Glossary 359“9x6” b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to HumanityPost-synaptic potential (PSP): Membrane potential of post-synaptic neuronal
cell body. There are two types: the excitatory (EPSP) and the inhibitory
(IPSP). The former corresponds to depolarization whereas the latter corre-
sponds to hyperpolarization of the membrane.
Prefrontal cortex (PFC): The part of the frontal lobe cortex minus the areas
dedicated to movement and speech, corresponding to the most frontal part
of the brain.
Protein conformation: The 3-dimensional shape of a protein molecule.
Protein: A macromolecule made up of amino acids linked together by
peptide bonds. It is involved in most of the work in a cell, including
metabolism (enzymes), signal transduction, and the building of cellular
structures.
Quorum sensing: A way of bacterial communication by which they are able to
sense their own population density.
Readiness potential: Action potential detected in the motor cortex before an
action is executed.
Red blood cells: Cellular components of blood that contains hemoglobin
(imparting a red color) and is responsible for the transport of oxygen.
REM sleep: Rapid-eye-movement sleep. Corresponds to a stage of sleep when
dreaming occurs. At this stage the eyes move rapidly while other muscle
movements are inhibited. EEG simulates a state of wakefulness.
Reticular activating system: Short afferent fiber tracts that diffusely carry
non-discrete sensation (alertness) from the spinal cord to the brain.
Ribose: A five-carbon sugar component in a ribonucleic acid (RNA).
Ribosomal RNA: RNA component of a ribosome.
Ribosome: Small particles in the cytoplasm where proteins are synthesized. It
is made up of RNA and protein.
RNA (ribonucleic acid): A type of nucleic acid that differs from DNA in that
the deoxyribose is replaced by ribose sugar. RNA does not form a double
helical structure but may form base pairing at irregular intervals. RNA is
responsible for transfer of message from DNA to protein, and plays a major
role in various aspects of protein synthesis and gene expression.
RNA interference (RNAi): A phenomenon in which a short piece (about 21
to 26 nucleotides long) of RNA interferes or modulates cellular function by
binding to messenger RNA or to DNA.b2726_Glossary.indd 359 6/12/2017 8:00:29 PM