PCC Biochemistry

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PCC Biochemistry
 

True/False
Indicate whether the statement is true or false. Write  + for true and  0 for false.
 1.
Atoms have a positive charge.
 2.
An element is made up of more than one kind of atom.
 3.
Hydrogen and oxygen atoms have an equal number of electrons.
 4.
A molecule is an atom that has gained or lost an electron.
 5.
An atom that gains or loses one or more electrons is called an ion.
 6.
An atom with more electrons than protons has a positive charge.
 7.
Ionic bonds form between two negatively charged particles.
 8.
A covalent bond forms between two atoms that share electrons to form a molecule.
 9.
Adhesion is an attraction between different substances.
 10.
The ability of water to retain heat helps cells maintain homeostasis.
 11.
Nonpolar molecules dissolve well in water.
 12.
Water molecules attract nonpolar molecules such as oil.
 13.
Organic compounds contain carbon atoms that are covalently bonded to other elements—typically hydrogen, oxygen, and other carbon atoms.
 14.
A nucleotide has four parts.
 15.
RNA is made up of a double strand of nucleotides.
 16.
DNA stores hereditary information that can be used to make proteins.
 17.
When cells break down food, the energy from the food is temporarily stored as ATP.
 18.
The amount of energy needed to cause a chemical reaction to start is called activation energy.
 19.
Without enzymes, chemical reactions necessary for life would not occur at a rate sufficient to sustain life.
 20.
Enzymes speed up a chemical reaction by increasing the activation energy of the reaction.
 21.
When an enzyme binds with its substrate, the activation energy needed for the chemical reaction to occur is increased.
 22.
Chemical reactions that occur in cells are called biochemical reactions.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 23.
Atoms are composed of
a.
protons.
c.
electrons.
b.
neutrons.
d.
All of the above
 24.
The electrons of an atom
a.
are found in the nucleus along with the protons.
b.
occupy the space surrounding the nucleus.
c.
have a positive charge.
d.
are attached to the positive charge of neutrons.
 25.
The smallest particle of matter that can retain the chemical properties of carbon is a(n)
a.
carbon molecule.
c.
carbon atom.
b.
carbon macromolecule.
d.
element.
 26.
A substance that is composed of only one type of atom is called a(n)
a.
nucleus.
c.
element.
b.
cell.
d.
molecule.
 27.
All matter is composed of
a.
cells.
c.
atoms.
b.
molecules.
d.
carbon.
 28.
A molecule that has a partial positive charge on one side and a partial negative charge on the other side is called a
a.
nonpolar molecule.
c.
charged molecule.
b.
polar molecule.
d.
bipolar molecule.
 29.
A chemical formula shows the
a.
kinds of bonds found in the molecule.
b.
kinds of bonds found in the compound.
c.
kinds of elements found in the compound.
d.
arrangement of the elements found in the compound.
 30.
Ionic bonds form between molecules that have
a.
opposite charges.
c.
no charges.
b.
the same charge.
d.
neutral charges.
 31.
The bond formed when two atoms share a pair of electrons is called a(n)
a.
hydrogen bond.
c.
covalent bond.
b.
ionic bond.
d.
water bond.
 32.
Sharing of electrons in the outer energy levels of two atoms
a.
results in ion formation.
b.
occurs in covalent bonds.
c.
only occurs if both are atoms of the same element.
d.
is found only among carbon atoms.
 33.
Water is important to life because it
a.
surrounds all cells.
b.
is found inside cells.
c.
influences the shape of the cell membrane.
d.
All of the above
 34.
Nonpolar molecules have
a.
no negative or positive poles.
c.
only a negative pole.
b.
both negative and positive poles.
d.
only a positive pole.
 35.
When placed in the same container, oil and water do not mix because
a.
they are both polar.
c.
they are both nonpolar.
b.
water is polar and oil is nonpolar.
d.
water is nonpolar and oil is polar.
 36.
Due to the polarity of water, compounds that dissolve best in water contain
a.
nonpolar bonds.
c.
polar bonds.
b.
ionic bonds.
d.
Both (b) and (c)
 37.
Water is a polar molecule because
a.
it contains two hydrogen atoms for each oxygen atom.
b.
it has a charge.
c.
different parts of the molecule have slightly different charges.
d.
it does not have a charge.
 38.
Acidic solutions have a pH that is
a.
less than 7.
c.
a negative number.
b.
between 7 and 14.
d.
more than 7.
 39.
Hydrogen ions, H+, react with hydroxide ions, OH-, to form
a.
water.
c.
a base.
b.
an acid.
d.
None of the above
 40.
Which of the following is not an organic macromolecule?
a.
carbohydrate
c.
lipid
b.
ice
d.
nucleic acid
 41.
All organic compounds contain the element
a.
carbon.
c.
calcium.
b.
nitrogen.
d.
sodium.
 42.
Which of the following organic molecules are classified as carbohydrates?
a.
amino acids
c.
nucleotides
b.
fatty acids
d.
sugars
 43.
Polysaccharides are
a.
carbohydrates.
c.
proteins.
b.
lipids.
d.
unsaturated fats.
 44.
Lipids are
a.
polar molecules.
c.
water soluble.
b.
similar to water molecules.
d.
nonpolar molecules.
 45.
Which of the following organic molecules are most closely related to proteins?
a.
amino acids
c.
nucleotides
b.
fatty acids
d.
sugars
 46.
Long chains of amino acids are found in
a.
carbohydrates.
c.
proteins.
b.
lipids.
d.
sugars.
 47.
All of the following are examples of lipids except
a.
saturated fats.
c.
cholesterol.
b.
starch.
d.
earwax.
 48.
Lipids are soluble in
a.
water.
c.
oil.
b.
salt water.
d.
All of the above
 49.
Which organic molecules below are most closely related to lipids?
a.
amino acids
c.
nucleotides
b.
fatty acids
d.
sugars
 50.
Which of the following organic molecules are most closely related to nucleic acids?
a.
amino acids
c.
nucleotides
b.
fatty acids
d.
sugars
 51.
Which of the following is a carbohydrate?
a.
DNA
c.
wax
b.
insulin
d.
sucrose
 52.
Carbohydrates and lipids have many carbon-hydrogen bonds; therefore, they both
a.
store energy in these bonds.
c.
dissolve only in vinegar.
b.
are easily dissolved in water.
d.
exist only in cells of plants.
nar001-1.jpg
nar001-2.jpg
Molecule A
Molecule B
 53.
Refer to the illustration above. Molecules like Molecule B are found in
a.
carbohydrates.
c.
nucleic acids.
b.
lipids.
d.
proteins.
 54.
Liquid fats called oils contain
a.
mostly unsaturated fatty acids.
c.
many glucose molecules.
b.
mostly saturated fatty acids.
d.
amino acids.
 55.
Animals store glucose in the form of
a.
cellulose.
c.
wax.
b.
glycogen.
d.
lipids.
 56.
The shape of a protein is primarily determined by
a.
the type and sequence of its amino acids.
b.
its size.
c.
its cell location.
d.
None of the above
 57.
The two types of nucleic acids are
a.
chlorophyll and retinal.
c.
lipids and sugars.
b.
DNA and RNA.
d.
glucose and glycogen.
 58.
DNA stores
a.
fat.
c.
protein.
b.
carbohydrates.
d.
heredity information.
 59.
The two strands of a DNA molecule are held together by
a.
ionic bonds.
c.
hydrogen bonds.
b.
covalent bonds.
d.
None of the above
 60.
A molecule shaped like a spiral staircase (double helix) is typical of
a.
deoxyribonucleic acid.
c.
lipids.
b.
ribonucleic acid.
d.
carbohydrates.
 61.
ATP (adenosine triphosphate) stores energy for cells to use in the bonds between its
a.
amino acids.
c.
nucleotides.
b.
carbon atoms.
d.
phosphates.
nar002-1.jpg
 62.
Refer to the illustration above. Which graph illustrates what happens during an energy-releasing reaction?
a.
Graph A
b.
Graph B
c.
both graphs because they each show a different stage of an energy releasing reaction
d.
None of the above
 63.
Refer to the illustration above. Which graph illustrates a reaction during which energy is released?
a.
Graph A
b.
Graph B
c.
both graphs because all chemical reactions release energy
d.
None of the above
nar003-1.jpg
 64.
Refer to the illustration above. Which of the following statements regarding the graph is true?
a.
Reaction 2 occurs faster than Reaction 3 because Reaction 2 requires more energy than Reaction 3.
b.
The difference between the graphs shown for Reaction 2 and Reaction 3 is because of a difference in the activation energy of these reactions.
c.
Reactant A contains more energy at the beginning of the reaction than product C has after the reaction.
d.
All of the above
 65.
Refer to the illustration above. Reaction 3 in the graph
a.
probably occurred in the presence of a catalyst.
b.
requires more activation energy than Reaction 2.
c.
is the same as Reaction 1, but faster.
d.
is slower than Reaction 2.
 66.
The molecule on which an enzyme acts is called a(n)
a.
active site.
c.
organic molecule.
b.
inactive site.
d.
substrate.
 67.
An enzyme
a.
is not used up when catalyzing a reaction.
b.
lowers the activation energy of a reaction.
c.
bonds with a substrate molecule at the enzyme’s active site.
d.
All of the above
 68.
Which of the following conditions affects the function of enzymes?
a.
pH
c.
enzyme concentration
b.
heat
d.
All of the above
 69.
Reducing activation energy
a.
is a violation of the laws of nature.
b.
requires higher temperatures than those found within cells.
c.
occurs only when reactants are quickly added to the reaction mixture.
d.
is accomplished by the action of catalysts on reactants.
 70.
Enzymes
a.
are able to heat up molecules so that they can react.
b.
always provide carbon dioxide for chemical reactions.
c.
are biological catalysts.
d.
absorb excess heat so that reactions occur at low temperatures.
 71.
A cell contains
a.
thousands of different kinds of enzymes, each promoting a different chemical reaction.
b.
one kind of enzyme that promotes thousands of different chemical reactions.
c.
approximately 100 kinds of enzymes, each promoting a different chemical reaction.
d.
one enzyme that promotes photosynthesis and one enzyme that promotes cellular respiration.
 72.
Amylase is a digestive enzyme that breaks down starch into
a.
amino acids.
c.
glycogen.
b.
glucose.
d.
cellulose.
 73.
The digestive enzyme pepsin works with hydrochloric acid to break down proteins in the stomach. Pepsin probably works best at a pH of
a.
11.
c.
3.
b.
7.
d.
Both (b) and (c).

 

        
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