← BACK The synthesis phase of the cell cycle, constituting the portion of interphase during which DNA is replicated.
The pacemaker of the heart, located in the wall of the right atrium.
Genes located on one sex chromosome but not the other.
A chain of supporting cells enclosing the axons of many neurons and forming an insulating layer called the myelin sheath.
A rigid, supportive plant cell type usually lacking protoplasts and possessing thick secondary walls strengthened by lignin at maturity.
The principle whereby every energy transfer or transformation increases the entropy of the universe.
Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.
The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages.