BIOS 222 Exam 1
(Ch. 11) Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? (a) switching between lipid layers (b) lateral movement (c) rotation (d) flexing of hydrocarbon chains
(a) switching between lipid layers
(Ch. 1) 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
(b) endoplasmic reticulum
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.
Both DNA and RNA are synthesized by covalently linking a nucleoside 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
(Ch. 11) Where does most new membrane synthesis take place in a eukaryotic cell? (a) in the Golgi apparatus (b) in the endoplasmic reticulum (c) in the plasma membrane (d) in the mitochondria (e) on ribosomes
(b) in the endoplasmic reticulum
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. By definition, catalysis allows a reaction to occur more __________________. Chemical reactions occur only when there is a loss of __________________ energy. Enzymes act more __________________ than other catalysts. A catalyst decreases the __________________ energy of a reaction. activation, free, selectively chemical bond, kinetic, slowly completely, rapidly, unfavorable favorable
By definition, catalysis allows a reaction to occur more rapidly. Chemical reactions occur only when there is a loss of free energy. Enzymes act more selectively than other catalysts. A catalyst decreases the activation energy of a reaction.
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.
C) spontaneous
(Ch. 11) While many prokaryotic cells have a single membrane bilayer, all eukaryotic cells have a complex system of internal membrane-bound compartments. How might it be advantageous for the cell to have these additional compartments?
Compartmentalization using intracellular membranes allows eukaryotic cells to separates a variety of cell processes. Although this requires a higher degree of coordination, the cell also gains a more stringent degree of control over these processes (examples include: the separation of transcription and translation; the separation of enzymes involved in protein modifications for secreted versus cytosolic substrates; the separation of proteolytic events in the lysosomes versus the cytosol etc.).
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
(Ch. 11) Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels? (a) They are made primarily of α helices. (b) They are made primarily of β sheets. (c) They cannot form narrow channels. (d) They have alternating hydrophobic and hydrophilic amino acids.
(a) They are made primarily of α helices.
(Ch. 1) By definition, prokaryotic cells do not possess __________. (a) a nucleus. (b) replication machinery. (c) ribosomes. (d) membrane bilayers.
(a) a nucleus.
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.
(Ch. 11) Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________. (a) cortex. (b) attachment complex. (c) cytoskeleton. (d) spectrin.
(a) cortex.
(Ch. 11) Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks? (a) flippases (b) phospholipases (c) convertases (d) glycosylases
(a) flippases
(Ch. 11) Which type of lipids are the most abundant in the plasma membrane? (a) phospholipids (b) glycolipids (c) sterols (d) triacylglycerides
(a) phospholipids
(Ch. 1) 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 of 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
(Ch. 1) A covalent bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d)transfer of electrons from one atom to the other.
(a) sharing of electrons.
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
Which of the following factors do not influence the length of a covalent bond? (a) the tendency of atoms to fill the outer electron shells (b) the attractive forces between negatively charged electrons and positively charged nuclei (c) the repulsive forces between the positively charged nuclei (d) the minimization of repulsive forces between the two nuclei by the cloud of shared electrons
(a) the tendency of atoms to fill the outer electron shells
(Ch. 11) Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference? (a) unsaturated hydrocarbons (b) longer hydrocarbon tails (c) higher levels of sterols (d) larger head groups
(a) unsaturated hydrocarbons
(Ch. 11) There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)? (a) 24 carbons with 1 double bond (b) 15 carbons with 2 double bonds (c) 20 carbons with 2 double bonds (d) 16 carbons with no double bonds
(b) 15 carbons with 2 double bonds
(Ch. 11) The amino acid sequences below represent the sequences of transmembrane helices. The characteristics of α helices that form a channel are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain. (a) VGHSLSIFTLVISLGIFVFF (b) IMIVLVMLLNIGLAILFVHF (c) ILHFFHQYMMACNYFWMLCE (d) VTLHKNMFLTYILNSMIIII
(b) IMIVLVMLLNIGLAILFVHF
(Ch. 11) A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? (a) Produce lipids with hydrocarbon tails that are longer and have fewer double bonds. (b) Produce lipids with hydrocarbon tails that are shorter and have more double bonds. (c) Decrease the amount of cholesterol in the membrane. (d) Decrease the amount of glycolipids in the membrane.
(b) Produce lipids with hydrocarbon tails that are shorter and have more double bonds.
(Ch. 11) Formation of a lipid bilayer is energetically favorable. How does this arrangement result in higher entropy for the system, and thus make bilayer formation energetically favorable? (a) Polar head groups form a hydrogen-bonding network at the interface with water. (b) Water molecules form cage like structures around hydrophobic molecules. (c) Hydrogen bonds form between neighboring polar head groups in the bilayer. (d) Fatty acid tails are highly saturated and flexible.
(b) Water molecules form cage-like structures around hydrophobic molecules.
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
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.
(Ch. 1) 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. Despite 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
(b) cell
(Ch. 1) 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
(Ch. 1) 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 combination of answers best completes the following statement: When atoms are held together by ___________ __________, they are typically referred to as _________. (a) hydrogen bonds, molecules. (b) ionic interactions, salts. (c) ionic interactions, molecules. (d) double bonds, nonpolar.
(b) ionic interactions, salts.
(Ch. 11) The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins? (a) intercellular communication (b) selective permeability (c) cellular movement (d) import/export of molecules
(b) selective permeability
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.
(Ch. 1) 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.
The equilibrium constant (K) for the reaction YàX 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]
(c) K = [X]/[Y]
(Ch. 1) __________ 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
(c) Peroxisomes
(Ch. 11) New membrane phospholipids are synthesized by enzymes bound to the _____________ side of the _________________ membrane. (a) cytosolic, mitochondrial (b) luminal, Golgi (c) cytosolic, endoplasmic reticulum (d) extracellular, plasma
(c) cytosolic, endoplasmic reticulum
(Ch. 11) Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify. Which of the following substances is most commonly used to help purify a membrane protein? (a) high salt solution (b) sucrose (c) detergent (d) ethanol
(c) detergent
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.
(c) heat.
Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they ____________________. (a) create a new arrangement of electron shells. (b) change the reactivity of the bonded atoms. (c) limit the rotation of the bonded atoms. (d) prevent additional bonds from being formed with the bonded atoms.
(c) limit the rotation of the bonded atoms.
(Ch. 1) 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
(c) sugar, ATP
(Ch .11) Which of the following statements is true? (a) Phospholipids will spontaneously form liposomes in nonpolar solvents. (b) In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. (c) Membrane lipids diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other.
(c). The remaining answers are false. Phospholipids form bilayers only in polar solvents. Nuclei and mitochondria are enclosed by two membranes. Membrane lipids rarely flip-flop between one monolayer and the other.
(Ch. 11) Which of the following membrane lipids does not contain a fatty acid tail? (a) phosphatidylcholine (b) a glycolipid (c) phosphatidylserine (d) cholesterol
(d) Cholesterol
(Ch. 11) We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for? (a) SDS (b) SPT (c) GFP (d) FRAP
(d) FRAP
(Ch. 1) Select the answer that best completes the following statement: Chemical reactions in living systems occur in an ____________ environment, within a narrow range of temperatures. (a) optimal (b) organic (c) extracellular (d) aqueous
(d) aqueous
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 à->ATP ΔG° = +7.3 kcal/mole (b) glucose 1-phosphate -> glucose 6-phosphate ΔG° = -1.7 kcal/mole (c) glucose + fructose -> sucrose ΔG° = +5.5 kcal/mole (d) glucose -> CO2 + H2O ΔG° = -686 kcal/mole
(d) glucose -> CO2 + H2O ΔG° = -686 kcal/mole
(Ch. 11) Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? (a) membrane permeability (b) membrane fluidity (c) membrane rigidity (d) membrane thickness
(d) membrane thickness
(Ch. 1) 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
(Ch. 1) 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
(Ch. 11) Membrane curvature is influenced by the differential lipid composition of the two membrane monolayers. Which factor do you think has the largest impact on the curvature of biological membranes? (a) amount of cholesterol (b) charge of the lipid head group (c) length of the hydrocarbon tails (d) size of the lipid head group
(d) size of the lipid head group
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 complementary between molecules
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.
(Ch. 1) An ionic bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d) transfer of electrons from one atom to the other.
(d) transfer of electrons from one atom to the other.
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? (a) cholesterol (b) palmitic acid (c) isoprene (d) triacylglycerol
(d) triacylglycerol
(Ch. 1) 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 1.)__________________ in length, to larger cells such as a frog's egg, which has a diameter of about one 2.)__________________. Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, the same 20 3.)__________________ are used to make proteins. Similarly, the genetic information of all cells is stored in their 4.)__________________. Although 5.)__________________ contain the same types 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 millimeter(s) yeast fatty acids plants meter plasma membranes
1. micrometers 2. millimeter 3. amino acids 4. DNA 5. Viruses
(Ch. 11) The specialized functions of different membranes are largely determined by the 1.)__________________ they contain. Membrane lipids are 2.)__________________ molecules, composed of a hydrophilic portion and a hydrophobic portion. All cell membranes have the same 3.)__________________ structure, with the 4.)__________________ of the phospholipids facing into the interior of the membrane and the 5.)__________________ on the outside. The most common lipids in most cell membranes are the 6.)__________________. The head group of a glycolipid is composed of 7.)__________________. amphipathic hydrophobic phosphatidylserine cholesterol lipid bilayer phospholipids fatty acid tails lipid monolayer proteins glycolipids lipids sterols hydrophilic head groups phosphatidylcholine sugars
1. proteins 2.amphipathic 3. lipid bi-layer 4. fatty acid tails 5. hydrophilic head groups 6. phospholipids 7. sugars.
(Ch. 11) There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called 1.)__________________ proteins and have 2.)__________________ regions that are exposed to the interior of the bilayer. On the other hand, membrane-associated proteins do not span the bilayer and instead associate with the membrane through an α helix that is 3.)__________________. Other proteins are 4.)__________________ attached to lipid molecules that are inserted in the membrane. 5.)__________________ membrane proteins are linked to the membrane through noncovalent interactions with other membrane-bound proteins. amphipathic hydrophilic noncovalently cortical hydrophobic peripheral covalently integral transmembrane detergent micelle unfolded
1. transmembrane 2. hydrophobic 3.amphipathic 4. covalently 5. Peripheral
(Ch. 1) Use the list of structures below to label the schematic drawing of an animal cell in Figure Q1-23. A. plasma membrane B. nuclear envelope C. cytosol D. Golgi apparatus E. endoplasmic reticulum F. mitochondrion G. transport vesicles
1.) Cytosol 2.) Golgi Apparatus 3.) Plasma Membrane 4.) Endoplasmic Reticulum 5.) Nuclear envelope 6.) Transport Vesicles 7.) Mitochondrion
(Ch. 1) 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 1.)__________________, usually the most prominent organelle. Another organelle found in essentially all eukaryotic cells is the 2.)__________________, which generates the chemical energy for the cell. In contrast, the 3.)__________________ 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 4.)__________________, which contains many long, fine filaments of protein that are responsible for cell shape and structure and thereby form the cell's 5.)__________________. chloroplast cytosol nucleus chromosome endoplasmic reticulum ribosomes cytoskeleton mitochondrion
1.) Nucleus 2.) Mitochondria 3.) Chloroplast 4.) Cytosol 5.) Cytoskeleton
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. Proteins are 1.)______________ built from amino acids, which each have an amino group and a 2.)_____________ group attached to the central 3.)_______________. There are twenty possible 4.)_______________ that differ in structure and are generally referred to as "R." In solutions of neutral pH, amino acids are 5.)_______________, carrying both a positive and negative charge. When a protein is made, amino acids are linked together through 6.)_______________, which are formed by condensation reactions between the carboxyl end of the last amino acid and the 7.)___________________ end of the next amino acid to be added to the growing chain. amino ionized polypeptides α-carbon length protein carbon noncovalent R group carboxyl peptide bonds side chains hydroxide
1.) Polypeptides 2.) Carboxyl 3.) α-carbon 4.) Side chains 5.) Ionized 6.) Peptide bonds 7.) Amino
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) 1.)__________________, covalent bonds between atoms form a(n) 2.)__________________. These covalent bonds have a characteristic bond 3.)__________________ and become stronger and more rigid when two electrons are shared in a(n) 4.)__________________. Equal sharing of electrons yields a(n) 5.)__________________ 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 6.)__________________ covalent bonds should not be confused with the weaker 7.)__________________ 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 noncovalent single bond ionic nonpolar weight
1.) Salt 2.) Molecule 3.) Length 4.) Double Bond 5.) Nonpolar 6.) Polar 7.) Noncovalent
(Ch. 1) 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.
1.) phase-contrast 2.) bright-field 3.) fluorescence 4.) confocal 5.) transmission electron 6.) bright-field
(Ch. 11) Which of the following phenomena will be observed if a cell's membrane is pierced? (a) the membrane reseals (b) the membrane collapses (c) a tear is formed (d) the membrane expands
A) the membrane reseals
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 lower the free energy released by the reaction that they facilitate. B. (True) Enzymes lower the activation energy for a specific reaction. C. (True) Enzymes increase the probability that any given reactant molecule will be converted to product. D. (True) Enzymes increase the average energy of reactant molecules.
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. C. The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure.
A. False. A disaccharide consists of two sugar molecules that undergo a condensation reaction to form a covalent bond (known as a glycosidic linkage). C. False. The presence of a double bond in the hydrocarbon chain of a fatty acid causes a kink in the chain, decreasing its flexibility and packing with neighboring hydrocarbon chains.
(Ch.11) Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. When a mouse cell is fused with a human cell, the movement of the respective membrane proteins is restricted to their original locations at the time of fusion. B. Epithelial cell membranes are asymmetric, and proteins from the apical side of the cell membrane cannot diffuse into the basal side of the membrane. D. The only role of the carbohydrate layer on the cell surface is to absorb water, which creates a slimy surface and prevents cells from sticking to each other.
A. False. After about 1 hour, the mouse and human proteins present on the surface of the fused cell are found evenly dispersed throughout the plasma membrane. C. False. The very long, branched polysaccharides that are attached to integral membrane proteins are much longer than the oligosaccharides covalently attached to membrane lipids. D. False. Although the absorption of water is an important role of the carbohydrates on the surface of the plasma membrane, a second critical role is that of cell-cell recognition important in immune responses, wound healing and other processes that rely on cell-type-specific interactions.
(Ch. 1) Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Electron shells fill discrete regions around the nucleus of the atom and limit the number of electrons that can occupy a specific orbit. C. Some atoms are more stable when they lose one or two electrons, even though this means they will have a net positive charge.
A. False. Although small molecules are important in many processes, the chemical reactions in living systems are regulated by the coordinated action of large polymeric molecules. B. True. C. False. The chemical reactions in living systems are very tightly controlled, ensuring that events occur at the proper time and at the proper location inside the cell.
(Ch. 11) Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Lipid-linked proteins are classified as peripheral membrane proteins because the polypeptide chain does not pass through the bilayer. B. A protein can be embedded on the cytosolic side of the membrane bilayer by employing a hydrophobic α helix. C. A protein that relies on protein-protein interactions to stabilize its membrane association is classified as a peripheral membrane protein because it can be dissociated without the use of detergents. D. Membrane proteins that pump ions in and out of the cell are classified as enzymes.
A. False. Lipid-linked proteins are classified as integral membrane proteins because although they are not transmembrane proteins, they are covalently bound to membrane lipids and cannot be dissociated without disrupting the membrane's integrity. B. False. An embedded protein employs an amphipathic helix. The hydrophobic side interacts with the fatty acid tails of the membrane lipids and the hydrophilic portion interacts with the aqueous components of the cytosol. C. True. D. False. Membrane proteins that pump ions in either direction across the membrane are in the functional class of transporters.
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 statements below are true or false. If a statement is false, explain why it is 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. Van der Waals attractions describe the general attractive forces between all atoms. The contact distance between any two non-bonded atoms is the sum of the van der Waals radii. Nonpolar interactions are based on the exclusion of hydrophobic molecules from a hydrophilic environment. B. True. C. True. D. False. One reason that nonpolar groups are excluded from an aqueous environment is that a hydrophobic surface would organize water into a highly structured network of hydrogen bonds, which is energetically unfavorable.
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 + Y -> Y-P + ADP ΔG = -100 kcal/mole 2: Y-P + A -> B 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. Reaction 1 is favorable because of the large negative ΔG associated with the hydrolysis of ATP is true B.Reaction 2 is an example of an unfavorable reaction is true C. Reactions 1 and 2 could be coupled reactions, and if they take place together, reaction 2 will proceed in the forward direction is true D. Reaction 2 can be used to drive reaction 1 in the reverse direction is false The above statement is false due to two reasons: A) Reaction 2 is unfavorable, as indicated by the positive free- energy change associated with the reaction B) The reverse reaction, although possibly more favorable, will yield the product for reaction 1, not reactants to help drive it forward.
(Ch. 11) Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like all other membrane lipids. B. The highly ordered structure of the lipid bilayer makes its generation and maintenance energetically unfavorable.
A.) True. B.) False. The formation of a lipid bilayer is energetically favorable.
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
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