Entire Course Weekly Quizzes

What is the mass number of an ion with 108 electrons, 159 neutrons, and a +1 charge?

268

Which four elements make up 96 percent of matter found in living organisms?

hydrogen, carbon, oxygen, nitrogen

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH₃)?

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge

A covalent bond is likely to be polar when….

one of the atoms sharing electrons is more electronegative than the other atom

when the atoms involved in a covalent bond have the same electronegativity, what type of bond results?

a nonpolar covalent bond

in a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by __.

polar covalent bonds

the partial negative charge in a molecule of water occurs because_

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

which type of bond must be broken for water to vaporize?

hydrogen bonds

to act as an effective coolant in a car’s radiator, a substance should 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?

specific heat

Why does ice float in liquid water?

stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water

you have two beakers. one contains pure water; the other contains pure methanol. the covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. you pour crystals of table salt into each beaker. predict what will happen

NaCl crystals will dissolve readily in water but will not dissolve in methanol

why are hydrocarbons insoluble in water?

the majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages

what is the defining characteristic of a condensation reaction?

two monomers are covalently bonded together and a water molecule is produced

the complexity and variety of organic molecules is due to __

the chemical versatility of carbon atoms

in a solution, condensation reactions __

result in polymerization of monomers

which of the following atoms determines molecular properties and the types of chemical reactions in which a molecule participates?

functional group

which two functional groups are bound to the central carbon of every free amino acid monomer?

an amino group and a carboxyl group

which of the following parts of an amino acid vary among different amino acids?

the side chain, or the r-group

which of the following is true of the peptide bond?

it is a covalent bond formed via a condensation reaction

what type of bond is directly involved in the formation of an α-helix

hydrogen bonds between amino acid residues

where would amino acid residues with nonpolar r-groups be found within the overall structure of a folded globular protein such as chymotrypsin

nonpolar amino acid residues would be found in the interior of chymotrypsin

a hydrophobic r-group would most likely be found __

buried in the interior of a protein

what bond type is responsible for the secondary structure of a protein?

hydrogen

a chemical that breaks disulfide bonds might destroy which levels of protein structure?

the tertiary structure

which marcomolecule performs the greatest diversity of cell functions?

proteins

what type of bond is formed between two sugars in a disaccharide?

glycosidic linkage

what holds cellulose molecules together in bundles large enough to form fibers?

hydrogen bonds

what are the primary functions of carbohydrates in cells?

cell identity, energy storage, raw material source for synthesis, and structure

lipids are insoluble in water because

the contain nonpolar C-C and C-H bonds

how do fats differ from proteins, nucleic acids, and polysaccharides?

only fats do not from from the polymerization of monomers

decreasing the saturation of the fatty acid chains on a particular type of phospholipid would result in the formation of __

more fluid bilayers

which of the following would decrease membrane fluidity?

increased level of saturation of fatty acids

if a solution surrounding a cell is hypertonic relative to the inside of the cell, how will the water move?

it will move out of the cell via osmosis

one of the roles of plasma membrane proteins is to __

allow passage of select molecules that could not otherwise cross the lipid bilayer

the movement of molecules through a plasma membrane channel protein is always __

down the molecule’s electrochemical gradient

molecules that move down a concentration gradient and require transport proteins to cross a membrane use __

facilitated diffusion

a prokaryotic cell is distinct from a eukaryotic cell because a prokaryotic cell lacks__

a nucleus

the bacterial cell wall functions to __

protect the cell and provide shape and rigidity

which of the following can both catalyze chemical reactions and carry information to copy itself?

RNA

there are hundreds, if not thousands, of proteins that are specifically localized to the cell nucleus. what is likely to be true about transport of these proteins into the nucleus?

proteins specifically localized to the nucleus must have the same or a similar nuclear localization signal that directs them to the nucleus

molecular “zip codes” direct molecules to particular destinations in the cell. how are these signal read?

they bind to receptor proteins

which of the following cell structures is found in all plant, animal, and prokaryotic cells?

ribosomes

a certain eukaryotic cell type specializes in synthesizing lipids. which organelle would be found in greater abundance in this cell type than in other cell types that don’t synthesize lipids

smooth endoplasmic reticulum

what central theme of biology helps explain why various cells can look so different from one another?

cell structure correlates with function

whole DNA chromosomes are kept in the nucleus while small nucleotide monomers move into and out of the nucleus through the __

nuclear pores

what is the correct sequence for secreted protein movement through the endomembrane system?

endoplasmic reticulum (ER), cis-Golgi, trans-Golgi, vesicles

all cells contain which three structures?

chromosomes, ribosomes, and a plasma membrane

you have added an irreversible inhibitor to a sample of enzyme and substrate. at this point, the reaction has stopped completely. what can you do to regain the activity of the enzyme?

the enzyme is inactive at this point. new enzyme must be added to regain enzyme activity

you have an enzymatic reaction proceeding at the optimum pH and optimum temperature. you add a competitive inhibitor to the reaction and notice that the reaction slows down. what can you do to speed the reaction up again?

add more substrate; it will outcompete the inhibitor and increase the reaction rate

among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

pyruvate, ATP, and NADH

In mitochondrial electron transport, what is the direct role of O2?

to function as the final electron acceptor in the electron transport chain

if you were to expose cells that are undergoing aerobic respiration to a radioactive oxygen isotope in the form of O2, which of the following molecules would you expect to be radiolabeled?

water

in muscle cells, fermentation produces __

lactate and NAD+

In fermentation __ is reduced and _ is oxidized

pyruvate; NADH

Why would fermentation alone not be sufficient to keep your cells alive?

fermentation has a much lower yield of ATP than the ETC

why are summer leaves green, even though carotenoids are present?

during summer, chlorophyll is more abundant than carotenoids in leaves

what is the importance of light-independent reactions in terms of carbon flow in the biosphere?

the light-independent reactions turn CO2, a gas, into usable carbon in the form of sugars

which molecule is regenerated in the regeneration phase of the Calvin cycle? without regeneration of the molecule, the Calvin cycle would stopn.

RuBP

at what part of the day would there be the highest concentration of four-carbon organic acids in the vacuoles of CAM plants

at sunrise, since these acids are made during the night and used up during the day

what would happen to a plant cell if it were treated with an enzyme that digests cellulose microfibrils?

the cell wall’s ability to resist tension would be diminished, and its plasma membrane could burst

predict what would happen if a mutant Ras protein was unable to exchange GDP for GTP

the proteins downstream from Ras would not become phosphorylated

what role does a transcription factor play in a signal transduction pathway?

by binding to DNA it triggers the transcription of a specific gene

calcium ions that act as a second messenger are stored in __

endoplasmic reticula

a protein kinase activating many other protein kinases is an example of __

amplification

nucleoli are present during __

interphase

cytokinesis often, but not always, accompanies __

telophase

chromosomes become visible during __

prophase

centromeres divide and sister chromatids become full-fledged chromosomes during __

anaphase

spindles fibers attach to kinetochores during __

prometaphase