Cytology PDF

Cytology Comparison between prok. And Euk.   Cytology Branch of Biology and medicine concerned with structure and function of the cells All living organisms are made up of cells Organisms Unicellular Multicellular...

Cytology Comparison between prok. And Euk.   Cytology Branch of Biology and medicine concerned with structure and function of the cells All living organisms are made up of cells Organisms Unicellular Multicellular Organism organism  The basic unit „Building block “ of multicellular organism is the cell. In unicellular organism, the single cell is a complete organism that preform all function   Level of organization The biological levels of organization of living things arranged from the simplest to most complex are: organelle, cells, tissues, organs, systems, organisms   Chemical structure of the Cell Cell Water Inorganic materials Represent about 70% of cell weight Organic materials Act as solvent where all biochemical Ca2+,(PO4)3-,Na1+,and reaction occurs Mg2+ Carbohydrates Lipids Proteins Nucleic Acid Other mineral like Co2+,Cu2+,Cu3+,I1-,Mn2+,and Zn2+   Carbohydrates Have the general formula (CnH2nOn), where n is integer number 3-7   Carbohydrates (CONT.) They linked together by glycosidic linkage They may bond to protein forming glycoproteins They may bond to lipid forming glycolipid   Lipids Includes fats, phospholipids, and steroids Are the major structural component of Cells Simplest unit are fatty acid Fatty Acids Long hydrocarbon chain Carboxylic group Hydrophilic (Water soluble) Hydrophobic (water insoluble) Not reactive chemically Chemically Active   Proteins Major structural components of cell The basic structural unit are amino acid Amino acid are chemically varied, but all have a carboxylic group and amino group Linked together by peptide bond A bout 20 amino acid are naturally occurring   Nucleic Acid Genetic material of the body Includes Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA). The building blocks are Nucleotides  Nitrogenous Base Purines Pyrimidines (Double heterocyclic (single heterocyclic Ring) Ring) Cytosine Thymine Uracil Adenine Guanine (C) (A) (G) (T) (U)   Animal Cell Structure All Cells are enclosed by the plasma membrane which forms a selective barrier allowing: 1. Nutrients to enter the cells. 2. Waste products to leave. The interior of cell is organized into many organelles ” specialized compartments surrounded by a separate membrane” e.g. Nucleus, mitochondria, lysosomes, endoplasmic reticulum, Golgi apparatus All these organelles swim in the cytoplasm “ Cytosol”  Plasma Membrane: A thin membrane of a bout 0.005 µm (5nm) thickness. Usually surrounds every living cells and delimiting the cell from the environment around it.  Function of Plasma Membrane: 1. Act as a barrier by keeping the constituents of the cell in and unwanted substances out. 2. Gate which allow the transport of nutrients and waste products in and out of the cells  Chemical Composition of Plasma Membrane: Plasma membrane Lipids Proteins Peripheral Integral Sterols Phospholipids “Extrinsic” “Intrinsic” “ Cholesterol” proteins proteins  Phospholipids bilayer (Amphiphilic character): Have a glycerol head and two hydrocarbones tails. The head is attached to a phosphoryl group with a negative charge. The tails are hydrophobic “ repelled by water and dissolve in organic solvents”.  Sterols: Have a complex hydrocarbon ring structure that represents the lipid soluble part. And hydroxyl group part which represent the water soluble part.  Membrane proteins are of two types: 1. Peripheral “ Extrinsic” Proteins: Loosely attached by ionic bonds or calcium bridges to the electrically charged phosphoryl surface of the lipid bilayer. They are also attached to the intrinsic proteins. 2. Integral “ Intrinsic” Proteins : Firmly attached within the lipid bilayer. Many of them contain from 20-24 membrane-long amino acid sequences that may extend through and bind to the fatty acid internal region of the membrane. Many intrinsic proteins bear an outer surface of side chains of complex sugars which is involved in cell-to-cell recognitions.  Transport Across The Plasma membrane: Transport cross the plasma membrane Permeation Transport of Facilitated Diffusion Active Transport “ simple Diffusion” Particles Channel Carrier mediated mediated Diffusion Diffusion 1- Permeation “ Simple Diffusion”: Is the diffusion of substances in solution through a barrier. Lipid soluble and small molecules can permeate through the membrane. Large, water soluble molecules and electrically charged ions are repelled by the lipid bilayer. Proteins and sugar polymers do not permeate at all. e.g. Oxygen and alcohols diffuse through most membranes.  2- Facilitated Diffusion A- Membranes Channels: Also known as channel mediated diffusion. Electrically charged ions have a special holes “ channels” in the plasma membrane which allow specific ions and small molecules to diffuse through the lipid bilayer. These channels are integral proteins that cross the plasma membrane forming a hole or pore. Some channels open and close spontaneously while other are gated and operate by chemical action of signaling substance such as Ca2+, acetylcholine, glycine, or change in the electrical action potential. e.g. Na +, K +, Ca2+ channels.  Facilitated Diffusion by Transporter Proteins: Also termed carrier mediated diffusion. Some molecules like sugars and amino acids are too large to fit through the open channels. These vital substances move a cross the membrane by the action of membrane transporters. Transporters proteins are intrinsic proteins that have a highly specific binding site to which the moving substance bind. Substance traveling down their concentration gradient through the membrane and does not require energy “ Passive transport” e.g. Glucose and bicarbonate transporter  Active Transport: Molecules moving against their concentration gradient by using specific pumps. It requires the cell to spend energy from the hydrolysis of Adenosine triphosphate (ATP)  Transport of Particles: Proteins and nucleic acid can not cross the plasma membrane by simple diffusion or any other routes. These large molecules are internalized to cell by endocytosis and externalized outside the cell by exocytosis.  Ribosomes: Particles that synthesize proteins from amino acids Composed of 4 RNA molecules “rRNA” and 50 proteins assembled into a large and small subunit Ribosomes are either free or bounded to endoplasmic reticulum “ER”  Function of Ribosomes: Lysosomal enzymes and proteins for ER, Golgi, and plasma membranes and proteins to be secreted from the cell are synthesized on ribosomes.  Endoplasmic Reticulum “ER”: Is a system of membranous vesicles extending through the cytoplasm. Endoplasmic Reticulum “ER” Smooth Endoplasmic Rough Endoplasmic Reticulum “SER” Reticulum ”RER”  Rough Endoplasmic Reticulum “RER”: Have ribosomes on their surface. A series of connected vesicles and flattened sacs.  Function of RER: RER usually found in the secretory cells and is responsible for the secretion that come out of the cell e.g. : In Liver cell secreting Albumin In salivary and pancreatic gland secreting digestive enzymes In mammary gland secreting milk proteins In cartilage cells secreting collagen and proteoglycans.  Continue function of RER: Glycosylation usually occurs in the lumen of RER. Glycosylation is the process of adding oligosaccharide to the protein to form a glycoprotein.  Smooth Endoplasmic Reticulum “SER: Network of fine tubular membrane vesicles. Lack ribosomes  Function of SER: Phospholipid and cholesterol synthesis. Detoxification in liver, SER have an enzyme called cytochrome P450 which catalyze breakdown of carcinogens and organic molecule. In adrenal and gonadal cells, a stage of cholesterol modification to steroid hormones done by SER. In muscle cell, SER termed as sarcoplasmic reticulum where calcium ions are stored.  Golgi Apparatus (GA) : Discovered by Camillo Golgi in 1898. Structure composed of 5-8 flattened, disk-shaped, membranous cisternae “ vesicles”, arranged in stack. Golgi is structurally polarized “ having two faces”: 1. Cis- Face : facing nucleus and where the transport vesicle fuses 2. Trans-face: facing the plasma membrane and where the secretory vesicle evolve.  Function of Golgi Apparatus : Golgi is the principal director of protein traffic in the cell. Secretory, lysosomal, plasma membrane proteins and glycoproteins pass through Golgi during their maturation. Removal of mannose residues and adding other sugar to galactose and sialic acid (oligosaccharides) are done within Golgi lumen. Activation of the secretory protein by cutting of some amino acid residues are done within Golgi lumen.  Lysosomes: Bodies which bounded by a single phospholipid bilayer membrane. Vary in size and probably originate by budding from Golgi membranes. Lysosomes contain digestive enzyme that hydrolyze proteins, nucleic acids, lipids, glycolipids, and glycoproteins.  Function of Lysosomes: Lysosomal enzymes fuses with the vacuoles containing worn- out organelles and material from inside or outside the cell to be digested.  Mitochondria: The power houses of the cells Long and slender organelles which can appear as oval or bean shaped Mitochondrion has two membrane: 1. Outer membrane: smooth and have lipid and proteins. 2. Inner membrane : which has a large numbers of infoldings , or cristae. Mitochondria have a matrix “ mixture of enzymes and proteins and mitochondrial DNA.  Function of Mitochondria: The most important function of the mitochondria is to produce energy. The simpler molecules of nutrition are sent to the mitochondria to be processed and to produce charged molecules. These charged molecules combine with oxygen and produce ATP molecules. This process is known as oxidative phosphorylation. The mitochondria also help in building certain parts of blood and hormones like testosterone and estrogen. The liver cells mitochondria have enzymes that detoxify ammonia. The mitochondria also play important role in the process of apoptosis or programmed cell death.  Cytoskeleton: A fibrous network formed by different types of long protein filaments in the eukaryotic cell “ cells have a true nucleus” There are three major types of cytoskeletal filaments: 1. Microfilament “ Actin filaments” 2. Microtubules 3. Intermediate filaments  Function of Cytoskeleton: it creates a framework that organize other cell constituents and maintains the shape of the cell.  Centrosomes: A spherical structure found near to the nucleus of animal , fungus, and algal cells. Each centrosomes contain a pair of centrioles  Function of Centrosomes: During cell division, centrosomes divides into two centrosomes, then each centrosomes travel to the opposite pole of the cell. Centrioles composed of array of microtubules from it the spindles fibers extend toward the nucleus to help chromosomes to separate. Nucleus:  Nucleus: It is the control center of the cell that contain the genetic materials the transmitted to the offspring. Each nucleus composed of the following: 1. Nuclear envelope: two layered membrane. 2. Nuclear pores: present around the circumference of the nuclear membrane and it allow the exchange of cellular material between nucleus and cytoplasm. 3. Nucleoplasm: cellular material enclosed by the nuclear envelope. 4. Nucleolus: it is the site for RNA synthesis and storage. 5. Strands of DNA wrapped a round proteins forming a string of beads  Chromosomes: It is an aggregates of DNA and proteins Chromosomal proteins are termed histones Genes are found on a particular location of chromosomes. Most organisms have two sets of paired chromosomes “ diploid number”, with one set “ haploid number” inherited from each parent. During most of the duration of the cell cycle, a chromosome consists of one long double-helix DNA molecule (with associated proteins). During S phase, the chromosome gets replicated, resulting in an X-shaped structure called a metaphase chromosome. Both the original and the newly copied DNA are now called chromatids.