Biology 103 - Module 2 Study Guide
What is the OH- concentration of a solution having a pH of 2?
1 × 10^12
What is the OH− concentration of a solution having a pH of 2?
1 × 10^12
What is the approximate pH of ammonia?
11
What is the atomic mass of the atom identified as A in the accompanying figure?
12 amu
What is the atomic mass of the most common isotope of carbon?
12.01 amu
Sulfur has six valence electrons. How many covalent bonds does a sulfur atom typically form?
2
In the accompanying figure, ionic bonds would form between the R groups of which amino acids?
2 and 4
In the accompanying figure, hydrophobic interactions would occur between the R groups of which two amino acids?
3 and 6
A chlorine atom has 17 protons and 18 neutrons. What is its atomic mass?
35 amu
How many molecules are present in one mole of C6 H12 O6?
6.02 × 10^23 molecules
Which of the following describes an amphipathic molecule?
A phospholipid with both a hydrophobic end and a hydrophilic end
What is the difference between a stable isotope and a radioisotope?
A radioisotope emits radiation.
Which statement best describes an atom?
A substance that cannot be broken into a simpler substance
What is the difference between an electrically neutral atom and an ion?
An ion has an equal number of protons and electrons, while an atom has an unequal number.
What differentiates an organic compound from an inorganic compound?
An organic compound contains carbon
Which of the following solutions has a pH value of 9.0?
Bleach
Why are hydrocarbons considered hydrophobic?
The covalent bonds between hydrogen and carbon are nonpolar
As water boils and turns to steam, what happens to the hydrogen bonds?
The hydrogen bonds break
Assume that the shaded portions of the molecule in the accompanying figure each represent different polypeptide chains. What does this represent?
The quaternary structure of a protein
Which is a property of unsaturated fats?
They are generally liquid at room temperature.
What is the purpose of molecular chaperones?
To assist the folding of other molecular proteins
What is the purpose of regulatory proteins?
To control the expression of specific genes
A disaccharide is composed of two monosaccharides joined by a glycosidic bond.
True
An essential amino acid is one that the body cannot synthesize in sufficient amounts.
True
Hemoglobin consists of 574 amino acids arranged in four polypeptide chains.
True
Most animals convert carotenoids to which vitamin?
Vitamin A
_____________ is a region where a polypeptide chain forms a uniform helical coil.
a-helix
When a small amount of hydrochloric acid (HCl) is added to a solution of Na2HPO4, the pH of the solution does not change markedly. The pH also does not change drastically when a small amount of sodium hydroxide (NaOH) is added to this same solution. Based on these observations, the compound Na2HPO4 is:
acting as a buffer
sticking together of unlike molecules
adhesion
A salt is a compound in which the hydrogen ion of ____ is replaced by some other cation.
an acid
Which of the following would most likely form electrolytes in water?
an inorganic compound
How can we identify a particular element?
by its number of protons
___________ in the muscle cell are required for muscle contraction.
calcium ions
tendency of water to move in narrow tubes
capillary action
cellulose
carbohydrate
monomers are joined by a glycosidic linkage
carbohydrate
Which element forms the backbone of organic molecules?
carbon
You isolate a compound that is insoluble in water, has alternating single and double bonds and has a bright orange color. You correctly conclude that this compound is a:
carotenoid
Which lipid can be identified by its isoprene units?
carotenoids
Which is the main structural component of the walls that surround plant cells?
cellulose
Sticking together of like molecules
cohesion
Water molecules have a strong tendency to stick to one another, a property known as ___________.
cohesion
What is the functionality of regulatory proteins?
control the activities of proteins, genes, cells, and tissues
Strong attractive force resulting from the sharing of electrons between atoms
covalent bonds
The helical coil shape of an α-helix fibrous protein provides what type of property to that protein?
elasticity
What type of protein accelerates the thousands of different chemical reactions that take place in an organism?
enzyme
A beta-pleated sheet is an example of a protein's tertiary structure.
false
A chemical formula shows the types and numbers of atoms in a molecule and their arrangement.
false
A combination of adhesive and cohesive forces accounts for surface tension.
false
A pyrimidine is a double-ring molecule.
false
A solution having a pH of 8 is slightly acidic.
false
An inorganic compound is one that contains carbon.
false
Condensation and hydrolysis reactions are catalyzed by the same enzymes.
false
Oxidation occurs when an atom gains one or more electrons.
false
Since a carbon atom has 4 valence electrons, it can complete its valence shell by forming a total of 4 hydrogen bonds.
false
The atomic mass determines the identity of an element.
false
The hydroxyl group is weakly acidic because of the presence of a strongly electronegative oxygen.
false
The valence shell of hydrogen or helium is unstable when it contains two electrons.
false
When glucose and fructose undergo condensation, maltose is produced as a product.
false
How many covalent bonds are formed by carbon atoms, producing a wide variety of molecular shapes and sizes?
four
When we know what kinds of ____ are present in an organic compound, we can predict its chemical behavior.
functional groups
What carbohydrate energy storage molecule is found in animal liver and muscle cells?
glycogen
Which of the following is sometime referred to as animal starch?
glycogen
Which of the following is a purine base found in nucleotides?
guanine
The covalent bond between a hydrogen atom and the oxygen atom in water is formed when:
hydrogen and oxygen share an electron pair
Holds adjacent water molecules together
hydrogen bond
The cohesiveness between water molecules is due largely to _________.
hydrogen bonds
Which of the following is responsible for the alpha-helical structure of proteins?
hydrogen bonds
Sugar dissolves readily in water because it is a(n) ____ substance.
hydrophilic
Strong attractive force resulting from the transfer of electrons between atoms
ionic bonds
Which component becomes oxidized in the following chemical reaction? 4 Fe + 3 O2 → 2 Fe2O3
iron
Why is ATP important in living organisms?
it can transfer some of its energy to other chemicals
Which substance is an example of a very strong acid?
lemon juice
cholesterol
lipid
most are nonpolar
lipid
Which element activates many enzymes and is needed in blood and other tissues of animals?
magnesium
Which of the following is a covalent compound?
methane
The products of the process in the accompanying figure are:
monosaccharides
A liquid with a pH of 7 is considered a(n) ____ solution.
neutral
Isotopes differ from each other with respect to the number of:
neutrons only
contains purines and pyrimidines
nucleic acid
may contain thymine
nucleic acid
Which pair matches the correct macromolecule with the bond that joins its subunits?
nucleic acid−phosphodiester linkage
When a nucleic acid undergoes hydrolysis, the resulting subunits are:
nucleotides
The chemical behavior of an atom is determined most directly by the:
number of valence electrons
Unlike lipids, hydrophilic functional groups typically contain ____ atoms, which make them more soluble in water.
oxygen
Which component is the oxidizing agent in the following chemical reaction? 4 Fe + 3 O2 → 2 Fe2O3
oxygen
Which of the following is a common oxidizing agent?
oxygen
It takes one calorie of heat to raise the temperature of one gram of water by one degree Celsius at sea level. This is referred to as the ___________ of water.
specific heat
The representation H−O−H is known as a(n):
structural formula
Glucose and fructose are ____ because they have identical molecular formulas but their atoms are arranged differently.
structural isomers
Which functional group in cysteine residues can form bridges that help stabilize a protein's tertiary structure?
sulfhydryl
enables certain insect to walk on water
surface tension
Which event illustrates evaporative cooling?
sweat evaporating from the skin
A molecule of a saturated triacylglycerol contains:
the maximum number of hydrogen atoms in the fatty acid chains
What is the difference between the two atoms in the accompanying figure?
the number of neutrons
Which statement about van der Waal interactions is false?
they are very strong
Nitrogen has five electrons in its valence shell. How many electrons does it need to gain to complete its valence shell?
three
Which of the following describes the tertiary structure of a protein molecule?
three-dimensional shape of an individual polypeptide chain
What is the purpose of a buffer?
to minimize the change in pH
A calorie is the amount of heat energy required to raise the temperature of 1 g of water 1 degree Celsius (C).
true
A phosphate group is weakly acidic.
true
An atom that has a filled valence shell is stable and unreactive.
true
Cellulose is the main structural component of the walls that surround plant cells.
true
Cyclic AMP is a type of nucleotide.
true
Molecular chaperones mediate the folding of other protein molecules.
true
The carboxyl group can exist in either an ionized or nonionized form.
true
The tetrahedron shape of a methane molecule is the result of orbital hybridization.
true
What does the accompanying figure represent?
two isotopes of the same element
Which of the following fatty acids include one or more adjacent pairs of carbon atoms joined by a double bond?
unsaturated fatty acids
Very weak attractive force joining nonpolar molecules
van der Waals interaction
What substance is removed during a condensation reaction?
water
Which substance is a reactant in the following chemical equation? CO2 + H2O ↔ H2CO3
water
A beta-pleated sheet is an example of a protein's tertiary structure.
False
An example of an anion is K+
False
By definition geometric isomers are mirror images of each other
False
Specific heat refers to the amount of energy required to change 1 gram of a substance from the liquid phase to the vapor phase.
False
When atoms react to form an ionic bond, electrons are shared between those atoms
False
What are compounds that have the same molecular formulas but different structures and different molecules?
Isomers
Which statement best describes the product of a chemical reaction?
It is the substance generated by the reaction.
Which organic compound is not only responsible for energy storage, but can also provide thermal insulation?
Lipids
At which level of protein structure are peptide bonds most important?
Primary
The primary difference between the amino acids commonly found in proteins is in their:
R or variable groups
The molecular fragment, represented in the accompanying figure is:
RNA
_______________________ are isomers that are mirror images of each other.
Enantiomers
When two amino acids combine in a condensation reaction, a ____________ is formed.
peptide bond
What group of molecules is represented in this structure?
phospholipids
Which of the following atoms can form five covalent bonds?
phosphorus
Which carbohydrate is the most structurally complex?
polysaccharide
a beta-pleated sheet is one typical structure
protein
has 20 different types of monomers
protein
A base is defined as a(n) ____________ acceptor.
proton
A steroid consists of carbon atoms arranged in four attached rings. How many carbon atoms do three of the rings contain?
six carbon atoms
Which atom would most likely be involved in an ionic bond?
sodium
