Plant Cell Biology Lecture Notes Fall2023 PDF

040407221: Plant Cell Biology (Lecture 1 hr + Practical 3 hrs) Lecture 1,part II Dr. Fatma M. Ashour Dr. Fatma Ashour Plant cell Biology 1 Contents What is cell biology. Cellular macromolecules. Signaling Pathways that Regulate Cell Division. Karyotype...

040407221: Plant Cell Biology (Lecture 1 hr + Practical 3 hrs) Lecture 1,part II Dr. Fatma M. Ashour Dr. Fatma Ashour Plant cell Biology 1 Contents What is cell biology. Cellular macromolecules. Signaling Pathways that Regulate Cell Division. Karyotype evolution & speciation. Cytogenetics and Cytotaxonomy. Dr. Fatma Ashour Plant cell Biology 2 What is cell biology? Cell biology is a branch of biology that studies the structure and function of the cell, which is the basic unit of life. Cell biology is concerned with the physiological properties, metabolic processes, signaling pathways, life cycle, chemical composition and interactions of the cell with their environment. Dr. Fatma Ashour Plant cell Biology 3 What is cell biology? Fundamentals of cell biology include the processes of mitosis and meiosis. Cell biology is the study of cells and how they function, from the subcellular processes which keep them functioning, to the way that cells interact with other cells. Dr. Fatma Ashour Plant cell Biology 4 What is cell biology? Whilst molecular biology concentrates largely on the molecules of life (largely the nucleic acids and proteins), cell biology concerns itself with how these molecules are used by the cell to survive, reproduce and carry out normal cell functions. Dr. Fatma Ashour Plant cell Biology 5 Cellular macromolecules The three most abundant biological macromolecules are: proteins, nucleic acids, and polysaccharides- are all polymers composed of multiple covalently linked identical or nearly identical small molecules, or monomers Dr. Fatma Ashour Plant cell Biology 6 Figure 1. Covalent linkage of monomers to form biopolymers. Dr. Fatma Ashour Plant cell Biology 7 Cellular macromolecules Proteins are polymers of amino acids (monomers). Which become linked by a peptide bond. Each protein is a linear, unbranched, polypeptide molecule. Dr. Fatma Ashour Plant cell Biology 8  1. Proteins The order in which amino acids occur is specific for each polypeptide. The protein molecules are very large and highly complex macromolecules. Dr. Fatma Ashour Plant cell Biology 9 Figure 2. linear, unbranched, polypeptide molecule. Dr. Fatma Ashour Plant cell Biology 10 Figure 3. Structure of amino acid Dr. Fatma Ashour Plant cell Biology 11 Figure 4. Linkage between two amino acids Dr. Fatma Ashour Plant cell Biology 12  Proteins Structure and Function Proteins, the working molecules of a cell, carry out the program of activities encoded by genes. Proteins, are constructed by the polymerization of only 20 different amino acids into linear chains. Dr. Fatma Ashour Plant cell Biology 13  Proteins Structure and Function Proteins, differ from each other according to the kind, number and arrangement of amino acids they contain. The structures and functions of proteins, are determined by the properties of the amino acids, which lies in their side chains (e.g. cysteine –SH form –S-S- disulphide bond with other cysteine) The side chains of different amino acids vary in size, shape, charge, hydrophobicity, and reactivity. Dr. Fatma Ashour Plant cell Biology 14 Proteins can be grouped into several broad functional classes structural proteins: which provide structural rigidity to the cell; transport proteins: which control the flow of materials across cellular membranes; regulatory proteins: which act as sensors and switches to control protein activity and gene function; Dr. Fatma Ashour Plant cell Biology 15 Proteins can be grouped into several broad functional classes signaling proteins: including cell surface receptors and other proteins that transmit external signals to the cell interior; and motor proteins: which cause motion. Dr. Fatma Ashour Plant cell Biology 16 Figure 6. The Four Levels of Protein Structure Dr. Fatma Ashour Plant cell Biology 17 The Four Levels of Protein Structure Primary structure: Is simply the linear arrangement, or sequence, of the amino acid residues that compose it. Secondary structures: are the core elements of protein architecture it consists of the various spatial arrangements (alpha helix & beta sheet) resulting from the folding of localized parts of a polypeptide chain. Dr. Fatma Ashour Plant cell Biology 18 Tertiary structure: refers to the overall conformation of a polypeptide chain, that is, the three-dimensional arrangement of all its amino acid residues. It is formed at a particular folds, called motifs (e.g. Ca binding motif and zinc finger motif). Dr. Fatma Ashour Plant cell Biology 19 Quaternary structure: describes the number and relative positions of the subunits in multimeric proteins conjugated with non protein ions or molecules as: - metalloproteins: , (e.g. hemoglobin, proteins conjugated with Fe ion, and chlorophyll, proteins conjugated with Mg ion); - mucoproteins: (or glycoproteins) proteins conjugated with sugars; - lipoproteins: proteins conjugated with lipids; - nucleoproteins: proteins conjugated with nucleic acids. Dr. Fatma Ashour Plant cell Biology 20  Protein folding In vivo, Protein folding occurs with assistance from molecular chaperones, which bind to nascent polypeptides emerging from ribosomes and prevent their misfolding. Chaperones, are a class of proteins which recognize motifs causing the correct folding of protein molecules. They are found in all organisms. Dr. Fatma Ashour Plant cell Biology 21 The proteome is the entire protein complement of an organism. - yeast proteome consists of about 6000 different proteins. - human proteome consists of about 32,000 different proteins. Dr. Fatma Ashour Plant cell Biology 22