CELLS.pdf

Cells basic unit of biologic organization of the human body. 50 to 100 trillions of cells Microns (µm) = 10­‾³ mm 10 – 100 µm in dm microscope ROBERT HOOKE English Physicist “Renaissance Man” , 17th Century Latin word, “cella”, small room Cellulae, six-sided cell of a honeycomb ANT...

Cells basic unit of biologic organization of the human body. 50 to 100 trillions of cells Microns (µm) = 10­‾³ mm 10 – 100 µm in dm microscope ROBERT HOOKE English Physicist “Renaissance Man” , 17th Century Latin word, “cella”, small room Cellulae, six-sided cell of a honeycomb ANTON VAN LEEUWENHOEK Father of Microscopy Dutch lens maker 300 fold or 270x Motile objects “animalcules” MATHIAS JAKOB SCHNEIDEN Botany Professor, University of Jena, Germany Different types of plants under the microscope THEODOR SCHWANN Physiology Professor, University of Louvain, Belgium Different types of animals under the microscope MODERN CELL THEORY Cells are the smallest complete living things. They are the basic units of organization of all organism. All organism is composed of one or more cells in which all life processes occur. Cell arise only from pre-existing cells through the process of cell division. All of today’s existing cells are descendants of the first cells formed early in the evolutionary history of life on earth. FUNCTIONS Cellular metabolism and energy use Synthesis of molecules Communication PROKARYOTES “Pro” means BEFORE “Karyose” means NUT OR KERNEL Bacteria and Arachaea Single celled EUKARYOTES “Eu” means TRUE “Karyose” means NUT OR KERNEL Animal and plant cells With nucleus and cell organelles BASIC CELL STRUCTURE CELL MEMBRANE CYTOPLASM NUCLEUS CELL MEMBRANE A.k.a PLASMA MEMBRANE Controls the movement of substances in and out of the cell Gives form to the cell Semi - permeable Lipids and proteins Phosphate - outside Fatty acid - inside MEMBRANE LIPIDS 45 - 50% Phospholipids - bilayer Cholesterol - 1/3 of the total lipids - helps stabilize the membrane and keep it flexible MEMBRANE PROTEINS 45 - 50% Integral Proteins - consist of regions made up of amino acids with hydrophobic R groups and other regions of amino acids with hydrophilic R groups. Peripheral Proteins - may be bound to integral membrane proteins, whereas others are bound to the polar heads of the phospholipid molecules Anchoring Proteins Recognition Proteins - identifiers Enzymes - catalyze reactions in the cytoplasm or the ECF Receptor Proteins - sensitive to ligands Carrier Proteins - bind solutes, needs ATP MEMBRANE CARBOHYDRATES 4- 8 % Proteoglycans Glycoproteins Glycolipids GLYCOCALYX Anchoring and locomotion Binding specificity Lubrication and Protection Recognition 3 ways cells are bound together: Glycoproteins in the glycocalyx act as an adhesive or cellular glue. Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion. Special cell membrane junctions are formed CELL MEMBRANE JUNCTION TIGHT JUNCTIONS are impermeable junctions that encircle the cells and bind them together into leakproof sheets. fuse together tightly like a zipper and prevent substances from passing through the extracellular space between cells. A tight junction is a protein complex between two cells that creates a seal to prevent any leakage of the content through the cell membranes  DESMOSOMES anchoring junctions scattered like rivets along the sides of adjacent cells prevent cells subjected to mechanical stress (such as heart muscle cells and skin cells) from being pulled apart button likeike thickenings of adjacent plasma membranes (plaques) that are connected by fine protein filaments strong guy wires GAP JUNCTIONS allow communication heart and between embryonic cells neighboring cells are connected by hollow cylinders composed of proteins (CONNEXONS) that span the entire width of the abutting membranes chemical molecules, such as nutrients or ions, can pass directly through the water-filled connexon channels from one cell to another. MOVEMENT THROUGH THE PLASMA MEMBRANE Passive Transport - no metabolic energy expenditure Active Transport - with metabolic energy expenditure Vesicular Transport - use of vesicles or membrane bound CYTOPLASM Protoplasm Matrix substance in which chemical reactions occur Gel-like material suspending all the organelles Contains cytosol and organelles ORGANELLES specialized cellular compartments that are the metabolic machinery of the cell specialized to carry out a specific function for the cell CENTRIOLES Paired cylindrical bodies that are each made up of nine triplets of microtubules During mitosis (cell division), they organize a microtubule network to form the spindle and asters. They form the bases of cilia and flagella ROUGH ENDOPLASMIC RETICULUM (RER) A membranous system that encloses a cavity (cistern). It coils through the cytoplasm and is externally studded with ribosomes Within the cisterns, sugar groups are attached to proteins. The proteins are bound in vesicles so they can be transported to the Golgi apparatus and other sites. Their external faces synthesize phospholipids. SMOOTH ENDOPLASMIC RETICULUM (SER) A membrandus system of sacs and tubules that lack ribosomes. The site of steroid (cholesterol) and lipid synthesis, lipid metabolism, and drug detoxification. GOLGI APPARATUS Located close to the nucleus, it is a stack of flattened membranes and associated vesicles. It packages, changes, and separates proteins for secretion from the cell, to be included in lysosomes, and to be incorporated into the plasma membrane. LYSOSOMES Membranous sacs that contain acid hydrolases. The sites of intracellular digestion PEROXISOMES Membranous sacs of oxidase and catalase enzymes. The enzymes detoxify a number of toxic substances such as free radicals. The most important enzyme, catalase, breaks down hydrogen peroxide MICROFILAMENT Fine filaments composed of actin, a protein Aid in muscle contraction and other intracellular movement and help to form the cell’s cytoskeleton INTERMEDIATE FILAMENT STRUCTURE Protein fibers; composition varies. The stable cytoskeletal elements; resist mechanical forces acting on the cell; help form desmosomes MICROTUBULES Cylindrically shaped structures made of tubulin proteins. They support the cell, giving it shape, and are involved in intracellular and cellular movements. Microtubules form centrioles and, if present, cilia and flagella. They form the mitotic spindles during cell division, binding to the chromosomes and separating the two strands MITOCHONDRIA Double-membrane structures that are rod-like in appearance; they are folded into projections (cristae). The site of ATP synthesis. The mitochondria are the powerhouses of cells. RIBOSOMES Dense particles made up of two subunits that are each composed of ribosomal RNA and protein. They may be either free or attached to the RER. The sites of protein synthesis. CELL NUCLEUS central role in the cell operation storage of information and distributed to guide the life processes of the cell. contains the genetic instructions needed to synthesize the proteins that determine cell structures and functions NUCLEOLUS Dense spherical (non-membrane bounded) bodies, composed of ribosomal RNA and proteins Site of ribosome subunit manufacture. CHROMATIN Granular, threadlike material composed of DNA and histone proteins. "Beads on a string." DNA constitute the genes, which carry instructions for building proteins. The structure of chromatin keeps DNA organized and prevents breakage. CELL CYCLE Interphase Cell Division (Mitosis) Cytoplasmic Division (Cytokinesis) Differentiation INTERPHASE An interval of time between cell divisions when they perform normal functions G1 phase - 8 hrs or more S phase - 6-8 hrs G2 phase - 2-5 hrs G1 PHASE cells are metabolically active with rapid protein synthesis and growth no cell division activities as this phase ends, the centrioles begin replication, preparing for cell division S PHASE DNA is replicated process of DNA replication involves enzymes attaching to origins or replication G2 PHASE cell division-influencing enzymes and other proteins are synthesized and moved to their required sites centriole replication finishes and the cell is now ready to divide two DNA molecules are formed from the original template strands MITOSIS somatic cells two new daughter cells result from cell division, receiving the same number of chromosomes present in the parent cell except cardiac muscles and neurons when the nucleus divides, it must be precise so an accurate copy of the DNA information can be made by the new cell CYTOKINESIS Division of the cytoplasm begins during Anaphase and is completed during Telophase APOPTOSIS  rogrammed cell death P A normal process by which cell number within various tissues is adjusted and controlled Damaged or potentially dangerous cells, virus-infected cells, and potential cancer cells regulated by specific genes GAMETOGENESIS Gametes - mature germ cells Spermatogenesis Oogeneis MEIOSIS SPERMATOGENESIS SPERMATOGONIA precursor cells in the testicular tubules contains 46 chromosomes divides via mitosis forming primary SPERMATOCYTES PRIMARY SPERMATOCYTES contains 46 chromosomes divides via Meiosis I forming two secondary SPERMATOCYTES SECONDARY SPERMATOCYTES contains 23 chromosomes divides via Meiosis Il forming two SPERMATIDS SPERMATIDS contains 23 chromosomes matures to become SPERM CELLS OOGENESIS OOGONIA - precursor cells contain 46 chromosomes, divide repeatedly in the fetal ovaries prior to birth forms PRIMARY OOCYTES PRIMARY OOCYTE surrounded by a single layer of granulosa cell or follicular cells, forming the PRIMARY FOLLICLES inside the follicles the Primary oocyte begin but does not complete Prophase of the Meiotic I during fetal life PRIMARY FOLLICLES large numbers are formed, with many degenerating during infancy and childhood 500,000 persist into adolescence loss of primary follicles continues throughout a female's reproductive years every reproductive cycle, several oocytes start to mature OOCYTE Meiosis I completed when the mature ovum is expelled Meiosis I| completed only after the oocyte is fertilized MEIOSIS Part of GAMETOGENESIS a reduction division of the nuclear material so that each gamete contains only half as much hereditary material as the parent cell. Meiosis I - chromosomes are reduced in half Meiosis I| - four daughter cells each containing only half the genetic material Spermatogenesis / oogenesis DIFFERENTITATION process of specialization of a cell New cells must be generated for growth and tissue repair to occur STEM CELLS can divide repeatedly without specializing can divide either into two identical daughter cells or so that one daughter cell becomes partially specialized (PROGENITOR CELLS) ability to heal the body in the future CELLULAR ASPECTS OF AGING 35% genetics CELLULAR CLOCK after a certain passage of time or a certain number of cell divisions, results in the death of a given cell line DEATH GENES turn on late in life, or sometimes prematurely, causing cells to deteriorate and die DNA DAMAGE through time, DNA is damaged, resulting in cell degeneration and death FREE RADICALS atoms or molecules with an unpaired electron DNA is also susceptible to direct damage, resulting in mutations that may result in cellular dysfunction and, ultimately, cell death MITOCHONDRIAL DAMAGE mitochondrial DNA damage may result in loss of proteins critical to mitochondrial function mitochondrial DNA more sensitive to free radicals