Cell Protein
Cell proteins are essential molecules that perform a wide range of functions within cells. They are involved in structural support, signaling, transport, and catalyzing chemical reactions. Proteins are made up of amino acids and are synthesized based on the instructions encoded in the cell's DNA. These versatile molecules play a crucial role in the overall functioning of living organisms.
6 Key excerpts on "Cell Protein"
eBook - ePub- David P. Clark(Author)
- 2009(Publication Date)
- Academic Cell(Publisher)
...They are responsible for most of the metabolic reactions and many of the structural components of cells. Not surprisingly, there is colossal variety in the functional role of proteins. Nonetheless, proteins may be subdivided into several major categories: 1. Enzymes 2. Structural proteins 3. Binding proteins (transport, carrier, and storage proteins) 4. Mechanical proteins 5. Information processing proteins Proteins play a wide variety of functional roles in the cell. Enzymes are proteins that catalyze chemical reactions. These are discussed in more detail below. Many of the characteristics of enzymes, such as the presence of binding pockets for small molecules and the ability to change shape, are shared by other proteins. Most metabolic reactions are catalyzed by proteins known as enzymes. Many sub-cellular structures consist largely or partly of structural proteins. The filaments of the flagella with which bacteria swim around, the microtubules used to control traffic flow inside cells of higher organisms, the fibers in connective tissue, and the outer coats of viruses (see Ch. 17) are examples of structures built using proteins. Specialized proteins are known that control the structure of water. Fish that live in polar regions have antifreeze proteins to keep their blood from freezing. These proteins bind to ice surfaces and prevent the growth of ice crystals. Conversely, surface proteins of certain bacteria, known as ice nucleation factors, promote the formation of ice crystals and are important in causing frost damage to plants. Damaging plant cells releases nutrients on which the bacteria can grow and may also allow colonization of plant tissue by the bacteria. Binding proteins bind small molecules but unlike enzymes they do not carry out a chemical reaction. Nonetheless, they also need “active sites” to accommodate the small molecules. Transport proteins or carrier proteins are involved in moving their substrates around within the organism...
eBook - ePub- Anthony S. Lubiniecki(Author)
- 2018(Publication Date)
- Routledge(Publisher)
...A broad definition of cell physiology might be all the vital functions, both physical and chemical, that interact to collectively form a living cell. A cell, in reality, is a "biological machine" with all the necessary machinery (enzymes, transporters, pumps, etc.) to perform the desired work. In our case the work is to make large quantities of complex, glycosylated proteins. To perform this work, cells must have sufficient energy for all their biosynthetic and maintenance needs, they must be able to transport and metabolize substrates for macromolecular synthesis, and they must possess the type and quantity of metabolic (enzymatic) machinery needed to accomplish the task. What are the rate-limiting chemical or physical processes in cells that govern the amount of genetically engineered protein made? Placing powerful expression vectors into mammalian cells and amplifying gene copies is all well and good, but do the cells possess the necessary internal machinery to process the message and make large quantities of the desired protein? Can they transform enough of their energy substrates into ATP to fuel the synthesis of large quantities of genetically engineered proteins? Are flux-regulating steps in metabolic pathways limiting the synthesis of macromolecules like mRNA and DNA? These are but a few of the many questions related to the physiology of mammalian cells that have only just begun to be asked. Many critical steps lie between transcription of the engineered gene and its secretion as the finished product. Identification of the rate-limiting steps, and their subsequent elimination through genetic engineering, could pay great dividends by increasing the amount of product synthesized per cell. Can we increase cell yield per volume of medium in mammalian cell culture? Mammalian cells reach only a small fraction of the dry cell mass that yeast and bacterial fermentations achieve in conventional batch fermentations...
eBook - ePubBiomaterials
A Systems Approach to Engineering Concepts
- Brian J. Love(Author)
- 2017(Publication Date)
- Academic Press(Publisher)
...Ultimately bioengineered solutions using materials require some haptic interface with biological tissue and by colocation, cells as well. There are multiple complete books that are dedicated to this one topic. Those are terrific references for this chapter. There are great image resources on the web that can supplement the bulk of the text. The presentation of this chapter coupled with Chapter 2, Cell Expression: Proteins and Their Characterization, tied to proteins and amino acids should help engineers reading this book appreciate the more detailed nuances of normal cell physiology, and allow readers to possess a deeper language linked with cell biology in the context of biomaterials used to replace tissue and organ function, and to seamlessly interface with viable tissues. Keywords Cell nomenclature; classifications; cell function; mitosis; motility; communication; trafficking; apoptosis; nucleus; mitochondria Learning Objectives By reading this chapter, the reader should be able to 1. Recognize the various naming conventions for cells including functions, tissues from which they are derived, morphological features, and what they ultimately produce as proteins. 2. Describe features and subunits of typical eukaryotic cells which include mitochondria, the nucleus, the cytosol, the lipid membrane, and other structural features that are tied to the cytoskeleton and to the glycocalyx. 3. Understand functions of cells, which include cell division, protein expression, extracellular sensing and communicating within the environment, assembly into larger tissue constructs, and cell death, whether by apoptosis, cell rupture, or some other mechanism. 4. Recognize cell types contained within blood, tissues, and organs. 1.1 Introduction The genesis of living matter is regulated and organized by cellular production, encoded by different genetic sequences by cells in the presence of local tissues and fluids...
eBook - ePubProtein Physics
A Course of Lectures
- Alexei V. Finkelstein, Oleg Ptitsyn(Authors)
- 2016(Publication Date)
- Academic Press(Publisher)
...Part I Introduction Lecture 1 Abstract Main functions of proteins. Amino acid sequence determines the three-dimensional structure, and the structure determines the function. The reverse is not true. Fibrous, membrane, and globular proteins. Primary, secondary, tertiary, and quaternary structures of proteins. Domains. Cofactors. Active sites and protein globules. Protein biosynthesis; protein folding in vivo and in vitro. Posttranslational modifications. Keywords Main functions of proteins; Three-dimensional structure; Fibrous proteins; Membrane proteins; Globular proteins; Domains; Protein folding This lecture contains an introduction to the whole course—a brief overview of what is given (or omitted) in the following lectures. Therefore, unlike other lectures, this one is not supplied with specific references; instead, it contains a list of textbooks that may be recommended for additional reading. Proteins are molecular machines, building blocks, and arms of a living cell. Their major and almost sole function is enzymatic catalysis of chemical conversions in and around the cell. In addition, regulatory proteins control gene expression, and receptor proteins (which sit in the lipid membrane) accept intercellular signals that are often transmitted by hormones, which are proteins as well. Immunoproteins and the similar histocompatibility proteins recognize and bind “foe” molecules as well as “friend” cells, thereby helping the latter to be properly accommodated in the organism. Structural proteins form microfilaments and microtubules, as well as fibrils, hair, silk, and other protective coverings; they reinforce membranes and maintain the structure of cells and tissues. Transfer proteins transfer (and storage ones store) other molecules. Proteins responsible for proton and electron transmembrane transfer provide for the entire bioenergetics, that is, light absorption, respiration, ATP production, etc...
eBook - ePubBiomaterials Science
An Introduction to Materials in Medicine
- Buddy D. Ratner, Allan S. Hoffman, Frederick J. Schoen, Jack E. Lemons(Authors)
- 2012(Publication Date)
- Academic Press(Publisher)
...maintaining viability. We will then revisit each of these structural features to illustrate important concepts in homeostatic maintenance (keeping the cell within certain functional boundary conditions) and response to the environment. Conceptually, cells may be viewed as independent collections of self-replicating enzymes and structural proteins that carry out certain general functions. The most essential cell attributes are: • protection from the environment • acquisition of nutrients • movement • communication • catabolism of extrinsic molecules • degradation and renewal of senescent intrinsic molecules • energy generation • self-replication. Intracellular constituents exist in a microcosm of water, ions, sugars, and small molecular weight molecules called the cytosol or cytoplasm. Within the cytosol is also a source of energy, typically adenosine triphosphate (ATP). Although long conceptualized as a randomly diffusing bag of soluble molecules, the cell is, in fact, a structurally highly-ordered and functionally integrated assembly of organelles, cytoskeletal elements, and enzymes. The cytosol is delimited and protected from the environment by a phospholipid bilayer, the plasma membrane, which permits the cell to maintain cytosolic constituents at concentrations different than those in the surrounding environment. Due to its hydrophobic inner core, the plasma membrane is impermeable to charged and/or large polar molecules; however, it is rendered selectively permeable (i.e., permits specific passage) to incoming or outgoing material (ions, sugars, amino acids, etc.) by pore or transport proteins inserted through it. Most nutrient acquisition is accomplished by the movement of desired substrates either through protein channels (driven by electrochemical gradients) or by energy-driven transport through carrier proteins...
eBook - ePub- Jose Perez-Castineira(Author)
- 2020(Publication Date)
- De Gruyter(Publisher)
...Moreover, the carbon skeleton of amino acids can be used to obtain metabolically useful energy and metabolites like glucose. All these properties make amino acids very versatile nutrients, although the use of the carbon skeleton implies the necessity of eliminating the nitrogen, with important metabolic consequences (see below). Proteins are involved in virtually all biological functions: Enzymatic. The vast majority of biochemical reactions are catalyzed by specific extremely efficient biological catalysts known as enzymes. With the only exception of ribozymes, composed of RNA [ 9 ], all known enzymes are proteins. Transport. This term may refer to two different processes, both mediated by proteins: Distribution of substances like lipids, fatty acids, or oxygen via bloodstream. Movement of solutes across biological membranes. Muscular contraction: actin and myosin. Immune system: antibodies. Hormones, like insulin, glucagon, or leptin. Structural: keratins (hair, nails and horns in mammals, feathers in birds), collagen (bones and teeth), fibroin (silk), elastin (ligament, tendons …). Storage of energy and amino acids, like milk caseins. DNA packaging: histones. Control of transcription and translation. Around 20,000 different proteins are estimated to be present in humans if we accept the hypothesis of “one gene = one protein,” that is, if only the sequences of the human genome that are potentially translatable are accounted for; however, it is estimated that about 100 different proteins can potentially be produced from a single gene by processes like alternative splicing, single amino acid polymorphisms, or post-translational modifications (PTMs) [ 10 ]...
