BIO 160 exam 1 Mastering Biology
Which statement best explains why G-T and A-C base pairs are not complementary?
.G-T and A-C base pairs cannot form as many hydrogen bonds as A-T and G-C base pairs.
If a double-stranded DNA sample were composed of 10 percent thymine, what would be the percentage of guanine?
40%
What feature of single nucleotides provides the energy needed for polymerization when nucleic acids are formed?
their phosphate groups
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine
True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.
true
True or false? Peptidoglycan is a polysaccharide found only in bacteria.
true
The tertiary structure of a protein is the _____.
unique three-dimensional shape of the fully folded polypeptide
By convention, nucleotide sequences are always written from the _____.
5' end to the 3' end
If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary strand would have the sequence _____.
5'TGCAAT3'
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.
Which statement best explains the effect on membrane permeability of cholesterol and/or temperature?
Adding cholesterol reduces permeability because its steroid rings fill gaps in the hydrophobic membrane interior.
Which of the following best explains why "carbs" (carbohydrates) are advertised by manufacturers of candy bars and sports drinks as a "quick energy boost"?
Carbohydrates are reduced molecules that have high-energy electrons
Part complete Which part of an amino acid is always acidic?
Carboxyl functional group
In what way do the membranes of a eukaryotic cell vary?
Certain proteins are unique to each membrane.
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 molecules do not normally cross the nuclear membrane?
DNA
Which of the following is the strongest evidence that protein structure and function are correlated?
Denatured (unfolded) proteins do not function normally.
What is the most likely pathway taken by a newly synthesized protein that will be secreted by a cell?
ER --> Golgi --> vesicles that fuse with plasma membrane
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.
True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.
False
Which of the following produces and modifies polysaccharides that will be secreted?
Golgi apparatus
How are nucleotides linked together to form a polynucleotide chain?
In DNA and RNA, a phosphodiester linkage connects the .3' carbon of one nucleotide and the 5' carbon of another.
Which feature is shared by all three-carbon monosaccharides?
In their linear forms, they all contain a carbonyl and several hydroxyl functional groups.
Peptidoglycan forms sheets that stiffen the cell walls of bacteria. How is the formation of sheets possible?
Individual strands are joined by peptide bonds, a type of covalent bond.
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 of the following statements about monosaccharide structure is true?
Monosaccharides can be classified according to the spatial arrangement of their atoms
Why do researchers think the first self-replicating molecule was RNA?
RNA can carry information and catalyze chemical reactions.
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.
What is the difference between a ribonucleotide and a deoxyribonucleotide?
Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
Bacteria, insects, and plants use carbohydrates to build structures. Which of the following is true of structural carbohydrates?
Structural carbohydrates are long strands, which are chemically linked into a network.
Cellulose, chitin, and peptidoglycan function as structural molecules and withstand pulling and pushing forces well. Which structural feature is most directly responsible?
Structural polysaccharides exist as sets of long, parallel strands that are linked to one another.
How does primary protein structure affect the function of protein enzymes?
Substrates interact with R-groups at the enzyme's active site.
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.
Why is it that RNA can catalyze reactions but DNA cannot?
The sugar of RNA is much more reactive than the sugar of DNA.
What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?
There is no difference
Which statement most accurately describes what happens to proteins that lack an ER signal sequence?
They are released into the cytosol.
Which statement most accurately describes how the carbohydrates you ate during breakfast today are functioning in your body right now?
They are storing chemical energy, indicating cell identity, and serving as raw material for synthesizing other molecules.
Which of the following structural features is common to cellulose, chitin, and peptidoglycan?
They can all form bonds between polymer chains that create parallel strands.
In plant cells, why are toxins like nicotine, cocaine, and caffeine stored in vacuoles instead of the cytosol?
Toxins in vacuoles are sequestered from the rest of the cell, where they could do harm.
When nucleotides polymerize to form a nucleic acid _____.
a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
Which of the following is a large organic molecule that is NOT assembled by polymerization of a few kinds of simple subunits?
a steroid
What are the components of a nucleotide?
a sugar, a phosphate group and a nitrogenous base
Which complex carbohydrate contains only a-1,4-glycosidic linkages?
amylose
Which of the following is not attached to the central carbon atom in an amino acid?
an oxygen
Steroids are considered to be lipids because they _____.
are not soluble in water
Which of the following would you expect to have the most free energy per gram? The most free energy per gram would be found in a molecule with _____.
carbon and hydrogen atoms only
Which of the following polysaccharides composes the cell wall of fungi?
chitin
Thylakoids, DNA, and ribosomes are all components found in _____
chloroplasts
What is the structural feature that allows DNA to replicate?
complementary pairing of the nitrogenous bases
Which of the following includes all of the pyrimidines found in RNA and DNA?
cytosine, uracil, and thymine
What determines the primary structure of a DNA molecule?
deoxyribonucleotide sequence
Identify three possible components of a DNA nucleotide.
deoxyribose, phosphate group, thymine
The presence of cholesterol in the plasma membranes of some animal cells _____.
enables the membranes to stay fluid when cell temperature drops
The evolution of eukaryotic cells most likely involved ________.
endosymbiosis of an aerobic bacterium in a larger host cell-the endosymbiont evolved into mitochondria
A peptide bond _____.
forms the primary structure in proteins
One of the primary functions of RNA molecules is to _____.
function in the synthesis of proteins
Which of these best reflects the following relationship: monosaccharide versus polysaccharide?
glucose versus glycogen
The bond that joins two monosaccharides into a disaccharide is a(n) _____.
glycosidic bond
What type of interaction is directly responsible for the formation of secondary structure?
hydrogen bonds between sections of the polypeptide backbone
Suppose you discovered a new amino acid. Its R-group contains only hydrogen and carbon atoms. Predict the behavior of this amino acid.
hydrophobic
In a plant cell, DNA may be found _____.
in the nucleus, mitochondria, and chloroplasts
Which of the following increases the strength of the hydrophobic interactions in lipid bilayers and thus makes them less permeable to polar molecules?
increasing length of the hydrocarbon chains
The membranes of winter wheat are able to remain fluid when it is extremely cold by _____.
increasing the percentage of unsaturated phospholipids in the membrane
Where are proteins produced other than on ribosomes free in the cytosol or ribosomes attached to the ER?
mitochondria
Which organelle is the primary site of ATP synthesis in eukaryotic cells?
mitochondria
Which plant cell organelle contains its own DNA and ribosomes?
mitochondrion
Nucleic acids are polymers made up of which of the following monomers?
nucleotides
Which monomers make up RNA?
nucleotides
A small protein (molecular weight = 25,000 daltons) is injected into a cell and observed in the nucleus a short time later. What type of transport has taken place?
passive transport
You disrupt all hydrogen bonds in a protein. What level of structure will be preserved?
primary structure
A cell with a predominance of free ribosomes is most likely _____.
producing primarily cytoplasmic proteins.
Which polymers are composed of amino acids?
proteins
The bonding of two amino acid molecules to form a larger molecule requires the _____.
release of a water molecule
An RNA molecule that can catalyze chemical reactions is called a_____
ribozyme
Which structure is the site of the synthesis of proteins that may be exported from the cell?
rough ER
The liver is involved in detoxification of many poisons and drugs. Which of the following structures is primarily involved in this process and, therefore, abundant in liver cells?
smooth ER
Which type of organelle or structure is primarily involved in the synthesis of oils, phospholipids, and steroids?
smooth endoplasmic reticulum
Where would you most likely find an integral membrane protein?
spanning the cell membrane, with parts of the protein visible from both the inside and the outside of the cell
Which of the following could amylase break down?
starch
At which level of protein structure are interactions between the side chains (R-groups) most important?
tertiary
What is the major structural difference between starch and glycogen?
the amount of branching that occurs in the molecule
How do carbohydrates contain and/or display information for cells?
the cell surface
What component of amino acid structure varies among different amino acids?
the components of the R-group
Which of the following can vary among monosaccharides?
the number of carbon atoms
Which of the following do starch and cellulose have in common?
the size of their monosaccharide subunits
What is/are the variable structure(s) of a nucleotide?
the sugar and the base
A series of hydrophobic side chains will congregate together as a protein folds in an aqueous solution and be stabilized by _____.
van der Waals interactions
Under what circumstances does membrane transport require energy?
whenever a solute is moved against its electrochemical gradient