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Protobranchia
Prosobranchia subclass of the class Gastropoda (phylum Mollusca), which undergo
torsion during larval development; nearly always with a shell and an operculum.
They have a visceral loop twisted in a figure of eight, the mantle cavity opens
anteriorly, the ctenidia are in front of the heart. Sexes are separate. The majority of the Gastropoda belong to this subclass and most of them are marine.
proteins extremely complex nitrogen-containing organic compounds of
numerous amino acids found in all animal and vegetable cells, where they constitute a major part of the living protoplasm. They differ from carbohydrates
and fats not only in their function in the organism, but also in elementary
composition. In addition to carbon (C), hydrogen (H), and oxygen (0), proteins invariably contain nitrogen (N) and generally also sulfur (S). The percentage composition of the large number of proteins falls between rather
narrow limits: C = 50 to 55 %, H = 6 to 7.3 %,0 = 19 to 24 %, N = 13 to
19 %, and S = 0 to 4 %. Proteins may also contain phosphorus, iron
(~hemoglobin), copper (~hemocyanin), iodine, manganese, zinc, and other elements. None of these elements, except iodine, has so far been found as a constituent of the amino acids, the fundamental units of which proteins are built
up by the organism. A protein molecule may consist of hundreds or thousands of amino-acid molecules, which are usually of about 20 different
kinds. The amino acids are linked together by peptide links. The possible different arrangements of the amino acids are evidently practically infinite,
and the diversity is fully exploited by living beings, every species, possibly
every individual, having kinds of protein molecules peculiar to itself. A protein molecule is very large (most have a molecular weight from about 20000
up to several million), and dissolved proteins therefore form colloidal solutions. Proteins are not soluble in fat solvents. Many are soluble in water or
dilute salt solutions (e.g., globulins); others, with elongated (fibrous) molecules, are insoluble in these solvents (e.g., scleroproteins, myosin). Proteins
are synthesized by all living beings, but only autotrophic organisms make
them from inorganic substances. Proteins are frequently combined with
other substances, especially nucleic acid (nucleoproteins), carbohydrates
(muco- or glycoproteins), and fats (lipoproteins).
Protista (protists) informal term, within the five-kingdoms classification, to
denote the microscopical organisms composed of a single or only a few cells
within the kingdom Protoctista.
Proto-Atlantic Ocean ~Iapetus Ocean.
Protobranchia the most primitive order of the Bivalvia in which the ctenidia are
unspecialized and retain their primitive function of respiration. The labial
palps are enlarged as a feeding mechanism. The foot is anteriorly bilobed.
There are two adductor muscles. Example: Nucula.
Protobranchia
Prosobranchia subclass of the class Gastropoda (phylum Mollusca), which undergo
torsion during larval development; nearly always with a shell and an operculum.
They have a visceral loop twisted in a figure of eight, the mantle cavity opens
anteriorly, the ctenidia are in front of the heart. Sexes are separate. The majority of the Gastropoda belong to this subclass and most of them are marine.
proteins extremely complex nitrogen-containing organic compounds of
numerous amino acids found in all animal and vegetable cells, where they constitute a major part of the living protoplasm. They differ from carbohydrates
and fats not only in their function in the organism, but also in elementary
composition. In addition to carbon (C), hydrogen (H), and oxygen (0), proteins invariably contain nitrogen (N) and generally also sulfur (S). The percentage composition of the large number of proteins falls between rather
narrow limits: C = 50 to 55 %, H = 6 to 7.3 %,0 = 19 to 24 %, N = 13 to
19 %, and S = 0 to 4 %. Proteins may also contain phosphorus, iron
(~hemoglobin), copper (~hemocyanin), iodine, manganese, zinc, and other elements. None of these elements, except iodine, has so far been found as a constituent of the amino acids, the fundamental units of which proteins are built
up by the organism. A protein molecule may consist of hundreds or thousands of amino-acid molecules, which are usually of about 20 different
kinds. The amino acids are linked together by peptide links. The possible different arrangements of the amino acids are evidently practically infinite,
and the diversity is fully exploited by living beings, every species, possibly
every individual, having kinds of protein molecules peculiar to itself. A protein molecule is very large (most have a molecular weight from about 20000
up to several million), and dissolved proteins therefore form colloidal solutions. Proteins are not soluble in fat solvents. Many are soluble in water or
dilute salt solutions (e.g., globulins); others, with elongated (fibrous) molecules, are insoluble in these solvents (e.g., scleroproteins, myosin). Proteins
are synthesized by all living beings, but only autotrophic organisms make
them from inorganic substances. Proteins are frequently combined with
other substances, especially nucleic acid (nucleoproteins), carbohydrates
(muco- or glycoproteins), and fats (lipoproteins).
Protista (protists) informal term, within the five-kingdoms classification, to
denote the microscopical organisms composed of a single or only a few cells
within the kingdom Protoctista.
Proto-Atlantic Ocean ~Iapetus Ocean.
Protobranchia the most primitive order of the Bivalvia in which the ctenidia are
unspecialized and retain their primitive function of respiration. The labial
palps are enlarged as a feeding mechanism. The foot is anteriorly bilobed.
There are two adductor muscles. Example: Nucula.