Unit 1 (UCONN Biology)
Fluorine has an atomic number of 9 and a mass number of 19. How many electrons are needed to complete the valence shell of a fluorine atom?
1
When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)?
1 L of 1.0 M NaCl
How many molecules of water are needed to completely hydrolyze a polymer that is 11 monomers long?
10 molecules of water
A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of . . .
120 Thymine and 120 Adenine molecules
How many structural isomers are possible for a substance having the molecular formula C4H10?
2
If one strand of a DNA molecule has the sequence of bases 5ʹATTGCA3ʹ, the other complementary strand would have the sequence . . .
3'TAACGT5'
What is the approximate atomic mass of an atom with 16 neutrons, 15 protons, and 15 electrons?
31 Daltons
How many electron pairs does carbon share in order to complete its valence shell?
4
You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCL and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be . . .
7.0
Which of the nitrogenous bases are of the purine type?
Adenine (A) and Guanine (G)
What types of molecules have an amino functional group?
C - NH
What types of molecules are water soluble because they have hydroxyl functional groups?
C - OH
What types of molecules contain a ketone functional group?
C = O
The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?
C18H32O16
What best summarizes the structural differences between DNA and RNA?
DNA nucleotides contain a different sugar than RNA nucleotides
What best describes the flow of information in eukaryotic cells?
DNA → RNA → proteins
What would be regarded as compounds?
H2O and CH4
What ionizes completely in solution and is considered to be a strong acid?
HCl
What types of molecules contain a carboxyl functional group?
O = C - OH
A water sample from a hot thermal vent contained a single-celled organism that had a cell wall but lacked a nucleus. What is its most likely classification?
Protista
There are 20 different amino acids. What makes one amino acid different from another?
R-groups
What is the best description of a carbonyl group?
a carbon atom joined to an oxygen by a double covalent bond
A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?
a compound with the same three-dimensional shape as part of the hormone
What description best fits the class of molecules known as nucleotides?
a nitrogenous base, a phosphate group, and a pentose sugar
A van der Waals interaction is the weak attraction between . . .
a nonpolar molecule and a nearby molecule that is also nonpolar
What results from an unequal sharing of electrons between atoms?
a polar covalent bond
What is a hypothesis?
a tentative explanation that can be tested and is falsifiable
What effect is produced by the high surface tension of water?
a water strider can walk across the surface of a small pond
Which of the following contains nitrogen in addition to carbon, oxygen, and hydrogen?
an amino acid such as glycine
What type of individual has the potential to be successful in an evolutionary sense?
an organism that dies after 5 days of life but leaves 10 offspring, all of whom survive to reproduce
Research indicates that Ibuprofen, a drug used to relieve inflammation and pain, is a mixture of two enantiomers; that is, molecules that . . .
are mirror images of one another
Lactose, a sugar in milk, is composed of one glucose molecule joined by a glycosidic linkage to one galactose molecule. How is lactose classified?
as a disaccharide
Each element is unique and different from other elements because of the number of protons in the nuclei of its atoms. Which of the following indicates the number of protons in an atomʹs nucleus?
atomic number
What are some facts regarding atoms?
atoms of the various elements differ in their number of subatomic particles; all atoms of a particular element have the same number of protons in their nuclei; the neutrons and protons present in the nucleus of an atom are almost identical in mass, each has a mass of about 1 Dalton; an atom is the smallest unit of an element that still retains the properties of the element
Atoms whose outer electron shells contain eight electrons tend to . . .
be stable and chemically nonreactive, or inert
A molecule with the chemical formula C6H12O6 is probably a . . .
carbohydrate or monosaccharide
Organic chemistry is a science based on the study of . . .
carbon compounds
About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?
carbon, hydrogen, nitrogen, and oxygen
On food packages, to what does the term "insoluble fiber" refer?
cellulose
What is the chemical mechanism by which cells make polymers from monomers?
condensation reaction (dehydration reaction)
A carbon atom is most likely to form what kind of bond(s) with other atoms?
covalent
What is the difference between covalent bonds and ionic bonds?
covalent bonds involve the sharing of electrons between atoms, and ionic bonds involve the electrical attraction between atoms
What best summarizes the relationship between dehydration reactions and hydrolysis?
dehydration reactions assemble polymers, and hydrolysis reaction break down polymers
The function of each protein is a consequence of its specific shape. What is the term used for a change in a proteinʹs three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?
denaturation
The molecular mass of glucose is 180 g. Which of the following procedures should you carry out to make a 1 M solution of glucose?
dissolve 180 g of glucose in water, and then add more water until the total volume of the solution is 1 L
What is true about DNA?
each chromosome has one very long DNA molecule with hundreds of thousands of genes; every cell is enclosed by a membrane; every cell uses DNA as its genetic information; DNA is the unit of inheritance that is transmitted from parent to offspring
A type of protein critical to all cells is organic catalysts called . . .
enzymes
Which of the following properties or processes do we associate with living things?
evolutionary adaptations; energy processing; responding to the environment; growth and reproduction
Species that are in the same __________ are more closely related than species that are only in the same __________.
family; order
What contains amino acids?
hemoglobin, antibodies, enzymes, and insulin
What explains most specifically the attraction of water molecules to one another?
hydrogen bond
What maintains the secondary structure of a protein?
hydrogen bonds
Why does ice float in liquid water?
hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water
Charles Darwin proposed a mechanism for descent with modification which stated that organisms of a particular species are adapted to their environment when they possess . . .
inheritable traits that enhance their survival and reproductive success in the local environment
A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism . . .
is more closely related to frogs than to humans
Different atomic forms of an element contain the same number of protons but a different number of neutrons. What are these different atomic forms called?
isotopes
What is the structural feature that allows DNA to replicate?
its double helix
The experimental approach taken in current biological investigations presumes that . . .
living organisms can be understood in terms of the same physical and chemical laws that can be used to explain all natural phenomena
When blood glucose level rises, the pancreas secretes insulin, and as a result blood glucose level declines. When blood glucose level is low, the pancreas secretes glucagon, and as a result blood glucose level rises. Such regulation of blood glucose level is the result of . . .
negative feedback
Hydrophobic substances such as vegetable oil are . . .
nonpolar substances that repel water molecules
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by . . .
polar covalent bonds
What type of bonds are created during the formation of the primary structure of a protein?
polypeptide bonds
A localized group of organisms that belong to the same species is called a . . .
population
Altering what levels of structural organization could change the function of a protein?
primary; secondary; tertiary; quaternary
What is correct about prokaryotic and eukaryotic cells?
prokaryotic cells lack a membrane-bound nucleus; eukaryotic cells contain a membrane-bound nucleus; DNA, or deoxyribonucleic acid, is present in both prokaryotic cells and eukaryotic cells; DNA or deoxyribonucleic acid is present in the nucleus of eukaryotic cells
What solution has a great concentration of hydroxyl ions [OH-]?
seawater at pH 8
Why are human sex hormones considered to be lipids?
sex hormones are considered to be lipids because they mix poorly with water; they are also synthesized from cholesterol, a steroid (which is a lipid)
In terms of the hierarchical organization of life, a bacterium is at the __________ level of organization, whereas a human is at the __________ level of organization.
single-celled organism; multicellular organism
Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other?
testosterone and estradiol have different functional groups attached to the same carbon skeleton
What statement about the 5' end of a polynucleotide strand of DNA is correct?
the 5ʹ end has a phosphate group attached to the number 5 carbon of ribose
An example of a hydrogen bond is the bond between . . .
the H of one water molecule and the O of another water molecule
One of the buffers that contribute to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood drops, one would expect . . .
the HCO3- to act as a base and remove excess H+ with the formation of H2CO3
What statement correctly defines a kilocalorie?
the amount of heat required to raise the temperature of 1 kg of water by 1°C
Pure, freshly-distilled water has a pH of 7. This means that . . .
the concentration of H+ ions in the water equals the concentration of OH- ions in the water
The dynamics of any ecosystem include the following major processes . . .
the flow of energy from sunlight to producers and then to consumers, and the recycling of chemical nutrients
Why are hydrocarbons insoluble in water?
the majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages
Which of the following describes any reaction that has reached chemical equilibrium?
the rate of the forward reaction is equal to the rate of the reverse reaction
The bonding of two amino acid molecules to form a larger molecule requires . . .
the release of a carbon dioxide molecule and the addition of a nitrogen atom
What provides evidence of the common ancestry of all life?
the universality of the genetic code
What statements concerning saturated fats are true?
they are more common in animals than in plants; they generally solidify at room temperature; they contain more hydrogen than unsaturated fats having the same number of carbon atoms; they are one of several factors that contribute to atherosclerosis
Which of the following statements is false for the class of biological molecules known as lipids?
they are soluble in water
What statement correctly describes geometric isomers?
they have variations in arrangement around a double bond
What is true about buffer solutions?
they maintain a relatively constant pH when either acids or bases are added to them
One difference between carbon-12 and carbon-14 is that carbon-14 has . . .
two more neutrons than carbon-12
The tertiary structure of a protein is the . . .
unique three-dimensional shape of the fully folded polypeptide
Why is it important that an experiment include a control group?
without a control group, there is no basis for knowing if a particular result is due to the variable being tested or to some other factor