Glossary - Letter P

P - Vitamin P or rutin. Water soluble vitamin that fights hair fragility. Main sources: leafy vegetables and legumes.

Parasite - An organism that lives on or within an organism of a different species and derives its nutrition from it adversely.

Cell Wall - Relatively rigid envelope, external to the plasma membrane, present in some cell types (see also Cellulosic Wall)

Cellulosic Wall - Algae and plant cell envelope formed by cellulose fibers; In the existing plants a thinner wall in the young cell (primary wall), later developing a second cellulose deposit (secondary wall)

Patau - See Patau syndrome.

Pathogen - Any causative agent organism of disease.

Pedigree - See genealogy.

Pellagra - Disorder due to lack of vitamin PP that leads to diarrhea, dermatitis (inflammation of the skin and nerve damage affecting the central nervous system, leading to dementia.

Pericarpo - Part of the fruit that surrounds the seed. It is divided into epicarp (outer part or bark), mesocarp (middle mars) and endocarp (inner part that usually coats the seed).

Permease - Plasma membrane associated enzyme, which facilitates the entry of substances into the cell.

Peroxisomes - Lysosome-like organelle, which contains catalase inside; Its function is to rid the cell of certain toxic waste and participate in the conversion of fat into glucose.

Petal - Each of the floral pieces (transformed leaves) that make up the corolla of the angiosperm flower.

Pigment - Naturally occurring substance that absorbs light.

Pinocytosis - The process by which the cell encompasses liquid droplets or small particles through the deep channels in the cell.

Piracema - migratory movement of fish towards river sources, with the purpose of reproduction. Occurs in times of the great rains in the spawning period.
Food pyramid - graphical representations of data provided by food chains which can be divided into three types: numbers, biomass and energy.

Pyrrophytes - Algae species that are known to form phytoplankton.

Pistil - See Carpel.

Plankton - Set of aquatic biome beings floating on the surface as they flow (see also Phytoplankton and Zooplankton)

Plasma - Transparent, colorless fluid, blood component; contains proteins and dissolved salts; it is the blood, the corpuscles removed.

Plasmids - Communication that is established between bacterial cell cytoplasms for exchange of genetic material, allowing a "sexual" reproduction with gene recombination, even without gamete exchange.

Plasmocytes - Connective tissue cell responsible for the production of tissue antibodies.

Plasmodesmos - Cytoplasmic filament that passes through a pore punctuation, putting in communication neighboring plant cells.

Plastos - Cytoplasmic organelle present exclusively in plant and algal cells; inside the green plastos (chloroplasts) photosynthesis occurs; there are colorless plaques (leukoplasts) whose function is the starch reserve.

Multicellular - See Multicellular.

Pollen - (From Latin: fine powder) Male gametophytes from seminiferous plants, at the stage at which they are released into the environment. Structure that will contain and carry the male gamete and its attachments in the vegetable.

Pollination - Transfer of the pollen from which it was formed (the anther) to the receiving surface (the stigma) in the flowers.

Polyribosomes - Chain of ribosomes interconnected by mRNA for protein synthesis.

Polysaccharides - Macromolecule resulting from the union of hundreds or thousands of monosaccharides (see also Starch, Glycogen and Cellulose)

PP - Vitamin PP or nicotinamide or niacin. Water soluble vitamin that fights pellagra. Main sources: leafy vegetables and legumes.

PPLO - Cellular, parasitic, viral agent of the Monera kingdom.

Predatism - ecological relationship that is established between a species called predator and another called prey. Predators are characterized by their ability to physically capture and destroy prey for food.

Prokaryotes - Or prokaryote; cell type that does not have internal membrane systems or organelles; there is no library involving hereditary material (see also eukaryotes)

Prophase - First phase of cell division. It is characterized by the beginning of chromosomal spiraling, disappearance of nucleoli and the beginning of formation of the achromatic spindles.

Progesterone - Hormone produced by the yellow ovary body and also by the placenta; its effect is to prepare the female organism for embryonic development; among other effects, causes the great development of the endometrium.

Protease - A genetic term for proteolytic enzymes, ie proteins that digest.

Protoplasma - Old name of cellular content.

Protozoan - Unicellular organism, free-living or parasitic, belonging to the Protist kingdom.

Pseudofruit - When the plant structure, popularly called fruit or fruit, does not correspond to a true fruit (see fruit), we say that it is a pseudo fruit (pseudo = false). Apple, banana, pineapple and strawberry are the most popular among pseudo-fruits.

Pseudopods - Cytoplasmic projection with which certain cell types move and capture particles by phagocytosis.

Pteridophyte - Name given to cryptogamous plants of the class Filicinae (filicinea); the name alludes to the fact that its leaves are formed by winglike leaflets (from the Greek pteris, wing). Ex. Ferns and fences. or of fused carpels containing the egg or eggs; The ovary ripens into fruit. (see fruit).