BIO 111 Final Exam

Place these steps of enzyme catalysis in the correct order: 1. The substrate and enzyme change shape. 2. The substrate enters the active site. 3. The enzyme reverts to its original configuration. 4. The product is expelled.

2, 1, 4, 3

Imagine that 1 milliliter of an experimental drug diluted in a saline solution is injected into 20 pregnant mice to determine possible side effects. Which of the following is a suitable control for this experiment?

20 pregnant mice injected with 1 milliliter of saline

If a strand of DNA has the nitrogen base sequence 5'-ATTTGC-3', what will be the sequence of the matching or complementary strand?

3'-TAAACG-5'

If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?

40%

The addition of a competitive inhibitor slows down a particular reaction. What could be done to increase the rate of the reaction, even in the presence of the inhibitor?

Add more substrate.

What is similar about exporting proteins from a cell and digesting food particles within a cell?

Both processes involve the formation of vesicles.

Which of the given scenarios is most likely irreversible and an example of noncompetitive inhibition?

Boy A is playing a video game on a video game system. Boy B trips over the cords, pulling the game system off the shelf and breaking it.

Which of the following components is NOT part of the modern cell theory?

Bacteria are examples of eukaryotic cells.

Choose the correct pathway of information flow in the cell.

DNA - RNA - protein

Which of the following best summarizes the relationship between dehydration (condensation) reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis breaks them down.

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis breaks them down.

Consider the two-step metabolic pathway: A—(enzyme 1)—>B—(enzyme 2)—>C How would inactivating enzyme 1 affect the concentrations of molecules A, B, and C relative to what they would be if the pathway were fully functional?

A would increase; B and C would decrease.

Which of the following cytoskeletal proteins are important in changing cell shape or location (any type of cell movement)?

Actin and myosin are among the cytoskeletal proteins important in cell movement.

For many enzymes, the rate of product formation increases as the concentration of the substrate increases. Eventually the rate of the reaction reaches a maximum at which further increases in the concentration of the substrate have no effect. Why?

At high concentrations of substrate, all of the enzyme active sites are being occupied by substrate molecules.

Which of the following represents a molecule characterized by polar covalent bonding?

H2O

Consider the buffering example discussed in class. Acetic acid (CH3COOH) and acetate (CH3COO- ) form a buffer system. Which one of the buffer components would increase in concentration if we were to add a strong acid to the solution containing the buffer?

CH3COOH

Which of the following can serve as an energy source and as structural support in plant cells?

Carbohydrates

Compare the molecular formula of a carbohydrate (CH2O)n with that of carbon dioxide (CO2). What does the presence of hydrogen atoms in carbohydrates indicate? (Hint: think about the electronegativities of the involved atoms, their position in the orbitals, and the phrase: "OIL RIG" or "LEO the lion goes GER"

Carbohydrates are more reduced than carbon dioxide.

Which scientist(s) is/are credited with developing the theory of evolution in the mid-1800s? Select all answers that apply.

Charles Darwin; Alfred Russel Wallace

In the last step of extracting energy from sugar, an enzyme called cytochrome c oxidase attaches electrons to oxygen and hydrogen ions, forming water. The electrons are temporarily bound to an iron atom in the enzyme before they are attached to oxygen. Cyanide is a poison that acts by permanently binding to the enzyme near this iron atom, preventing oxygen from getting near enough to accept the electrons. How would you describe the action of cyanide?

Cyanide is a competitive inhibitor of cytochrome c oxidase.

How do energy carriers participate in coupled reactions?

Energy carriers can be broken apart to power an endergonic reaction or assembled using energy from an exergonic reaction.

Which of the following statements regarding enzymes is FALSE?

Enzymes provide energy for the reactions they catalyze.

Which of the following statements represents a major difference between prokaryotic cells and eukaryotic cells?

Eukaryotic cells tend to have much more extensive inner membrane systems and larger numbers of ntracellular organelles than do prokaryotes.

Both carbohydrates and fats are used as fuel in cells, but fats store twice as much energy per gram as carbohydrates. Which statement best explains why?

Fats have more C-C and C-H bonds with high potential energy, and fewer C-O bonds with low potential energy.

Which of the following statements is a hypothesis rather than a theory?

Female birds prefer to mate with male birds that have longer tails.

Free radicals contain unpaired electrons in their outermost energy shell, so they react readily with other atoms or molecules to reach a more stable state. Which of the following could potentially be a free radical? Select all correct answers!

Flourine (atomic number 9); Bromine (atomic number 35)

In animal cells, harmful molecules like nicotine, cocaine, and caffeine can be stored and broken down in an particular organelle instead of the cytosol. Which organelle would you expect of find them in if they were metabolized or broken down and yielded even more toxic by-products?

Harmful products can be degraded in the peroxisomes, preventing them and any of their break down by products from harming the cell.

Which of the following properties of water enable(s) it to function as a regulator of temperature for living organisms? (Hint: Think about what happens when you are sunbathing.)

High specific heat and low heat of vaporization

Suppose you have discovered a new virus and have isolated its nucleic acids. What feature could you look for to determine whether the nucleic acids of this virus are RNA or DNA?

If it is RNA, it will contain ribose.

ATP is an energy carrier. Where is the energy actually located?

In the bonds between phosphate groups

If an atom has a charge of -2, which of the following must be true?

It has two more electrons than protons and is considered an anion.

As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?

It is used to establish and maintain a proton gradient to make ATP.

What is the most likely role of a cell that contains an extensive smooth ER?

It synthesizes large quantities of steroid hormones.

Consider the following reaction at equilibrium: CO2 + H2O ↔ H2CO3. What would be the effect of adding additional H2CO3? Select all correct answers, there may be more than one!

It would drive the equilibrium dynamics to the left.; The amounts of CO2 and H2O would increase.

Lard is a solid fat at room temperature. What does this tell you about the triglycerides in lard?

Lard is composed of saturated fats.

How does a cell rid itself of defective or malfunctioning organelles?

Lysosomes assist in the removal of defective organelles by digesting them.

Imagine that you are conducting an experiment on an enzyme known as sucrase. This enzyme is synthesized and used by yeast cells to break down the disaccharide sucrose (table sugar) into the monosaccharides glucose and fructose. You decide to conduct an experiment to test whether the sucrase enzyme can break down the artificial sweetener sucralose. Sucralose (a "chlorinated" carbohydrate) has some chemical similarity to sucrose, but is different in that three of its hydroxyl groups are missing and replaced with chlorine atoms instead. Based on the details provided in this scenario, do you think the sucrase enzyme will be able to interact with sucralose?

No; all enzymes are highly specific and can react with only a specific substrate.

Which of the following is LEAST affected by the presence of water?

Nonpolar covalent bond

If you examined the human body on a chemical composition basis, which of the following combinations of elements would be most common?

O, C, H, N

Which type of lipid is most important in biological membranes?

Phospholipid

Which of the following correctly matches an organic polymer with its monomers, respectively?

Protein; amino acids

What activity occurs in the nucleolus?

Ribosomes are created in the nucleolus.

Scientists found that polypeptides that are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the endoplasmic reticulum. What is/are possible explanations for the greater length of these polypeptides?

The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing.

Phosphorus has an atomic number of 15, so what is the distribution of its electrons?

The first energy level or orbital has 2, the second has 8, and the third has 5.

Over the past several decades, natural selection has caused populations of Staphylococcus aureus (an infectious wound bacterium) to evolve resistance to most antibiotics. If antibiotic use were stopped, what would you predict would happen to these S. aureus populations?

The frequency of nonresistant forms will increase in these populations.

If water were a linear (not bent) molecule, electrostatic interactions between water molecules would be much weaker. Why?

The partial negative charge on the oxygen atom would stick out less and therefore be less able to participate in hydrogen bonding with hydrogen atoms

Which of the following statements is true about enzyme-catalyzed reactions?

The reaction is faster than the same reaction in the absence of the enzyme.

Soap and detergent molecules have a long, hydrophobic tail and a polar, hydrophilic head. They are sometimes referred to as bridge molecules because they allow oils and fats to be suspended and dissolved in water (which they otherwise would not be able to do). Imagine that you are using soap to wash away dirt that is being held against your skin in an oily film. In this scenario, how are the soap, dirt/oil, and water arranged at the molecular level?

The soap molecules encase the dirt/oil within a small droplet that has a hydrophilic exterior and a hydrophobic interior.

Which statement is an accurate description of water molecules?

They are slightly charged and polar.

Which statement most accurately describes what happens to proteins that lack an ER signal sequence?

They are translated by ribosomes and released into the cytoplasm.

Environments all over the world are changing as a result of global warming. Could this influence natural selection?

Yes. Traits that help individuals produce more offspring in warmer environments will increase in frequency.

Entropy is a tendency towards ______.

a decrease in order

Which reaction is most spontaneous?

a reaction that is slightly exothermic and leads to a huge increase in entropy

When designing an experiment, which of the following is critical in determining that your results are due to a specific treatment, and not to random variation or other factors that might affect outcome?

control group(s)

If the primary structure of a protein is incorrect

any higher level folding of the protein will be incorrect.

Liquid water is considered to be of a higher density than its solid form (ice) because:

both A and B are correct: more hydrogen bonds are present in liquid water than solid ice; ice forms a crystal lattice the results in the creation of air pockets

You isolate a molecule and determine it is nonpolar. Based on this property, the molecule is largely composed of the elements _____.

carbon and hydrogen

We usually compare all eukaryotic cells as a group to all prokaryotic cells. However, some types of eukaryotic cells have characteristics that are found in prokaryotic cells but not in other eukaryotic cells. What feature do plant cells share with prokaryotic cells but not with animal cells?

cell wall

Which of the following cell structures is NOT found in a bacterial cell?

central vacuole

Imagine a candy bar sitting on a table in front of you. Which specific types of energy are present in the candy bar? Select all correct answers that apply!

chemical energy; potential energy; heat energy

Use the following words to fill in the appropriate blank: mitochondria/viruses/cyanobacteria/chloroplasts/vacuoles/lysosomes Applying Margulis's theory of endosymbiosis to plant cells, it is likely that __________evolved from ___________ in plant cells.

chloroplasts; cyanobacteria

In a(n) __________ reaction, the reactants contain more energy than the products; energy is released in this type of reaction; while in a(n) __________reaction, the products contain more energy than the reactants, an energy input is required in order for this type of reaction to occur.

exergonic; endergonic

You've been asked to analyze a reaction that took place at a temperature of 300 Kelvins (K). ∆H was -150 and ∆S was +0.4. Is the reaction endothermic or exothermic?

exothermic

Science cannot answer certain faith-based questions because ___________________________.

faith-based beliefs are impossible to either prove or disprove.

All of the following lipids or lipid components are hydrophobic EXCEPT

fatty acid heads.

The end product of a biosynthetic pathway often acts to block the initial step in that pathway. This phenomenon is called _____.

feedback inhibition.

Which of the following cell structures is found external to the plasma membrane in bacteria?

flagella

The element carbon has atomic number 6. Carbon most likely

forms four covalent bonds.

A double covalent chemical bond represents the sharing of how many electrons?

four

The formation of ions involves the

gain or loss of electrons

Evolution is sometimes described as the change from preexisting life-forms to modern-day organisms. What actually changes, in every case of evolution, is the ____________________.

genetic makeup of the species, due to mutations.

Researchers have been able to study the pathway of a secreted protein by "tagging" it with a fluorescent marker. Using this method, you would observe fluorescence moving from the ER to which organelle?

golgi apparatus

Energy transformations are not 100% efficient. Often, energy is released or "lost" in the form of ________, which is in agreement with the second law of thermodynamics.

heat

The main difference between an autotroph and a heterotroph is __________.

how they obtain energy.

What type of bond is easily disrupted in aqueous solutions (one in which the solvent is water)?

ionic

Milk of magnesia is often used to treat stomach upset. It has a pH of 10. Based on this information, milk of magnesia

is a base

Lactose is a disaccharide of glucose and galactose, and its digestion requires the actions of the enzyme lactase. If lactose is eaten as part of the diet but is not digested by lactase, this sugar is then metabolized by bacteria in the intestine, leading to the symptoms of lactose intolerance. Lactose intolerance, therefore, results from a(n)

lack of hydrolysis of lactose.

Cells can't import large extracellular molecules like proteins and complex carbohydrates across lipid bilayers but these molecules are recycled and used by the cell. Which of the following cell structures would you expect to be required for this function of the cells? NOTE: There may be more than one correct answer!!

lysosomes; the cytoplasmic membrane

After you drink a glass of acidic lemonade, your body's pH does not change. This is an example of how humans and other organisms

maintain precise internal conditions through homeostasis.

You have a distant cousin, age 4, who is always tired and fatigued and is not able to play games and sports like other healthy children. He most likely has an enzyme deficiency or defect associated with which intracellular organelle?

mitochondria

RNA carries information for protein synthesis from the DNA in the nucleus to the ribosomes in the cytoplasm. To get from the nucleus to the cytoplasm, RNA must pass through a ________________ in the nuclear membrane.

nuclear pore

The condensation reaction that forms nucleic acid polymers occurs between a _____ group on one nucleotide and a _____ group on a second nucleotide.

phosphate, hydroxyl

The type of bond that forms between a 3'-OH (hydroxyl) group of one nucleic acid and the 5'-P (phosphate) group of another nucleic acid is called a _________________ bond and its formation ___________ a molecule of water.

phosphodiester; generates

You are studying a protein that is shaped like a doughnut. The shape is a function of which level(s) of protein structure?

primary, secondary, and tertiary

A new form of life has been found in the soils on Mars. The life appears to be small at about 5 microns in size and contains no nucleus or other lipid bilayer based membrane organelles. How might you initially classify this organism?

prokaryotic cell

In theory, magnification is unlimited, but in practice, magnification is limited by __________; the ability to see two objects as separate and distinct entities. This property is limited by __________________, the bending or scattering of light that occurs as light moves through different substances on its way to capture by the objective lens of a brightfield microscope.

resolution; refraction

You observe a plant on your windowsill that is growing at an angle toward the outside. This is an example of a living thing

responding to stimuli.

Suppose you are testing a treatment for AIDS patients and find that 75% respond well, whereas 25% show no improvement or a decline in health. You should

review the results, modify the drug or the dosage, and repeat the experiment.

The "backbone" of a nucleic acid molecule is made of

sugar and phosphate groups.

If you place a feather on the surface of a bowl of water, the feather remains suspended on the surface due to the

surface tension of the water

Adaptations include all of the following EXCEPT ____________.

teaching a pet parrot to talk.

A scientific theory assumes all the following except __________.

that it can never be proven wrong

What aspects of amino acid structure vary among different amino acids?

the components of the R-group

In a famous experiment that helped disprove the possibility of spontaneous generation, Francesco Redi hypothesized that, contrary to popular belief, maggots did not appear spontaneously but came from flies. He predicted that if flies were kept away from meat, then maggots would not appear. To test his hypothesis, Redi placed identical pieces of meat in two identical jars and placed the two jars on the same windowsill. He placed a lid on one jar and left the other uncovered for several days. In the experiment, the control was __________.

the meat in the jar without the lid

If you find a mouse in your basement, it is likely Mus musculus. Peromyscus leucopus is also common. Or, you may get lucky and find a relatively rare Peromyscus maniculatus instead. Out of these three species, which two are the most closely related (from an evolutionary standpoint)?

the two species in the Peromyscus genus

Electrons tend to have more potential energy when ____.

they are in electron shells far from the nucleus

An atom has 5 electrons in its valence shell. How many single covalent bonds would you expect it to form in most circumstances?

three

You are telling your friend that organic molecules are all made up of carbon backbones with hydrogens. She doesn't understand how there can be so many different organic molecules if they all are made up of the same basic components. You explain that organic molecules:

vary because they possess different functional groups.

Which sequence accurately describes the flow of electrons in photosynthesis?

water, photosystem II, photosystem I, NADP+

When are atoms most stable?

when all of the electrons in their outer or valence orbital shell are filled