Cytology Lecture 3 - Practical Biology - University of Al-Ameed PDF

University of Al-Ameed College of Medicine Department of anatomy and histology CYTOLOGY MSc. Zainab. R. Radhi WHAT IS A CELL ? • Cells are the basic Structural and functional unit of living organisms. • All cells come from preexisting cells. • living organisms are made up of one or more cells: ...

University of Al-Ameed College of Medicine Department of anatomy and histology CYTOLOGY MSc. Zainab. R. Radhi WHAT IS A CELL ? • Cells are the basic Structural and functional unit of living organisms. • All cells come from preexisting cells. • living organisms are made up of one or more cells: Unicellular Organisms An organism that is made up of only one cell is called as unicellular organism(e.g. bacteria and protozoans). euglena paramecium yeast Multicellular Organisms . An organism that is made up of more than one cell is called as multicellular organism. . human body is composed of about 100 trillion cells plants animals fungus divide the cell into three main parts : 1. plasma membrane 2. cytoplasm 3. Nucleus . A collection of cells that function together to perform the same activity is known as tissue. Masses of tissue work collectively to form an organ that performs specific functions in the body. . The functions of the human cell varies based on the type of cell and its location in the human body. The main organelles are as follows : . Nucleus Cell membrane . Endoplasmic reticulum . Golgi apparatus . Lysosomes . Mitochondria . Microfilaments and microtubules. Animal cell NUCLEUS The nucleus is the master control of the cell. It contains genes, collections of DNA, The DNA which is arranged into Chromosomes. Nucleolus: dark spot in the middle of the nucleus that helps make ribosomes. Function: holds the DNA Plant and animal cells. Cell Membrane: The cell membrane is the outer coating of the cell and contains the cytoplasm, substances within it and the organelle. It is a double-layered membrane composed of proteins and lipids. The cytoplasm : consists of all the cellular contents between the plasma membrane and the nucleus. Golgi Apparatus The Golgi apparatus: is a stacked collection of flat vesicles. Function: packages, modifies, and transports materials to different location inside/outside of the cell. Lysosomes Lysosomes are spherical bodies enclosed by a single membrane. They are produce by the Golgi apparatus. Lysosomes are not visible under a light microscope. function: break down food into particles the rest of the cell can use and to destroy old cell. Mitochondria These are the powerhouses of the cell and break down nutrients to yield energy. Endoplasmic Reticulum (ER) Function: synthesizes protein Rough: has ribosome, transport protein. Smooth: no ribosome , synthesizes lipids. Microfilaments and microtubules are rigid protein substances that form the internal skeleton of the cell known as the cytoskeleton .