Hemoglobin color

The sacroplasmic proteins myoglobin and hemoglobin are responsible for much of the color in meat. Species vary tremendously in the amount of sacroplasmic proteins within skeletal muscle with catde, sheep, pigs, and poultry Hsted in declining order of sarcoplasmic protein content. Fat is also an important component of meat products. The amount of fat in a portion of meat varies depending on the species, anatomy, and state of nutrition of the animal. The properties of processed meat products are greatiy dependent on the properties of the fat included. Certain species, such as sheep, have a relatively higher proportion of saturated fat, whereas other species, such as poultry, have a relatively lower proportion of saturated fat. It is well known that the characteristic davors of meat from different species are in part determined by their fat composition. 

One Anson unit is the amount of enzyme that, under standard conditions, digests hemoglobin at an initial rate, Hberating per minute an amount of TCA-soluble product which produces the same color with phenol reagent as one milliequivalent of tyrosine (91). 

The most conspicuous use of iron in biological systems is in our blood, where the erythrocytes are filled with the oxygen-binding protein hemoglobin. The red color of blood is due to the iron atom bound to the heme group in hemoglobin. Similar heme-bound iron atoms are present in a number of proteins involved in electron-transfer reactions, notably cytochromes. A chemically more sophisticated use of iron is found in an enzyme, ribo nucleotide reductase, that catalyzes the conversion of ribonucleotides to deoxyribonucleotides, an important step in the synthesis of the building blocks of DNA. 

Most nitrites are soluble in water and mildly toxic. Despite their toxicity, nitrites are used in the processing of meat products because they retard bacterial growth and form a pink complex with hemoglobin that inhibits the oxidation of blood (a reaction that would otherwise turn the meat brown). Nitrites are responsible for the pink color of ham, sausages, and other cured meat. 

Much research focuses on the structures, properties, and uses of the complexes formed between d-metal ions acting as Lewis acids and a variety of Lewis bases, partly because they participate in many biological reactions. Hemoglobin and vitamin B12, for example, are both complexes—the former of iron and the latter of cobalt (Box 16.1). Complexes of the d-metals are often brightly colored and magnetic and are used in chemistry for analysis, to dissolve ions (Section 11.13), in the... 

Figure 6-7. During transition of the T form to the R form of hemoglobin, one pair of subunits (a2/P2) rotates through 15 degrees relative to the other pair (a,/p,) The axis of rotation is eccentric, and the a2/P2 pair also shifts toward the axis somewhat. In the diagram, the unshaded a,/p, pair is shown fixed while the colored a2/P2 pair both shifts and rotates.

Figure 19, The effect of 2% hemoglobin solution on the color produced with toluidine on glucose...

Recently, this problem has been approached by reverting to reading the color of the bilirubin directly. This used to be called an "Icterus Index", in which the color of the serum was compared to a dilute dichromate solution (39). However, the new approach has been to use two wavelengths. This can be used in either of two different procedures. In one procedure the reading is made at the peak for bilirubin which is at 453 nm and at an isosbestic point for hemoglobin (40). The effect on the reading due to hemoglobin is subtracted from the bilirubin value. Commercial instruments based on this principle have not been successful. 

The method of color development may be nonspecific and therefore the reaction may be affected by many interfering factors commonly found in serum such as turbidity, hemoglobin and bilirubin. 

Red blood cells owe their color to the iron complex heme, a component of hemoglobin. This provides the human body with oxygen, right up to the finest capillary. In the absence of oxygen, the blood goes dark red (venous blood). 

Cyanosis A dark bluish or purplish coloration of the skin and mucous membrane due to deficient oxygenation of the blood, evident when reduced hemoglobin in the blood exceeds 5 g per 100 ml. 

Fig. 10.12 The most efficient regions for nanotube absorption lie where water and hemoglobin have absorption minima between 700 and 900nm and around 1,100nm (Braun and Smirnov 1993 Reprinted from Weissleder, 2001. With permission from Elsevier) (See Color Plates)... 

Carbon monoxide binds to cytochrome a/Oj but less tightly than cyanide. It also binds to hemoglobin, displacing oxygen. Symptoms include headache, nausea, tachycardia, and tachypnea. Lips and cheeks turn a cherry-red color. Respiratory depression and coma result in death if not treated by giving oxygen. Sources of carbon monoxide include ... 

The yellow color of urine is due to uro-chromes, which are related to the bile pigments produced by hemoglobin degradation (see p. 194). If urine is left to stand long enough, oxidation of the urochromes may lead to a darkening in color. 

Red fibers provide for their ATP requirements mainly (but not exclusively) from fatty acids, which are broken down via 3-oxidation, the tricarboxylic acid cycle, and the respiratory chain (right part of the illustration). The red color in these fibers is due to the monomeric heme protein myoglobin, which they use as an O2 reserve. Myoglobin has a much higher af nity for O2 than hemoglobin and therefore only releases its O2 when there is a severe drop in O2 partial pressure (cf p.282). 

Erythrocytes—Red blood cells the color comes from the oxygen-carrying protein hemoglobin inside the cell. 

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