How to use Proteid in a sentence
It has been proved that the secretion contains a digestive ferment capable of rendering proteid matter soluble.
The whole cavity of the cell is sometimes stuffed with proteid contents.
The sieve-tubes differ, however, from the tracheids in being immediately associated, apparently constantly, not with starchy parenchyma, but with parenchymatous cells, containing particularly abundant proteid contents, which seem to have a function intimately connected with the conducting function of the sieve-tubes, and which we may call proteid-cells.
Of the suspended substances, grains of caoutchouc, drops of resin and oil, proteid crystals and starch grains may be mentioned.
Among Gymnosperms the secondary xylem is similarly simple, consisting of tracheids which act as stereom as well as hydrom, and a little amylom; while the phloem-parenchyma sometimes undergoes a differentiation, part being developed as amylom, part as proteid cells immediately associated with the sieve-tube, in other cases the proteid cells of the secondary phloem do not form part of the phloem-parenchyma, but occupy the top and bottom cellrows of the medullary rays, the middle rows consisting of ordinary starchy cells.Advertisement
If we examine the seat of active growth in a young root or twig, we find that the cells in which the organic substance, the protoplasm, of the plant is being formed and increased, are not supplied with carbon dioxide and mineral matter, but with such elaborated material as sugar and proteid substances, or others closely allied to them.
Proteid Formation.We have seen that it has been suggested that the chlorophyll apparatus may perhaps be concerned in the manufacture of proteids as well as of carbohydrates.
The proteolvtic enzymes, or those which digest proteids, are usually divided into two groups, one which breaks down ordinary proteids into diffusible bodies, known as peptones, which are themselves proteid in character.
They are composed of a homogeneous proteid substance, and often contain albuminoid or proteid crystals of the same kind as those which form the pyrenoid.
Whether the formation of the starch grain is due to a secretion from the plastid (Meyer, 1895) or to a direct transformation of the proteid of the plastid (Timberlake, 1901) has not been definitely established.Advertisement
Aleurone.Aleurone is a proteid substance which occurs in seeds especially those containing oil, in the form of minute granules or large grains.
Water and carbonic acid are synthesized, under the action of sunlight, to form sugar, starch or some other carboh y drate and this is then combined with simple nitrogenous salts to form proteid.
It has been compared with that of milk and of blood, which depend essentially on the coagulation or separation in curds of a proteid or albuminous substance, such as takes place when white of egg is warmed.
The effect of chemical agents in producing coagulation are in consonance with what is known of other instances of polymeric or condensation changes, whilst the fact that the collection of globules separated by creaming after thorough washing, and therefore removal of all proteid, is susceptible of solidification into caoutchouc by a merely mechanical act such as churning, strongly supports the view that the character of the change is distinct from that of any alteration which may occur in the proteid constituents of the latex.
The rubber is usually dark in colour and is often contaminated with proteid impurities derived from the latex.Advertisement
In order to prevent decomposition of any proteid impurity which may remain incorporated with the rubber, the freshly coagulated rubber is sometimes cured in the smoke of burning wood or a small quantity of an antiseptic such as creosote is added during coagulation.
The globules in the latex, however, consist more probably of a distinct liquid substance which readily changes into the solid caoutchouc. The coagulation of the latex often originates with the " curding " of the proteids present, and this alteration in the proteid leads to the solidification of the globules into caoutchouc. The latter, however, is probably a distinct effect.
Under certain conditions, as when latex is allowed to stand or is centrifugalized, a cream is obtained consisting of the liquid globules, which may be washed free from proteid without change, but, either by mechanical agitation or by the addition of acid or other chemical agent, the liquid gradually solidifies to a mass of solid caoutchouc. The phenomenon therefore resembles the change known to the chemist as polymerization, by which through molecular aggregation a liquid may pass into a solid without change in its empirical composition.
All crude rubber contains more or less proteid, and in the opinion of some technical experts its presence even affords strength to the material, but this cannot be accepted as proved.
Quite likely the amyloid may be a combination of the substance with a proteid.Advertisement
Krawkow in 1897 clearly demonstrated it to be a proteid in firm combination with chrondroitin-sulphuric acid.
The proteid constituents are very much like those of blood-serum, although they never come up to them in amount (Runeberg).
The quantity of proteid matter in a purely dropsical effusion never amounts to that of an inflammatory exudation (Lassar).
In a given case of anasarca due to a cause acting generally, it will be found that the liquid of the pleural cavity always contains the highest percentage of proteid, that of the peritoneal cavity comes next, that of the cerebral ventricles follows this, and the liquid of the subcutaneous areolar tissue contains the lowest.
Now differences in the amount of crystalloids cause alteration in osmotic pressure while the proteid content affects it but little; and of the crystalloids the chlorides appear to be those most liable to variation.Advertisement
Later the nitrogen-content of the nodule decreases, most of the organisms, which are largely composed of proteid material, becoming digested and transformed into soluble nitrogenous compounds which are conducted to the developing roots and seeds.
The animal cell can absorb its carbohydrate and proteid food only in the form of carbohydrate and proteid; it is dependent, in fact, on the pre-existence of these organic substances, themselves the products of living matter, and in this respect the animal is essentially a parasite on existing animal and plant life.
An animal may be defined as a living organism, the protoplasm of which does not secrete a cellulose cell-wall, and which requires for its existence proteid material obtained from the living or dead bodies of existing plants or animals.
Among those directly visible to the microscope are oil drops, often coloured (Uredineae) crystals of calcium oxalate (Phallus, Russula), proteid crystals (Mucor, Pilobolus, &c.) and resin (Polyporei).
The water taken up by the root from the soil contains nitrogenous and mineral salts which combine with the first product of photo-synthesis - a carbohydrate - to form more complicated nitrogen-containing food substances of a proteid nature; these are then distributed by other elements of the vascular bundles (the phloem) through the leaf to the stem and so throughout the plant to wherever growth or development is going on.Advertisement
When it persists as a massive element of the seed its nutritive function is usually apparent, for there is accumulated within its cells reserve-food, and according to the dominant substance it is starchy, oily, or rich in cellulose, mucilage or proteid.
The pyrenoid seems to be of proteid nature and gelatinous consistency, and to arise as a new formation or by division of pre-existing pyrenoids.
Some Siphonales (Codium) give rise to proteid crystalloids, and they are of constant occurrence among Florideae.
This consists, in most cases, in adding to the wine proteid matter in a finely divided state.
The proteid matter combines with a part of the tannin in the wine, forming an insoluble tannate, and this gradually subsides to the bottom of the cask, dragging with it the mechanically suspended matters which are the main cause of the wine's turbidity.Advertisement
It is probable that the kidneys also have an internal secretion, and that the great oedema sometimes found in kidney disease is rather due to the action of some proteid body resembling in its effects the streptococcus anti-toxin, than to accumulation of water due to imperfect action of the kidney.
Should these rules be insufficient, then (4) proteid and farinaceous food should be taken in separate meals - farinaceous food at breakfast, proteid alone at lunch; farinaceous in the afternoon, and proteid again in the evening.
The reason for this is that farinaceous foods are digested in the intestine and not in the stomach, where they may undergo fermentation, whereas proteid foods are to a great extent digested in the stomach.
It is usual to reduce the quantity of proteid food to a minimum, in order to lessen the amount of nitrogenous waste to be excreted by the kidneys.
Though an enormous of amount of work has been done on the subject, no important bacterial toxin has as yet been obtained in a pure condition, and, though many of them are probably of proteid nature, even this cannot be asserted with absolute certainty.Advertisement
A later research by Brieger along with Fraenkel pointed to the extracellular toxins of diphtheria, tetanus and other diseases being of proteid nature, and various other observers have arrived at a like conclusion.
Such a powder gives a proteid reaction, and is no doubt largely composed of albumoses, hence the name toxalbumoses has been applied.
The question has, however, been raised whether the toxin is really itself a proteid, or whether it is not merely carried down with the precipitate.
Brieger and Boer, by precipitation with certain salts, notably of zinc, obtained a body which was toxic but gave no reaction of any form of proteid.
There is of course the possibility in this case that the toxin was a proteid, but was in so small amount that it escaped detection.Advertisement
It may also be mentioned that many toxins have now been obtained by growing the particular organism in a proteid-free medium, a fact which shows that if the toxin is a proteid it may be formed synthetically by the bacterium as well as by modification of proteid already present.
Salts of silver are most useful as an injection in subacute and chronic gonorrhoea, either the nitrate (I to 5% solution) being employed, or protargol, which is a proteid compound containing 8% of silver nitrate, is used in 1% solution; they also benefit in leucorrhoea.
Proteid, which consists of carbon, hydrogen, nitrogen, oxygen and sulphur, is present in all protoplasm, is the most complex of all organic bodies, and, so far, is known only from organic bodies.
We attain, therefore, our first generalized description of life as the property or peculiar quality of a substance composed of none but the more common elements, but of these elements grouped in various ways to form compounds ranging from proteid, the most complex of known substances to the simplest salts.
Living substance always contains proteid, and although we know that proteid contains only common inorganic elements, we know neither how these are combined to form proteid, nor any way in which proteid can be brought into existence except in the presence of previously existing proteid.Advertisement
The central position of the problem of life lies in the chemistry of proteid, and until that has been fully explored, we are unable to say that there is any problem of life behind the problem of proteid.
A living organism usually displays active metabolism of proteid, but the metabolism may slow down, actually cease and yet reawaken; a dead organism is one in which the metabolism has ceased and does not reawaken.
But it suggests a method by which, when the chemistry of protoplasm and proteid is better known, the proper substances which compose protoplasm may be brought together to form a simple kind of protoplasm.
On the other hand, it may be that the initial conditions for the synthesis of proteid are different from those under which proteid and living matter display their activities.
Pfliiger has argued that the analogies between living proteid and the compounds of cyanogen are so numerous that they suggest cyanogen as the startingpoint of protoplasm.
Until greater knowledge of protoplasm and particularly of proteid has been acquired, there is no scientific room for the suggestion that there is a mysterious factor differentiating living matter from other matter and life from other activities.
But if we accept either view we have still to examine the process of construction in detail, with a view to ascertaining the stages by which proteid is built up. Here unfortunately we find ourselves in the region of speculation and hypothesis rather than in that of fact.
In the chromatophores of many Algae and in the Liverwort Anthoceros there are present homogeneous, highly refractive, crystal-like bodies, called pyrenoids or starch-centres, which are composed of proteid substances and surrounded by an envelope of starch-grains.
Not only are the blood corpuscles of Limulus more like in form and granulation to those of Scorpio than to those of any Crustacean, but the fluid is in both animals strongly impregnated with the blue-coloured respiratory proteid, haemocyanin.
The gland evidently excretes, or at any rate gets rid of, a certain waste product of a proteid nature, which otherwise tends to accumulate in the tissues and to excite certain nervous and tissue phenomena.
The steps in the breaking down of the highly complex nitrogenous proteid compounds contained in the humus of the soil, or applied to the latter by the farmer in the form of dung and organic refuse generally, are many and varied; most frequently the insoluble proteids are changed by various kinds of putrefactive bacteria into soluble proteids (peptones, &c.), these into simpler amido-bodies, and these again sooner or later into compounds of ammonia.
The food is alike in both cases; it consists of water, certain inorganic salts, carbohydrate material and proteid material.
The plant, on the other hand, if it be a green plant, containing chlorophyll, is capable, in the presence of light, of building up both carbohydrate material and proteid material from inorganic salts; if it be a fungus, devoid of chlorophyll, whilst it is dependent on pre-existing carbohydrate material and is capable of absorbing, like an animal, proteid material as such, it is able to build up its proteid food from material chemically simpler than proteid.
It is plain that we cannot discuss adequately the origin of life or the possibility of the artificial construction of living matter (see Abiogenesis and Biogenesis) until the chemistry of protoplasm and specially of proteid is more advanced.