Cell and Cell Cycle PDF

CELL AND CELL CYCLE Kean Roe F. Mazo Faculty, Forest Sciences Department Mindanao State University at Naawan CELL STRUCTURE Cell is the basic structure and physiological unit of living organisms. Cell are the building blocks of life. Cell are maintained...

CELL AND CELL CYCLE Kean Roe F. Mazo Faculty, Forest Sciences Department Mindanao State University at Naawan CELL STRUCTURE Cell is the basic structure and physiological unit of living organisms. Cell are the building blocks of life. Cell are maintained the division of cells. Cells will exist as long as life exits. The diameter of the plant cell lie between 0.1-0.001 millimeter CELLULAR STRUCTURE  TYPES OF CELLS PROKARYOTE CELL EUKARYOTIC CELL PRO means “before” EU means “true” KARYOTE is derived from the word KARYOTE means “Karyon” “KARYON” meaning nucleus or “kernel” Prokaryotic organisms are those which Eukaryotes are those cells which have were evolved before the nucleus or they nucleus inside the cell and comprise of don't have any nucleus inside the cell. proper organelles and boundaries.  MAJOR DIFFERENCES PROPERTIES PROKARYOTES EUKARYOTES NUCLEUS Not Present Present DNA DNA is present but it is DNA is present and (location) openly located in enclosed in the nucleus cytoplasm Organization of Cells Usually cells are Cells are connected with separated from each each other , works with other, and doing work as division of labor. a single unit  PROPERTIES PROKARYOTES EUKARYOTES Size of Cell Prokaryotic cells are usually While eukaryotic cells are bigger, they smaller in size. may be so bigger as could be seen by naked human eye e.g. EGG Metabolism of cell Usually the metabolic reactions Oftenly reactions are tremendously are the simplest and occur as complex and occur as multi cells. per single cell. Organelles Not found Highly complex organelles; double membrane e.g. mitochondria, Golgi complex etc Chromosome ▪Found in cytoplasm. ▪Found in nucleus and usually invisible. ▪ single celled with plasmid ▪ Many in one cell, human body has 46 chromosomes in a cell. EXAMPLES OF PROKARYOTES Prokaryotes are all single-celled organisms, most of which you know of as bacteria. Amoeba, Bacteria, Paramecium, Chlaymadomonas etc.  EXAMPLES OF EUKARYOTES Usually multicellular but sometimes, unicellular too. Some common examples are as follows; Animal cell, plant cell, mushrooms, yeasts etc TYPES OF CELLS NUCLEUS membrane bound structure that contains the cell's hereditary information (DNA). the center for all cellular activities. Nucleolus - structure within the nucleus that helps in the synthesis of ribosomes. Nucleopore - tiny hole within the nuclear membrane that allows nucleic acids and proteins to move into and out of the nucleus. CELL WALL outer covering of the cell that protects the plant cell and gives it shape. gives support and form to the cell and the tree as a whole and protects the protoplasm within. THE DISTINCT PARTS OF A CELL WALL: Middle lamella - a layer between adjacent cells and compost of sticky, gelatinous calcium pectate as pectic substance. Primary wall – the first wall formed by the protoplast composed of cellulose, lignin, oil. Secondary wall – a complete and mature wall the cell through deposition which is laid the primary wall composed of cellulose and suberin, oils water, etc. Pit – A minutes thin area of a cell wall that permits passage of water and dissolved Perforation – A minutes thin area of a cell wall that permits passages of strands of protoplasm adjacent cells. CHLOROPLAST the sites of photosynthesis is in a plant cell. They contain chlorophyll, a green pigment that absorbs energy from sunlight. CYTOPLASM gel-like substance within the cell membrane containing water, enzymes, salts, organelles, and various organic molecules. CYTOSKELETON a network of fibers throughout the cytoplasm that helps the cell maintain its shape and gives support to the cell. ENDOPLASMIC RETICULUM (ER) extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). synthesizes proteins and lipids. GOLGI COMPLEX responsible for manufacturing, storing and shipping certain cellular products including proteins. MITOCHONDRIA these organelles generates energy for the cell by converting glucose (produced by photosynthesis) and oxygen to ATP. This process is known as respiration. “the powerhouse of the cell” RIBOSOME - consisting of RNA and proteins, ribosomes are responsible for protein assembly. They can be found either attached to the rough ER or free in the cytoplasm. LYSOSOME acts as the cellular scavenger, digesting cytoplasmic particle. NUCLEUS membrane bound structure that contains the cell's hereditary information (DNA). the center for all cellular activities. Nucleolus - structure within the nucleus that helps in the synthesis of ribosomes. Nucleopore - tiny hole within the nuclear membrane that allows nucleic acids and proteins to move into and out of the nucleus. THE CHROMOSOMES composed of DNA, carrying the hereditary information (gene) FLOW OF BIOLOGICAL INFORMATION DNA RNA Proteins CELL CYCLE AND CELL DIVISION THE CELL CYCLE MITOSIS MEIOSIS A series of events which includes the growth, replication, and division of eukaryotic cells. CELL DIVISION IN PLANTS Mitosis occurs in somatic/vegetative cells Meiosis occurs in gametic (reproductive) cells MITOSIS VS. MEIOSIS Both mitosis and meiosis start with diploid parent cells. MITOSIS MEIOSIS ALL SOMATIC CELLS SEX CELLS EXCEPT SEX CELLS Its goal is to make 2 identical daughter cells daughter cells with exactly are produced half as many chromosomes as the starting cell. CELL THEORY 1. All living things are composed of cells. 2. All cells arise from preexisting cells through cell division. 3. Cells contain hereditary material, which is pass on to daughter cells during cell division. 4. The chemical composition of all cells is quite similar. 5. The metabolic processes associated with life occur within cells WHY DOES CELL DIVISION OCCUR? Cell division occurs so that multicellular organisms can maintain a stable state, basically for growth, reproduction, and repair. In unicellular organisms cell division occurs for the production of new organisms CELL DIVISION Cell division is a very important process in all living organisms. During the division of a cell, DNA replication and cell growth also take place. All these processes, i.e., cell division, DNA replication, and cell growth, hence, have to take place in a coordinated way to ensure correct division and formation of progeny cells containing intact genomes.  The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle.  G1 phase (Gap 1) approximately every 24 hours Interphase S phase (Synthesis) G2 phase Cell Cycle Prophase Metaphase M Phase (Mitotic Phase) Anaphase Telophase INTERPHASE G1 phase corresponds to the interval between mitosis and initiation of DNA replication. During G1 phase the cell is metabolically active and continuously grows but does not replicate its DNA. S or synthesis phase marks the period during which DNA synthesis or replication takes place. During this time the amount of DNA per cell doubles. M PHASE This is the most dramatic period of the cell cycle, involving a major reorganization of virtually all components of the cell. Since the number of chromosomes in the parent and progeny cells is the same, it is also called as equational division. Though for convenience mitosis has been divided into four stages of nuclear division, it is very essential to understand that cell division is a progressive process and very clear-cut lines cannot be drawn between various stages. Mitosis is divided into the following four stages:  Prophase  Metaphase  Anaphase  Telophase PROPHASE Prophase which is the first stage of mitosis follows the S and G2 phases of interphase. In the S and G2 phases the new DNA molecules formed are not distinct but intertwined.  3 MAJOR EVENTS chromosomes condense spindle fibers form (spindle fibers are specialized microtubules radiating out from centriole) chromosomes are captured by spindle METAPHASE The complete disintegration of the nuclear envelope marks the start of the second phase of mitosis, hence the chromosomes are spread through the cytoplasm of the cell. By this stage, condensation of chromosomes is completed. METAPHASE At this stage, metaphase chromosome is made up of two sister chromatids, which are held together by the centromere. The plane of alignment of the chromosomes at metaphase is referred to as the metaphase plate. THE KEY FEATURES OF METAPHASE ARE: Spindle fibres attach to kinetochores of chromosomes. Chromosomes are moved to spindle equator and get aligned along metaphase plate through spindle fibres to both poles. ANAPHASE At the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles. As each chromosome moves away from the equatorial plate, the centromere of each chromosome is towards the pole and hence at the leading edge, with the arms of the chromosome trailing behind TELOPHASE At the beginning of the final stage of mitosis, i.e., telophase, the chromosomes that have reached their respective poles decondense and lose their individuality. The individual chromosomes can no longer be seen and chromatin material tends to collect in a mass in the two poles.  THIS IS THE STAGE WHICH SHOWS THE FOLLOWING KEY EVENTS: Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements. Nuclear envelope assembles around the chromosome clusters. Nucleolus, golgi complex and ER reform. CYTOKINESIS Mitosis accomplishes not only the segregation of duplicated chromosomes into daughter nuclei (karyokinesis), but the cell itself is divided into two daughter cells by a separate process called cytokinesis. The formation of the new cell wall begins with the formation of a simple precursor, called the cell-plate that represents the middle lamella between the walls of two adjacent cells. END OF PRESENTATION