The average volume of a red blood cell is 87 μ m 3 . The mean concentration of hemoglobin in red blood cells is 0.34 g ⋅ ml − 1 . What is the weight of the hemoglobin contained in an average red blood cell? hemoglobin weight: 3 ×10 −11 g How many hemoglobin molecules are there in an average red blood cell? Assume that the molecular weight of the human hemoglobin tetramer is 65 kDa.

A)

Concentration of hemoglobin = weight of the hemoglobin / total volume of RBCs

Therefore,

weight of the hemoglobin = concentration of the hemoglobin x Total volume of RBCs

weight of hemoglobin = (8.7x 10⁻¹¹ x 0.34) g

                                     = 2.96 x 10⁻¹¹ g

B)

molar mass of hemoglobin is 64500g/mol.

molar mass (m) = number of moles (n) x M,

∴ n = m/M

so number of moles in 2.96 x 10⁻¹¹ g of hemoglobin with molar mass 64500g/mole

= 2.96 x 10⁻¹¹ / 64500

= 4.5 x 10⁻¹⁶ moles

using Avogadro’s number to calculate the number of molecules from moles.

1 mole = 6.022 x 10²³ molecules

so, 4.5 x 10⁻¹⁶ moles

= 4.5 x 10⁻¹⁶ x 6.022 x 10²³

= 2.71 x 10⁸ molecules

Explanation:

Note: Average volume of a red blood cell = 87 μm³ = 8.7 x 10⁻¹¹ ml

        The mean concentration of hemoglobin in red cells = 0.34g/ml.