318 ❯ Glossary
casparian stripObstacle that blocks the passage of
water through the endodermis of plants.
catalase Enzyme that assists in the conversion of
hydrogen peroxide to water and oxygen. Found in
peroxisomes.
catalysts Molecules that speed up reactions by low-
ering the activation energy of a reaction.
cation Ion with a positive charge that contains more
protons than electrons.
cell body The main body of the neuron.
cell cycle A cycle that consists of four stages: G 1 , S,
G 2 , and M. G 1 and G 2 are growth stages, S is the
part of the cell cycle in which the DNA is dupli-
cated, and the M phase stands for mitosis—the cell
division phase.
cell-mediated immunity This type of immunity
involves direct cellular response to invasion as
opposed to antibody-based defense.
cell platePlant cell structure constructed in the
Golgi apparatus composed of vesicles that fuse
together along the middle of the cell, completing
the separation process.
cellular slime molds Protists with a unique eating
strategy. When plenty of food is available, they eat
alone. When food is scare, they clump together
and form a unit.
cellulose Polysaccharide composed of glucose used
by plants to form cell walls.
cell wallWall that functions to shape and protect
cells. Present in plant but not animal cells.
central nervous system (CNS) The CNS is made up
of the brain and the spinal cord. The CNS con-
trols skeletal muscles and voluntary movement.
cephalization The concentration of sensory machin-
ery in the anterior end of a bilateral organism.
cerebellum Portion of brain in charge of coordina-
tion and balance.
cerebrum Portion of the brain that controls func-
tions such as speech, hearing, sight, and motor
control. Divided into two hemispheres and four
lobes per hemisphere.
cervix The uterus connects to the vaginal opening
via this narrowed region.
CF Seecystic fibrosis.
character A heritable feature, such as flower color,
that varies among individuals.
checkpoints Stop points throughout the cell cycle
where the cell verifies that there are enough nutrients
and raw materials to progress to the next stage of
the cycle.
chemical communication Mammals and insects
communicate through the use of chemical signals
calledpheromones.
chemiosmosisThe coupling of the movement of
electrons down the electron transport chain with
the formation of ATP using the driving force pro-
vided by a proton gradient. Seen in both photo-
synthesis and respiration.
chemoautotrophsAutotrophs that produce energy
through oxidation of inorganic substances.
chitin Polysaccharide that is an important part of the
exoskeletons of arthropods such as insects, spiders,
and shellfish.
chlorophyll A photosynthetic pigment.
chlorophytes Green algae that are probably the
common ancestors of land plants.
chloroplast The site of photosynthesis and energy
production in plant cells and algae.
choanoflagellate Accepted to be the common
ancestor of the animal kingdom.
choice Refers to the selection of mates by one sex (in
mammals, it is usually females who exercise choice
over males).
choice chamberChamber used in scientific experi-
ments to study kinesis.
cholesterol Steroid that is an important structural
component of cell membranes and serves as a
precursor molecule for steroid sex hormones.
chorionFormed from the trophoblast, it is the outer
membrane of the embryo and the site of implanta-
tion onto the endometrium. It contributes to for-
mation of the placenta in mammals.
chromatin The raw material that gives rise to the
chromosomes (genetic material is uncoiled).
chromosomal translocations Condition in which a
piece of one chromosome is attached to another,
nonhomologous chromosome.
chromosome duplication Error in chromosomal
replication that results in the repetition of a
genetic segment.
chromosome inversion Condition in which a piece
of a chromosome separates and reattaches in the
opposite direction.
chronic myelogenous leukemia A cancer affecting
white blood cell precursor cells. In this disease, a
portion of chromosome 22 has been swapped with
a piece of chromosome 9.