Collagen is the most abundant protein in the mammalian body. It is a fibrous protein that serves to strengthen and support tissues. Suppose a collagen fiber can be stretched reversibly with a force constant of k = 10.0 N m^ˆ’1and that the force, F (see Table 2.1), is given by F = kl. When a collagen fiber is contracted reversibly, it absorbs heat q_rev= 0.050 J. Calculate the change in the Helmholtz energy, ΔA, as the fiber contracts isothermally from l = 0.20 to 0.10 cm. Calculate also the reversible work performed w_rev, ΔS, and ΔU. Assume that the temperature is constant at T = 310.K..

Table 2.1

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Types of Work Conventional Units Variables Equation for Work Pressure (P), volume (V) Volume expansion Pa m3 = J Pexternal dV Stretching Force (F), length (1) Nm = J F. dl Surface expansion Surface tension (y), area (o) (N m-)(m²) = J Y• do Joi Electrical Electrical potential (4), electrical charge (Q) VC = J фао