biology-dictionary_11-06-2009

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Cuboidal ciliated epithelium
Cuboidal epithelia are epithelial cells having a cube-like shape; that is, their width is
approximately equal to their height. They may exist in single layers (simple cuboidal
epithelium) or multiple layers (stratified cuboidal epithelium) depending on their location
(and thus function) in the body.
Cutaneous
Relating to skin or Integumentary system (skin).
Cuticle
(1) A waxy covering on the surface of stems and leaves that acts as an adaptation to
prevent desiccation in terrestrial plants.
(2) The exoskeleton of an arthropod, consisting of layers of protein and chitin that are
variously modified for different functions.
Cutin
A waxlike, water-repellent material present in the walls of some plant cells and forming the
cuticle, which covers the epidermis.
Cyanobacteria
Photosynthetic, oxygen-producing bacteria (formerly know as blue-green algae).
Cyclic AMP
Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common
intracellular signaling molecule (second messenger) in eukaryotic cells, for example, in
vertebrate endocrine cells. It is also a regulator of some bacterial operons.
Cyclic electron flow
A route of electron flow during the light reactions of photosynthesis that involves only
photosystem I and produces ATP but not NADPH or oxygen.
Cyclin
A regulatory protein whose concentration fluctuates cyclically.
Cyclin-dependent kinase (Cdk)
A protein kinase that is active only when attached to a particular cyclin.
Cycloid
Thin, rounded, and smooth-edged; disklike. Used of fish scales.
Cyclosis or rotation
The circulation of cytoplasm within a cell is called a cyclosis or rotation.

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