Classify Proteins With Suitable Examples Based On Their Biol

Classify proteins with suitable examples based on their biological functions

SURNAME 2 Student’s Name Professor’s Name Course Date Assignment 1. Classify proteins with suitable examples based on their biological functions and levels of organization of their structures. This classification of protein is based on shape or structure and composition. They are classified into three types; fibrous, globular and derived protein. (a). Fibrous protein: They are elongated or finger like protein with an axial ratio which is more than ten, they are also static in nature with simple structure and they are mostly present in animals. Fibrous protein they are further classified as- simple and conjugated fibrous protein. Simple fibrous protein include scleoprotein which make the animal skeleton and they are water soluble while conjugated fibrous proteins include pigments present in chicken feather. (b). Globular proteins: They are spherical in shape with an axial ratio which always less than ten, there are dynamic in nature with high degree of complexity in structure. They include enzymes, hormones etc. Globular protein is further classified on the basis of composition which are; simple or homo globular proteins composing of amino acids only and complex or hetero globular proteins which are always linked by non- protein moiety to become functional. So they are composed of both protein and non- protein component known as prosthetic group. (c) Derived protein: These proteins are derivatives of either simple or complex proteins resulting from action of heat, enzymes and chemicals. They are classified as primary derived protein and secondary derived protein, examples of primary derived proteins are; proteans, metaprotein and coagulated protein while examples of secondary derived proteins are proteosis. Proteins are structurally organized into four level; primary structure, secondary structure, tertiary structure and quaternary structure. (a) Primary structure: it refers to the sequence and arrangement of amino acids in polypeptide chain where carboxyl group (R- COOH) of one group of the amino acids is linked with amino group (R-NH2) of other amino acid by peptide bond. The peptide bond links successive amino acids in polypeptide chain. In polypeptide chain carboxyl group and amino group of most amino acids are involved in formation of peptide bond. However, two amino acids which are situated at either end of polypeptide chain have R-COOH free or RNH2 group free. The edge at which -NH2 is free is called N-terminal and other edge which -COOH group is free is called C- terminal. Since, most of R-COOH and R-NH2 group formed peptide bond, they are not available for other bonding except Hydrogen bond. The peptide bond occur in trans configuration and have partial body character. (b) Secondary structure of protein: Formation of secondary structure involves local folding of polypeptide chain. They include; Alpha helix, Beta sheets and Beta bends. (c) Tertiary structure of protein: It refers to the overall folding of a polypeptide chain to form a final three- dimensional structure for example, a globular protein which are larger than 200 amino acids units forms two or more domains by folding of polypeptide chain by either Alpha helix or Beta pleated sheet or Beta bend. Finally, these domains associates with each other to form 3D structure. (d) Quaternary structure of protein: Some proteins are composed of more than one polypeptide chain. Each polypeptide chain in such protein are called sub units thus the quaternary structure refer to the interaction between these sub units to large final 3D structure. Therefore, quaternary structure is interaction between different polypeptide chains of multi chain protein. Quaternary structure is found only in protein which are composed of more than one polypeptide chains such as Hemoglobin. Bonds such as H- bonds, hydrophobic interactions, helps to form quaternary structure. The biological functions of proteins are classified into 9 groups which include; (a) Catalytic proteins which include the enzymes and they are used to speed up the reaction of biochemical reactions. (b) Structural proteins; they make the various structural components of living beings for example the collagen makes the bone. (c) Nutrient proteins; they have nutritional value and provide nutrition when consumed for example casein in milk. (d) Regulatory proteins; They regulate metabolic and cellular activities in cells and tissues they include Hormones. (e) Defense protein; they provide defensive mechanism against pathogens and they include the antibodies and complement protein. (f) Transport protein; They transport nutrients and other molecules from one organ to the other for example, hemoglobin. (g) Storage proteins; they store various molecules and ions in cells and they include Ferritin store iron. (h) Contractile or mobile proteins; they help in movement of various body parts for examples are; Actins, myosin and Tublins. (i) Toxic proteins ; this are proteins which can damage the tissues for example; Snake venom and bacterial exotoxins. 2. Explain how this level of organization occur and stabilized. (20 marks) Protein structure are made by condensation of amino acids forming peptide bonds. The sequence of amino acid in a protein is called its primary structure. The secondary structure is determined by dihedral angles of the peptide bonds, the tertiary structure by the folding of protein chains in space. Association of folded polypeptide molecules to complex functional proteins results in quaternary structure. Folded proteins are stabilized by thousands of noncovalent bonds between amino acids. In addition, chemical forces between a protein and its immediate environment contribute to protein shape and stability. 3. Give an overview of how DNA is capable of replicating and repairing itself. (15marks) DNA unwinds at the origin of replication; new bases are added to the complementary parental strands. The matching of free nucleotides to the parental strands is accomplished by an enzyme called DNA polymerase. Primers are removed, new DNA nucleotides are put in place of the primers and the backbone is sealed by DNA ligase. DNA polymerase can make mistakes while adding nucleotides. It’s edits the DNA by proofreading every newly added base. Incorrect bases are removed and replaced by the correct base and then polymerization continues. 4. Explain active and passive transport across cell membrane. (10 marks) Active transport moves molecules and ions from a region of lower concentration to a region of higher concentration with the help of energy in the form of Adenosine triphosphate; it is a dynamic and rapid process which transports all molecules such as proteins, large cells, complex sugars and ions. During the active transport process, carrier proteins are required and the process is influenced by temperature. Active transport processes include; exocytosis, endocytosis and the sodium-potassium pump. On the other hand, passive transport moves ions and molecules from a region of higher concentration to a region of lower concentration without any energy; it is a physical and comparatively slow process. The main aim is to transport all soluble molecules including oxygen, water, carbon dioxide, lipids and sex hormones. This process includes; osmosis, diffusion and facilitated diffusion. 5. How do structures of hemoglobin and myoglobin relate to their functions? (5 marks) Hemoglobin; It transports both oxygen and carbon dioxide. This function occurs because of hemoglobin’s unique shape, which is globular and made of four subunits of proteins surrounding an iron group. Hemoglobin undergoes changes to its shape to help make it more efficient in carrying oxygen. Myoglobin; it has a globular structure and contains a heme group which is responsible for carrying oxygen molecules to muscle tissues. Myoglobin can exist in the oxygen-free form, called deoxymyoglobin, or in a form in which the oxygen molecule is bound, called oxymyoglobin. Work cited Gichaga, 04, biology

Paper For Above instruction

Proteins are fundamental biomolecules essential for various biological processes, structures, and functions within living organisms. They are diversified in their shape, composition, and roles, allowing them to perform a multitude of tasks vital for life. Their classification based on structure and function includes fibrous, globular, and derived proteins, each with distinct characteristics and examples demonstrating their biological roles. An understanding of these classifications, their levels of structural organization, and their biological relevance is crucial for comprehending cellular functions and life processes.

Classification of Proteins and Their Functions

Fibrous proteins are elongated, thread-like structures characterized by their high axial ratio, typically greater than ten. They are mostly static, insoluble in water, and primarily serve structural functions. These proteins include keratin, the principal component of hair and nails, and are crucial for providing mechanical support. Simple fibrous proteins like scleroproteins, which contribute to the animal skeleton, contain only proteinaceous material and are water-soluble. Conjugated fibrous proteins, such as pigments in chicken feathers, have additional non-protein components, which modify their functions. Globular proteins are spherical, dynamic, and highly complex in their structures, enabling them to participate actively in physiological processes. Examples include enzymes like amylase and lipases, and hormones such as insulin, which regulate metabolic activities. These proteins are classified further as either simple (composed solely of amino acids) or complex (linked to non-protein prosthetic groups), facilitating diverse functions like oxygen transport and catalysis.

Derived proteins are modifications or derivatives of primary or complex proteins, formed via physical or chemical means such as heating, enzyme activity, or chemical reactions. Primary derived proteins include proteans, meta-proteins, and coagulated proteins, which result from protein denaturation or coagulation processes, often impacting their biological activity. Secondary derived proteins, like proteosis, arise through further chemical modifications. Structurally, proteins are organized into four levels: primary, secondary, tertiary, and quaternary. The primary structure is the linear sequence of amino acids linked by peptide bonds, with the amino (N-terminal) and carboxyl (C-terminal) ends defining the chain's orientation. Secondary structures involve local folding into alpha helices, beta sheets, and beta bends, stabilized mainly by hydrogen bonds. The tertiary structure results from the overall folding of the polypeptide chain into a three-dimensional conformation, stabilized by various interactions, including hydrogen bonds, hydrophobic forces, covalent disulfide bonds, and ionic interactions. Quaternary structure is the arrangement of multiple polypeptide chains (subunits) into a functional protein, exemplified by hemoglobin, where subunits interact through non-covalent bonds.

Biological Functions of Proteins

Proteins perform vital roles categorized into nine groups, reflecting their functional diversity. Catalytic proteins, primarily enzymes, accelerate biochemical reactions, acting as biological catalysts. Structural proteins such as collagen provide support and shape to tissues. Nutrient proteins, like casein in milk, supply essential amino acids, serving nutritional needs. Regulatory proteins, including hormones like insulin and adrenaline, control metabolic and cellular processes. Defense proteins, such as antibodies and components of the complement system, protect against pathogens. Transport proteins, for example, hemoglobin, facilitate the movement of molecules across tissues and within cells. Storage proteins, like ferritin, store essential ions and nutrients for cellular needs. Contractile proteins, including actin and myosin, are responsible for muscle contraction and movement. Toxic proteins, such as snake venom and bacterial exotoxins, can damage tissues or serve defense mechanisms. The diversity of protein functions underpins the complexity and functioning of biological systems.

Levels of Protein Organization and Their Stability

Protein organization begins at the primary level, where amino acids linearly form chains through condensation reactions, creating peptide bonds. The secondary structure involves folding of these chains into alpha helices and beta sheets, stabilized mainly by hydrogen bonds. The tertiary structure arises from the spatial folding of the entire polypeptide, influenced by interactions among side chains, including hydrophobic interactions, hydrogen bonds, ionic bonds, and covalent disulfide bridges. The stabilization of tertiary structure is vital for protein functionality and is maintained through these numerous non-covalent and covalent bonds. The quaternary structure results from the association of multiple polypeptide subunits into a functional complex; interactions like hydrogen bonds, hydrophobic interactions, and ionic bonds hold these subunits together. Protein stability is profoundly influenced by the environment, including pH, temperature, and ionic strength, which can disrupt or maintain their structures. Chaperone proteins also assist in folding and stabilization by preventing misfolding and aggregation, ensuring functional integrity of proteins essential for physiological health.

DNA Replication and Repair Mechanisms

DNA possesses the remarkable capacity to replicate and repair itself, ensuring genetic fidelity across generations. Replication begins at the origin of replication, where the DNA unwinds facilitated by enzymes such as helicase. This unwinding produces single-stranded templates needed for new strand synthesis. DNA polymerase adds complementary nucleotides to each parental strand in the 5' to 3' direction, following base pairing rules (A pairs with T; G pairs with C). The enzyme also has proofreading activity, correcting mismatched bases during replication. Leading and lagging strands are synthesized continuously and discontinuously, respectively, with okazaki fragments joined later by DNA ligase to form a complete daughter strand. Repair mechanisms, including mismatch repair, base excision repair, and nucleotide excision repair, correct errors and damages caused by environmental factors or replication errors. Enzymes such as excision endonucleases recognize damaged bases, remove them, and fill the gaps with correct nucleotides, maintaining the integrity of the genetic code essential for cellular function and stability.

Active and Passive Transport in Cell Membranes

Transport across the cell membrane is critical for maintaining cellular homeostasis and involves two main mechanisms: active and passive transport. Active transport moves molecules and ions from areas of lower concentration to higher concentration, against their electrochemical gradient, requiring energy input in the form of adenosine triphosphate (ATP). This process involves carrier proteins and facilitates the transport of large molecules, ions, and complex sugars. Examples include the sodium-potassium pump, which maintains cellular ion gradients essential for nerve impulse transmission, and processes like endocytosis and exocytosis, which transport large molecules and particles across the membrane. Conversely, passive transport does not require energy; it relies on the natural movement of molecules down their concentration gradient. Key forms include diffusion, osmosis (the movement of water), and facilitated diffusion, which involves carrier proteins to transport specific molecules like glucose and amino acids. These mechanisms are essential for nutrient uptake, waste removal, and maintaining the osmotic balance within cells.

Structure-Function Relationships of Hemoglobin and Myoglobin

Hemoglobin and myoglobin are specialized oxygen-binding proteins with structural features directly related to their functions. Hemoglobin, found in red blood cells, has a tetrameric structure consisting of four subunits, each containing a heme group capable of binding oxygen. Its globular shape and quaternary structure allow cooperative binding, where oxygen affinity increases as more oxygen molecules bind—a trait called allosteric regulation—making it highly efficient for oxygen transport from lungs to tissues. Hemoglobin also transports carbon dioxide, contributing to acid-base regulation. Myoglobin, in contrast, is a monomeric globular protein primarily in muscle tissue. It contains a single heme group, allowing it to store oxygen and release it during muscle activity. Its high affinity for oxygen enables muscle cells to maintain oxygen supply under low concentrations. These structural distinctions—hemoglobin’s tetrameric form and cooperative binding versus myoglobin’s monomeric storage—are critical for their respective roles in oxygen delivery and storage.

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