it across the membrane.
Phosphorylation of the Na
causes the pump protein to change shape so that it “pumps” Na
the membrane. K
binding to the pump protein triggers the release of
phosphate and the pump protein returns to its original shape.
plasma membrane expands as a result of exocytosis.
engulf debris, and a smoker’s lungs would be laden with carbon particles
and other debris from smoke inhalation.
Cholesterol is taken in by
Diﬀusion of ions, mainly the
diﬀusion of K
from the cell through leakage channels, establishes the
resting membrane potential.
In a polarized membrane, the inside
is negative relative to its outside.
Signaling chemicals that bind to
membrane receptors are called ligands. G protein–linked receptors direct
intracellular events by promoting formation of second messengers.
Mitochondria are the major sites of A±P synthesis.
are the sites of protein synthesis. Te rough ER provides a site for ribo-
some attachment, and its cisterns package in vesicles the proteins made
on the ribosomes for transport to the Golgi apparatus. Te Golgi appa-
ratus modiﬁes and packages the proteins it receives for various destina-
tions within or outside the cell.
Te lysosomal enzymes digest foreign
substances engulfed by the cell, nonuseful or deteriorating organelles, or
even the cell itself to prevent the buildup of cellular debris. Te enzymes
in peroxisomes detoxify harmful chemicals and neutralize free radicals.
Both microﬁlaments and microtubules are involved in organelle
movements within the cell and/or movements of the cell as a whole.
Intermediate ﬁlaments are the most important cytoskeletal elements
in maintaining cell shape.
Te major function of microvilli is to
increase the cell’s surface area for absorption of substances.
If a cell
loses its nucleus, it is doomed to die because it will be unable to make
proteins, which include the enzymes needed for all metabolic reactions.
Nucleoli are the site of synthesis of ribosomal subunits.
proteins provide the means to pack DNA in a compact, orderly way, and
they play a role in gene regulation.
Te base sequence of the corre-
sponding strand will be GC±±AC.
DNA is synthesized during the S
Nuclear envelope breaks up, spindle forms, nucleoli disappear,
and the chromosomes coil and condense.
Codons are three-base
sequences in mRNA, each of which speciﬁes an amino acid. Anticodons
are three-base sequences in tRNA that are complementary to the codons
specifying the amino acid they transport to the ribosome during protein
Te A site is the entry site for tRNA at the ribosome. Te
P site is where the tRNA carrying the growing polypeptide is located. Te
E site is the tRNA exit site from the ribosome.
DNA provides the
coded instructions (is the template) for protein synthesis via the mRNA
synthesized on it.
Ubiquitin attaches to misfolded, damaged, or un-
needed proteins, tagging them for destruction by proteasomes.
plasma is extracellular ﬂuid that transports nutrients, gases, hormones,
and other substances throughout the body. Interstitial ﬂuid is an im-
portant transport and dissolving medium.
Apoptosis is a process
of programmed cell death which rids the body of cells that are stressed,
damaged, old, or no longer needed.
Te wear-and-tear theory of ag-
ing attributes aging to little chemical insults and free radicals, which have
cumulative detrimental eﬀects.
Review Questions 1.
Check Your Understanding 1.
Fixing tissue preserves it and prevents it
Heavy metal salts are used to stain tissues viewed
by electron microscopes.
Epithelial tissue lines body cavities and cov-
ers the body’s external surface; thus polarity with one free (apical) surface
is a requirement.
Epithelial tissue can regenerate and its cells are joined
by lateral contacts.
Simple epithelia are “built” to provide for eﬃcient
absorption and ﬁltration across their thin epithelial barriers.
stratiﬁed epithelia appear to be stratiﬁed because their cells’ nuclei lie at
diﬀerent distances from the basement membrane. However, all cells rest
on the basement membrane.
±ransitional epithelium is found in the
urinary bladder and other hollow urinary organs. Te ability of this epi-
thelium to thin allows the urinary organs to handle (store or transport)
a larger urine volume when necessary.
All unicellular exocrine glands
secrete the protein mucin (which becomes mucus on mixing with water).
Tese exocrine glands are classiﬁed by duct structure and secretory
Holocrine glands have the highest rate of cell division. Te
secretory cells fragment and are lost in the secretion; thus the secretory
cells must be continuously replaced.
Connective tissue functions to
bind, support, protect, and insulate body organs. In addition, blood acts
to transport substances throughout the body.
Reticular, collagen, and
elastic ﬁbers are found in the various connective tissues.
nective tissue, because of its loose weblike nature, is capable of serving as
a ﬂuid reservoir.
Dense regular connective tissue is damaged when
you lacerate a tendon.
Hyaline cartilage forms the growth plates.
Cardiac muscle cells have striations and are branching cells.
etal muscle tissue is voluntary and is the muscle tissue injured when you
“pull a muscle” while exercising.
With extended processes, a neuron
can conduct electrical signals a great distance within the body.
mucous membrane consists of both connective tissue and epithelium.
It lines body cavities open to the exterior.
Te serous membranes
called pleurae line the thorax walls and cover the lungs.
main steps of tissue repair are inﬂammation, organization, and regenera-
tion and ﬁbrosis (which is a permanent repair).
More severe injuries
damage and destroy more tissue, requiring greater replacement with scar
Te three embryonic germ layers are the ectoderm, mesoderm,
Ectoderm gives rise to the nervous system.
thelium and blood-forming tissue remain highly mitotic all through life.
Review Questions 1.
(1)a, (2)c, (3)d, (4)b;
(1)b, (2)f, (3)a, (4)d,
Check Your Understanding 1.
Since the sole of the foot has thick
skin, the layers from most superﬁcial to deepest would be the stratum
corneum, stratum lucidum, stratum granulosum, stratum spinosum,
and stratum basale.
Te stratum basale undergoes almost continuous
mitosis to replace cells lost by abrasion.
Te skin is subjected to a lot
of abrasion and physical trauma. Te desmosomes, which are connect-
ing junctions, help to hold the cells together during such stress.
stratum basale, which abuts the dermis where the blood supply is, has
the best nourished cells.
Te papillary layer of the dermis gives rise to
Fatty tissue in the hypodermis gives it insulating
and shock-absorbing properties.
Because there is no bleeding, the cut
has penetrated into the avascular epidermis only.
Te third pigment
contributing to skin color is hemoglobin, the pigment contained in red
blood cells found in blood vessels of the dermis.
Cyanosis is a bluish
cast of the skin that indicates that hemoglobin in the red blood cells in
the dermal capillaries is poorly oxygenated.
Jaundice or a yellow cast
to the skin due to the deposit of yellow bile pigments in body tissues
may indicate a liver disorder.
Te regions of a hair from outside in
are the cuticle, cortex, and medulla.
Tere are no nerves in a hair, so
cutting hair is painless.
Te arrector pili muscles pull the hair (nor-
mally slanted) to the upright position (when cold or scared).
papilla contains a knot of capillaries that supplies nutrients to cells of the
Te lunule of the nail is white because the thick nail matrix
that underlies it blocks the rosy color of the dermal blood supply from
Nails are hard because the keratin they contain is
the hard keratin variety.
Sebaceous (oil) glands and apocrine glands
are associated with the hair follicles.
His sympathetic nervous system
activated his eccrine sweat glands and caused heat-induced sweating