When a fresh, uncooked beef roast is sliced into two, the surface of the meat fi

Question

When a fresh, uncooked beef roast is sliced into two, the surface of the meat first appears purplish but then turns red. Explain why. Why does meat turn brown when it is cooked? Why might a retailer choose to package meat using oxygen permeable plastic wrap instead of a vacuum sealed package. Plasmodium falciparum, the protozoan that causes malaria, slightly decreases the pH of the red blood cells it infects. Invoke the Bohr effect to explain why Plasmodium-infected cells are more likely to undergo sickling in individuals with the Hb S variant.

Explanation / Answer

a).  When an uncooked beef roast is first cut, the internal color is described as a purplish color. The native pigment present is deoxymyoglobin (DMb, no bound oxygen).

When fresh, uncooked beef roast is sliced and exposed to oxygen, the bright red color seen is due to oxygen being bound to the heme iron of myoglobin forming oxymyoglobin (OMb).

b)before you cook the meat, the iron atom oxidation level is +2 and it is bound to a dioxygen molecule (O2), which makes the meat appear bright red. As you cook the meat, this iron atom loses an electron and goes to a +3 oxidation level with this process ending up turning the meat brown.

c)Fresh ground beef placed in an oxygen impermeable package, for instance packaged in a vacuum-sealed chub, will have consumed all of the oxygen present in one to two days and the primary pigment will be DMb. Ground beef that is on display in a retail store that has a bright red color is likely overwrapped with an oxygen permeable film or possibly in a modified atmosphere package that contains elevated levels of oxygen.

2). bohr effect state that haemoglobin's oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide. Since carbon dioxide reacts with water to form carbonic acid, an increase in CO2 results in a decrease in blood pH, resulting in haemoglobin proteins releasing their load of oxygen. Conversely, a decrease in carbon dioxide provokes an increase in pH, which results in haemoglobin picking up more oxygen.

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.