Cell Biology Exam 1 Practice

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Fill in the blanks, selecting from the choices below. Light + _________ + __________________ + heat + sugars CO, CO2, O2, H2, H2O, N2, NO

H20, CO2, O2

You are measuring the effect of temperature on the rate of an enzyme-catalyzed reaction. If you plot reaction rate against temperature, which of the graphs in Figure Q3-57 would you expect your plot to resemble? Graphs: 1. Increasing then decreasing 2. Vertical line 3. Increasing slope 4. Decreasing slope

graph 1

During respiration, energy is retrieved from the high-energy bonds found in certain organic molecules. Which of the following, in addition to energy, are the ultimate products of respiration? (a) CO2, H2O (b) CH3, H2O (c) CH2OH, O2 (d) CO2, O2

(a) CO2, H2O

Table Q2-16 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements form stable but reactive diatomic gases?

(a) nitrogen, oxygen

2-8 The first task you are assigned in your summer laboratory job is to prepare a concentrated NaOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 ml solution that has a concentration of 10 M? (a) 800 g (b) 200 g (c) 400 g (d) 160 g

(b) 200 grams

Oxidation is the process by which oxygen atoms are added to a target molecule. Generally, the atom that is oxidized will experience which of the following with respect to the electrons in its outer shell? (a) a net gain (b) a net loss (c) no change (d) an equal sharing

(b) a net loss

A. thaliana, or Arabidopsis, is a common weed. Biologists have selected it over hundreds of thousands of other flowering plant species to serve as an experimental model organism because __________________. (a) it can withstand extremely cold climates. (b) it can reproduce in 8-10 weeks. (c) it produces thousands of offspring per plant. (d) Both (b) and (c) are true.

(b) can reproduce in 8-10 weeks

Brewer's yeast, apart from being an irreplaceable asset in the brewery and in the bakery, is an experimental organism used to study eukaryotic cells. However, it does have some limitations. Which of the processes below cannot be studied in yeast? (a) DNA replication (b) cell motility (c) exocytosis (d) cell division

(b) cell motility

24.Even though cellular macromolecules contain a large number of carbon and hydrogen atoms, they are not all spontaneously converted into CO2 and H2O. This absence of spontaneous combustion is due to the fact that biological molecules are relatively __________ and an input of energy is required to reach lower energy states. (a) large (b) polar (c) stable (d) unstable

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is: _____________. uphill. uncatalyzed. spontaneous. activated.

Spontaneous

The cytoplasm is: a place for key catabolic reactions to take place a place for key anabolic reactions to take place an aqueous solution all of the above

all of the above

Eukaryotic cells are able to trigger the release of material from secretory vesicles to the extracellular space using a process called exocytosis. An example of materials commonly released this way is _____________. (a) hormones. (b) nucleic acids. (c) sugars. (d) cytosolic proteins.

(A) hormones

What information regarding an enzyme-catalyzed reaction is obtained in a plot of the inverse of the initial velocities against the inverse of the corresponding substrate concentrations? (a) 1/Vmax and 1/Km (b) 1/V and 1/[S] (c) Vmax and Km (d) V and [S]

(a) 1/Vmax and 1/Km

Larger molecules have hydrogen-bonding networks that contribute to specific, high-affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea (Figure Q2-22) form if dissolved in water? (a) 6 (b) 5 (c) 3 (d) 4

(a) 6

Figure Q2-1 depicts the structure of carbon. Use the information in the diagram to choose the correct atomic number and atomic weight, respectively, for an atom of carbon. (a) 6, 12 (b) 12, 12 (c) 6, 18 (d) 12, 6

(a) 6,12

Drosophila melanogaster is a/an __________. This type of animal is the most abundant of all animal species, making it an appropriate choice as an experimental model. (a) insect (b) bird (c) amphibian (d) mammal

(a) insect

Oligosaccharides are short sugar polymers that can become covalently linked to proteins and lipids through condensation reactions. These modified proteins and lipids are called glycoproteins and glycolipids. Within a protein, which of the amino acids (shown in Figure Q2-30) is the most probable target for this type of modification? Figure Q2-30 (a) serine (b) glycine (c) phenylalanine (d) methionine

(a) serine

Which of the following elements is least abundant in living organisms? (a) sulfur (b) carbon (c) oxygen (d) nitrogen

(a) sulfur

Which of the following organelles has both an outer and an inner membrane? (a) endoplasmic reticulum (b) mitochondrion (c) lysosome (d) peroxisome

(b) mitochondrion

Motor proteins use the energy in ATP to transport organelles, rearrange elements of the cytoskeleton during cell migration, and move chromosomes during cell division. Which of the following mechanisms is sufficient to ensure the unidirectional movement of a motor protein along its substrate? (a) A conformational change is coupled to the release of a phosphate (Pi). (b) The substrate on which the motor moves has a conformational polarity. (c) A conformational change is coupled to the binding of ADP. (d) A conformational change is linked to ATP hydrolysis.

(d) A conformational change is linked to ATP hydrolysis.

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell. Their energy is stored in a readily transferable form such as high-energy electrons or chemical groups. Which of the molecules below is the most widely used activated carrier? (a) FADH2 (b) NADH (c) NADPH (d) ATP

(d) ATP

Antibodies are excellent examples of protein structure. This is because they demonstrate which of the following characteristics? quarternary structure disulfide bonds alpha helices and beta sheets tertiary structure All of these

All of these

Which of the following amino acids contain a sulfer atom? Tryptophan Cysteine Methionine A and B B and C

B and C

Living systems are incredibly diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Depsite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit? (a) DNA (b) cell (c)organelle (d)protein

Cell

Assume that the average human adult requires 2000 kilocalories per day to sustain all normal processes and maintain a constant weight. If manufactured solar panels could somehow provide power directly to the human body, what size solar panel would be required (in cm2)? Assume there are 10 hours of sunlight per day, and that the usable energy output for a typical solar panel is 850 kJ/ft2 per hour. Note: 1 kcal = 4.184 kJ 1 ft2 = 929.03 cm2

Conversion factors: 1 kcal = 4.184 kJ 1 ft2 = 929.03 cm2 If there are 10 hours of sunlight each day hitting the solar panel, there are 8500 kJ/ft2 produced per day. The average adult human requires 8368 kJ per day; thus, with a conventional solar panel, we would require a surface area of about a square foot, or more precisely in cm2: 8368 kJ/X = 8500 kJ/929.03 cm2 929.03 μltiply 8368/8500 = XX = 914.57 cm2

Which of the following characteristics do all cells share (check all that apply) All cells have DNA All cells have a plasma membrane All cells have a nucleus All cells have ribosomes All cells have mitochondria

DNA, plasma membrane, ribosomes

Use your knowledge of amino acid characteristics to order the peptides below by their degree of polarity. Each peptide contains eight amino acids. Use the single-letter amino acid designations to generate your list, placing the most polar peptide on the left and the most nonpolar peptide on the right. A. SGAKKRAH B. CATWNGQV C. FWGTSILA D. DDAEIHW A E. SSTAMYRK

E, A, D, B, C

Cells obtain energy through reduction reactions. True False

False

Energy, in the form of electrons, captured by electron carriers (e.g. NADH) is usable as is and does not need to be converted into another form. True False

False

if given an animal cell diagram, be able to identify the following: 1.) plasma membrane 2.) nuclear envelope 3.) cytosol 4.) Golgi apparatus 5.) endoplasmic reticulum 6.) mitochondrion 7.) transport vesicle

N/A

Cells require one particular monosaccharide as a starting material to synthesize nucleotide building blocks. Which of the monosaccharides below fills this important role? glucose fructose ribulose ribose

Ribose

An ionic bond between two atoms is formed as a result of the ______________. sharing of electrons. loss of electrons from both atoms. loss of a proton from one atom. transfer of electrons from one atom to the other.

Transfer of electrions from one atom to the other

Serine and threonine belong to which group of amino acids? uncharged polar acidic basic uncharged nonpolar

Uncharged polar

The Ras protein is a GTPase that functions in many growth-factor signaling pathways. In its active form, with GTP bound, it transmits a downstream signal that leads to cell proliferation; in its inactive form, with GDP bound, the signal is not transmitted. Mutations in the gene for Ras are found in many cancers. Of the choices below, which alteration of Ras activity is most likely to contribute to the uncontrolled growth of cancer cells? (a) a change that prevents Ras from being made (b) a change that increases the affinity of Ras for GDP (c) a change that decreases the affinity of Ras for GTP (d) a change that decreases the rate of hydrolysis of GTP by Ras

(d) a change that decreases the rate of hydrolysis of GTP by Ras

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term "protein domain." (a) a small cluster of α helices and β sheets (b) the tertiary structure of a substrate-binding pocket (c) a complex of more than one polypeptide chain (d) a protein segment that folds independently

(d) a protein segment that folds independently

Which of the following statements about amino acids is true? (a) Twenty-two amino acids are commonly found in proteins. (b) Most of the amino acids used in protein biosynthesis have charged side chains. (c) Amino acids are often linked together to form branched polymers. (d) All amino acids contain an NH2 and a COOH group

(d) all amino acids contains an NH2 and COOH group

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies? (a) amenability to genetic manipulation (b) ability to grow under controlled conditions (c) rapid rate of reproduction (d) all of the above

(d) all of the above

Choose the answer that best fits the statement. Cholesterol is an essential component of biological membranes. Although it is much smaller than the typical phospholipids and glycoplipids in the membrane, it is a(n) _________________ molecule, having both hydrophilic and hydrophobic regions. (a) polar (b) oxygen-containing (c) hydrophobic (d) amphipathic

(d) amphipathic

Figure Q3-28 is an energy diagram for the reaction XY. Which equation below provides the correct calculation for the amount of free-energy change when X is converted to Y? (reactants (a) are higher than products (c) and (b) is highest peak) (a) a+b-c (b) a-b (c) a-c (d) c-a

(d) c-a

Despite the differences between eukaryotic and prokaryotic cells, prokaryotes have proteins that are distantly related to eukaryotic actin filaments and microtubules. What is likely to be the most ancient function of the cytoskeleton? (a) cell motility (b) vesicle transport (c) membrane support (d) cell division

(d) cell division

The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of _____________. (a) Brownian motion. (b) heat. (c) light waves. (d) chemical bonds.

(d) chemical bonds.

73. NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. (a) protons, electron. (b) electrons, phosphate. (c) hydrogens, electron. (d) electrons, proton.

(d) electrons, proton.

The cell constantly exchanges materials by bringing nutrients in from the external environment and shuttling unwanted by-products back out. Which term describes the process by which external materials are captured inside vesicles and brought into the cell? (a) degradation (b) exocytosis (c) phagocytosis (d) endocytosis

(d) endocytosis

A chemical reaction is defined as spontaneous if there is a net loss of free energy during the reaction process. However, spontaneous reactions do not always occur rapidly. Favorable biological reactions require ______________ to selectively speed up reactions and meet the demands of the cell. (a) heat (b) ATP (c) ions (d) enzymes

(d) enzymes

ΔG° indicates the change in the standard free energy as a reactant is converted to product. Given what you know about these values, which reaction below is the most favorable? (a) ADP + Pi ATP (ΔG° = +7.3 kcal/mole) (b) glucose 1-phosphateglucose 6-phosphate (ΔG° = -1.7 kcal/mole) (c) glucose + fructose sucrose (ΔG° = +5.5 kcal/mole) (d) glucoseCO2 + H2O (ΔG° = -686 kcal/mole)

(d) glucoseCO2 + H2O (ΔG° = -686 kcal/mole)

Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements? (a) specific amino acid sequences (b) side-chain interactions (c) the hydrophobic-core interactions (d) hydrogen bonds along the protein backbone

(d) hydrogen bonds along the protein backbone

Lysozyme is an enzyme that specifically recognizes bacterial polysaccharides, which renders it an effective antibacterial agent. Into what classification of enzymes does lysozyme fall? (a) isomerase (b) protease (c) nuclease (d) hydrolase

(d) hydrolase

The pH of an aqueous solution is an indication of the concentration of available protons. However, you should not expect to find lone protons in solution; rather, the proton is added to a water molecule to form a(n) ______________ ion. (a) hydroxide (b) ammonium (c) chloride (d) hydronium

(d) hydronium

Chloroplasts are found only in eukaryotic cells that carry out photosynthesis: plants and algae. Plants and algae appear green as a result of the presence of chlorophyll. Where is chlorophyll located in the chloroplast? (a) in the first, outer membrane (b) in the space between the first and second membranes (c) in the second, inner membrane (d) in the third, innermost membrane

(d) in the third, innermost membrane

Table Q2-15 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +2 in solution? Table Q2-15 (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

(d) magnesium, calcium

What unit of length would you generally use to measure a typical plant or animal cell? (a) centimeters (b) nanometers (c) millimeters (d) micrometers

(d) micrometers

The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum. (a) plasma membrane (b) Golgi network (c) mitochondrial membrane (d) nuclear envelope

(d) nuclear envelope

72. The synthesis of glutamine from glutamic acid requires the production of an activated intermediate followed by a condensation step that completes the process. Both amino acids are shown in Figure Q3-72. In the condensation step, _______________ is displaced by ________________. (a) OH, NH3. (b) ADP, NH2. (c) ATP, NH3. (d) phosphate, NH3.

(d) phosphate, NH3.

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable? (a) the size of each molecule (b) the concentration of each molecule (c) the rate of synthesis (d) surface complementarity between molecules

(d) surface complementarity between molecules

The maximum velocity (Vmax) of an enzymatic reaction is an important piece of information regarding how the enzyme works. What series of measurements can be taken in order to infer the maximum velocity of an enzyme-catalyzed reaction? (a) the rate of substrate consumption after the system reaches equilibrium, for several reactant concentrations (b) the rate of product consumption shortly after mixing the enzyme and substrate (c) the rate of substrate consumption at high levels of enzyme concentration (d) the rate of substrate consumption shortly after mixing the enzyme and substrate, for several substrate concentrations

(d) the rate of substrate consumption shortly after mixing the enzyme and substrate, for several substrate concentrations

The study of enzyme kinetics is usually performed with purified components and requires the characterization of several aspects of the reaction, including the rate of association with the substrate, the rate of catalysis, and _____________. (a) the enzyme's structure. (b) the optimal pH of the reaction. (c) the subcellular localization of the enzyme. (d) the regulation of the enzyme activity.

(d) the regulation of the enzyme activity.

Cell biologists employ targeted fluorescent dyes or modified fluorescent proteins in both standard fluorescence microscopy and confocal microscopy to observe specific details in the cell. Even though fluorescence permits better visualization, the resolving power is essentially the same as that of a standard light microscope because the resolving power of a microscope is limited by the __________ of light. (a) absorption (b) intensity (c) filtering (d) wavelength

(d) wavelength

33. ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). When [Y] =[X], ΔG is equal to _____________. (a) ΔG° + RT (b) RT (c) ln [X]/[Y] (d) ΔG°

(d) ΔG°

In the case of a simple conversion reaction such as XY, which value of ΔG° is associated with a larger concentration of X than Y at equilibrium? (Hint: How is ΔG° related to K?) (a) ΔG° = -5 (b) ΔG°=-1 (c) ΔG°=0 (d) ΔG°=1

(d) ΔG°=1

β Sheets can participate in the formation of amyloid fibers, which are insoluble protein aggregates. What drives the formation of amyloid fibers?(a) denaturation of proteins containing β sheets (b) extension of β sheets into much longer β strands (c) formation of biofilms by infectious bacteria (d) β-sheet stabilization of abnormally folded proteins

(d) β-sheet stabilization of abnormally folded proteins

An ionic bond between two atoms is formed as a result of the ______________. (a) sharing of electrons (b) loss of a neutron from one atom (c) loss of electrons from both atoms (d) loss of a proton from one atom (e) transfer of electrons from one atom to the other

(e) transfer of electrons from one atom to the other

What would be the net charge of the following peptide in a neural buffer (pH = 7.4)? ARG-LYS-ARG-GLU-LYS-LYS-GLY-VAL. +4 -4 +2 -2 0

If the isotope 32S has 16 protons and 16 neutrons, how many protons and how many neutrons will the isotope 35S have? (not a multiple choice question)

16 protons and 19 neutrons

You wish to produce a human enzyme, protein A, by introducing its gene into bacteria. The genetically engineered bacteria make large amounts of protein A, but it is in the form of an insoluble aggregate with no enzymatic activity. Which of the following procedures might help you to obtain soluble, enzymatically active protein? Select all options that may be useful. A. Make the bacteria synthesize protein A in smaller amounts. B. Dissolve the protein aggregate in urea, then dilute the solution and gradually remove the urea. C. Treat the insoluble aggregate with a protease. D. Make the bacteria overproduce chaperone proteins in addition to protein A. E. Heat the protein aggregate to denature all proteins, then cool the mixture.

A, B and D

Use your knowledge of amino acid characteristics to order the peptides below according to the net charge contributed by their side chains at physiological pH (~pH 7). Each peptide contains eight amino acids. Use the single-letter amino acid designations to generate your list, placing the most negatively charged peptide on the left and the most positively charged peptide on the right. In addition, for each peptide, list the total number of positive and negative charges. Remember that, at neutral pH, the amino terminus carries a positive charge and the carboxyl terminus carries a negative charge. A. YGAKKRA B. ARRKSTRK C. DERKQNST D. DDAEIYSA E. NQSTYEEG

(A) 4 positive charges and one negative charge. (B) 6 positive charges and one negative charge. (C) 3 negative charges and 3 positive charges. (D) 4 negative charges and one positive charge. (E) 3 negative charges and one positive charge.

Oxidation is a favorable process in an aerobic environment, which is the reason cells are able to derive energy from the oxidation of macromolecules. Once carbon has been oxidized to _______________, its most stable form, it can only cycle back into the organic portion of the carbon cycle through __________________. (a) CO2, photosynthesis. (b) CH3, combustion. (c) CO2, respiration. (d) CO, reduction.

(a) CO2, photosynthesis.

The process of generating monoclonal antibodies is labor-intensive and expensive. An alternative is to use polyclonal antibodies. A subpopulation of purified polyclonal antibodies that recognize a particular antigen can be isolated by chromatography. Which type of chromatography is used for this purpose? (a) affinity (b) ion-exchange (c) gel-filtration (d) any of the above

(a) affinity

select the option that best finishes the following statement "evolution is a process ________" (a)can be understood based on principles of mutations and selection (b) that result from repeated cycles of adaption over billions of years (b)by which present day cells rose from 4-5 ancestral cells (d)that requires hundreds of thousands of years

(a) can be understood based on principles of mutations and selections

Many of the mechanisms that cells use for maintenance and reproduction were first studied at the molecular level in bacteria. Which bacterial species had a central role in advancing the field of molecular biology? (a) E. coli (b) D. melanogaster (c) S. pombe (d) C. elegans

(a) e.coli

Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form multisubunit complexes, which also have a rounded shape. Fibrous proteins, in contrast, span relatively large distances within the cell and in the extracellular space. Which of the proteins below is not classified as a fibrous protein? (a) elastase (b) collagen (c) keratin (d) elastin

(a) elastase

In the first stage of photosynthesis, light energy is converted into what other form of energy? (a) electrical (b) chemical (c) potential (d) kinetic

(a) electrical or (d) kinetic

Indicate whether the statements below are true or false A. "Nonpolar interactions" is simply another way of saying "van der Waals attractions." B. Condensation reactions occur in the synthesis of all the macromolecules found in cells. C. All proteins and RNAs pass through many unstable conformations as they are folded, finally settling on one single, preferred conformation. D. When nonpolar molecules are placed in an aqueous solution, the water molecules surrounding the nonpolar surface become completely disordered.

(a) false (b) true (c) true (d) false

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. A disaccharide consists of a sugar covalently linked to another molecule such as an amino acid or a nucleotide. B. The hydroxyl groups on monosaccharides are reaction hotspots and can be replaced by other functional groups to produce derivatives of the original sugar. C. The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure. D. Glycerol is a three-carbon compound that connects the fatty acid tails with the polar head group in phospholipids.

(a) false (b)true (c)false (d)true

Which of the following methods would be the most suitable to assess whether your protein exists as a monomer or in a complex? (a) gel-filtration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

(a) gel-filtration chromatography

Which of the following are examples of isomers? (a) glucose and galactose (b) alanine and glycine (c) adenine and guanine (d) glycogen and cellulose

(a) glucose and galactose

Although there are many distinct prokaryotic species, most have a small range of shapes, sizes, and growth rates. Which of the following characteristics are not observed in prokaryotes? (a) a highly structured cytoplasm (b) endoplasmic reticulum (c) the ability to divide rapidly (d) a cell wall

(a) highly structured cytoplasm, (b) endoplasmic reticulum

Cyclic AMP (cAMP) is a small molecule that associates with its binding site with a high degree of specificity. Which types of noncovalent interactions are the most important for providing the "hand in a glove" binding of cAMP? (a) hydrogen bonds (b) electrostatic interactions (c) van der Waals interactions (d) hydrophobic interactions

(a) hydrogen bonds

In a folded protein, most of the nonpolar amino acids are buried inside the protein fold, whereas the polar and charged side chains are exposed to the components in the cytosol. This fold is more stable because of the expulsion of nonpolar atoms from contact with water, favoring the interaction of nonpolar atoms with each other. What is this fourth type of noncovalent interaction called? (a) hydrophobic interaction (b) hydrophilic interaction (c) apolar interaction (d) hydrocarbon interaction

(a) hydrophobic interactions

Each nucleotide in DNA and RNA has an aromatic base. What is the principal force that keeps the bases in a polymer from interacting with water? (a) hydrophobic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

(a) hyrophobic interactions

The amino acids glutamine and glutamic acid are shown in Figure Q2-29. They differ only in the structure of their side chains (circled). At pH 7, glutamic acid can participate in molecular interactions that are not possible for glutamine. What types of interaction are these? Figure Q2-29 (a) ionic bonds (b) hydrogen bonds (c) van der Waals interactions (d) covalent bonds

(a) ionic bonds

Which of the following is not a feature commonly observed in α helices? (a) left-handedness (b) one helical turn every 3.6 amino acids (c) cylindrical shape (d) amino acid side chains that point outward

(a) left-handedness

By definition, prokaryotic cells do not possess __________. (a) a nucleus. (b) replication machinery. (c) ribosomes. (d) membrane bilayers. A

(a) nucleus

The mitochondrial proteins found in the inner membrane are involved in the conversion of ADP to ATP, a source of energy for the cell. This process consumes which of the following substances? (a) oxygen (b) nitrogen (c) sulfur (d) carbon dioxide

(a) oxygen

Which of the following expressions accurately describes the calculation of pH? (a) pH = -log10[H+] (b) pH = log10[H+] (c) pH = -log2[H+] (d) pH = -log10[OH-]

(a) pH = -log10[H+]

71. The synthesis of glutamine from glutamic acid requires the production of an activated intermediate followed by a condensation step that completes the process. Both amino acids are shown in Figure Q3-71. Which molecule is added to glutamic acid in the activation step? (a) phosphate (b) NH3 (c) ATP (d) ADP

(a) phosphate

Instead of studying one or two proteins or protein complexes present in the cell at any given time, we can now look at a snapshot of all proteins being expressed in cells being grown in specific conditions. This large-scale, systematic approach to the study of proteins is called _______________. (a) proteomics. (b) structural biology. (c) systems biology. (d) genomics.

(a) proteomics.

The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series biochemical reactions from the options presented here. (a) replication, transcription, translation (b) replication, translation, transcription (c) translation, transcription, replication (d) translation, replication, transcription

(a) replication, transcription, translation

Aromatic carbon compounds such as benzene are planar and very stable. Double-bond character extends around the entire ring, which is why it is often drawn as a hexagon with a circle inside. This characteristic is caused by electron __________. (a) resonance (b) pairing (c) partial charge (d) stacking

(a) resonance

For some proteins, small molecules are integral to their structure and function. Enzymes can synthesize some of these small molecules, whereas others, called vitamins, must be ingested in the food we eat. Which of the following molecules is not classified as a vitamin but does require the ingestion of a vitamin for its production? (a) retinal (b) biotin (c) zinc (d) heme

(a) retinal

The three-dimensional coordinates of atoms within a folded protein are determined experimentally. After researchers obtain a protein's structural details, they can use different techniques to highlight particular aspects of the structure. What visual model best displays a protein's secondary structures (α helices and β sheets)? (a) ribbon (b) space-filling (c) backbone (d) wire

(a) ribbon

The net distance a molecule travels through the cytosol via diffusion is relatively short in comparison with the total distance it may need to travel. This is because movement governed by diffusion alone is a ________________ process that is most effective for the dispersion of small molecules over short distances. (a) slow (b) random (c) regulated (d) complicated

(a) slow

What is the smallest distance two points can be separated and still resolved using light microscopy? (a) 20 nm (b) 0.2 μm (c) 2 μm (d) 200 μm

(b) .2 micrometers

Because there are four different monomer building blocks that can be used to assemble RNA polymers, the number of possible sequence combinations that can be created for a RNA molecule made of 100 nucleotides is _______. (a) 100^ 4 (b) 4^100 (c) 4 × 100 (d) 100/4

(b) 4^100

Which of the following statements would not be true of a favorable binding equilibrium? (a) The free-energy change is negative for the system. (b) The concentration of the complex remains lower than the concentration of the unbound components. (c) The complex dissociation rate is slower than the rate for component association. (d) The binding energy for the association is large and negative.

(b) The concentration of the complex remains lower than the concentration of the unbound components.

To study how proteins fold, scientists must be able to purify the protein of interest, use solvents to denature the folded protein, and observe the process of refolding at successive time points. What is the effect of the solvents used in the denaturation process? (a) The solvents break all covalent interactions. (b) The solvents break all noncovalent interactions. (c) The solvents break some of the noncovalent interactions, resulting in a misfolded protein. (d) The solvents create a new protein conformation.

(b) The solvents break all noncovalent interactions.

Studies conducted with a lysozyme mutant that contains an AspAsn change at position 52 and a GluGln change at position 35 exhibited almost a complete loss in enzymatic activity. What is the most likely explanation for the decrease in enzyme activity in the mutant? (a) increased affinity for substrate (b) absence of negative charges in the active site (c) change in the active-site scaffold (d) larger amino acids in the active site decreases the affinity for substrate

(b) absence of negative charges in the active site

Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The specific subset of these reactions that break down nutrients in food can be described as _____________. (a) metabolic. (b) catabolic. (c) anabolic. (d) biosynthetic.

(b) catabolic.

The nucleus, an organelle found in eukaryotic cells, confines the __________, keeping them separated from other components of the cell. (a) lysosomes (b) chromosomes (c) peroxisomes (d) ribosomes

(b) chromosomes

Which of the following choices best describes the role of the lysosome? (a) transport of material to the Golgi (b) clean-up, recycling, and disposal of macromolecules (c) sorting of transport vesicles (d) the storage of excess macromolecules

(b) clean-up, recycling, and disposal of macromolecules

Which of the following is not a feature commonly observed in β sheets? (a) antiparallel regions (b) coiled-coil patterns (c) extended polypeptide backbone (d) parallel regions

(b) coiled-coil patterns

Coiled-coils are typically found in proteins that require an elongated structural framework. Which of the following proteins do you expect to have a coiled-coil domain? (a) insulin (b) collagen (c) myoglobin (d) porin

(b) collagen

select the option that correctly finishes the following statement "a cell genome _____" (a) is defined as all the genes being used to make protein (b) contains all of a cell's DNA (c)constantly changes, depending upon the cell's environment (d)is altered during embryonic development

(b) contains all of a cell's DNA

Enzymes facilitate reactions in living systems. Figure Q3-29 presents an energy diagram for the reaction XY. The solid line in the energy diagram represents changes in energy as the reactant is converted to product under standard conditions. The dashed line shows changes observed when the same reaction takes place in the presence of a dedicated enzyme. Which equation below indicates how the presence of an enzyme affects the activation energy of the reaction (catalyzed versus uncatalyzed)? (a) d - c versus b - c (b) d - a versus b - a (c) a + d versus a + b (d) d - c versus b - a

(b) d - a versus b - a

The second law of thermodynamics states that the disorder in any system is always increasing. In simple terms, you can think about dropping NaCl crystals into a glass of water. The solvation and diffusion of ions is favored because there is an increase in _____________. (a) pH. (b) entropy. (c) ions. (d) stored energy.

(b) entropy.

Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called _____________. (a) proteins. (b) enzymes. (c) cofactors. (d) complexes.

(b) enzymes.

Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of __________. (a) mutation (b) evolution (c) heredity (d) reproduction

(b) evolution

Which of the following methods would be the most suitable to assess the relative purity of a protein in a sample you have prepared? (a) gel-filtration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

(b) gel electrophoresis

Table Q2-13 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements are chemically inert? (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

(b) helium, neon

Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by ________________ interactions. (a) hydrophilic (b) hydrophobic (c) van der Waals (d) ionic

(b) hydrophobic

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure? (a) on the surface of the protein (b) inside a cavity on the protein surface (c) buried in the interior of the protein (d) forms on the surface of the protein in the presence of ligand

(b) inside a cavity on the protein surface

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA? (a) It contains uracil. (b) It contains thymine. (c) It is single stranded. (d) It has 5′-to-3′ directionality.

(b) it contains thymine

You wish to explore how mutations in specific genes affecting sugar metabolism might alter tooth development. Which organism is likely to provide the best model system for your studies, and why? (a) horses (b) mice (c) E. coli (d) Arabidopsis

(b) mice

The cytoskeleton provides support, structure, motility, and organization, and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below is the thickest? (a) actin filaments (b) microtubules (c) intermediate filaments (d) none of the above (all the same thickness)

(b) microtubules

decays very slowly. Compared to the common, stable carbon-12 isotope, carbon-14 has two additional ______________. (a) electrons (b) neutrons (c) protons (d) ions

(b) neutrons

Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process? (a) reduction (b) oxidation (c) dehydration (d) solvation

(b) oxidation

Seed oils are often dehydrogenated and added back into processed foods as partly unsaturated fatty acids. In comparison with the original oil, the new fatty acids have additional double carbon-carbon bonds, replacing what were once single bonds. This process could also be described as _____________. (a) isomerization. (b) oxidation. (c) reduction. (d) protonation.

(b) oxidation.

When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been _____________. (a) protonated. (b) oxidized. (c) hydrogenated. (d) reduced.

(b) oxidized.

The variety and arrangement of chemical groups on monomer subunits contribute to the conformation, reactivity, and surface of the macromolecule into which they become incorporated. What type of chemical group is circled on the nucleotide shown in Figure Q2-28? (a) pyrophosphate (b) phosphoryl (c) carbonyl (d) carboxyl

(b) phosphoryl

Caenorhabditis elegans is a nematode. During its development, it produces more than 1000 cells. However, the adult worm has only 959 somatic cells. The process by which 131 cells are specifically targeted for destruction is called ______________. (a) directed cell pruning. (b) programmed cell death. (c) autophagy (d) necrosis.

(b) programmed cell death

The phosphorylation of a protein is typically associated with a change in activity, the assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modification that can affect the protein function. Ubiquitylation often results in ______________. (a) membrane association. (b) protein degradation. (c) protein secretion. (d) nuclear translocation.

(b) protein degradation.

The variations in the physical characteristics between different proteins are influenced by the overall amino acid compositions, but even more important is the unique amino acid ______________. (a) number. (b) sequence. (c) bond. (d) orientation.

(b) sequence.

Photosynthesis enables plants to capture the energy from sunlight. In this essential process, plants incorporate the carbon from CO2 into high-energy __________ molecules, which the plant cell mitochondria use to produce ATP. (a) fat (b) sugar (c) protein (d) fiber

(b) sugar

The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of _______________ in a process called _____________. (a) ATP, phosphorylation. (b) water, hydrolysis. (c) hydroxide, hydration. (d) acetate, acetylation.

(b) water, hydrolysis.

Which of the following is true for a reaction at equilibrium? (a) ΔG = ΔG° (b) ΔG°+RTln[X]/[Y]=0 (c) RT ln [X]/[Y] = 0 (d) ΔG+ΔG°=RTln[X]/[Y]

(b) ΔG°+RTln[X]/[Y]=0

Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos ______________. (a) are exceptionally large. (b) develop slowly. (c) are transparent. (d) are pigmented.

(c)

When the polymer X-X-X... is broken down into monomers, it is "phosphorylyzed" rather than hydrolyzed, in the following repeated reaction: X-X-X... + PX-P + X-X... (reaction 1) Given the ΔG° values of the reactions listed in the following table, what is the expected ratio of X-phosphate (X-P) to free phosphate (P) at equilibrium for reaction 1 X-X-X... + H2OX + X-X... (ΔG°=-4.5 kcal/mole) X + ATP X-P +ADP (ΔG° = -2.8 kcal/mole) ATP + H2O ADP + P (ΔG°=-7.3 kcal/mole) (a) 1:106 (b) 1:104 (c) 1:1 (d) 104:1

(c) 1:1 Reaction 1 can be written as the sum of the three reactions given, because the ATP used in step 2 is restored in step 3. Because ΔG° values are additive, ΔG°total = 0, and if ΔG° = 0, Keq = 1, meaning that [products]/[reactants] = 1, and the ratio of X-P to P is 1:1.

Most types of molecule in the cell have asymmetric (chiral) carbons. Consequently there is the potential to have two different molecules that look much the same but are mirror images of each other and therefore not equivalent. These special types of isomer are called stereoisomers. Which of the four carbons circled in Figure Q2-33 is the asymmetric carbon that determines whether the amino acid (threonine in this case) is a D- or an L- stereoisomer? (a) 1 (b) 2 (c) 3 (d) 4

The small molecule cyclic AMP (cAMP) takes about 0.2 second to diffuse 10 μm, on average, in a cell. Suppose that cAMP is produced near the plasma membrane on one end of the cell; how long will it take for this cAMP to diffuse through the cytosol and reach the opposite end of a very large cell, on average? Assume that the cell is 200 μm in diameter. (a) 4 seconds (b) 16 seconds (c) 80 seconds (d) 200 seconds

Fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following would not occur to help accommodate an internal, polar side chain? (a) A hydrogen bond forms between two polar side chains. (b) A hydrogen bond forms between a polar side chain and the protein backbone. (c) A hydrogen bond forms between a polar side chain and an aromatic side chain. (d) Hydrogen bonds form between polar side chains and a buried water molecule.

The biosynthetic pathway for the two amino acids E and H is shown schematically in Figure Q4-60. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Enzyme T is most likely to be subject to feedback inhibition by __________________ alone. (a) H (b) B (c) C (d) E

Some prokaryotes can live by utilizing entirely inorganic materials. Which of the following inorganic molecules would you predict to be the predominant building block for fats, sugars, and proteins? (a) O2 (b) N2 (c) CO2 (d) H2

The equilibrium constant for complex formation between molecules A and B will depend on their relative concentrations, as well as the rates at which the molecules associate and dissociate. The association rate will be larger than the dissociation rate when complex formation is favorable. The energy that drives this process is referred to as ___________. (a) dissociation energy. (b) association energy. (c) binding energy. (d) releasing energy.

Which of the following mechanisms best describes the manner in which lysozyme lowers the energy required for its substrate to reach its transition-state conformation? (a) by binding two molecules and orienting them in a way that favors a reaction between them (b) by altering the shape of the substrate to mimic the conformation of the transition state (c) by speeding up the rate at which water molecules collide with the substrate (d) by binding irreversibly to the substrate so that it cannot dissociate

Choose the phrase that best completes this sentence: Microtubules ____________ and are required to pull duplicated chromosomes to opposite poles of dividing cells. (a) generate contractile forces (b) are intermediate in thickness (c) can rapidly reorganize (d) are found in especially large numbers in muscle cells

Energy cannot be created or destroyed, but it can be converted into other types of energy. Cells use potential kinetic energy to generate stored chemical energy in the form of activated carrier molecules, which are often employed to join two molecules together in _____________ reactions. (a) oxidation (b) hydrolysis (c) condensation (d) reduction

You are studying a biochemical pathway that requires ATP as an energy source. To your dismay, the reactions soon stop, partly because the ATP is rapidly used up and partly because an excess of ADP builds up and inhibits the enzymes involved. You are about to give up when the following table from a biochemistry textbook catches your eye. Which of the following reagents are most likely to revitalize your reaction? (a) a vast excess of ATP (b) glucose 6-phosphate and enzyme D (c) creatine phosphate and enzyme A (d) pyrophosphate

Mitochondria contain their own genome, are able to duplicate, and actually divide on a different time line from the rest of the cell. Nevertheless, mitochondria cannot function for long when isolated from the cell because they are __________________. (a) viruses. (b) parasites. (c) endosymbionts. (d) anaerobes.

At first glance, it may seem that living systems are able to defy the second law of thermodynamics. However, on closer examination, it becomes clear that although cells create organization from raw materials in the environment, they also contribute to disorder in the environment by releasing _____________. (a) water. (b) radiation. (c) heat. (d) proteins.

which statement is not true about mutations? (a) a mutation is a change in the DNA that can generate offspring less fit for survival than their parents (b)mutations can be result of imperfect DNA duplications (c) a mutation is a result of sexual reproduction (d) a mutation is a change in the DNA that can generate offspring that are more fit for survival than their parents are

Which of the following methods used to study proteins is limited to proteins with a molecular mass of 50 kD or less? (a) X-ray crystallography (b) fingerprinting (c) nuclear magnetic resonance (d) mass spectroscopy

__________ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. These chemicals are both generated and broken down in the same location. (a) Nucleosomes (b) Lysosomes (c) Peroxisomes (d) Endosomes

Table Q2-14 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +1 in solution? (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is: _____________. (a) uphill. (b) uncatalyzed. (c) spontaneous. (d) activated.

Mitochondria perform cellular respiration, a process that uses oxygen, generates carbon dioxide, and produces chemical energy for the cell. Which answer below indicates a correct pairing of material "burned" and the form of energy produced during cellular respiration? (a) fat, ADP (b) sugar, fat (c) sugar, ATP (d) fat, protein

Antibody production is an indispensible part of our immune response, but it is not the only defense our bodies have. Which of the following is observed during an infection that is not a result of antibody-antigen interactions? (a) B cell proliferation (b) aggregation of viral particles (c) systemic temperature increase (d) antibody secretion

The graph in Figure Q3-52 illustrates the relationship between reaction rates and substrate concentration for an enzyme-catalyzed reaction. What does the Km value indicate with respect to enzyme-substrate interactions? (a) the maximum rate of catalysis (b) the number of enzyme active sites (c) the enzyme-substrate binding affinity (d) the equilibrium rate of catalysis

Oxidation and reduction states are relatively easy to determine for metal ions, because there is a measurable net charge. In the case of carbon compounds, oxidation and reduction depend on the nature of polar covalent bonds. Which of the following is the best way to describe these types of bond? (a) hydrogen bonds in a nonpolar solution (b) covalent bonds in an aqueous solution (c) unequal sharing of electrons across a covalent bond (d) equal sharing of electrons across a covalent bond

Which of the following methods would be the most suitable to assess levels of expression of your target protein in different cell types? (a) gel-filtration chromatography (b) gel electrophoresis (c) western blot analysis (d) ion-exchange chromatography

Biological membranes are composed of specialized lipids that form bilayers. Which of the following is formed by unmodified fatty acids? (a) fat droplets (b) bilayers (c) micelles (d) planar lipid patches

(c)micelles

Which of the following characteristics would not support the idea that the ancestral eukaryote was a predator cell that captured and consumed other cells? (a) dynamic cytoskeleton (b) large cell size (c) ability to move (d) rigid membrane

(d)

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B? (a) kon/koff = K (b) K = [A][B]/[AB] (c) K = [AB]/[A][B] (d) (a) and (c)

(d) (a) and (c)

Which pair of values best fills in the blanks in this statement: On average, eukaryotic cells are __________ times longer and have _________ times more volume than prokaryotic cells. (a) 5, 100 (b) 10, 200 (c) 10, 100 (d) 10, 1000

(d) 10, 1000

You have a concentrated stock solution of 10 M NaOH and want to use it to produce a 150 ml solution of 3 M NaOH. What volume of water and stock solutions will you measure out to make this new solution? (a) 135 ml of water, 15 ml of NaOH stock (b) 115 ml of water, 35 ml of NaOH stock (c) 100 ml of water, 50 ml of NaOH stock (d) 105 ml of water, 45 ml of NaOH stock

(d) 105 ml of water, 45 ml of NaOH stock

Avogadro's number, calculated from the atomic weight of hydrogen, tells us how many atoms or molecules are in mole. The resulting base for all calculations of moles and molarity (how many molecules are present when you weigh out a substance or measure from a stock solution) is the following: 1 g of hydrogen atoms = 6 * 1023 atoms = 1 mole of hydrogen Sulfur has a molecular weight of 32. How many moles and atoms are there in 120 grams of sulfur? (a) 3.75 and 6 × 10^23 (b) 32 and 6 × 10^23 (c) 1.75 and 1.05 × 10^24 (d) 3.75 and 2.25 × 10^24

(d) 3.75 and 2.25 * 10^24

The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins? (a) They are degraded. (b) They bind a different target protein. (c) They form structured filaments. (d) They form protein aggregates.

(d) They form protein aggregates.

Molecular chaperones can work by creating an "isolation chamber." What is the purpose of this chamber? (a) The chamber acts as a garbage disposal, degrading improperly folded proteins so that they do not interact with properly folded proteins. (b) This chamber is used to increase the local protein concentration, which will help speed up the folding process. (c) This chamber serves to transport unfolded proteins out of the cell. (d) This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

(d) This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. The human genome is roughly 30 times larger than the Arabidopsis genome, but contains approximately the same number of protein-coding genes. B. The variation in genome size among protozoans is larger than that observed across all species of mammals, birds, and reptiles. C. The vast majority of our genome encodes functional RNA molecules or proteins and most of the intervening DNA is nonfunctional.

A. True. B. True. C. False. It is a relatively small proportion of our DNA that encodes RNA and protein molecules. The majority of nonencoding sequences is probably involved in critical regulatory processes.

Which statement is NOT true about the events/conclusions from studies during the mid-1800s surrounding the discovery of cells? (a) Cells came to be known as the smallest universal building block of living organisms. (b) Scientists came to the conclusion that new cells can form spontaneously from the remnants of ruptured cells. (c) Light microscopy was essential in demonstrating the commonalities between plant and animal tissues. (d) New cells arise from the growth and division of previously existing cells.

B. scientist came to the conclusion that new cells can form spontaneously from remnants of ruptured cells

Scientists learned that cell death is a normal and even important part of life by studying the development of the nematode worm C. elegans. What was the most important feature of C. elegans for the study of programmed cell death? (a) The nematode is smaller and simpler than the fruit fly. (b) 70% of C. elegans genes have homologs in humans. (c) The developmental pathway of each cell in the adult worm was known. (d) Its genome was partially sequenced.

C. This is the best answer because it was the prior developmental studies tracing cell lineages from the egg to the adult that allowed scientists to identify the precise time and location of cells that were being targeted for cell death. It was observed that this cell death was a normal and necessary part of the developmental pathway in the worm. Programmed cell death has since become known to be an important process in all multicellular eukaryotic organisms.

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Cells can be very diverse: superficially, they come in various sizes, ranging from bacterial cells such as Lactobacillus, which is a few __________________ in length, to larger cells such as a frog's egg, which has a diameter of about one __________________. Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, the same 20 __________________ are used to make proteins. Similarly, the genetic information of all cells is stored in their __________________. Although __________________ contain the same type of molecules as cells, their inability to reproduce themselves by their own efforts means that they are not considered living matter. -amino acids -micrometer(s) -viruses -DNA -fatty acids -meter -plasma membranes -millimeters -yeast

Cells can be very diverse: superficially, they come in various sizes, ranging from bacterial cells such as Lactobacillus, which is a few micrometers in length, to larger cells such as a frog's egg, which has a diameter of about one millimeter. Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, the same 20 amino acids are used to make proteins. Similarly, the genetic information of all cells is stored in their DNA. Although viruses contain the same type of molecules as cells, their inability to reproduce themselves by their own efforts means that they are not considered living matter.

Eukaryotic cells are able to trigger the release of material from secretory vesicles to the extracellular space using a process called exocytosis. An example of materials commonly released this way is _____________. hormones. nucleic acids. sugars. cytosolic proteins.

Hormones

Hydrophobic

Which subatomic particles can vary between isotopes of the same element, without changing the observed chemical properties? electrons protons and neutrons neutrons neutrons and electrons

Neutrons

Which of the following statements is false about model organisms: -should be easy to take care of. -should, as closely as possible, represent they system you are interested in studying -are cheaper to maintain in the lab than more complex organisms -can help relieve some of the ethical concerns of research on more complex organisms -None of the above statements is false

None of the above statements is false

Arrange the following molecules in order with respect to their relative levels of oxidation (assign 5 to the most oxidized and 1 to the most reduced). _______ CH2O (formaldehyde) _______ CH4 (methane) _______ CHOOH (formic acid) _______ CH3OH (methanol) _______ CO2 (carbon dioxide)

__3__ CH2O (formaldehyde) __1__ CH4 (methane) __4__ CHOOH (formic acid) __2__ CH3OH (methanol) __5__ CO2 (carbon dioxide)

This organelle has an acidic pH and digestive enzymes and is used to digest phagocytized material. lysosome mitochondria nucleus peroxisome

Lysosome

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. A. base B. glycosidic bond C. nucleoside D. nucleotide E. phosphoanyhydride bond F. phosphoester bond G. ribose H. phosphodiester bond I. deoxyribose 1. __ _ the linkage between two nucleotides 2. ____ the linkage between the 5′ sugar hydroxyl and a phosphate group 3. ____ the nitrogen-containing aromatic ring 4. ____ five-carbon sugar found in DNA 5. ___ sugar unit linked to a base 6. ____ linkage between the sugar and the base 7. ____ linkages between phosphate groups 8. ____ sugar linked to a base and a phosphate 9. ____ five-carbon sugar found in RNA

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. A. base B. glycosidic bond C. nucleoside D. nucleotide E. phosphoanyhydride bond F. phosphoester bond G. ribose H. phosphodiester bond I. deoxyribose 1. __ H_ the linkage between two nucleotides 2. _f___ the linkage between the 5′ sugar hydroxyl and a phosphate group 3. _a___ the nitrogen-containing aromatic ring 4. _i___ five-carbon sugar found in DNA 5. __c_ sugar unit linked to a base 6. __b__ linkage between the sugar and the base 7. __e__ linkages between phosphate groups 8. _d___ sugar linked to a base and a phosphate 9. __g__ five-carbon sugar found in RNA

Match the basic protein functions in the left column with a specific example of that type of protein in the column on the right. ___ gene regulatory ___ motor ___ storage ___ enzyme ___ transport ___ structural ___ special purpose ___ receptor ___ signal A. insulin B. carboxylase C. rhodopsin D. hemoglobin E. ferritin F. myosin G. green fluorescent protein H. tubulin I. homeodomain proteins

gene regulatory __I_ motor __F_ storage __E_ enzyme __B_ transport __D_ structural __H_ special purpose __G_ receptor __C_ signal __A_

ΔG° indicates the change in the standard free energy as a reactant is converted to product. Given what you know about these values, which reaction below is the most favorable? ADP + Pi ATP ΔG° = +7.3 kcal/mole glucose 1-phosphate glucose 6-phosphate ΔG° = -1.7 kcal/mole glucose + fructose sucrose ΔG° = +5.5 kcal/mole glucose CO2 + H2O ΔG° = -686 kcal/mole

glucose CO2 + H2O ΔG° = -686 kcal/mole

ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). When [Y] =[X], ΔG is equal to _____________. ΔG° + RT RT ln [X]/[Y] ΔG°

ΔG°

2-43 Both DNA and RNA are synthesized by covalently linking a nucleotide triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together? (a) ionic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

(B) Hydrogen bonds

Prokaryotic cells are able to evolve very fast, which helps them to rapidly adapt to new food sources and develop resistance to antibiotics. Which of the options below lists the three main characteristics that support the rapid evolution of prokaryotic populations? (a) microscopic, motile, anaerobic (b) aerobic, motile, rapid growth (c) no organelles, cell wall, can exchange DNA (d) large population, rapid growth, can exchange DNA

(D) large population, rapid growth, can exchange DNA

Isomerization of glucose 1-phosphate to glucose 6-phosphate is energetically favorable. At 37°C, ΔG° = -1.42 log10K. What is the equilibrium constant for this reaction if ΔG° = -1.74 kcal/mole at 37°C? (a) 16.98 (b) 0.09 (c) -0.09 (d) 0.39

(a) 16.98

Which of the following statements about allostery is true? (a) Allosteric regulators are often products of other chemical reactions in the same biochemical pathway. (b) Allosteric regulation is always used for negative regulation of enzyme activity. (c) Enzymes are the only types of proteins that are subject to allosteric regulation. (d) Binding of allosteric molecules usually locks an enzyme in its current conformation, such that the enzyme cannot adopt a different conformation.

(a) Allosteric regulators are often products of other chemical reactions in the same

Protein folding can be studied using a solution of purified protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution? (a) The polypeptide returns to its original conformation. (b) The polypeptide remains denatured.(c) The polypeptide forms solid aggregates and precipitates out of solution. (d) The polypeptide adopts a new, stable conformation.

(a) The polypeptide returns to its original conformation.

The study of enzymes also includes an examination of how the activity is regulated. Molecules that can act as competitive inhibitors for a specific reaction are often similar in shape and size to the enzyme's substrate. Which variable(s) used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor? (a) Vmax (b) V (c) Vmax and Km (d) Km

(a) Vmax

Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of ________________. (a) a water molecule. (b) an amino group. (c) a carbon atom. (d) a carboxylic acid group.

(a) a water molecule.

You have two purified samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a single amino acid substitution. When washed through the same gel- filtration column, mutant protein Y runs through the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely to explain this result? (a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers (b) a change that results in the mutant protein acquiring an overall positive instead of a negative charge (c) a change that results in the mutant protein being larger than the wild-type protein (d) a change that results in the mutant protein having a slightly different shape from the wild-type protein

(a) the loss of a binding site on the mutant-protein surface through which protein Y normally forms dimers

Proteins can assemble to form large complexes that work coordinately, like moving parts inside a single machine. Which of the following steps in modulating the activity of a complex protein machine is least likely to be directly affected by ATP or GTP hydrolysis? (a) translation of protein components (b) conformational change of protein components (c) complex assembly (d) complex disassembly

(a) translation of protein components

Indicate whether the statements below are true or false. If a statement is false A. Electrons are constantly moving around the nucleus of the atom, but they can move only in discrete regions. B. There is no limit to the number of electrons that can occupy the fourth electron shell. C. Atoms with unfilled outer electron shells are especially stable and are therefore less reactive. D. Covalent bonds are formed when electrons are either shared or transferred between atoms.

(a) true (b) false (c) false (d) false

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. Membrane components in the cell are made in the endoplasmic reticulum. B. The Golgi apparatus is made up of a series of membrane-enclosed compartments through which materials destined for secretion must pass. C. Lysosomes are small organelles where fatty acid synthesis occurs.

(a) true (b) true (c)False. Lysosomes house enzymes that break down nutrients for use by the cell and help recycle materials that cannot be used, which will later be excreted from the cell.

Which of the following globular proteins is used to form filaments as an intermediate step to assembly into hollow tubes? (a) tubulin (b) actin (c) keratin (d) collagen

(a) tubulin

34. For the reaction YX at standard conditions with [Y] = 1 M and [X] = 1 M, ΔG is initially a large negative number. As the reaction proceeds, [Y] decreases and [X] increases until the system reaches equilibrium. How do the values of ΔG and ΔG° change as the reaction equilibrates? (a) ΔG becomes less negative and ΔG° stays the same. (b) ΔG becomes positive and ΔG° becomes positive. (c) ΔG stays the same and ΔG° becomes less negative. (d) ΔG reaches zero and ΔG° becomes more negative.

(a) ΔG becomes less negative and ΔG° stays the same.

There are 20100 different possible sequence combinations for a protein chain with 100 amino acids. In addition to the amino acid sequence of protein, what other factors increase the potential for diversity in these macromolecules? (a) free rotation around single bonds during synthesis (b) noncovalent interactions sampled as protein folds (c) the directionality of amino acids being added (d) the planar nature of the peptide bond

(a)free rotation around a single bond during synthesis

Which of the following statements is true? (a) Disulfide bonds are formed by the cross-linking of methionine residues. (b) Disulfide bonds are formed mainly in proteins that are retained within the cytosol. (c) Disulfide bonds stabilize but do not change a protein's final conformation. (d) Agents such as mercaptoethanol can break disulfide bonds through oxidation.

The anhydride formed between a carboxylic acid and a phosphate (Figure Q3-69A) is a high-energy intermediate for some reactions in which ATP is the energy source. Arsenate can also be incorporated into a similar high-energy intermediate in place of the phosphate (Figure Q3-69B). Figure Q3-69C shows the reaction profiles for the hydrolysis of these two high-energy intermediates. What is the effect of substituting arsenate for phosphate in this reaction? (a) It forms a high-energy intermediate of lower energy. (b) It forms a high-energy intermediate of the same energy. (c) It decreases the stability of the high-energy intermediate. (d) It increases the stability of the high-energy intermediate.

The equilibrium constant (K) for the reaction YX can be expressed with respect to the concentrations of the reactant and product molecules. Which of the expressions below shows the correct relationship between K, [Y], and [X]? (a) K = [Y]/[X] (b) K=[Y]*[X] (c) K = [X]/[Y] (d) K=[X]-[Y]

Which of the following statements is true? (a) Peptide bonds are the only covalent bonds that can link together two amino acids in proteins. (b) The polypeptide backbone is free to rotate about each peptide bond. (c) Nonpolar amino acids tend to be found in the interior of proteins. (d) The sequence of the atoms in the polypeptide backbone varies between different proteins.

Protein E can bind to two different proteins, S and I. The binding reactions are described by the following equations and values:E+SES Keq forES=10 E+IEI Keq forEI=2 Given the equilibrium constant values, which one of the following statements is true? (a) E binds I more tightly than S. (b) When S is present in excess, no I molecules will bind to E. (c) The binding energy of the ES interaction is greater than that of the EI interaction. (d) Changing an amino acid on the binding surface of I from a basic amino acid to an acidic one will probably make the free energy of association with E more negative.

Which of the following is not true of molecular chaperones? (a) They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway. (b) They can isolate proteins from other components of the cells until folding is complete. (c) They can interact with unfolded polypeptides in a way that changes the final fold of the protein. (d) They help streamline the protein-folding process by making it a more efficient and reliable process inside the cell.

The graph in Figure Q3-53 illustrates the change in the rate of an enzyme-catalyzed reaction as the concentration of substrate is increased. Which of the values listed below is used to calculate the enzyme turnover number? (a) 1⁄2Vmax (b) Km (c) Vmax (d) Vmax - Km

Energy required by the cell is generated in the form of ATP. ATP is hydrolyzed to power many of the cellular processes, increasing the pool of ADP. As the relative amount of ADP molecules increases, they can bind to glycolytic enzymes, which will lead to the production of more ATP. The best way to describe this mechanism of regulation is ___________. (a) feedback inhibition. (b) oxidative phosphorylation. (c) allosteric activation. (d) substrate-level phosphorylation.

Proteins are important architectural and catalytic components within the cell, helping to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions. (a) nucleotides (b) sugars (c) amino acids (d) fatty acids

When there is an excess of nutrients available in the human body, insulin is released to stimulate the synthesis of glycogen from glucose. This is a specific example of a(n) __________ process, a general process in which larger molecules are made from smaller molecules. (a) metabolic (b) catabolic (c) anabolic (d) biosynthetic

Which of the following statements is false? (a) ATP contains high-energy phosphoanhydride bonds. (b) ATP is sometimes called the "universal currency" in the energy economy of cells. (c) ATP can be incorporated into DNA. (d) ATP can be hydrolyzed to release energy to power hundreds of reactions in cells. (e) ATP comprises a sugar, phosphate groups, and a nitrogenous base.

(c) atp can be incorporated into DNA ATP is used in energy conversions, contains ribose, and can be incorporated into RNA. But synthesis of DNA requires the deoxyribose form of the nucleotide, dATP. All the other statements about ATP are true.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. A virus is a living organism. B. Cells of different types can have different chemical requirements. C. A human white blood cell is larger than a Paramecium cell.

A. False. A virus lacks the full machinery required to copy itself and is therefore not considered a living organism. B. True. C. False. A human white blood cell is about 10-celled paramecium is roughly 10 times that size.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. Plants do not require a cytoskeleton because they have a cell wall that lends structure and support to the cell. B. The cytoskeleton is used as a transportation grid for the efficient, directional movement of cytosolic components. C. Thermal energy promotes random movement of proteins, vesicles, and small molecules in the cytosol.

A. False. Although plant cells do have a cell wall that lends structure and support, they still need a cytoskeleton, which also helps with connections between cells and the transport of vesicles inside the cell. B. True C. True

Indicate whether the following statements about enzymes are true or false. If a statement is false, explain why it is false. A. Enzymes alter the equilibrium point of a reaction. B. Vmax can be determined by measuring the amount of product accumulated late in the reaction. C. Competitive inhibitors bind irreversibly to the enzyme active site, lowering Vmax.

A. False. An enzyme catalyzes its reaction in both directions, lowering the energy of activation for both the forward and reverse reactions. Enzymes do not affect the free energy of the reactants and products are the same, and thus they do not affect the reaction equilibrium. B. False. Initial reaction velocities are measured to determine Vmax. C. False. Competitive inhibitors bind reversibly to an enzyme's active site.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. The terms "prokaryote" and "bacterium" are synonyms. B. Prokaryotes can adopt several different basic shapes, including spherical, rod-shaped, and spiral. C. Some prokaryotes have cell walls surrounding the plasma membrane.

A. False. Archaea make up a class of prokaryotic organisms that are significantly different from bacteria. B. True C. True

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Collagen is a protein that participates in both the cytoskeleton and the extracellular matrix. B. Collagen fibers and elastin fibers serve similar functions, which is expected because the structure of these two types of fibers is quite similar. C. The assembly of both collagen and elastin fibers requires the formation of disulfide bonds.

A. False. Collagen is not used inside the cell; it is secreted and incorporated into the existing collagen fibers in the extracellular matrix. False. Collagen fibers and elastin fibers are very different in structure and function. Collagen fibers are highly organized, triple-strand coiled-coils that provide strength to hold tissue together. Elastin molecules are linked together in a loose network with disulfide bonds; this allows the fibers (and tissues) to stretch without tearing. True.

32. Which of the following statements are true or false? If a statement is false, explain why it is false. A. Enzymes lower the free energy released by the reaction that they facilitate. B. Enzymes lower the activation energy for a specific reaction. C. Enzymes increase the probability that any given reactant molecule will be converted to product. D. Enzymes increase the average energy of reactant molecules.

A. False. Enzymes do not affect the initial energy of the reactants nor the final energy of the products after the reaction is complete, which are the values that determine the change in free energy of a reaction. B. True. C. True. D. False. By lowering the energy of activation, enzymes increase the number of molecules in a population that can overcome the activation barrier.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. When two macromolecules form a complex, the free energy of the system increases because there is a net increase in the amount of order in the cell. B. Sequential pathways can help drive unfavorable reactions by siphoning off the products into the next energetically favorable reaction in the series. C. The cytosol is densely packed with molecules, creating what is more an aqueous gel than a solution. D. The diffusion rates for smaller molecules in the cytosol are much lower than what is observed for the same molecules in water.

A. False. Even nonspecific interactions between macromolecules can be favorable if there is a large number of water molecules and ions displaced at the interaction interface. This would lead to an overall increase in disorder, even though the two larger molecules become associated and more ordered. B. True. C. True. D. False. Small molecules diffuse through the cytosol nearly as rapidly as they diffuse in water.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Feedback inhibition is defined as a mechanism of down-regulating enzyme activity by the accumulation of a product earlier in the pathway. B. If an enzyme's allosteric binding site is occupied, the enzyme may adopt an alternative conformation that is not optimal for catalysis. C. Protein phosphorylation is another way to alter the conformation of an enzyme and serves exclusively as a mechanism to increase enzyme activity. D. GTP-binding proteins typically have GTPase activity, and the hydrolysis of GTP transforms them to the "off" conformation.

A. False. Feedback inhibition occurs when an enzyme acting early in a metabolic pathway is inhibited by the accumulation of a product late in the pathway. The inhibitory product binds to a site on the enzyme that lowers its catalytic activity. B. True. C. False. Although phosphorylation of a protein can change its conformation, this modification may be either as a positive or a negative regulator of enzyme activity, depending on the protein in question. D. True.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. With respect to cellular respiration, the only organelles used by animal cells are mitochondria, while plant cells use both mitochondria and chloroplasts. B. The number of mitochondria inside a cell remains constant over the life of the cell.

A. False. In plants, only mitochondria perform cellular respiration (using oxygen to break down organic molecules to produce carbon dioxide) just as in animal cells. Chloroplasts perform photosynthesis in which water molecules are split to generate oxygen and fix carbon dioxide molecules. B. False. Mitochondria have their own division cycle and their numbers change based on the rate of division.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Photosynthetic organisms release only O2 into the atmosphere, while nonphotosynthetic organisms release only CO2. B. The cycling of carbon through the biosphere first requires the incorporation of inorganic CO2 into organic molecules. C. The oxidation of one molecule is always coupled to the reduction of a second molecule. D. During cellular respiration, carbon-containing molecules become successively more oxidized until they reach their most oxidized form, as CO2.

A. False. Plants, as well as photosynthetic algae and bacteria, perform both photosynthesis and respiration. This means that photosynthetic organisms release both O2 and CO2 into the atmosphere. B. True. C. True. This forms the basis for redox pairs. D. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. The amino acids in the interior of a protein do not interact with the ligand and do not play a role in selective binding. B. Antibodies are Y-shaped and are composed of six different polypeptide chains. C. ATPases generate ATP for the cell. D. Hexokinase recognizes and phosphorylates only one of the glucose stereoisomers.

A. False. The interior amino acids form a structural scaffold that maintains the specific orientation for those that directly interact with the ligand. Changes to these interior amino acids can change the protein shape and render it nonfunctional. B. False. Although antibodies are Y-shaped, they are composed of four, not six, polypeptide chains. There are two heavy chains and two light chains. C. False. ATPases hydrolyze ATP; they do not produce it. These enzymes enable the cell to harness the chemical energy stored in the high-energy phosphate bonds. D. True.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. Primitive plant, animal, and fungal cells probably acquired mitochondria after they diverged from a common ancestor. B. Protozoans are single-celled eukaryotes with cell morphologies and behaviors that can be as complex as those of some multicellular organisms. C. The first eukaryotic cells on Earth must have been aerobic; otherwise, they would not have been able to survive when the planet's atmosphere

A. False. The mitochondria in modern plant, animal, and fungal cells are very similar, implying that these lines diverged after the mitochondrion was acquired by the ancestral eukaryote. B. True. C. False. The first eukaryotic cells likely contained a nucleus but no mitochondria. These ancestral eukaryotes subsequently adapted to survive in a world filled with oxygen by engulfing primitive aerobic prokaryotic cells.

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. The nucleus of an animal cell is round, small, and difficult to distinguish using light microscopy. B. The presence of the plasma membrane can be inferred by the well-defined boundary of the cell. C. The cytosol is fairly empty, containing a limited number of organelles, which allows room for rapid movement via diffusion.

A. False. The nucleus is one of the largest organelles and is the easiest organelle to discern within a typical cell. B. True C. False. The cytosol is actually brimming with individual proteins, protein fibers, extended membrane systems, transport vesicles, and small molecules. And although cellular components do move by diffusion, the rate of movement is limited by the space available and the size of the component in question.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Generally, the total number of nonpolar amino acids has a greater effect on protein structure than the exact order of amino acids in a polypeptide chain. B. The "polypeptide backbone" refers to all atoms in a polypeptide chain, except for those that form the peptide bonds. C. The chemical properties of amino acid side chains include charged, uncharged polar, and nonpolar. D. The relative distribution of polar and nonpolar amino acids in a folded protein is determined largely by hydrophobic interactions, which favor the clustering of nonpolar side chains in the interior.

A. False. The order in which amino acids are linked is unique for each protein and is the most important factor in determining overall protein structure. B. False. Peptide bonds are planar amide bonds that are central to the polypeptide backbone formation. The atoms in the amino acid side chains are not considered to be part of the backbone. C. True. D. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. The second law of thermodynamics states that the total amount of energy in the Universe does not change. B. The ultimate source of energy for living systems is chlorophyll. C. CO2 gas is fixed in a series of reactions that are light-dependent. D. H2 is the most stable and abundant form of hydrogen in the environment

A. False. The second law of thermodynamics states that components of any system move toward greater disorder. It is the first law of thermodynamics that states that energy is neither created nor destroyed. B. False. The ultimate source of energy for living organisms is sunlight. C. False. The fixation of carbon from CO2 occurs independently of light. D. False. The most stable form of hydrogen is H2O.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Van der Waals interactions and hydrophobic interactions are two ways to describe the same type of weak forces that help proteins fold. B. A large number of noncovalent interactions is required to hold two regions of a polypeptide chain together in a stable conformation. C. A single polypeptide tends to adopt 3-4 different conformations, which all have equivalent free-energy values (G).

A. False. Van der Waals attractions are weakly attractive forces that occur between all atoms. Hydrophobic interactions are only observed between nonpolar molecules in the context of an aqueous solution. B. True. C. False. There is a single, final fold for every polypeptide. The fold adopted is the "best" conformation, for which the free energy (G) of the molecule is at a minimum.

For each polypeptide sequence listed, choose from the options given below to indicate which secondary structure the sequence is most likely to form upon folding. The nonpolar amino acids are italicized. A. Leu-Gly-Val-Leu-Ser-Leu-Phe-Ser-Gly-Leu-Met-Trp-Phe-Phe-Trp-Ile B. Leu-Leu-Gln-Ser-Ile-Ala-Ser-Val-Leu-Gln-Ser-Leu-Leu-Cys-Ala-Ile C. Thr-Leu-Asn-Ile-Ser-Phe-Gln-Met-Glu-Leu-Asp-Val-Ser-Ile-Arg-Trp amphipathic α helix hydrophilic β sheet amphipathic β sheet hydrophobic α helix hydrophilic α helix

A. Hydrophobic α helix B. Amphipathic α helix C. Amphipathic β sheet

Indicate whether the following statements are true or false. If the statement is false, explain why it is false. A. Oxygen is toxic to certain prokaryotic organisms. B. Mitochondria are thought to have evolved from anaerobic bacteria. C. Photosynthetic bacteria contain chloroplasts.

A. True B. False. Mitochondria use oxygen to generate energy and are thought to have evolved from aerobic bacteria. C.C. False. Photosynthetic bacteria have enzyme systems similar to those found in chloroplasts, which allow them to harvest light energy to fix carbon dioxide.

On the basis of the two reactions below, decide which of the following statements are true and which are false. If a statement is false, explain why it is false. 1: ATP + YY-P + ADP ΔG = -100 kcal/mole 2: Y-P + AB ΔG = 50 kcal/mole A. Reaction 1 is favorable because of the large negative ΔG associated with the hydrolysis of ATP. B. Reaction 2 is an example of an unfavorable reaction. C. Reactions 1 and 2 are coupled reactions, and when they take place together, reaction 2 will proceed in the forward direction. D. Reaction 2 can be used to drive reaction 1 in the reverse direction.

A. True. B. True. C. True. D. False. This is false for two reasons: (1) reaction 2 is unfavorable, as indicated by the positive free-energy change associated with the reaction; (2) the reverse reaction, although possibly more favorable, will yield the product for reaction 1, not reactants to help drive it forward.

Given what you know about the differences between prokaryotic cells and eukaryotic cells, rate the following things as "good" or "bad" processes to study in the model organism E. coli. A. formation of the endoplasmic reticulum B. DNA replication C. how the actin cytoskeleton contributes to cell shape D. how cells decode their genetic instructions to make proteins E. how mitochondria get distributed to cells during cell division

A. bad B. good C. bad D. good E. bad

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. A. forming ionic bonds with negatively charged DNA B. forming hydrogen bonds to aid solubility in water C. binding to another water-soluble protein D. localizing an "integral membrane" protein that spans a lipid bilayer E. tightly packing the hydrophobic interior core of a globular protein acidic nonpolar basic uncharged polar

A. basic B. uncharged polar C. uncharged polar, basic, and acidic D. nonpolar E. nonpolar

For each of the following, indicate whether the individual folded polypeptide chain forms a globular (G) or fibrous (F) protein molecule. A. keratin B. lysozyme C. elastin D. collagen E. hemoglobin F. actin

A—F B—G C—F D—F E—G F—G

Match each biological process with the model organism that is best suited or most specifically useful for its study, based on information provided in your textbook. You may list individual processes more than once. A. cell division B. development (multicellular) C. programmed cell death D. photosynthesis E. immunology _____ A. thaliana (Arabidopsis) _____ M. musculus (mouse) _____ S. pombe _____ C. elegans _____ S. cerevisiae _____ D. rerio (zebrafish) _____ D. melanogaster

B, D A. thaliana (Arabidopsis) B, E M. musculus (mouse) A S. pombe C C. elegans A S. cerevisiae B D. rerio (zebrafish) B D. melanogaster

Match the type of microscopy on the left with the corresponding description provided below. There is one best match for each. A. confocal B. transmission electron C. fluorescence D. phase-contrast E. scanning electron F. bright-field ____ uses a light microscope with an optical component to take advantage of the different refractive indices of light passing through different regions of the cell. ____ employs a light microscope and requires that samples be fixed and stained in order to reveal cellular details. ____ requires the use of two sets of filters. The first filter narrows the wavelength range that reaches the specimen and the second blocks out all wavelengths that pass back up to the eyepiece except for those emitted by the dye in the sample. ____ scans the specimen with a focused laser beam to obtain a series of two- dimensional optical sections, which can be used to reconstruct an image of the specimen in three dimensions. The laser excites a fluorescent dye molecule, and the emitted light from each illuminated point is captured through a pinhole and recorded by a detector. ____ has the ability to resolve cellular components as small as 2 nm. ____ requires coating the sample with a thin layer of a heavy metal to produce three-dimensional images of the surface of a sample.

D F C A B E

Since plants have chloroplasts, they do not need or have mitochondria. True False

False

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Eukaryotic cells are bigger and more elaborate than prokaryotic cells. By definition, all eukaryotic cells have a __________________, usually the most prominent organelle. Another organelle found in essentially all eukaryotic cells is the __________________, which generates the chemical energy for the cell. In contrast, the __________________ is a type of organelle found only in the cells of plants and algae, and performs photosynthesis. If we were to strip away the plasma membrane from a eukaryotic cell and remove all of its membrane-enclosed organelles, we would be left with the __________________, which contains many long, fine filaments of protein that are responsible for cell shape and structure and thereby form the cell's __________________. chloroplast chromosome cytoskeleton cytosol nucleus endoplasmic reticulum ribosomes mitochondrion

Eukaryotic cells are bigger and more elaborate than prokaryotic cells. By definition, all eukaryotic cells have a nucleus, usually the most prominent organelle. Another organelle found in essentially all eukaryotic cells is the mitochondrion, which generates the chemical energy for the cell. In contrast, the chloroplast is a type of organelle found only in the cells of plants and algae, and performs photosynthesis. If we were to strip away the plasma membrane from a eukaryotic cell and remove all of its membrane-enclosed organelles, we would be left with the cytosol, which contains many long, fine filaments of protein that are responsible for cell shape and structure and thereby form the cell's cytoskeleton.

Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets? cholesterol palmitic acid isoprene triacylglycerol

Triacylglycerol

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Whereas ionic bonds form a(n) _____ covalent bonds between atoms form a(n) ______ These covalent bonds have a characteristic bond ___ ______________ and become stronger and more rigid when two electrons are shared in a(n) ____ Equal sharing of electrons yields a(n) __________________ covalent bond. If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These _____covalent bonds should not be confused with the weaker _________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules. charge length polar covalent molecule salt double bond non-covalent single bond ionic non-polar weight

Whereas ionic bonds form a(n) _____salt_____________, covalent bonds between atoms form a(n) ______molecule____________. These covalent bonds have a characteristic bond ____length______________ and become stronger and more rigid when two electrons are shared in a(n) ____double bond______________. Equal sharing of electrons yields a(n) ___nonpolar_______________ covalent bond. If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These ______polar____________ covalent bonds should not be confused with the weaker _________noncovalent_________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules.

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