cancer-critical genes Genes whose alteration contributes to the causation or evolution of cancer by driving tumorigenesis.
capsid   Protein coat of a virus, formed by the self-assembly of one or more types of protein subunit into a geometrically regular structure. (Figure 3–27) carbohydrate layer The carbohydrate-rich zone on the eukaryotic cell surface attributable to glycoproteins, glycolipids, and proteoglycans of the plasma membrane.
carbon-fixation reaction   Process by which inorganic carbon (as atmospheric CO2) is incorporated into organic molecules. The second stage of photosynthesis. (Figure 14–40) carcinogenesis   The generation of cancer.
carcinoma Cancer of epithelial cells. The most common form of human cancer.
cargo The membrane components and soluble molecules carried by transport vesicles.
cartilage Form of connective tissue composed of cells (chondrocytes) embedded in a matrix rich in type II collagen and chondroitin sulfate proteoglycan.
caspase   Intracellular protease that is involved in mediating the intracellular events of apoptosis.
catalyst Substance that can lower the activation energy of a reaction (thus increasing its rate), without itself being consumed by the reaction.
caveola (plural caveolae) Invaginations at the cell surface that bud off internally to form pinocytic vesicles. Thought to form from lipid rafts, regions of membrane rich in certain lipids.
caveolins   Family of unusual integral membrane proteins that are the major structural proteins in caveolae,
CD4   Co-receptor protein on helper T cells and regulatory  T cells that binds to a nonvariable part of class II MHC proteins (on antigen-presenting cells) outside the peptide-binding groove. (Figure 24–40)
CD8   Co-receptor protein on cytotoxic T cells that binds to a nonvariable part of class I MHC proteins (on antigen-presenting cells and infected target cells) outside the peptide-binding groove. (Figure 24–40)
Cdc20   Activating subunit of the anaphase-promoting complex (APC/C).
Cdc25   Protein phosphatase that dephosphorylates Cdks and increases their activity.
Cdc42 Member of the Rho family of monomeric GTPases that regulate the actin and microtubule cytoskeletons, cell-cycle progression, gene transcription, and membrane transport.
Cdc6   Protein essential in the preparation of DNA for replication. With Cdt1 it binds to an origin recognition complex on chromosomal DNA and helps load the Mcm proteins onto the complex to form the prereplicative complex.
Cdh1   Activating subunit of the anaphase-promoting complex (APC/C).
Cdk inhibitor protein (CKI) Protein that binds to and inhibits cyclin–Cdk complexes, primarily involved in the control of G1 and S phases.
Cdk-activating kinase (CAK) Protein kinase that phosphorylates Cdks in cyclin–Cdk complexes, activating the Cdk.
cDNA clone Clone containing double-stranded cDNA molecules derived from the protein-coding mRNA molecules present in a cell.
cDNA library Collection of cloned DNA molecules representing complementary DNA copies of the mRNA produced by a cell.
Cdt1   Protein essential in the preparation of DNA for replication. With Cdc6 it binds to origin recognition complexes on chromosomes and helps load the Mcm proteins on to the complex, forming the prereplicative complex.
cell cortex Specialized layer of cytoplasm on the inner face of the plasma membrane. In animal cells it is an actin-rich layer responsible for movements of the cell surface.