In Pasteur's experiment, the purpose of the swan neck on the flask was to _____.
trap cells from the air before they reached the growth medium
Pasteur's experiment provided conclusive evidence to reject the spontaneous generation hypothesis, which states that cells arise from nonliving material. As a consequence, his results supported the all-cells-from-cells hypothesis. Which element of Pasteur's experimental design was most important and why?
His two treatments differed only in the shape of the flask, resulting in exposure of only one of the treatments to preexisting cells.
Imagine that researchers start with the same population of maize as shown in the figure, but instead of selecting individuals with the highest kernel protein content to be parents of each generation they select individuals with the lowest kernel protein content. Which statement best describes how the average protein content of the population would differ from the starting population after 50 and 100 generations?
It would be lower after both 50 and 100 generations. Because lowest protein content is artificially selected, this trait will become more common in the population, resulting in lower average protein content.
Over the generations shown, protein content of corn kernels increases more than it decreases.
Starting from the wild mustard Brassica oleracea, breeders have created the strains known as Brussels sprouts, broccoli, kale, and cabbage. Which of the following statements is supported by this observation?
In this species, there is enough heritable variation to create a variety of features.`
Which of the following accurately summarizes sources of evidence that support the pattern and process components of the cell theory?
Pattern: Hooke's microscopic examination of cork; Process: Pasteur's experiment
To answer questions about life, biologists use the scientific method, which involves hypotheses, predictions and experiments. Which statement most accurately summarizes the relationship among these three elements?
A hypothesis is a proposed answer to a tightly focused question; a prediction is a specific claim that follows from a hypothesis and can be tested in an experiment.
In a natural population of a grass species, the average protein content of seeds would increase over time if seeds with higher protein content survive better and grow into individuals that produce many seeds with high protein content when they mature. Which statement best explains why?
Seeds with higher protein content become more common in the population because this characteristic is heritable and increases survival.
The role of controls in scientific experiments is to _____,
test for factors other than the one being investigated that might influence the outcome of the experiment
most of the time, giraffes do not extend their necks fully when feeding
Switching the ants to a new channel for the return trip may have altered their behavior.
In this case, the results for stilts and stumps would also be called into question because these ants were also switched to a new channel.
depicts the three major domains of life
the common ancestor of life; the common ancestor of Archaea and Eukarya
Both tuna (fish) and dolphins (mammals) have a streamlined body shape and large tail fins that they use to move through the water. Many other anatomical and molecular data indicate, however, that tuna and dolphins are not closely related from an evolutionary perspective. The latter data suggest that _____.
Tuna and dolphins faced similar selective pressures on body shape for reproductive success
On an evolutionary tree, any group that includes a common ancestor and all of its descendants is called monophyletic ("one-tribe"). Recall the current evolutionary tree for Bacteria, Archaea, and Eukarya. According to this tree, are all organisms alive today monophyletic?
What is the relationship between Bacteria, Archaea, and Eukarya?
These groups are descendants of a single common ancestor cell.
These groups are descendants of a single common ancestor cell.
These groups are descendants of a single common ancestor cell.
Which of the following statements about natural selection is true?
Natural selection favors individuals that reproduce more than others.
Which term describes a trait that increases an individual's ability to survive in a particular environment?
Which term describes the ability of a trait to be passed on to offspring?
Which of the following organisms could be produced by artificial selection?
A cow that produces a large quantity of milk.
Which pair of chickens should a farmer breed to produce larger chickens?
large hen, large rooster
Individual A—Yield: 179 bushels/acre; drought resistance: high Individual C—Yield: 185 bushels/acre; drought resistance: medium Individual E—Yield: 200 bushels/acre; drought resistance: medium
Which of the following crosses would produce the highest corn yield with the highest resistance to drought?
Prokaryotic cells are found in the domain(s) _____.
Bacteria and Archaea
In the five-kingdom system, prokaryotes are placed in the kingdom _____.
A human is classified in domain _____ and kingdom _____.
Eukarya ... Animalia
A rose bush is classified in domain _____ and kingdom _____.
Eukarya ... Plantae
Protists are mostly unicellular eukaryotes, though they also include multicellular algae.
Protists are mostly unicellular eukaryotes, though they also include multicellular algae.
In the two-kingdom system, why were fungi classified in the kingdom Plantae?
They are sedentary.
This is why fungi were placed in the same kingdom as plants.
There is(are) _____ eukaryotic domain(s).
Which of the following statements is not true of scientific experiments?
They must occur under carefully controlled conditions found in a laboratory.
In an experiment, investigators try to control all of the variables except one—the one that tests the hypothesis. Which of the following reasons is the primary rationale for controlling variables in an experiment?
To eliminate alternative explanations for the results of an experiment
Which of the following statements could not be supported or rejected by a scientific experiment?
The first living cell on Earth came from outer space
Which of the following statements is true of a hypothesis?
A hypothesis can be supported or rejected through experimentation.
Which of the following variables did Pasteur change in his experiment to test the hypothesis of spontaneous generation?
The shape of the flask
In Pasteur's experiment to test the hypothesis of spontaneous generation, why did he boil the broth in both flasks?
To kill any existing organisms in the broth
What results from the Zonosemata experiment support the sub-hypothesis that wing waving alone reduces predation by jumping spiders?
Zonosemata flies with housefly wings are attacked less frequently.
Suppose that Zonosemata flies whose own wings had been clipped and reattached were attacked more frequently than untreated Zonosemata flies. How would this result affect the reliability of the other experimental results?
All results for the experimental groups involving wing surgery would be invalid.
Nodes in phylogenetic trees indicate _____.
spirochaetes and actinobacteria
You were asked to analyze the number of each tree species in a hectare of deciduous forest. What is the best way to present the data graphically?
Plot the number of trees on the vertical axis, the tree species on the horizontal axis, and use a bar for each species.
A researcher wished to determine the effect of fertilizer concentration on plant growth. She put bean seedlings into four groups, with 10 plants in each group. One group was not fertilized. She measured each plant's height weekly for three weeks. How should she plot the data to analyze the effect of fertilizer on plant growth?
Plot the plant height on the y-axis and time in weeks on the x-axis. Each fertilizer concentration should be plotted on a separate line.
LAC (light-absorbing carbon)
A biology student wanted to know if Drosophila (fruit flies) would be attracted to a yeast/vinegar mixture. He set up choice chambers to see if the flies would move toward or away from the mixture or the water control. What was his null hypothesis for the experiment?
Drosophila are not attracted to or repelled by the yeast/vinegar mixture.
A biology class soaked some bean seeds overnight to demonstrate that the beans imbibed water. The students weighed the beans after 24 hours. What is the null hypothesis for this experiment?
Soaking beans has no effect on bean weight.
The null hypothesis states that the treatment has no effect.
Why is it important to replicate an experiment several times before performing a statistical test?
to reduce the likelihood that the outcome was due to chance
The treatment reduced memory retention, but there was no difference between the groups.
There was no significant difference between deep and shallow study at 10 minutes and 24 hours.
The atomic number for carbon is _____.
An element with the atomic number of eight has how many protons?
A chemical bond that results from sharing electrons between two elements with very similar electronegativity would best be termed _____.
Which of the following properties of water come about because of water's polar bonds and bent structure?
Water has a high adhesiveness, or ability for water molecules to stick to other polar molecules.
Water has a high cohesiveness, or ability for water molecules to stick together.
Liquid water is denser than solid water (ice).
A substance that gives up a proton during a chemical reaction, raising the hydrogen ion concentration of water, is most appropriately called _____.
A functional group can best be defined as _____.
a carbon-containing (organic) or inorganic (without carbon) chemical group that contains H, N, or O.
Which of the following statements most accurately describes the relative locations of the covalently bonded electrons in methane () and ammonia ()?
Electrons are shared equally in and unequally in .
C and H have approximately equal electronegativities, so electrons are shared equally in CH4 . N is significantly more electronegative than H, so electrons are shared unequally in NH3.
Water has a high specific heat because of the _____.
hydrogen bond formed between the hydrogen of one water molecule and the oxygen of another water molecule
To act as an effective coolant in a car's radiator, a substance has to be a liquid at the temperatures found in your car's engine and have the capacity to absorb a great deal of heat. You have a reference book with tables listing the physical properties of many liquids. In choosing a coolant for your car, which table would you check first?
Why do chemical reactions tend to speed up when the concentration of the reactants is increased?
The reactants collide more often.
Carbon is an important element for biology because _____.
of the variety of carbon skeletons and functional groups that can be built on them
What is the mass number of an ion with 106 electrons, 157 neutrons, and a +1 charge?
A(n) _____ refers to two or more atoms held together by covalent bonds.
This atom can form up to _____ single covalent bond(s).
There are four electrons in the outermost electron shell.
Atoms with the same number of protons but with different electrical charges _____.
are different ions
ions are charged atoms
In salt, what is the nature of the bond between sodium and chlorine?
An ionic bond involves _____.
an attraction between ions of opposite charge
correctly illustrates the nature of the bonding of H2O
Oxygen is more electronegative than hydrogen.
single (nonpolar) covalent
What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
This is an atom of carbon, an element with 6 protons. Atomic number is the number of protons in an atom.
Which of these refers to atoms with the same atomic number but different atomic masses?
These atoms are isotopes.
Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
Atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
The atomic number is equal to the number of protons.
How many electrons are involved in a single covalent bond?
water molecules cling to plant cell walls, water molecules cling to side of a beaker
A drop of water spilled on a table forms a drop on the table, rather than spreading out over the surface.
Water molecules are attracted to eachother
a water strider runs across a pond without breaking the surface
a sewing needle floats when it is placed gently on the top of water in a bucket
In a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
The solution on the right is basic relative to the solution on the left.
7.59 × 10−4
What name is given to the bond between water molecules?
Each water molecule is joined to _____ other water molecules by ____ bonds.
four ... hydrogen
The unequal sharing of electrons within a water molecule makes the water molecule _____.
The tendency of an atom to pull electrons toward itself is referred to as its _____.
Hydrogen Bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.
If water were a linear (not bent) molecule, electrostatic interactions between water molecules would be much weaker. Why?
The partial negative charge on oxygen would stick out less and be less able to participate in hydrogen bonding.
Which statement best explains the physical basis for why oil and water don't mix?
Oils are nonpolar molecules that cannot interact with water molecules via hydrogen bonding.
While water has many exceptional and useful properties, which is the rarest property among compounds?
Solid water is less dense than liquid water.
Why is a space station orbiting Earth exhibiting kinetic energy?
Kinetic energy is energy of motion.
"Conservation of energy" refers to the fact that _____.
energy cannot be created or destroyed but can be converted from one form to another
Chemical energy is a form of _____ energy.
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
Which of these are by-products of cellular respiration?
heat, carbon dioxide, and water
The energy that is stored in the chemical bonds of a molecule is called _____.
A chemical reaction that proceeds spontaneously _____.
must proceed without an input of external energy
What factors affect(s) the process of a chemical reaction?
substrate concentration, temperature, catalyst
Since carbon atoms are tetravalent (able to form four bonds), atoms may branch off a carbon atom in as many as four places. The ability of a carbon atom to form four different bonds allows carbon to form many different sizes and types of molecules. Carbon atoms may form chains, rings, or combinations of chains and rings. The tetravalence of carbon makes it particularly well-suited to forming the backbone of a huge diversity of organic molecules.
One of these hydrocarbons is longer than the other.
One of these hydrocarbons is branched.
One of these hydrocarbons has a double bond.
One of these hydrocarbons has a ring structure.
Which of these groups is characteristic of thiols?
B- Phosphate groups are a component of ATP.
L-dopa is used to treat _____.
What kind of effect does R-dopa have on Parkinson's disease?
Enantiomers are molecules that _____.
are mirror images
Geometric isomers are molecules that _____.
differ in the arrangement of their atoms about a double bond
Why is carbon so important in biology?
It forms up to four covalent bonds.
_____ atoms give organic molecules their overall shape; _____ atoms determine the overall chemical behavior of organic molecules.
Carbon; H, N, and O
Which list shows the correct positions of the molecules on an electron-sharing continuum, with equal sharing on the left and no sharing (i.e., transfer of electrons) on the right?
O2, CO2, CaCl2
Which polymers are composed of amino acids?
Which of the following is not attached to the central carbon atom in an amino acid?
Which part of an amino acid is always acidic?
Carboxyl Functional Group
Which monomers make up RNA?
Which of the following statements about the formation of polypeptides from amino acids is true?
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.
True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.
Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.
a condensation reaction that forms a covalent bond
Which of the following parts of an amino acid vary between different amino acids?
The side chain, or R group
During protein synthesis, the covalent bond between amino acids is formed by the process of _____.
Which class(es) of amino acids possess side chains that would be unable to form hydrogen bonds with water?
amino acids with nonpolar side chains
Which of these does NOT contain a structural protein?
Ovalbumin is a storage protein.
Defensive proteins are manufactured by the _____ system.
achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids
describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain
the sequence of amino acids in a protein
is the result of two or more protein subunits assembling to form a larger, biologically active protein complex
Proteins are polymers of _____.
What type of bond joins the monomers in a protein's primary structure?
The secondary structure of a protein results from _____.
Tertiary structure is NOT directly dependent on _____.
Which of the following statements about the primary structure of a protein is true?
Primary structure is produced by the unique sequence of amino acids in a protein.
rate of reaction =
change in concentration/change in time
In which region is the enzyme saturated with substrate?
Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?
Increase the enzyme concentration.
An enzyme is a ____ when it loses its native conformation and its biological activity
An enzyme is considered a __ because it speeds up chemical reactions without being used up
An enzyme is considered ____ because of its ability to recognize the shape of a particular molecule
a ___, such as a vitamin, binds to an enzyme and plays a role in catalysis
When properly aligned, the enzyme and subtrate form an enzyme-subtrate (ES) ____
A substrate binds to an enzyme at the ___ where the reaction occurs
In a catalyzed reaction a reactant is often called a ____
Why does an enzyme alter the activation energy for a reaction but not the overall free-energy change?
An enzyme brings reactants together in precise orientations and reduces the free energy of the transition state; it does not change the free energies of the reactants or products.
In a nucleic acid polymer, the hydrogen bonds that help to hold regions of double-strandedness together occur between what parts of the nucleotide monomers?
The condensation reaction that forms nucleic acid polymers occurs between a _____ group on one nucleotide and a _____ group on a second nucleotide.
Compare proteins to nucleic acids. Which of the following is true?
Both have primary and secondary structure.
Which structure is not a component of a nucleotide?
Sulfhydryl Oxygen group
Which of the following statements about nucleotide structure is false?
The phosphate group is bonded to the nitrogenous base.
True or false? Guanine and uracil are examples of nitrogenous bases.
Which linkage forms the backbone of a nucleic acid?
A sugar-phosphate linkage
Which of the following statements about DNA structure is true?
The nucleic acid strands in a DNA molecule are oriented antiparallel to each other.
What is the complementary DNA sequence to 5’ ATGCATGTCA 3’?
5’ TGACATGCAT 3’
The interactions between nucleotides in an RNA double-stranded "stem" occur between what parts of the nucleotides?
RNA molecules can have tertiary and quaternary structure, whereas DNA molecules do not. Which statement best explains why?
RNA's secondary structure can leave bases free for interactions that produce tertiary and quaternary structure; DNA's secondary structure does not.
In terms of structure and function how do DNA, RNA, and proteins compare?
RNA is intermediate between the complexity of proteins and the simplicity of DNA.
DNA molecules with a high percentage of guanine (G) and cytosine (C) are particularly stable. Why?
A G-C base pair has three hydrogen bonds, whereas an A-T base pair has two.
Which statement accurately summarizes a difference between ribonucleotides and deoxyribonucleotides?
Ribonucleotides have a hydroxyl group bonded to their 2’ carbon; deoxyribonucleotides have an H at the same location.
Nucleic acids are polymers made up of which of the following monomers?
What is the difference between a ribonucleotide and a deoxyribonucleotide?
Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
What is/are the variable structure(s) of a nucleotide?
The sugar and the base
Which of the following includes all of the pyrimidines found in RNA and/or DNA?
cytosine, uracil, and thymine
When nucleotides polymerize to form a nucleic acid _____.
a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
DNA double helices are soluble in water but insoluble in alcohol. How do these physical properties reflect the chemical structure of the molecule?
The charged phosphate groups and sugars of DNA "like" to interact with polar water molecules.
Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?
One end has an unlinked 3 carbon; the other end has an unlinked 5 carbon.
What is gel electrophoresis used for?
to separate macromolecules by size or charge
You have a polymer of DNA with 10 adenine bases followed by 10 cytosine bases. If that strand bonded to a strand of 20 thymine bases, how would the double helix shape vary from a typical DNA double helix?
Only half of the molecule would have the double-helix shape.
DNA forms secondary structure only when two DNA strands align in antiparallel-instead of parallel-fashion. Which statement best explains why?
Bases on antiparallel strands form G-C and A-T pairs via hydrogen bonding; bases on parallel strands do not.
Which statement concerning the DNA double helix is correct?
Base pairing allows production of identical daughter molecules.
In a DNA double helix, the chemical bonds that form between the complementary nitrogenous bases are _____.
If a segment of DNA contains 28 percent T nucleotides, then the percentage of A nucleotides in that segment will be _____.
Which of the following best describes DNA's secondary structure?
Double antiparallel helical strands
Which of the terms or phrases below apply to both DNA and RNA?
an information-containing structure
In the context of chemical evolution, DNA's structure is interesting because it suggests a possible copying mechanism. What about DNA's structure facilitates copying?
The strands of the double helix are complementary.
Although DNA is the main hereditary material in all life-forms, it lacks one important characteristic of being a candidate for the first life-form. Why have researchers rejected the idea that DNA was found in the first life-form?
It does not function as a catalyst.
An RNA molecule that can catalyze chemical reactions is called a(n) _____.
Which type(s) of nucleic acid molecules is/are capable of storing and/or transferring information in a cell?
RNA and DNA
RNA and proteins combine in cells to form structures called ribosomes. Ribosomes contain the active site for peptide bond formation. Based on their chemical structures, do you think protein or RNA molecules actually form the active site within the ribosome?
It could be either, because both molecules have catalytic properties.
Which one of the following is not a way that RNA is seen as intermediate between DNA and proteins?
RNA has 5 and 3 termini like DNA, but it also has amino and carboxy termini like protein.
Many researchers who study the origin of life propose that the first life-form capable of templating its own replication and catalyzing self-replication was made of _____.
In a Northern blot, _____ is detected using a nucleotide probe.
DNA and RNA contain negatively charged phosphate groups. In an electric field, these nucleic acids will _____.
migrate toward the positive electrode
For organic compounds to be separated by electrophoresis, the compounds must be _____.
Which statement is most accurate regarding similarities and differences between proteins and nucleic acids?
Proteins and nucleic acids both have a backbone and are formed by condensation reactions.
A null allele is _____.
a mutated form of a gene that does not make a functioning product
The proteome is all the proteins produced by an organism. The genome is the totality of all genes of an organism. If the proteome is much larger than the genome, which of the following statements would be accurate?
At least in some cases, a single gene must code for more than one protein.
Which answer best explains why errors in transcription might lead to changes in a cell's phenotype?
Changes in mRNA base sequence might result in changes in amino acid sequences of proteins.
In eukaryotic cells the first step in protein synthesis is the _____.
transferring of information from DNA to messenger RNA
The idea that the sequence of bases in DNA specifies the sequence of bases in an RNA molecule, which specifies the sequence of amino acids in a protein, is _____.
the central dogma
The process of using the information in mRNA to synthesize a protein is _____.
According to the original central dogma, what is directly responsible for an organism's phenotype?
Which of the following is not synthesized from a DNA template?
Which of the following molecules must move across the membrane after being synthesized from a DNA sequence and is then translated by a ribosome?
What molecule serves as a link between the information-containing macromolecule, DNA, and protein synthesis?
According to the central dogma, what molecule should go in the blank?
DNA → _____ → Proteins
mRNA because it transfers information from DNA
True or false? A codon is a group of three bases that can specify more than one amino acid.
Which of the following statements about mutations is false?
A knock-out mutation results in a total absence of the mutated protein.
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
One addition and one deletion mutation.
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?
An addition mutation and a deletion mutation.
How many amino acids could be specified by a four-base genetic code?
Each codon shown below specifies an amino acid. For which one is it possible that a change in a single base could create a stop codon?
The redundancy of the genetic code is a consequence of _____.
having more codons than amino acids
When an amino acid is specified by more than one codon, what is usually shared by the set of codons that specifies this amino acid?
the first and second bases
There are three stop codons (nonsense codons); all remaining codons specify addition of an amino acid (sense codons). How many sense codons are there?
Which of the following molecules is not required for translation?
The central dogma has been challenged on several levels (e.g., the discovery of RNA viruses, which use their RNA to directly synthesize proteins; and the discovery of reverse transcriptase, which makes DNA from RNA). Which of the following is another example of an exception to the central dogma?
Prions are infectious protein molecules capable of altering the folding of normal proteins.
A base substitution mutation
can occur if the DNA polymerase inserts the wrong nucleotide base as it synthesizes a new strand of DNA.
A frameshift mutation can occur
if the DNA polymerase leaves out a nucleotide or adds an extra nucleotide to the sequence.
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
a frameshift deletion at the beginning of the gene
A point mutation that results in the substitution of one amino acid for another within a protein is a _____.
How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?
Only a single amino acid could change, because the reading frame is unaffected.
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
What name is given to the process in which pre-mRNA is edited into mRNA?
Polypeptides are assembled from _____.
RNA processing converts the RNA transcript into _____.
Which statement is most accurate concerning how the terms transcription and translation are used to refer to the flow of genetic information in cells: DNA→RNA→Proteins?
Transcription refers to the first step because a copy of information is made; translation refers to the second step because information is converted from one type of molecule to another.
Which statement best explains why some changes in DNA sequence do not change the corresponding protein?
The genetic code is redundant
Glycogen is _____.
a polysaccharide found in animals
glucose + glucose —> _____ by _____.
maltose + water ... dehydration synthesis
Which of these is a source of lactose?
Which of these is a polysaccharide?
_____ is the most abundant organic compound on Earth.
Which of the following classes of macromolecules always contains a carbohydrate portion?
How do the α and β forms of glucose differ?
Their ring structures differ in the location of a hydroxyl group.
You isolate an organic molecule that contains C, H, O, N, and S. This molecule _____.
could be a glycoprotein
A carbohydrate that yeilds many monosaccharides when hydrolyzed is a ____
A ___ cannot be hydrolyzed any further
A simple sugar is composed of equal parts carbon and water, which gave rise to thegeneral name of any sugar as a
Lactose, the sugar in milk, is a ____, because it can be split into two monosaccharides
Which statement best explains why two four-sugar polysaccharides can be different, even if both consist of two glucose monomers and two galactose monomers?
The sequence of monomers along the chain or the location and geometry of glycosidic linkages could vary (or both).
A glycosidic linkage is a covalent bond that links two _____.
Which of the following do starch and cellulose have in common?
the size of their monosaccharide subunits
Enzymes that readily break starch apart cannot hydrolyze the glycosidic linkages found in cellulose. Why is this logical?
The geometry of the bonds is different, and the shapes of enzyme active sites are highly specific.
Dairy cattle were unknown in Thai culture until recently, and 97% percent of Thai people are lactose intolerant as adults. Which explanation for such widespread lactose intolerance is most likely correct?
Evolutionarily, producing an enzyme to break down a sugar that will never be encountered is wasteful.
Carbohydrates that function as structural molecules are extraordinarily resistant to degradation and decay. Which structural feature best explains why?
Structural polysaccharides are built with Beta -1,4-glycosidic linkages, which only a few enzymes can break.
Carbohydrates that function as structural molecules withstand pulling and pushing forces well. Which structural feature best explains why?
Structural polysaccharides exist as sets of long, parallel strands that are linked to one another.
Which statement most accurately describes how the carbohydrates you ate for breakfast are functioning in your body right now?
They are storing chemical energy, indicating cell identity, and serving as raw material for synthesizing other molecules.
Where are carbohydrates found in relationship to the cell?
They are found both inside and outside the cell.
Which of the following types of molecules would have the highest capacity to store chemical energy?
a six-carbon molecule rich in C-H bonds, such as a lipid
What is the difference between an aldose sugar and a ketose sugar?
the position of the carbonyl group
Glucose (C6H12O6) has a single carbonyl group (-C=O) in its linear form. Based on the number of oxygen atoms in glucose, how many hydroxyl groups (-OH) would you expect glucose to have?
Which of the following carbohydrates contains a peptide bond?
Which of these best reflects the following relationship: monosaccharide versus polysaccharide?
glucose versus glycogen
Which molecule is not a carbohydrate?
Which of the following statements about monosaccharide structure is true?
Monosaccharides can be classified according to the spatial arrangement of their atoms.
True or false? Peptidoglycan is a polysaccharide found only in bacteria.
Which complex carbohydrate contains only a-1,4-glycosidic linkages?
Which of the following complex carbohydrates is listed with its correct function?
Cellulose: structural component of plant cell walls
Which polysaccharide contains a modified monosaccharide?
Bacteria, insects, and plants use carbohydrates to build structures. Which of the following is true of structural carbohydrates?
Structural carbohydrates are long strands of monomers; the strands are chemically linked together to form a network.
Different types of glycosidic linkage cause glucose polymers to form a helix (e.g., in glycogen) versus a straight chain (e.g., in cellulose). Which statement best explains why?
The geometry of the Beta -1,4-glycosidic linkage results in a flipped orientation of adjacent glucose monomers; the alpha -1,4-glycosidic linkage does not.
Which of these is NOT a lipid?
A function of cholesterol that does not harm health is its role _____.
as a component of animal cell membranes
Which statement most accurately describes how the structures of fats, steroids, and phospholipids compare?
Fats and phospholipids contain glycerol, steroids do not.
The plasma membranes of all known cells are largely composed of what class of macromolecules?
Molecules that are amphipathic contain _____.
regions that are hydrophobic and regions that are hydrophilic
The term phospholipid can best be described by which of the following?
a nonpolar lipid molecule that is made amphipathic by the addition of a phosphate
Cooking oil and gasoline (a hydrocarbon) are not amphipathic molecules. Why?
They do not have a polar or charged region.
Which statement most accurately explains why cholesterol and phospholipids are amphipathic but fats are not?
Cholesterol and phospholipids contain both hydrophilic and hydrophobic regions; fats are primarily hydrophobic.
Which statement best explains the effect on membrane permeability of cholesterol and/or temperature?
Adding cholesterol reduces permeability because its steroid rings increase the density of the hydrophobic membrane interior.
In a phospholipid bilayer, the polar heads are oriented toward the _____ of the bilayer.
A "mystery molecule" was isolated in a laboratory and scientists found that the molecule readily crossed artificial membranes. Which of the following molecules can be ruled out as the "mystery molecule"?
Decreasing the saturation of the fatty acid chains on a particular type of phospholipid would result in the formation of _____.
more fluid bilayers
You have just discovered an organism that lives in extremely cold environments. Which of the following would you predict to be true about the phospholipids in its membranes, compared to phospholipids in the membranes of organisms that live in warmer environments?
The membrane phospholipids of cold-adapted organisms will have more unsaturated hydrocarbon tails.
Which of the following crosses lipid bilayers the slowest?
a sodium ion
Which of the following is the best explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?
Vegetable oil has more double bonds than animal fats.
Diffusion is the movement of particles down their concentration gradient.
Which of the following factors does not affect membrane permeability?
The polarity of membrane phospholipids
How can a lipid be distinguished from a sugar?
Lipids are mostly nonpolar.
True or false? Osmosis is a type of diffusion.
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Which of the following particles could diffuse easily through a cell membrane?
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Lipid vesicles are formed so that they contain pure water. If these vesicles are transferred to a solution that contains a rather high concentration of solutes, what will be the net direction of water movement?
It will move out of the vesicles.
Lipids that form membranes have what kind of structure?
polar heads and nonpolar tails; the polar heads interact with water
You place yeast in a glucose solution and plot the rate of glucose uptake. You see an increase in glucose uptake over time (that is, the longer the yeast are in the sugar solution, the faster they can take sugar into the cell). The most likely explanation for this is the cell membrane is becoming more permeable because _____.
The yeast is inserting more glucose protein transporters into its membrane
Diffusion is occurring via a transport protein.
stabilization of the phospholipids
phospholipid bilayer of membrane
What distinguishes facilitated diffusion from simple diffusion?
Membrane proteins help move molecules across the membrane.
Which of the following transporters does not use passive transport to move molecules across a membrane?
True or false? Active transport differs from passive transport in that active transport does not require an input of energy.
Which membrane protein would be used to move glucose across a membrane from a region of higher concentration to a region of lower concentration?
Which of the following statements is true about the net movement of an ion across a membrane by passive diffusion through a membrane channel?
The charge on the other side of the membrane is generally the opposite of the ion's charge.
True or false? During active transport through the sodium-potassium pump, ATP hydrolysis provides the energy to pump three sodium ions into the cell for every two potassium ions pumped out of the cell.
Lactose transport by membrane proteins occurs under conditions in which the concentration of lactose inside the cell is higher than the concentration outside the cell. What type of transport is used to move lactose into the cell?
Which statement most accurately summarizes a feature of passive transport?
It is a spontaneous process.
One of the roles of plasma membrane proteins is to __________.
allow passage of select molecules that could not otherwise cross the lipid bilayer
Which of the following means of transport would most likely be used for moving a medium-sized molecule (like a monosaccharide or an amino acid) from a low concentration on the outside of a cell to a high concentration on the inside of a cell?
active transport through a "pump" protein
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