STRUCTURE AND FUNCTION OF CELL PART 1.pptx

biology of cell and structure of cell

1. CELL- Part 1 Dr. Pranav Kulkarni Dept of Periodontology

2. CONTENTS PART - I HISTORY INTRODUCTION OF CELL CELL DIVERSITY COMPONENTS OF CELL CHARACTERISTICS OF CELL CLASSIFICATION PART - II CELL GROWTH CELL METABOLISM ENDOCYTOSIS CELL REPRODUCTION CELL JUNCTIONS CELLULAR ADAPTATIONS CELL INJURY.

3. HISTORY Anton van Leeuwenhoek (1675): was the first person to observe living cells. Matthias Schleiden (1838): concluded that all plants are composed of cells. Theodor Schwann (1839): concluded that all animals are composed of cells. Rudolph Virchow (1855): determined that cells come only from other cells. Robert Brown(1883) - provided the very first insights into the cell structure. Discovered nucleus.

4. INTRODUCTION “A cell is defined as the smallest, basic unit of life that is responsible for all of life’s processes.” Cell is the structural and functional unit of life . Cell – from latin “ cella ” means a small room, often referred to as the “building blocks of life”. All living things are composed of one or more cells. Cell is regarded as the basic unit of biological activity.

5. DIVERSITY OF CELLS Human body is composed of about 250 types of specialized cells. Cell diversity includes: - size - shape - internal organization

6. DIVERSITY Smallest cell in the world is Mycoplasma gallicepticum . The largest cell in the world is an ostrich's egg . Smallest cell in the human body is sperm cell . Largest cell in human body is egg cell . Longest cell in human body is neuron (nerve cell) which can be over a meter long. CELL SIZE Usually, the cells are cuboidal elongated or spherical . There are also some cells which are long and pointed on both the ends. Such cells exhibit spindle shape . Cells differ widely in shape. Most cells are roughly cuboidal or spherical. CELL SHAPE

7. DIVERSITY CELL SIZE CELL SHAPE

8. BASIC STRUCTURE OF CELL

9. BASIC STRUCTURE OF CELL

10. COMPONENTS OF CELLS Nucleus Cell Membrane Endoplasmic Reticulum Golgi Complex Mitochondrion Lyosomes Ribosomes Vacuoles Peroxizomes

11. The Nucleus The  nucleus  is a membrane-bound organelle that contains genetic material (DNA) of eukaryotic organisms.  Nucleus is present in all the eukaryotic cells. It controls all the cellular activities including reproduction of the cell. Nucleus contains DNA , the repository of genetic information. Information and control center of the cell. Site where almost all DNA replication and RNA synthesis takes place. Penetrated by several nuclear pores allowing large protein molecules to pass through

12. The nucleus consists of – Nuclear membrane - The nuclear membrane is double-layered porous structure having a 40–70 nm wide space called perinuclear cistern, which is continuous with the lumen of ER. Nucleoplasm - The nucleoplasm or the nuclear matrix is a gel-like ground substance containing a large quantity of genetic material in the form of DNA. Nucleolus - The nucleus may contain one or more rounded bodies called nucleoli . The nucleoli are the site of synthesis of ribosomal RNA. Nuclear chromatin – The main substance of the nucleus is comprised by the nuclear chromatin which is in the form of shorter pieces of thread-like structures called chromosomes .

13. FUNCTIONS OF NUCLEUS Controls all the activities of the cell. Transcription: Synthesis of RNA. Replication : Synthesis of new DNA. Sending information to the cytoplasm for protein synthesis. Formation of subunits of ribosomes . Storage of hereditary information in genes . Control of cell division .

14. Cell Membrane

15. Cell Membrane Outer layer of cell It is a membrane that envolopes the cell Allows nutrients into the cell and wastes outside of the cell Cell membranes mainly consist of Phospholipids - 25% Cholesterol - 13% Proteins - 25% - Integral proteins Peripheral proteins Carbohydrates - 3% - Glycolipids - Glycoproteins Cell Membrane

16. MEMBRANE LIPIDS The major classes of membrane lipids are: – Phospholipids – Glycolipids – Cholesterol They all are amphipathic molecules , i.e. they have both hydrophobic and hydrophilic ends. Membrane lipids spontaneously form bilayer in aqueous medium, burrying their hydrophobic tails and leaving their hydrophilic ends exposed to the water

17. MEMBRANE PROTEINS Proteins of the membrane are classified into two major categories: – Integral or intrinsic proteins or transmembrane proteins – Peripheral or extrinsic proteins . Integral proteins are either partially or totally immersed in the lipid bilayer. Peripheral proteins are attached to the surface of the lipid bilayer by electrostatic and hydrogen bonds.

18. MEMBRANE CARBOHYDRATES Membrane carbohydrate is not free. It occurs in combination with proteins or lipids in the form of glycoproteins or glycolipids . Most of the integral proteins are glycoproteins and about one-tenth of the membrane lipid molecules are glycolipids. Many of the carbohydrates act as receptor for hormones .

19. FUNCTIONS OF CELL MEMBRANE Protective - Protects cytoplasm and its organelles. Selective permeability - Allows selective substances to pass. Excretory - Metabolites and other waste products are excreted from the cell through the cell membrane. Maintains size and shape of the cell. Transport across cell membrane between the external and internal environment.

20. FLUID MOSAIC MODEL In 1972 , Singer and Nicolson postulated a theory of membrane structure called the fluid mosaic model, which is now widely accepted. According to this model,  membranes are made up of lipids, proteins and carbohydrates   Fluid mosaic model allows the membrane proteins to move around laterally in two dimensions and that they are free to diffuse from place to place within the plane of the bilayer. Whereas they cannot tumble from one side of the lipid bilayer to the other.

21. Endoplasmic Reticulum Transportation system of cell Rough ER- ribosome's attached Smooth ER- no ribosome’s Endoplasmic reticulum is the interconnected network of tubular and flat vesicular structures in the cytoplasm. Contains ribosomes on its surface hence the name rough endoplasmic reticulum Forms the link between nucleus and cell membrane Have large, parallel, flattened membranous sacs called “ cisternae ”.

22. The rough ER is characterized by the presence of – a number of ribosomes on its surface Transports proteins made by the ribosomes through the cisternae. Especially well developed in cells active in protein synthesis , e.g. Russell’s bodies of plasma cells ROUGH ENDOPLASMIC RETICULUM

23. SMOOTH ENDOPLASMIC RETICULUM Smooth ER is devoid of ribosomes on its surface. Site of lipid and steroid synthesis. Found in abundance with the leydig cells and cells of the adrenal cortex. The skeletal and cardiac muscles - smooth ER is modified - Sarcoplasmic reticulum which is involved in the release and sequestration of calcium ions during muscular contraction.

24. FUNCTIONS OF ENDOPLASMIC RETICULUM Biosynthesis of protein Site of the metabolism of certain drugs, toxic compounds and carcinogens

25. GOLGI APPARATUS

26. GOLGI APPARATUS Eukaryotic cells contains a unique cluster of membrane vesicles known as golgi apparatus. Discovered by Camillo Golgi in 1898. Situated near the nucleus and is continuous with the endoplasmic reticulum. Particularly well developed in exocrine glandular cells Consists of four or more membranous sacs .

27. FUNCTIONS OF GOLGI APPARATUS Synthesis of carbohydrates and complex proteins . Packaging of proteins synthesized in the rough ER into vesicles. Site of formation of lysosomal enzymes . Transport of the material to the other parts of cell or to the cell surface membrane and secretion. Glycosylation of proteins to form glycoproteins.

28. Mitochondria

29. Mitochondria Power house of the cell Provides the energy the cell needs to move, divide, etc. Mitochondria are called “ Power House ” of the cell since they convert energy to form ATP that can be used by cell. A mitochondrion is a double-membrane organelle The outer membrane forms a smooth envelope . The inner membrane is folded to form cristae , which gives it a large surface area and are the site of oxidative phosphorylation . Present at intramembranous sites of maximum energy requirement.

30. The space within the inner membrane is called the mitochondrial matrix . Mitochondria contain dna ( mtdna ) which encodes a few polypeptides involved in oxidative phosphorylation. Functions of mitochondria : Metabolism of carbohydrate, lipids and amino acid (citric acid cycle, beta-oxidation Atp , the energy currency generated in mitochondria is exported to all parts of the cell to provide energy for cellular work .

31. LYSOSOMES Lysosomes are rounded to oval membrane-bound organelles containing powerful lysosomal digestive (hydrolytic) enzymes . Formed by the golgi apparatus. Have the thickest covering membrane to prevent the enclosed hydrolytic enzymes from coming in contact with other substances.

32. They have more than 40 different hydrolytic enzymes – lyzozymes . There are three forms of lysosomes Primary lysosomes or storage vacuoles - formed from the various hydrolytic enzymes synthesized by rough ER and packaged in the Golgi apparatus Secondary lysosomes or autophagic vacuoles - formed by fusion of primary lysosomes with parts of damaged or worn-out cell components Residual bodies - undigestible materials in the lysosomes

33. The Lysosome This bacterium about to be eaten by an immune system cell will spend the last minutes of its existence within a lysosome.

34. FUNCTIONS OF LYSOSOMES Digestive functions - Lysozymes present in lysosomes digest proteins, carbohydrates, lipids and nucleic acids. Destruction of bacteria and other foreign bodies. Removal of excessive secretory products in the cells of the glands. Removal of unwanted cells in embryo.

35. CHARACTERISTICS OF CELL Cells provide structure and support to the body of an organism. The cell interior is organised into different individual organelles surrounded by a separate membrane. The nucleus (major organelle) holds genetic information necessary for reproduction and cell growth. Every cell has one nucleus and membrane-bound organelles in the cytoplasm. Mitochondria, a double membrane-bound organelle is mainly responsible for the energy transactions vital for the survival of the cell. Lysosomes digest unwanted materials in the cell. Endoplasmic reticulum plays a significant role in the internal organisation of the cell by synthesising selective molecules and processing, directing and sorting them to their appropriate locations.

36. CLASSIFICATION OF CELLS Based on Internal Structure A Prokaryotic cell A Eukaryotic cell A prokaryotic cell A eukaryotic cell

37. CHARACTERISTICS PROKARYOTIC CELL EUKARYOTIC CELL SIZE Small(1-10mm) Large(10-100mm) 2. CELL MEMBRANE Enveloped by a rigid cell wall Enveloped by a flexible plasma membrane 3. SUB-CELLULAR ORGANELLES Absent Distinct organelles found( eg:mitochondria , nucleus, lysosomes) 4.NUCLEUS Not well defined; DNA is found as nucleoid, histones are absent Well defined; surrounded by a membrane ;DNA associated with histones. 5. ENERGY METABOLISM Mitochondria absent; enzymes of energy metabolism are bound to membrane enzymes of energy metabolism are located in mitochondria 6. CELL DIVISION Binary fission. Mitosis/meiosis. 7. CYTOPLASM Organelles & cytoskeleton absent Contains Organelles & cytoskeleton

38. PEROXISOMES Spherical structures enclosed by a single layer of unit membrane . Resemble the lysosomes in their appearance, but they differ both in function and in their synthesis Predominantly present in hepatocytes and tubular epithelial cells Functions The peroxisomes are involved in the detoxification of peroxide . Peroxisomes are also capable of carrying out β-oxidation of fatty acid .

39. CYTOSKELETON The cytoskeleton is a complex network of fibres that maintains the structure of the cell and allows it to change shape and move . Made up of microtubules (hollow tubes) and microfilaments (threads made up of actin). The cytoplasmic filaments are of three types – Microtubule- form the transport system of the cells Microfilaments Intermediate filaments- mechanically integrate the cell organelles within the cytoplasm

40. CYTOSOL The cellular matrix is collectively referred to as cytosol. Cytosol is basically a compartment containing several enzymes, metabolite and salts in an aqueous gel like medium. Cytoplasm actually contains a complex network of protein filaments. It is an aqueous substance containing a variety of cell organelles and other structures.

41. REFERENCES Essentials of Biochemistry Pankaja Naik Textbook of Microbiology 5 th edition Dr. C.P. Baveja Textbook of Human Physiology for Dental Students Indu Khurana 2nd Molecular Biology of the Cell. 4th edition . Textbook of Medical Physiology, Guyton.

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