Introduction to Cell Structure (PDF)

Republic of Iraq Ministry of Higher Education and Stage:S1 Scientific Research Module: Medical Biology Wasit Universty College of medicine Lecture Title: Introduction Cell – Structur...

Republic of Iraq Ministry of Higher Education and Stage:S1 Scientific Research Module: Medical Biology Wasit Universty College of medicine Lecture Title: Introduction Cell – Structure and Function Asst Prof : Dr –Dhamyaa K. Kadhim  What is Cell? Cell is the basic Structural and functional unit of living organisms. In other words, cells make up living things and carry out activities that keep a living thing alive.  Cell 1 All known living things are made up of one or more cells. Theory Cell theory is a collection of ideas and conclusions 2 All living cells arise from cells by division. pre-existing from many different scientists over time that describes cells and how cells operate. 3 The cell is the basic unit of structure and function in all living organisms.  Cell Theory Timeline 1674 Anton Van Leeuwenhoek Observed living cell 1665 1883 Robert Hooke Robert Brown Discovered cell Discovered nucleus  Unicellular Organisms An organism that is made up of only one cell is called as unicellular organism. Euglena Paramecium Yeast  Multicellular Organisms An organism that is made up of more than one cell is called as multicellular organism. Plants Animals Fungus Size of Smallest cell Cells Mycoplasma Size: 0.1 µm Cells vary in size. Most cells are very small (microscopic), some may be very large (macroscopic). Largest cell The unit used to measure size of a Ostrich egg cell is micrometer. Size: 18 cm 1 µm = 1/1000 millimeter  Size of Cells in Humans Smallest cell Largest cell Longest cell Sperm cell Ovum cell Nerve cell Size: 5 µm Size: 120 µm Size: 1 m  Human RBCs are circular Shape of biconcave for easy passage through human capillaries. Cells Cells vary in shape. Nerve cells are branched to conduct impulses from one Variation depends mainly upon the point to another. function of cells. Some cells like Euglena and Amoeba can change their shape, but most cells have a fixed shape. Human WBCs can change their shape to engulf the microorganisms that enter the body. Structure Compound Of Cell microscope Magnification 2000X The detailed structure of a cell has been studied under compound microscope and electron microscope. Certain structures can be seen only under an electron microscope. Electron The structure of a cell as seen under an microscope electron microscope is called ultrastructure. Magnification 500000X  Animal Cell 12 11 1 10 1. Nucleus 2. Golgi body 9 3. Vesicle 4. Plasma membrane 8 5. Mitochondria 6. Cytoskeleton 7. Centriole 8. Lysosome 2 9. Cytoplasm 7 3 10. Rough endoplasmic reticulum 11. Smooth endoplasmic reticulum 4 12. Nucleolus 6 5 Plant Cell 12 11 1 10 1. Nucleus 2. Golgi body 9 3. Vesicle 2 4. Lysosome 5. Plasma membrane 8 3 6. Mitochondria 7. Chloroplast 8. Cell wall 4 9. Vacuole 10. Smooth endoplasmic reticulum 5 11. Rough endoplasmic reticulum 7 12. Nucleolus 6 Bacterial 9 10 Cell 8 1. Capsule 7 2. Cell wall 3. Plasma membrane 6 1 4. Cytoplasm 5. Flagellum 6. Food granule 2 7. Plasmid (DNA) 3 8. Ribosomes 4 5 9. Nucleoid 10. Pili Structure 1. Plasma Membrane 2. Nucleus Of Cell 3. Cytoplasm A. Cytosol B. Cell Organelles If we study a cell under a microscope, we would come across three features in almost a) Endoplasmic reticulum every cell: plasma membrane, nucleus and b) Golgi body cytoplasm. c) Lysosomes All activities inside the cell and interactions d) Vacuoles of the cell with its environment are possible e) Mitochondria due to these features. f) Plastids g) Centrosome h) Cytoskeleton Plasma Membrane Extremely delicate, thin , elastic, living and semi-permeable membrane Made up of two layers of lipid molecules in Carbohydrates which protein molecules are floating Thickness varies from 75-110 A˚ Can be observed under an electron microscope only Functions: Maintains shape & size of the cell Protects internal contents of the cell Regulates entry and exit of substances in and Proteins out of the cell Lipids Maintains homeostasis  Nucleus Dense spherical body located near the centre of the cell Nucleus Diameter varies from 10-25 µm Present in all the cells except red blood cells and sieve tube cells Well developed in plant and animal cells Undeveloped in bacteria and blue-green algae (cyanobacteria) Most of the cells are uninucleated (having only one nucleus) Few types of cells have more than one nucleus (skeletal muscle cells)  Nucleus Nucleus has a double layered covering called Nuclear nuclear membrane Nucleolus pores Nuclear membrane has pores of diameter about 80-100 nm Colourless dense sap present inside the nucleus known as nucleoplasm Nucleoplasm contains round shaped nucleolus and network of chromatin fibres Fibres are composed of deoxyribonucleic acid (DNA) and protein histone Chromatin These fibres condense to form chromosomes during cell division Nuclear envelope Nucleoplasm  Nucleus Gene DNA Chromosomes contain stretches of DNA called genes Genes transfer the hereditary information from one generation to the next Chromatin Functions: Control all the cell activities like metabolism, protein synthesis, growth and cell division Histone Nucleolus synthesizes ribonucleic acid (RNA) to constitute ribosomes Store hereditary information in genes Chromatin fibre Chromosome Cytoplasm Jelly-like material formed by 80 % of water Present between the plasma membrane and the Organelles nucleus Contains a clear liquid portion called cytosol and various particles Particles are proteins, carbohydrates, nucleic acids, lipids and inorganic ions Also contains many organelles with distinct structure and function Some of these organelles are visible only under an electron microscope Granular and dense in animal cells and thin in plant cells Cytoplasm  Endoplasmic Network of tubular and vesicular structures Reticulum which are interconnected with one another Some parts are connected to the nuclear membrane, while others are connected to the cell membrane Two types: smooth(lacks ribosomes) and rough(studded with ribosomes) Functions: Gives internal support to the cytoplasm RER synthesize secretory proteins and membrane proteins Rough ER SER synthesize lipids for cell membrane Smooth ER In liver cells SER detoxify drugs & poisons In muscle cells SER store calcium ions Ribosomes  Golgi body Discovered by Camillo Golgi Formed by stacks of 5-8 membranous sacs Incoming Sacs are usually flattened and are called the Cis face transport cisternae Cisternae vesicle Has two ends: cis face situated near the Lumen endoplasmic reticulum and trans face situated near the cell membrane Functions: Modifies, sorts and packs materials synthesized in the cell Delivers synthesized materials to various targets inside the cell and outside the cell Outgoing Produces vacuoles and secretory vesicles Newly Trans face forming transport Forms plasma membrane and lysosomes vesicle vesicle  Nucleus Smooth ER Lysosomes Golgi Body At Work Rough ER Golgi body Plasma Vesicles membrane  Lysosomes Small, spherical, single membrane sac Found throughout the cytoplasm Filled with hydrolytic enzymes Hydrolytic enzymes Membrane Occur in most animal cells and in few type of plant cells Functions: Help in digesting of large molecules Protect cell by destroying foreign invaders like bacteria and viruses Degradation of worn out organelles In dead cells perform autolysis Vacuoles Single membrane sac filled with liquid or sap (water, sugar and ions) In animal cells, vacuoles are temporary, small in size and few in number Tonoplast In plant cells, vacuoles are large and more in number May be contractile or non-contractile Functions: Store various substances including waste products Maintain osmotic pressure of the cell Vacuole Store food particles in amoeba cells Provide turgidity and rigidity to plant cells  Mitochondria Small, rod shaped organelles bounded by two membranes - inner and outer Outer membrane is smooth and encloses the contents Ribosomes of mitochondria Matrix Inner membrane is folded in the form of shelf like inward projections called cristae Cristae Inner cavity is filled with matrix which contains many enzymes Contain their own DNA which are responsible for many enzymatic actions DNA Functions: Synthesize energy rich compound ATP Outer membrane ATP molecules provide energy for the vital Inner membrane activities of living cells Mitochondrial Diseases  Centrosome Centrosome is the membrane bound organelle Centrosome present near the nucleus matrix Consists of two structures called centrioles Centrioles are hollow, cylindrical structures made of Microtubules microtubules Centrioles are arranged at right angles to each other Functions: Centrioles Form spindle fibres which help in the movement of chromosomes during cell division Help in the formation of cilia and flagella  Cytoskeleton Formed by microtubules and microfilaments Cell membrane Microtubules are hollow tubules made up of protein called tubulin Microfilaments are rod shaped thin filaments made up of protein called actin Functions: Determine the shape of the cell Give structural strength to the cell Responsible for cellular movements Microtubules Microfilaments Prokaryotic cell Eukaryotic cell 1. Nucleus is undeveloped 1. Nucleus is well developed 2. Only one chromosome is present 2. More than one chromosomes are present 3. Membrane bound organelles are absent 3. Membrane bound organelles are present 4. Size ranges from 0.5-5 µm 4. Size ranges from 5-100 µm 5. Examples: Bacteria and blue green algae 5. Examples: All other organisms Animal cell Plant cell 1. Generally small in size 1. Generally large in size 2. Cell wall is absent 2. Cell wall is present 3. Plastids are absent 3. Plastids are present 4. Vacuoles are smaller in size 4. Vacuoles are larger in size and less in number and more in number 5. Centrioles are present 5. Centrioles are absent THANK YOU...