Phenotype
The physical and physiological traits of an organism.
Pheromone
A small, volatile chemical signal that functions in communication between animals and acts
much like a hormone in influencing physiology and behavior.
Phloem
The portion of the vascular system in plants consisting of living cells arranged into elongated
tubes that transport sugar and other organic nutrients throughout the plant.
Phosphate group
A functional group important in energy transfer.
Phospholipids
Molecules that constitute the inner bilayer of biological membranes, having a polar,
hydrophilic head and a nonpolar, hydrophobic tail.
Phosphorylation
Addition of a phosphate group or groups to a molecule.
Phosphoester bonds
A phosphoester bond is a group of strong covalent bonds between the phosphrous atom in
a phosphate group and two other molecules over two ester bonds.
Phospholytic
The organic compounds of phosphorus. The blood phosphate level is normally 2.5 mg to 5
mg/100 mL. It is low in rickets and early hyperparathyroidism and high in tetany and
nephritis
Photic zone
The narrow top slice of the ocean, where light permeates sufficiently for photosynthesis to
occur.
Photoautotroph
An organism that harnesses light energy to drive the synthesis of organic compounds from
carbon dioxide.
Photoheterotroph
An organism that uses light to generate ATP but that must obtain carbon in organic form.
Photon
A quantum, or discrete amount, of light energy.
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