Cytology - First Year Students 2024-2025 PDF

HELWAN NATIONAL UNIVERSITY FACULTY OF SCIENCE BIOTECHNOLOGY & GENETIC ENGINEERING PROGRAM Cytology First year students 2024-2025 What is Cytology ? Cytology Cyto- which -logy which meaning study meaning cell of some thing (s...

HELWAN NATIONAL UNIVERSITY FACULTY OF SCIENCE BIOTECHNOLOGY & GENETIC ENGINEERING PROGRAM Cytology First year students 2024-2025 What is Cytology ? Cytology Cyto- which -logy which meaning study meaning cell of some thing (science) Cytology is a branch of biology dealing with cells (structure, functions, pathology)  What is Cell ? The functional and structural unit of all organisms The smallest building unit of all living organisms Cells vary in size, shape, function according to their sites in body According to number of cells, organisms are classified to Unicellular Multicellular organisms organisms (whole body is only (body is more than one cell) one cell)  Unicellular Multicellular organisms organisms Bacteria Fungi protozoa Plants Blue-green algae Animals Landmarks 1- Anton Van Leeuwenhoek in the study - Invented the microscope in 1668. of a cell 2- Robert Hooke - Cork under microscope composed from small compartments (cells). 3- Anton Van Leeuwenhoek - Observed bacteria, sperms and red blood cells (RBCs). 4- Robert Brown - All cells had a centrally positioned body which he termed the nucleus  Cell Theory (Schleiden and Theodore Schwann) All organisms are composed of cells Cell is the structural and functional unit of life Cells arise from pre-existing cells Nerve cell Cells vary in shape and size Muscle cell Definition of cell Unit of protoplasm bound by a plasma membrane What is the difference between protoplasm and cytoplasm ? Cytoplasm It contains organelles as ribosomes, mitochondria, Golgi bodies, lysosomes, endoplasmic reticulum. Protoplasm It contains nucleus and cytoplasm. Every cell has three major components 1- Plasma membrane (cell membrane – plasma lemma) 2- Cytoplasm 3- DNA (naked or covered with membrane)  Two basic Eukaryotic cell types of cells (Eu=true, karyon=nucleu (according to s) nucleus) Prokaryotic cell (pro=primary or primitive, karyon=nucleu s)  Compartment Nucleus 3 main s differences Organelles  COMPARISON BETWEEN EUKARYOTIC AND PROKARYOTIC CELLS Type of cells Eukaryotic cell Prokaryotic cell Nucleus Distinct nucleus with well Not-distinct in the form of nuclear formed nuclear zone (nucleoid) with no nuclear membrane membrane Organelles Double-membrane cell Only single-membrane cell organelles organelles as mesosomes with absence of (mitochondria, nucleus) double-membrane cell organelles and single-membrane (endoplasmic reticulum and Golgi cell organelles (Golgi apparatus are absent) apparatus, ER) Compartments Distinct compartments No distinct compartments found in Eukaryotic cell Under electron Diagram of the eukaryotic microscope cell Prokaryotic cell Under electron Diagram of the microscope prokaryotic cell  Structure of cell 1- Plasma membrane (Cell membrane)  Plasma membrane (Cell membrane) It is a limiting boundary which called plasma lemma. It is outermost in animal cells but it is internal to cell wall in plant cells It is flexible membrane as it can fold in (forming food vacuoles) or fold out (forming pseudopoda)  Proteins and lipids are main components of plasma membrane Structure of plasma The more accepted model is the fluid membrane mosaic model (1972) Fluid mosaic model It is proposed by Singer and Nicholson. Plasma membrane is composed of a phospholipid bilayer with embedded proteins. Each phospholipid molecule has 2 ends; outer head (hydrophilic = water attracting) and inner tail (hydrophobic = water repelling). What is the function of Cholesterol plays cholesterol in plasma a decisive role in the elasticity of membrane ? cell membranes  Proteins in plasma membrane Peripheral proteins (extrinsic Integral proteins (intrinsic proteins) on outer and inner proteins) which pass through lipid surfaces of lipid bilayer bilayer Proteins penetrate the lipid Proteins penetrate the lipid layer partially bilayer wholly  Glycolipids = carbohydrates + lipids Carbohydrates in plasma membrane Glycoproteins = carbohydrates + proteins  SUMMARY (Structure of plasma membrane) Phospholipid molecules Lipids Cholesterol Glycolipids Peripheral or extrinsic proteins Proteins Integral or intrinsic proteins Glycoproteins Carbohydrates Glycolipids Glycoproteins Plasma membrane (cell membrane) under electron microscope Functions of plasma lemma 1) The plasma membrane encloses the cell contents 2) It provides cell-shape 3) It allows the transport of certain substances into and out of the cell and prevent other substances (selective permeability)  Diffusion Transportatio n of small Osmosis molecules Transportation Active transport through plasma membrane Phagocytosis Transportatio Endocytosis n of large Pinocytosis (bulk) molecules Exocytosis  TRANSPORTATION OF SMALL MOLECULES (1) Diffusion (2) Osmosis Movement of small molecules from Movement of water molecules from higher higher concentration to lower concentration to lower concentration (with concentration (with concentration concentration gradient) without ATP through gradient) without ATP through semi- semi-permeable membrane permeable membrane Example: absorption of water Example: absorption of glucose Diffusion Osmosis  TRANSPORTATION OF SMALL MOLECULES (3) Active transport Movement of certain molecules (as ions) from lower concentration to higher concentration (against concentration gradient) with ATP through carrier protein  Active transport  TRANSPORTATION OF LARGE (BULK) MOLECULES (this type of transportation causes a change in the shape of plasma membrane) (1) Endocytosis (2) Exocytosis (taking the substance in) ( passing the substance out) a) Pinocytosis b) Phagocytosis (intake of fluid droplets as (intake of solid particles plasma membrane folds in as plasma membrane forming cup-like structure folds out forming cavity and sucks droplets) and engulfs the particles) TRANSPORTATION OF LARGE MOLECULES Pinocytosis Phagocytosis Exocytosis