Answers to Check Your Understanding, Multiple Choice,
Matching Questions, and Case Study
Check Your Understanding 1.
Te operation or function of a structure
is promoted or prevented by its anatomy. For example, oxygen and car-
bon dioxide are exchanged across the very thin membranes of the lungs
but not across the skin.
Muscle shortening is a topic of physiology.
Te body location of the lungs is an anatomy topic.
the cellular level of organization.
Te order in the structural hierarchy
is cell, tissue, organ, and organism.
Bones and cartilages are part of
the skeletal system. Te nasal cavity, lungs, and trachea are respiratory
Living organisms can maintain their boundaries, move,
respond to environmental changes, digest nutrients, carry out metabo-
lism, dispose of wastes, reproduce, and grow. While inanimate objects
may exhibit some of these properties, they do not exhibit all of them.
Metabolism is the term that encompasses all the chemical reactions
that occur in body cells.
In ﬂight, the cabin must be pressurized be-
cause the atmosphere is thinner at high altitudes and the amount of
oxygen entering the blood under such conditions may be insuﬃcient
to maintain life.
Negative feedback mechanisms allow us to adjust to
conditions outside the normal temperature range by causing heat to be
lost from the body (in hot conditions) and retained or generated by the
body (in cold conditions).
Tirst is part of a negative feedback con-
trol system because it prods us to drink, which ends the thirst stimulus
and returns body ﬂuid volume to the normal range.
Tis is a positive
feedback mechanism because it enhances the change (formation of a
platelet plug) set into motion by the stimulus (damage to the blood ves-
sel). Te response ends when the platelet plug has plugged the hole in the
Te position in which a person is standing erect with
feet slightly separated and palms facing anteriorly. Knowing the ana-
tomical position is important because directional terms refer to the body
as if it is in this position.
Axillary region is the armpit. Acromial area
is the tip of the shoulder.
A frontal (coronal) section would separate
the brain into anterior and posterior parts.
He may have appendicitis
if the pain is in the lower right quadrant of his abdomen.
organs, only the spinal cord is in the dorsal body cavity.
organs (heart, lungs, digestive organs) work, friction is greatly reduced by
the presence of serous ﬂuid. Serous ﬂuid allows the surrounding serous
membranes to glide easily over one another.
Review Questions 1.
(a) wrist (b) hip bone (c) nose
(d) toes (e) scalp;
neither c nor d would be visible in the median
(a) dorsal (b) ventral (c) dorsal (d) ventral;
Check Your Understanding 1.
Foods contain chemical energy.
trical energy is the energy used by nerve cells to transmit messages in the
Potential energy (PE) is available when we are still. PE is con-
verted to kinetic (working) energy when we exercise.
and nitrogen, carbon and oxygen help to make up the bulk of living
Tis element has 82 protons in its nucleus and 82 electrons in
its orbitals (electron cloud).
Atomic mass indicates the sum of the pro-
tons and neutrons in a given atom’s nucleus. Atomic weight indicates the
average mass of all the isotopes of a given element.
A molecule is 2 or
more atoms held together by chemical bonds.
A compound is formed
when two or more diﬀerent kinds of atoms chemically bond together, as
in NaCl. Oxygen gas is 2 oxygen atoms (the same kind of atom) bonded
Blood is a mixture because its components are not changed
by their combination and they can be separated by physical means.
Hydrogen bonds (linking H of one water molecule to O of another)
form between water molecules.
Argon’s valence shell is full: )2e )8e
)8e. Hence it is nonreactive.
Electrons would spend more time in the
vicinity of the more electronegative atom in XY, whereas electrons in XX
would orbit both X atoms to an equal extent.
Fats are digested in the
small intestine by decomposition reactions.
Biochemical reactions in
the body tend to be irreversible because (a) one or more of the products
is removed from the reaction site or (b) the product is needed more than
the reactants, so the cell would not provide energy to reverse the reaction.
Decomposition reactions in which foods are broken down for energy
are oxidation-reduction (redox) reactions.
Water is an excellent sol-
vent because of its polarity. As a dipole, it can orient itself to the end of
other molecules, causing them to dissociate or go into solution.
trolytes are substances like salts that will conduct an electrical current in
is responsible for acidity.
It is better to add
a weak base, which will act to buﬀer the strong acid.
carbohydrates are called monosaccharides or simple sugars. Glucose is
Te animal form of stored carbohydrate is glycogen.
±riglycerides, the major source of stored energy in the body, are com-
posed of three fatty acid chains and a glycerol molecule and are found in
fat tissue. Phospholipids consist of two fatty acid chains and a charged
P-containing group. Tey are found in all cell membranes and form the
basis of those membranes.
Hydrolysis reactions break down polymers
or macromolecules to their monomers by adding water to each bond
An “amino acid” has an amine group (NH
) and a
COOH group that has acidic properties.
Te primary structure of pro-
teins is the stringlike chain of amino acids.
Te secondary structures
of proteins are the alpha helix and the beta-pleated sheet.
chaperones prevent inaccurate or inappropriate folding in the 3-D struc-
ture of a protein.
Enzymes hold the substrate(s) in a desirable position
DNA contains deoxyribose sugar and the bases A, ±, G,
C. RNA contains ribose sugar and the bases A, U, G, C.
protein structure by its base sequence and reproduces itself before a cell
divides to ensure that the genetic information in the daughter cells is
A±P stores energy in smaller packets that are more readily
released and transferred (during A±P hydrolysis) than the energy stored
in glucose. Hence the use of A±P as an energy source keeps energy waste
to a minimum.
When A±P releases energy, it loses a phosphate group
and becomes ADP (also energy rich).
Review Questions 1.
Check Your Understanding 1.
Te cell is the structural and functional
unit of life. Te activity of an organism depends on the activities of its
cells. Te activities of cells depend on their form and relative numbers
of subcellular structures. Continuity of life has a cellular basis.
the cell concept that includes structures and functions common to all
All cellular membranes consist of a double layer of phospholi-
pids in which proteins are embedded.
Hydrophobic regions (tails of
phospholipid molecules) orient toward each other while the hydrophilic
regions (phospholipid heads) orient to the aqueous ﬂuid inside and
outside the cell.
Te sugar residues of the glycocalyx provide recogniz-
able biological markers for cells to recognize each other.
Te heart has
desmosomes (anchoring junctions) that secure cardiac cells together as
the heart works and gap junctions (communicating junctions) that al-
low ions to ﬂow from cardiac cell to cardiac cell.
Diﬀusion is driven
by kinetic energy of the molecules.
Te relative concentration of the
substance in diﬀerent areas determines the direction of diﬀusion. Dif-
fusion occurs from regions of high concentration to regions of low
In channel-mediated diﬀusion, the diﬀusing substance
moves through a membrane channel. In carrier-mediated diﬀusion, the
diﬀusing substance attaches to a membrane (protein) carrier that moves