Cytology PDF

 Figure 6.8a ENDOPLASMIC RETICULUM (ER) Nuclear Rough Smooth envelope Flagellum ER ER NUCLEUS...

 Figure 6.8a ENDOPLASMIC RETICULUM (ER) Nuclear Rough Smooth envelope Flagellum ER ER NUCLEUS Nucleolus Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome  Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope (LM), visible light is passed through a specimen and then through glass lenses Lenses refract (bend) the light, so that the image is magnified © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Figure 6.2 10 m Human height 1m Length of some nerve and Unaided eye muscle cells 0.1 m Chicken egg 1 cm Frog egg 1 mm Light microscopy Human egg 100 m Most plant and animal cells 10 m Nucleus Most bacteria Electron microscopy Mitochondrion 1 m Smallest bacteria Super- 100 nm Viruses resolution microscopy Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms  Figure 6.3 Light Microscopy (LM) Electron Microscopy (EM) Brightfield Confocal Longitudinal section Cross section (unstained specimen) of cilium of cilium Cilia 50 m Brightfield (stained specimen) 50 m 2 m 2 m Transmission electron Scanning electron microscopy (TEM) Deconvolution microscopy (SEM) Phase-contrast 10 m Differential-interference- contrast (Nomarski) Super-resolution Fluorescence 1 m 10 m  LMs can magnify effectively to about 1,000 times the size of the actual specimen Various techniques enhance contrast and enable cell components to be stained or labeled Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LM © 2011 Pearson Education, Inc.  Two basic types of electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen TEMs are used mainly to study the internal structure of cells © 2011 Pearson Education, Inc. Light and electron microscopy - are 2 mane methods in histology  Levels of biological systems Biomolecules membranes organelles CELL  Eukaryotic cells are characterized by having – DNA in a nucleus that is bounded by a membranous nuclear envelope – Membrane-bound organelles – Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells © 2011 Pearson Education, Inc.  The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins © 2011 Pearson Education, Inc.  The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell The general structure of a biological membrane is a double layer of phospholipids © 2011 Pearson Education, Inc. Figure 6.6 (a) TEM of a plasma Outside of cell membrane Inside of cell 0.1 m Carbohydrate side chains Hydrophilic region Hydrophobic region Hydrophilic Phospholipid Proteins region (b) Structure of the plasma membrane  Figure 6.7 Surface area increases while total volume remains constant 5 1 1 Total surface area [sum of the surface areas (height  width) of all box 6 150 750 sides  number of boxes] Total volume [height  width  length  number of boxes] 1 125 125 Surface-to-volume (S-to-V) ratio [surface area  volume] 6 1.2 6 Membrane contents:  Lipids may be: Phospholipids – triglycerides (polar) Cholesterol (non-polar)  Phosphate group (hydrophilic heads) Glycerol Fatty acids (hydrophobic tails)  Figure 6.30 Collagen Polysaccharide EXTRACELLULAR FLUID molecule Proteoglycan Carbo- complex hydrates Fibronectin Core protein Integrins Proteoglycan molecule Plasma membrane Proteoglycan complex Micro- CYTOPLASM filaments  Figure 6.30a Collagen EXTRACELLULAR FLUID Proteoglycan complex Fibronectin Integrins Plasma membrane CYTOPLASM Micro- filaments Figure 6.30b Polysaccharide molecule Carbohydrates Core protein Proteoglycan molecule Proteoglycan complex  Structure of a typical cell 1. Cell membrane 2. Nucleus 3. Cytoplasm organelles Cytosol = matryx, inclusions hialoplasm  - consist of multiprotein complexes that provide contact between neighbouring cells or between a cell and the extracellular matrix. Where Cells contact -- Cell junction G 1 2  Cell junction Communicating or Gap junctions junction Tight junction Desmosomes Figure 6.32 Tight junctions prevent fluid from moving Tight junction across a layer of cells TEM 0.5 m Tight junction Intermediate filaments Desmosome TEM 1 m Gap junction Ions or small molecules Space between cells TEM Extracellular Plasma membranes matrix of adjacent cells 0.1 m Figure 6.32a Tight junctions prevent fluid from moving across a layer of cells Tight junction Intermediate filaments Desmosome Gap junction Ions or small Plasma membranes molecules of adjacent cells Space between cells Extracellular matrix  Tight junction present in different types of epithelia two layers of glycocalyx are fused. act as a barrier, that prevents the movement of molecules into the intercellular spaces G  Gap junction allow for direct chemical communication between adjacent cellular cytoplasm through diffusion without contact of the extracellular fluid numerous in muscle tissue Gap junction Consists of six connexin proteins, interacting to form a cylinder with a pore in the centre - connexon. This protrudes across the cell membrane, and when two adjacent cell connexons interact, they form the gap junction channel Desmosome - is the most common type of junction Provides cell attachment  Cytoplasm and nucleus  Inside the cell … Cytoplasm consists of: Matrix (hialoplasm, cytozol) Organelles Inclusions  Inclusions Inclusions are "nonliving" components of the cell. They include granules with secretions, pigment granules, lipid droplets, and glycogen.  Organelles: classification by structure Membranous or Non-membranous "membrane-bound"  Organelles: classification by function General (present in Special (in every cell, perform specialised cell, general function) perform special function)  Rough (rough-surfaced) endoplasmic reticulum is a membranous network of sac-like structures cisternae. the cisternal space (or lumen) is continuous with the perinuclear space but separate from the cytosol.  The surface of the RER is studded with ribosomes giving it a "rough" appearance (hence its name). Function - synthesis of proteins Smooth(-surfaced) endoplasmic reticulum, SER  SER consists of tubules that are located near the cell periphery. Function: It synthesizes lipids - phospholipids and steroids. It also carries out the metabolism of carbohydrates (synthesis of glycogen, gluconeogenesis ), drug detoxification, and steroid metabolism. Storage of Ca-ions (only in muscle cell)  also known as the Golgi complex, Golgi body, or Golgi apparatus simply the Golgi, is an organelle found in most eukaryotic cells. It was identified in 1897 by the Italian physician Camillo Golgi and named after him in 1898. Loks as a pack of sacs. Golgi apparatus Golgi complex is connected with endoplasmic reticulum Golgi apparatus Functions. 1. synthesis of substances, which has begun in endoplasmic reticulum and is accomplished in the Golgi complex. Golgi apparatus Functions. 2. formation of compound molecules – glycoproteins, lipoproteins. Golgi apparatus Functions. 3. production of lysosomes and secretory vesicles. Mitochondrion is a membrane- enclosed organelle found in most eukaryotic cells.  Mitochondrion A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. Folds of inner membrane – cristae Inside M. lie matryx  Mitochondrion Mitochondria provide energy for various cellular functions , Produce ATP molecules by Krebs cycle  Lysosome Lysosomes are round vesicles that contain acid hydrolase enzymes that break down waste materials and cellular debris. Lysosomal enzymes help in digesting the materials within phagosomes. They can be described as the stomach of the cell. Lysosome Cycle lysosomes are formed from Golgi complex The nearly produced lysosome is primary lysosome Lysosome Cycle primary lysosome fuses with the phagosome -- secondary lysosome or phagolysosome part of undigesting material may remain within the cell as residual bodies.  Non-membranous organelles: Microfilaments Microtubules Centrioles (Cell Center) Ribosomes  The cytoskeleton - is made up of three kinds of protein filaments: Actin filaments (also called microfilaments) Intermediate filaments Microtubules Microfilaments, Microtubules form “Skeleton” of the cell  Cell center Centriole = 9 x 3 microtubules; 2 centrioles = cell center = Β-tubulin function -formation of mitotic spindle (mitosis, meiosis), flagella, basal bodies and cilia Cell center  Nucleus Eukaryotes have nucleus  Nucleus is a membrane-limited structure: Nucleolemma - nuclear envelope Nucleoplasm Nucleolus Chromatin, chromosomes  Nuclear envelope - Consists of two membranes. The outer layer is continuous with endoplasmic reticulum. The inner layer provides attachment to the ends of the chromosomes.  Nuclear envelope There are gaps, called nuclear pores The nuclear pore transports some substances from nucleus into cytoplasm  Nucleolus Nucleolus is the site very amplificated molecule of DNA. It is the site of active synthesis of ribosomal RNA.  In the nucleolus RNA binds with protein and forms ribosomal subunits, which leave the nucleus via nuclear pores to the cytoplasm as ribosomes.  Chromosome - DNA molecules which contain genetic information DNA molecule is coiled around the histone core, which consists of eight gistone molecules. Such particles, consisting of gistone core and DNA, are called nucleosomes.  Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are 1) to package DNA into a smaller volume to fit in the cell, 2) to strengthen the DNA to allow mitosis, 3) to prevent DNA damage, and 4) to control gene expression and DNA replication  Sites where chromatin fibrils are packed very tightly together are heterochromatin sites – non-active. there are less condensed chromatin fibrils loops - euchromatin sites - active.  Euchromatin predominates in metabolically active nuclei, Heterochromatin predominates in metabolically inactive nuclei  Chromosome is an organized structure of DNA and protein found in cells.  Cell Cycle The life of a somatic cell is a cyclic process It is called cell cycles consists of two periods: interphase and mitosis.  Interphase Interphase is a period between two divisions of the cell. Consists of 3 phases - G1 , S , G 2  In G1 phase: cell grows, performs its routine functions.  In G1 phase Nondividing cells complete period G1 by growing old and death of the cell Dividing cell – prepare for next phase  S- phase = synthesis phase DNA molecules are duplicated each chromosome now consists of two DNA molecules or two chromatids. At the beginning of this phase, the chromosome number is 2N and at the end, the chromosome number is 4N.  G2 phase In this phase synthesis of proteins, which are required for cell division, takes place. After phase G2 mitosis always begins  G0 phase cell can leave the cycle in any phase, except G2, and enter to so-called G0 phase (outside the cycle). The cell that leaves the cycle is considered as reserve stem cell.  Mitosis is the process of somatic cells division. Mitosis consists of four phase: prophase, metaphase, anaphase, telophase.  Prophase Chromosomes becomes more and more coiled become recognisable. the nuclear membrane breaks down and the nucleoli disappear  Two centrioles separate and move to opposite poles of the cell. Сentrioles produce a number of microtubules which pass from one centriole to other and form a spindle of division.  Metaphase - chromosomes move to a position midway between the two centrioles at the equator of the cell and form the equatorial plate  anaphase - the chromatids separate and move to opposite poles of the cell At the end of anaphase chromatids are called chromosomes.  Telophase - two daughter nuclei are formed by appearance of nuclear membranes around them. The chromosomes gradually elongate and become indistinct. Nucleoli reappear.