In this dissertation,we developed microstructure-based elastic models for two important cytoskeletal proteins, Microtubule and Spectrin,which are the essential components for erythrocyte and cytoskeleton in cells.The modelings of microtubule and spectrin are closely associated with study of the biological function of cellular flow sensing and erythrocyte membrane modeling that can capture red blood cell nonlinear behaviors underneath large deformation. Microtubules are characterized as the nonlinear anisotropic protein dominated by energy, which is closely associated with primary cilium.Mechanical properties of primary cilium incompletely characterized as a fluid flow sensor.We applied analytical modeling to derive the mean-squared displacement of the trapped tip of a cilium and compared the results with experimental measurements. We provide, for the first time, evidence that the effective flexural rigidity of a ciliary axoneme is length-dependent, and longer cilia are stiffer than shorter cilia. We then provide a rational explanation for both effects. We demonstrate that the apparent length-dependent flexural rigidity can be understood by a combination of modeling axonemal microtubules orthotropic elastic shells and including (actin-driven) active stochastic basal body motion. It is hoped that our improved characterization of cilia will result in deeper understanding of the biological function of cellular flow sensing by this organelle. Our model could be profitably applied to motile cilia and our results also demonstrate the possibility of using easily observable ciliary dynamics to probe interior cytoskeletal dynamics. Spectrin is characterized as the entropy dominated nonlinear elastic protein chain, which is the most important component of inner layer of red blood cell membrane.In this work,We present an analytical hyperelastic constitutive model of the red blood cell (erythrocyte) membrane based on recently improved characterizations of density and microscopic structure of its spectrin network from proteomics and cryo-electron tomography. The model includes distributions of both orientations and natural lengths of spectrin and updated copy numbers of proteins. By applying finite deformation to the spectrin network, we obtain the total free energy and stresses in terms of invariants of shear and area deformation. We generalize an expression of the initial shear modulus, which is independent of the number of molecular orientations within the network and also derive a simplified version of the model. We apply the model and its simplified version to analyze micropipette aspiration computationally and analytically, and explore the effect of local cytoskeletal density change. We also explore the discrepancies among shear modulus values measured using different experimental techniques reported in the literature. We find that the model exhibits hardening behavior and can explain many of these discrepancies. Moreover, we find that the distribution of natural lengths plays a crucial role in the hardening behavior when the correct copy numbers of proteins are used. The initial shear modulus values we obtain using our current model (5.9∼15.6 pN/μm) are close to the early estimates (6-9 pN/μm). This new constitutive model establishes a direct connection between the molecular structure of spectrin networks and constitutive laws, and also defines a new picture of a much denser spectrin network than assumed in prior studies.