Biological Sciences
Structural Proteins
Structural proteins are a class of proteins that provide support and shape to cells and tissues. They are essential for maintaining the structural integrity of cells, tissues, and organs. Examples of structural proteins include collagen, which provides strength to connective tissues, and keratin, which forms the structure of hair, nails, and the outer layer of skin.
Written by Perlego with AI-assistance
Related key terms
1 of 5
8 Key excerpts on "Structural Proteins"
eBook - PDF- Sharma, Dipiti(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
These proteins includes Actin and myosin; which are present in form of filamentous protein in muscle cells for functioning in the contractile systems. Tubulin is another contractile protein present in each cell type inform of micro tubes. Micro tubes are main constituent of cilice and flagella which help in movement of cells. 5.4.4.5 Structural Proteins Many proteins give support and structure. They serve as a supporting filaments, cables or sheets to give biological structures strength and protection. This type of protein form major component of tendons, cartilages and bones. These include Fibrous proteins which are long and are less soluble in water. These physical properties are consistent with their biological role as Structural Proteins. Ligaments are contains special structural protein capable of stretching in two dimensions called as elastin. Hairs finger nails, feathers of birds consists of tough insoluble protein named keratin. Major component of silk fibers, threads of spider web contain structural protein named fibroin. Fibrin, elastin, keratin and collagen are included in the group. Globular Proteins are compact and spherical and usually are soluble in water. Enzymes, hormones, antibodies, transport proteins and respiratory proteins have a globular structure. Thus the globular proteins show more diverse functional properties because of their less rigid structures. 5.4.4.6 Defense Proteins Many proteins in body of organisms posses defensive action against the invasion and attack of foreign entities or protect the body from injury. Among these proteins special globular protein named immunoglobulin’s or This ebook is exclusively for this university only. Cannot be resold/distributed. antibodies in vertebrate’s body is the most indispensible protein. It synthesized by lymphocytes and they can neutralize the foreign protein produced by bacteria, virus and other harmful microbes called antigens through precipitation or glutination.
eBook - PDFWaves in Biomechanics
THz Vibrations and Modal Analysis in Proteins and Macromolecular Structures
- Domenico Scaramozzino, Giuseppe Lacidogna, Alberto Carpinteri(Authors)
- 2022(Publication Date)
- Springer(Publisher)
7 C H A P T E R 2 Proteins: The Basis of Biological Mechanisms Proteins are one of the most important building blocks for the achievement of the numerous biological reactions that occur every day in our body. The oxygen that we introduce into our lungs while we are breathing is successfully delivered to tissues and organs by the relentless job of hemoglobin, a protein contained in our red blood cells. The biochemical process which allows our eyes to interpret the images of the real world is mediated by proteins in charge of facilitating the conversion of photons into electrochemical signals which are then sent to the brain for final interpretation. Other proteins, such as collagen, are extremely important to provide specific parts of our body adequate levels of stiffness and mechanical resistance. Proteins like kinesin are essential for the transportation of nutrients throughout the cell environment. The function of transmembrane proteins, which are embedded within the cellular membrane, is crucial for regulating the movement of ions, nutrients and small molecules to and from the cell. Proteins also act as enzymes, catalyzing biochemical reactions and improving the reaction rate by lowering the activation energy. Other classes of proteins, the antibodies, are extremely important to fight against and neutralize viruses and bacteria. As can be seen from the examples reported above, the role of proteins can be very diverse. All these activities contribute to the correct functioning of our body as a whole.
eBook - PDF- Morris Rockstein(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Active proteins, which are not enzymes but which specifically bind ligands, have been called emphores. Since contractile proteins have an important structural purpose, they are usually included in the Structural Proteins. The same may be said of the histones and nonhistones although we now know they appear to partici-pate in the regulation of gene expression. It is unfortunate that few insect proteins have been obtained in a pure state. As a result, information on the chemical structure of insect proteins is scarce. The subject of this chapter is a correlation of structure and biological function of the proteins, restricted whenever possible to those proteins which have been chemically charac-terized to a reasonable extent. 96 Moises Agosin II. STRUCTURE PROTEINS Conveniently grouped under structure proteins are the fibrous or insoluble proteins and some globular proteins that serve a structural role but without substantial enzyme activity. Studies on fibrous proteins are often compli-cated by the wide variety of cross-links that may join subunits either to one another or to another tissue component. Such cross-links, as in elastin, make it difficult to recognize and isolate the precursor subunit, which makes the examination of primary structure very difficult. In terms of amino acid sequence, it is now clear that Structural Proteins are no exception to the general rule that primary structure governs the three-dimensional structure. For example, every third residue in the collagen chain must be glycine if the desired triple helix is to form. A. Contractile Proteins One of the characteristics of animals is motility, which is associated with the presence of contractile proteins. In insects, as well as other differ-entiated organisms, these contractile proteins are present in a single tissue, muscle. The major protein components of muscles are actin and myosin, but several other protein components involved in muscle contraction have also been described.
eBook - PDF- Arne Engström, J. B. Finean(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
C H A P T E R IV The Role of Proteins The proteins, as the name impHes, are of first importance in the structure of fiving matter. No Hving cell is without them, and any discussion of biological ultrastructure must inevitably start with a consideration of the structure of the proteins. They form the foundation upon which the com-plex systems which constitute living material are built. The proteins provide some of the largest molecules, and are capable of the widest variation in size, shape, and constitution. They may occur in nature as pure protein systems, or in combination with substances such as lipids, carbohydrates, nucleic acids, and other organic molecules, as well as with a variety of inorganic ions. The combination may be loose, or it may be through stable chemical bonds, the number and variety of these providing endless possibilities for the stability of the general association. But these complex associations will be developed in all possible detail in later chapters, the purpose of the present chapter being, as it were, to iso-late the protein itself and to extract its structural characteristics. This process has been going on for a long time, and despite the significant ad-vances of the past few years, the first complete solution still lies ahead of us, although perhaps it may be close enough to consider the possibility of being able to add it in the proof of this volume. The tasks of identification, isolation, and physical and chemical characterization, have occupied biol-ogist, chemist, and physicist for over a hundred years, although neither the intensity of the study nor the method of attack has pursued a steady course. It is therefore perhaps as well to forget the chronological approach and to start from the fundamental structural units.
eBook - PDF- J. B. Finean(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
C H A P T E R I V The Role oC Proteins The proteins, as the name implies, are of first importance in the struc-ture of living matter. No living cell is without them, and any discussion of biological ultrastructure must inevitably start with a consideration of the structure of the proteins. They form the foundation upon which the complex systems which constitute living material are built. The proteins include some of the largest known molecules, and have the widest variation in size, shape, and constitution. They may occur in nature as pure protein systems, or in combination with substances such as lipids, carbohydrates, nucleic acids, and other organic molecules, as well as with a variety of inorganic ions. The combination may be loose or stable, and the number and variety of these provide endless possibilities for the stability of the general association. These complex associations will be developed in detail in later chapters; the purpose of the present chapter is to isolate the protein and extract its structural characteristics. Since the first edition of this book, we have seen the first detailed descriptions of the spatial configurations of protein molecules, and the collection of experimental data and the development of ideas which have led to these recent triumphs can now be arranged in logical rather than chronological order. Astbury's broad generalizations, based on a superficial knowledge of the chemical constitution of the polypeptide chain and a few struc-tural parameters derived from X-ray diffraction patterns, pointed the way toward clarification of protein structure and they have proved to be remarkably accurate in broad concept although understandably in-accurate in detail. Significant detailed information came from the com-plete chemical and crystallographic analyses of the amino acids and small peptides by a team of investigators at Caltech inspired by Pauling and Corey. These studies resulted in precise structural specifications of poly-105
- Peter Tompa, Alan Fersht(Authors)
- 2009(Publication Date)
- Chapman and Hall/CRC(Publisher)
1 1 Principles of Protein Structure and Function The principles of protein structure surveyed in this chapter have been established mostly by studying globular proteins. The structure of a globular protein can be described by the coordinates of all its atoms, but this information is often too complex to interpret in terms of function. Thus, scientists have devised a hierarchical vocabulary that can describe different levels of structure from the sequence of amino acids to the spatial arrangement of subunits. Further levels of complexity, such as post-translational modifications, the process of acquiring the 3-D structure (folding), and the description of the unfolded state resembling intrinsically disordered proteins (IDPs), also pertain to the comprehensive structural description of proteins. It has long been thought that the description of (ordered) proteins by these concepts provides a universal key to understanding protein function, a notion termed the classical structure-function paradigm. This book is devoted to demon-strating how this knowledge can be extended to understand how IDPs function. 1.1 PHYSICAL FORCES THAT SHAPE PROTEIN STRUCTURE Because structural biology has its roots in studying globular (ordered) proteins, the classical concepts of protein structure are better suited for the description of ordered than disordered proteins. Usually, four hierarchical levels are distinguished, such as primary structure (sequence of amino acids in the polypeptide chain), secondary struc-ture (local, often repetitive structural elements [i.e., α -helix, β -strand, turn and coil]), tertiary structure (the fold in space of the entire polypeptide chain, also meaning the spatial arrangement of its secondary structural elements), and quaternary structure (stoichiometry and spatial arrangement of subunits in a multi-subunit protein).
eBook - PDF- H. Stephen Stoker(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Fibrous proteins are generally water insoluble, whereas globular proteins dis-solve in water. This enables globular proteins to travel through the blood and other body fluids to sites where their activity is needed. 2. Fibrous proteins usually have a single type of secondary structure, whereas globular proteins often contain several types of secondary structure. ◀ 3. Fibrous proteins generally have structural functions that provide support and external protection, whereas globular proteins are involved in metabolic chemistry, performing functions such as catalysis, transport, and regulation. 4. The number of different kinds of globular protein far exceeds the number of dif-ferent kinds of fibrous protein. However, because the most abundant proteins in the human body are fibrous proteins rather than globular proteins, the total mass of fibrous proteins present exceeds the total mass of globular proteins present. The characteristics of two fibrous proteins ( a -keratin and collagen) and two glob-ular proteins (hemoglobin and myoglobin) as representatives of their types are now examined. a -Keratin The fibrous protein a -keratin is particularly abundant in nature, where it is found in protective coatings for organisms. It is the major protein constituent of hair, feathers (Figure 9-19), wool, fingernails and toenails, claws, scales, horns, turtle shells, quills, and hooves. ▶ Globular proteins denature more readily than fibrous proteins because of weaker secondary and tertiary attractive forces.
- Zdzislaw E. Sikorski(Author)
- 2001(Publication Date)
- CRC Press(Publisher)
Fibers of connective tissue are arranged in a specific pattern in the outer tu-nic but appear less ordered in the inner tunic. All connective tissue fibers are The Structural Role of Proteins in Various Food Raw Materials 19 Figure 2.4 (a) SEM micrograph of muscle fibers of squid, (b) SEM micrograph of hake mus-cle. Longitudinal muscle fibers with sarcomeres between Z-disks (Z). composed of aggregates of smaller fibrils ( 0 .1 pirn diam), but fiber size and shape differ in each tunic. The visceral lining appears as a nonfibrous sheet tightly attached to the fibers of the inner tunic. Much of the connective tissue is found in the fibrous tunics, but a net-like meshwork of small, extracellular fibers of connective tissue is observed in raw muscle tissue. 20 PROTEINS IN FOOD STRUCTURES 2.2.2. PROTEIN BODIES IN PLANT TISSUES 2.2.2.1. Cereals All kernels of cereals consist of a germen and starchy endosperm surrounded by several layers, including the aleurone, the testa, and the pericarp. Seeds of cereals are composed of storage tissue, in which starch granules, the main com-ponents, are packed closely within parenchyma cells, which contain no vacuoles and little free water, protein bodies, and oil droplets. The endosperm in wheat is composed of two very distinct cell types: the outermost layer of cells is the aleurone layer which is composed of rectangu-lar cells with thick walls and densely packed contents, rich in protein bodies, lipid, and mineral elements. The remainder is the starchy endosperm (Figure 2.5) with thin-walled, prism-shaped cells. In seeds of most of the cereals and legumes, proteins are structured like spherical globules of membrane or protein bodies, but these membranes are destroyed during wheat maturation, and protein bodies are not observed in-side of wheat endosperm cells (Cheftel et al., 1989).
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
