Microbiology, 2021

E • Glossary 1201
intact ribosome that binds charged tRNAs
carrying amino acids that have formed
peptide bonds with the growing
polypeptide chain but have not yet
dissociated from their corresponding
tRNA
palatine tonsil lymphoid tissue located
near the oropharynx
pandemic disease an epidemic that is
worldwide as opposed to regional
papilloma growth on the skin associated
with infection by any of the human
papilloma viruses (HPV); commonly
known as a wart
paracrine function refers to a cytokine
signal released from a cell to a receptor on
a nearby cell
parasitism type of symbiosis in which one
population benefits while harming the
other parasitology the study of parasites
parenteral route means of entry by a
pathogen through skin or mucous
membranes when these barriers are
breached
paroxysmal stage most serious stage of
pertussis (whooping cough), characterized
by severe and prolonged coughing spells
passive carrier an individual capable of
transmitting a pathogen to another
individual without becoming infected
passive immunity adaptive immune
defenses received from another individual
or animal
pasteurization form of microbial control
using heat that is applied to foods; kills
pathogens and reduces the number of
spoilage-causing microbes while
maintaining food quality
pathogen a disease-causing
microorganism
pathogen-associated molecular patterns
(PAMPs) common molecular motifs found
on pathogens
pathogenicity ability of a microbial agent
to cause disease
pattern recognition receptors (PRRs)
receptors on the surface or in the interior
of phagocytic cells that bind to pathogenassociated
molecular patterns (PAMPs)
pellicle structure that underlies the
plasma membrane in protists, providing
additional support
pelvic inflammatory disease (PID)
infection of the female reproductive
organs that may spread from the vagina to
the cervix, uterus, fallopian tubes, and
ovaries
penetration entry of phage or virus into a
host cell through injection, endocytosis, or
membrane fusion
penicillin β-lactam antibacterial that was
the first cell wall synthesis inhibitor
developed
penis external genital organ in males
through which urine and semen are
discharged
pentamidine antiprotozoan drug that
appears to degrade kDNA in target cells, as
well as inhibit protein synthesis
pentose phosphate pathway (PPP)
alternative glycolytic pathway that
produces intermediates used for the
biosynthesis of nucleotides and amino
acids; also called the phosphogluconate
pathway or the hexose monophosphate
shunt
peptic ulcer an ulcer in the lining of the
stomach or duodenum, often associated
with Helicobacter pylori
peptide bond bond between the carboxyl
group of one amino acid and the amine
group of another; formed with the loss of a
water molecule
peptidoglycan (murein) the polymer of
alternating N-acetylmuramic acid NAM
and N-acetylglucosamine (NAG) subunits
linked together by peptide chains; a major
constituent of bacterial cell walls
peptidyl transferase RNA-based
ribozyme that is part of the 50S ribosomal
subunit and catalyzes formation of the
peptide bond between the amino acid
bound to a tRNA and the growing
polypeptide chain
perforin compound released from a
natural killer cell that creates pores in the
target cell through which other toxins
(particularly granzymes) can gain access
to the cytoplasm
pericarditis inflammation of the sac that
surrounds the heart
period of convalescence fifth stage of
acute disease, during which the patient
returns to normal function
period of decline fourth stage of disease,
during which the number of pathogens
present in the host decreases, along with
signs and symptoms of disease
period of illness third stage of acute
disease, during which the number of
pathogens present in the host is greatest
and the signs and symptoms of disease are
most severe
periodontal disease a condition in which
the gums are inflamed and may erode
periodontitis inflammation of the gums
that is more severe than gingivitis,
spreading deeper into the tissues
peripheral nervous system network of
neurons that connects the CNS with
organs, sensory organs, and muscles
throughout the body
peripheral tolerance mechanism by
which regulatory T cells inhibit selfreactive
immune responses in T cells that
have already exited the thymus
periplasmic space the space between the
cell wall and the plasma membrane,
primarily in gram-negative bacteria
peristalsis muscular contractions of the
gastrointestinal tract that propel ingested
material through the stomach, intestines,
and, eventually, through the rectum and
out of the body
peritrichous having numerous flagella
covering the entire surface of a bacterial
cell
peroxidase enzyme that catalyzes the
detoxification of peroxides
peroxisome in eukaryotic cells, a
membrane-bound organelle (not part of
the endomembrane system) that produces
hydrogen peroxide to break down various
types of molecules; also plays a role in
lipid biosynthesis
peroxygen type of strong oxidizing agent
that causes free radical formation in cells;
can be used as a disinfectant or antiseptic
persister dormant cell that survives in the
death phase and is resistant to most
antibiotics
pertussis contagious illness caused by
Bordetella pertussis that causes severe
coughing fits followed by a whooping
sound during inhalation; commonly
known as whooping cough
pertussis toxin main virulence factor
accounting for the symptoms of whooping
cough