wall The endoplasmic reticulum The intermediate filaments The nuclear envelope The plasma membrane

Cell Wall

Which statement is NOT true of chloroplasts? Chloroplasts are present in essentially all eukaryotic cells and in certain photosynthetic bacteria. Chloroplasts are thought to have originated from bacteria. Chloroplasts contain their own DNA. Chloroplasts produce food molecules and generate oxygen. Each has an internal stack of membranes and is enclosed by two membranes.

Chloroplasts are present in essentially all eukaryotic cells and in certain photosynthetic bacteria.

The largest single compartment in most cells is: the cytosol. the endoplasmic reticulum. the Golgi apparatus. the mitochondrial matrix. the nucleus.

Cytosol

In plant cells, a tough cell wall takes the place of a cytoskeleton. False True

False

Which of the following results in increased disorder? Compressing a spring to a tense state Dissolving salt in water Joining two sugars to make a sucrose molecule Protein synthesis

Dissolving salt in water

Which statement is NOT true of E. coli? E. coli can be grown in the laboratory. E. coli is a model eukaryote. E. coli is a small, rod-shaped cell. E. coli normally lives in the gut of humans and other vertebrates. E. coli stores genetic information in the form of DNA.

E. coli is a model eukaryote

Which energy conversion characterizes photosynthesis? Electromagnetic (light) energy → chemical-bond energy Electromagnetic (light) energy → CO2 Electromagnetic (light) energy → heat energy Electromagnetic (light) energy → kinetic energy Electromagnetic (light) energy → oxidation energy

Electromagnetic (light) energy → chemical-bond energy

Which structure could NOT be seen using an electron microscope? -An individual cell -DNA -Electron -Plasma membrane -Ribosomes

Electron

What is the name of the process by which eukaryotic cells engulf material captured from an external medium? Cytokinesis Endocytosis Endomitosis Endosymbiosis Exocytosis

Endocytosis

Which of the following organelles is an irregular maze of interconnected spaces enclosed by a membrane and functions as the site where most cell membrane components, as well as materials destined for export from the cell, are made? Lysosome Peroxisome Ribosome The endoplasmic reticulum The Golgi apparatus

Endoplasmic Reticulum

In thermodynamics, what does the term "free energy" refer to? Energy required to initiate a chemical reaction Energy that can be harnessed to do work or drive chemical reactions Energy that cannot be harnessed to do work or drive chemical reactions Energy that cells borrow from the environment Excess energy from a reaction that a cell does not use

Energy that can be harnessed to do work or drive chemical reaction

What is the measure of disorder in a system called? Catabolism Enthalpy Entropy Free energy Second law of thermodynamics

Entropy

Genetic change followed by selection are the fundamentals of what process? -DNA duplication -Evolution -Genetic drift -Regeneration -Reproduction

Evolution

After an enzyme catalyzes a reaction, the enzyme has been altered and cannot perform additional reactions. False True

False

All cells require oxygen to live. -False -True

False

An organism that can survive life in a hydrothermal vent at the bottom of the ocean can thrive anywhere. False True

False

Another thing all cells have in common is the ability to divide. -False -True

False

Because they generate order (by surviving, growing, and forming complex communities), living cells defy the second law of thermodynamics. False True

False

Cells are either prokaryotic, eukaryotic, or archaeic. False True

False

What role is NOT performed by the cytoskeleton? Controlling cell shape and cell movement Generating chemical energy for the cell Generating contraction in muscle cells Pulling duplicated chromosomes to opposite poles in dividing cells Transporting organelles and molecules from one place to another in the cytoplasm

Generating chemical energy for the cell

Which reaction can be driven by the hydrolysis of a molecule of ATP? CO2 + water → glucose + oxygen (ΔG = 686 kcal/mole) Glucose + oxygen → CO2 + water (ΔG = -686 kcal/mole) Sucrose → glucose + fructose (ΔG = -5.5 kcal/mole) Glucose + fructose → sucrose (ΔG = 5.5 kcal/mole)

Glucose + fructose → sucrose (ΔG = 5.5 kcal/mole)

Which of the following is a stack of flattened membrane-enclosed sacs, functioning in receiving and often chemically modifying the molecules made in the endoplasmic reticulum, and then directing them to the exterior of the cell or to various locations inside the cell? Lysosome Peroxisome Ribosome The endoplasmic reticulum The Golgi apparatus

Golgi Apparatus

Which of the following represents energy in its most disordered form? Chemical-bond energy Electromagnetic (light) energy Heat energy Potential energy The kinetic energy of a moving object

Heat Energy

Which term describes genes (and gene products) related by a common ancestral gene? Analogous Familial Homologous Superfluous Vestigial

Homologous

Which of the following statements is NOT true? Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions. Oxidation and reduction reactions always occur simultaneously. When a carbon atom in a C-H bond has somewhat more than its share of electrons, it is said to be reduced. When a sugar molecule is oxidized to CO2 and H2O, the O2 molecules involved in forming the H2O are reduced.

Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions.

A reaction A → B has a negative ΔG under experimental conditions. Which statement is true about this reaction? Increasing the concentration of B will increase the ΔG, making it more positive. The formation of product B will decrease the entropy of the universe. The reaction cannot proceed until it is coupled to a reaction with a positive ΔG. The reaction is energetically unfavorable. The reaction will proceed spontaneously and rapidly.

Increasing the concentration of B will increase the ΔG, making it more positive.

What is NOT a reason scientists study yeast? It can be grown in the laboratory. It can reproduce as rapidly as bacteria. It carries out all the basic tasks a eukaryotic cell must perform. It is as closely related to animals as it is to plants. It lacks a nucleus so it is easy to genetically manipulate.

It lacks a nucleus so it is easy to genetically manipulate

Consider the reaction A + B → AB. How is the equilibrium constant expressed for this reaction with two substrates and a single product? K = ([A] + [B]) / [AB] K = [AB] / ([A] + [B]) K = [AB] / [A][B] K = [A] [B] / [AB]

K = [AB] / [A][B]

Chemical reactions proceed spontaneously only in the direction that: goes "uphill." is energetically unfavorable. leads to a loss of free energy. leads to an increase in orderliness. releases water.

Leads to loss in free energy

Which of the following organelles is a small, irregularly shaped organelle in which intracellular digestion occurs? Lysosome Nucleosome Peroxisome The endoplasmic reticulum The Golgi apparatus

Lysosome

Which is not evidence for the endosymbiotic origins of mitochondria and chloroplasts? Mitochondria and chloroplasts are surrounded by a double membrane. Mitochondria and chloroplasts contain their own DNA. Mitochondria and chloroplasts have similar DNA. Mitochondria and chloroplasts reproduce by dividing in two. Mitochondria and chloroplasts resemble bacteria.

Mitochondria and chloroplasts have similar DNA

Which statement is NOT true of mitochondria? Mitochondria are not present in plant cells. Mitochondria are thought to have originated from bacteria. Mitochondria contain their own DNA. Mitochondria generate chemical energy for the cell. Mitochondria have an inner and outer membrane.

Mitochondria are not present in plant cells

Which organelle's ancestor was likely engulfed by primitive eukaryotes to help the cell survive in an oxygen-rich atmosphere? Chloroplast Lysosome Mitochondrion Nucleus Peroxisome

Mitochondrion

Which of the following is an activated carrier? ADP CoA FAD NADH NADP+

NADH

What is the difference between NAD+ and NADH? NADH carries an extra phosphate group. NADH carries an extra proton and two high-energy electrons. NADH is an electron acceptor, whereas NAD+ is an electron donor. NADH is involved in biosynthetic reactions. NADH is the oxidized form, while NAD+ is the reduced form.

NADH carries an extra proton and two high-energy electrons.

Which of the following is true? NADH carries electrons in animal calls and NADPH does the same in plants. NADPH and NADH are used in independent pathways in cells. NADPH and NADH deliver electrons to the same set of enzymes. NADPH loses a phosphate group to form NADH during biosynthetic reactions.

NADPH and NADH are used in independent pathways in cells.

Which of the following statements is NOT true? NADH is an activated carrier molecule that is usually used in oxidation reactions to produce ATP. NADPH is an activated carrier molecule that is used primarily by plants. NADPH is an activated carrier molecule that is usually used in biosynthetic reactions to build energy-rich molecules.

NADPH is an activated carrier molecule that is used primarily by plants.

A reaction occurs spontaneously only if the change in free energy (ΔG) is: large. negative. positive. small. zero.

Negative

The genome of the bacterium E. coli contains 4.6 million (4.6 x 106) nucleotide pairs, whereas the human genome contains some 3200 x 106 nucleotide pairs. Based on these numbers, one can conclude that: (A) E. coli are unicellular, whereas humans are multicellular. (B) humans are a more complex life-form than E. coli. (C) human cells are larger than E. coli. (D) human cells have 700 times more genes than E. coli. (E) All of the above (F) None of the above

None of the above

The DNA in the nucleus of eukaryotic cells is separated from the cytoplasm by the: cell wall. endoplasmic reticulum. nuclear envelope. nucleoplasm. plasma membrane.

Nuclear Envelope

In both plants and animals, the process of "controlled burning" that extracts energy from food molecules is a process of gradual: biosynthesis. hydrolysis. oxidation. photosynthesis. reduction.

Oxidation

Which of these is NOT part of the cytoskeleton? Actin filaments Intermediate filaments Microtubules Plasma membrane

Plasma Membrane

Which structure could NOT be seen using a light microscope? -Bacterium -Cell wall -Mitochondrion -Nucleus -Plasma membrane

Plasma Membrane

Which statement is true? Polymer breakdown requires an input of free energy and involves the consumption of water. Polymer breakdown requires an input of free energy and involves the release of water. Polymer synthesis requires an input of free energy and involves the consumption of water. Polymer synthesis requires an input of free energy and involves the release of water

Polymer synthesis requires an input of free energy and involves the release of water

What is the origin of the energy that animals acquire by eating plants or other animals? Carbohydrates Fats Heat Sugars Sunlight

Sunlight

Which of the following statements about oxidation and reduction is true? A dehydrogenation reaction is a reduction. A molecule is oxidized if it gains an electron (plus a proton) in a reaction. In an organic molecule, the number of C-H bonds increases as a result of oxidation. Oxidation of food in all organisms requires oxygen. The carbon atom is more oxidized in formaldehyde (CH2O) than in methanol (CH3OH).

The carbon atom is more oxidized in formaldehyde (CH2O) than in methanol (CH3OH).

In a cell, the rate at which an enzyme will encounter its substrate depends on: the concentration of other proteins in the cytosol. the concentration of the substrate. the size of the enzyme. the way that the cytosol is structured.

The concentration of the substrate

Which of the following does NOT describe an oxidation reaction? The addition of oxygen atoms to a molecule The conversion of Fe2+ to Fe3+ The conversion of a chlorine atom to Cl− The removal of electrons from a molecule

The conversion of a chlorine atom to Cl−

Which statement is NOT true about the differences between liver cells and kidney cells in the same animal? -The different cells are generated during the animal's development. -The different cells express different genes. -The different cells have different DNA. -The different cells have different roles in the body. -The different cells produce different proteins.

The different cells have different DNA.

Which statement is true? A cell generates order by decreasing the entropy of its surroundings. A cell takes in heat from the environment to power its biosynthetic reactions, thus obeying the second law of thermodynamics. Cells obey the first law of thermodynamics, but are exempt from the second law. The breakdown of food molecules generates heat, which cells then use to drive the synthesis of large molecules. The heat released by an animal cell comes from the chemical-bond energy present in the food molecules it metabolizes.

The heat released by an animal cell comes from the chemical-bond energy present in the food molecules it metabolizes.

Which statement is true about the removal of a terminal phosphate from ATP? The reaction is a condensation reaction. The reaction is associated with a positive change in ΔG°. The reaction is energetically favorable.

The reaction is energetically favorable

Which of the following does NOT occur in cells? The conversion of sunlight into energy stored in chemical bonds during photosynthesis The metabolism of nutrients to produce useful energy stores The use of chemical energy to transport organelles through the cytosol The use of heat to burn foodstuffs

The use of heat to burn foodstuffs

In the second step of glycolysis, the pathway that begins the oxidative breakdown of sugars, the enzyme phosphoglucose isomerase converts glucose 6-phosphate to fructose 6-phosphate. The equilibrium constant, K, for this reaction is 0.36. If ΔG° = -1.42 x log K, which conclusion can be made about this reaction? The ΔG° is negative, but whether the reaction proceeds would depend on ΔG, not ΔG°. The ΔG° is negative, so the reaction must be coupled to the hydrolysis of ATP. The ΔG° is negative, so the reaction will proceed in the forward direction. The ΔG° is positive, but in a cell that is actively burning sugars, the reaction can still proceed in the forward direction. The ΔG° is positive, so the reaction will proceed in the reverse direction.

The ΔG° is positive, but in a cell that is actively burning sugars, the reaction can still proceed in the forward direction.

In what way are all cells alike? -They are about a tenth of a millimeter in diameter. -They are round in shape. -They are surrounded by a tough outer coat made of protein. -They require other cells to survive and reproduce. -They store their genetic instructions in DNA.

They store their genetic instructions in DNA

What mediates the exchange of materials between the endoplasmic reticulum, Golgi apparatus, the lysosomes, and the outside of the cell? Diffusion Peroxisomes The cytosol The extracellular matrix Transport vesicles

Transport Vessicles

Activated carriers that transfer methyl, carboxyl, and glucose groups for the purpose of biosynthesis are typically generated in reactions coupled to ATP hydrolysis. False True

True

An enzyme can lower the activation energy of a reaction. False True

True

An individual ribosome can be seen with a fluorescence microscope. -False -True

True

At a molecular level, the members of the two domains of prokaryotes—the archaea and bacteria—differ as much from each other as either does from the eukaryotes. False True

True

Energetically favorable reactions are those that create disorder by decreasing the free energy of the system to which they belong. False True

True

Energetically unfavorable reactions can occur if they are coupled to a second reaction with a negative ΔG so large that the net ΔG of the entire process is negative. False True

True

Human cells are capable of surviving in a culture dish. False True

True

If two genes from different organisms have closely similar DNA sequences, it is highly probable that both genes descended from a common ancestral gene. False True

True

In cells, small molecules can diffuse over short distances quickly. False True

True

In isolation, the formation of an activated carrier, such as ATP, NADH, or NADPH, is an energetically unfavorable reaction. False True

True

The free-energy change (ΔG) and the standard free-energy change (ΔG°) of a reaction differ in that ΔG depends on the concentrations of the molecules in the reaction, whereas for ΔG°, these concentrations are set to a fixed value. False True

True

The overall free-energy change for coupled reactions is equal to the sum of the free-energy changes for each individual reaction. False True

True

When an enzyme lowers the activation energy for the forward reaction X → Y, it also lowers the reaction rate for the reverse reaction Y → X by the same amount. False True

True

In an enzyme-catalyzed reaction, a small value of KM indicates that a substrate binds: very tightly to the enzyme. very weakly to the enzyme.

Very tightly to the enzyme

For the simple reaction Y → X, the equilibrium constant K is: [X]*[Y] [X]/[Y] [Y]*[X] [Y]/[X]

X / Y

In overworked muscle cells, the pyruvate generated during the breakdown of glucose is converted to lactic acid by the enzyme lactate dehydrogenase according to the reaction: CH3(CO)COO− + X → CH3(CHOH)COO− + Y Based on this reaction, X and Y represent what molecules? X = ATP, Y = ADP + Pi X = NAD+, Y = NADH + H+ X = NADH + H+, Y = NAD+ X = NADP+, Y = NADPH + H+ X = NADPH + H+, Y = NADP+

X = NADH + H+, Y = NAD+

Which of the following is frequently studied as a model vertebrate? Arabidopsis Didinium Drosophila Jellyfish Zebrafish

Zebrafish

Which organism would be the most useful for studying how mutations that cause sudden death in young athletes can affect the development of the heart? Arabidopsis thaliana Caenorhabditis elegans Raphus cucullatus Saccharomyces cerevisiae Zebrafish

Zebrafish

At equilibrium, the free energy of a reaction is: at its highest point. at its lowest point. energetically favorable. energetically unfavorable. equal to ΔG°.

at its lowest point

Mitochondria are essentially the same in all eukaryotes, including plants, animals, and fungi. From this observation, it can be concluded that mitochondria were most likely acquired: by an ancestral eukaryotic cell and then replaced by chloroplasts in the line that led to plant cells. by an ancestral eukaryotic cell before the lines that led to animal cells, plant cells, and fungi diverged. by an ancestral prokaryote and then lost in the line that led to archaea. by an ancestral prokaryotic cell. from a free-living, photosynthetic bacterium.

by an ancestral eukaryotic cell before the lines that led to animal cells, plant cells, and fungi diverged.

One drawback of electron microscopy is that it: -can only be used to view atomic details in structures larger than a ribosome. -can only be used to view samples that are sliced very thinly. -cannot be used to view a whole cell or organism. -cannot be used to view living cells. -requires the use of fluorescent probes.

cannot be used to view living cells.

Early studies of Drosophila melanogaster showed that: chromosomes are made exclusively of protein. chromosomes exist in sets of three. DNA exists only in eukaryotic organisms. eukaryotes carry their genes in circular plasmids. genes are carried on chromosomes.

genes are carried on chromosomes.

Inhibitor molecules can block an enzyme's activity. Some inhibitors, called competitive inhibitors, compete directly with the substrate for the enzyme's active site. Such inhibitors will: decrease the KM of the reaction. decrease the Vmax of the reaction. have an effect that cannot be reversed. have no effect on the Vmax of the reaction. increase the Vmax of the reaction.

have no effect on the Vmax of the reaction.

Two molecules will bind to each other by means of noncovalent bonds if the ΔG° of the interaction is: negative (the free energy of the product is lower than the sum of the free energies of the unbound partners). positive (the free energy of the product is higher than the sum of the free energies of the unbound partners). zero (the free energy of the product is the same as the sum of the free energies of the unbound partners).

negative (the free energy of the product is lower than the sum of the free energies of the unbound partners).

Consider two molecules that associate with each other through hydrogen bonds. The larger the equilibrium constant, K, for this association: the less tightly the two molecules will bind. the more tightly the two molecules will bind.

the more tightly the two molecules will bind.

Scientists were studying yeast cells in which a mutation inactivated a gene required for cell division. Without this gene—and the protein it encoded—these mutant yeast cells were unable to divide normally. But the scientists discovered that introducing a related protein from human cells could "rescue" these mutant yeast cells, allowing the cells to resume normal division. Based on this finding, the most likely conclusion is that: modern humans most likely obtained their cell-division proteins from ancient yeast. the proteins that control cell division in yeast and humans are functionally equivalent and have been conserved, almost unchanged, for more than a billion years. yeast and humans diverged from a common ancestor much more recently than previously thought, perhaps fewer than a million years ago. yeast cells most likely obtained their cell-division proteins from the cells of early humans. yeast cells require human proteins to divide.

the proteins that control cell division in yeast and humans are functionally equivalent and have been conserved, almost unchanged, for more than a billion years

When an enzyme is operating at its maximum rate: half of the substrate-binding sites on the enzyme molecules are occupied. increasing the substrate concentration will increase the turnover number. the concentration of substrate is equal to the KM. the concentration of substrate is half of the KM. the substrate-binding sites on the enzyme molecules are fully occupied.

the substrate-binding sites on the enzyme molecules are fully occupied.

Small molecules diffuse through the cytosol very efficiently by: binding to larger molecules. forming noncovalent bonds with other molecules. hitching a ride on microtubules. taking the shortest path from one location to another. wandering randomly, knocked around by collision with other molecules.

wandering randomly, knocked around by collision with other molecules.

When the concentrations of substrate and product are equal: ΔG = ΔG°. ΔG = 0. ΔG° = 0. ΔG° = K. a reaction is at equilibrium.

ΔG = ΔG°.

In the first reaction of glycolysis, the pathway that begins the oxidative breakdown of sugars, the enzyme hexokinase uses ATP to catalyze the phosphorylation of glucose to glucose 6-phosphate and ADP. The ΔG° of this reaction is a favorable -4.06 kcal/mole. An enzyme called glucose 6-phosphatase effectively "reverses" this reaction, hydrolyzing glucose 6-phosphate back to glucose and releasing a phosphate. The ΔG° of this reaction is -3.34 kcal/mole. Based on these values, what is the ΔG° for the hydrolysis of ATP: ATP + H2O → ADP + Pi? +0.72 kcal/mole −0.72 kcal/mole +7.4 kcal/mole −7.4 kcal/mole +14.8 kcal/mole

−7.4 kcal/mole