Cells - The Basics PDF

 What are the characteristics of living things?  What is a Cell ? “A cell is defined as the smallest, basic unit of life that is responsible for all of life’s processes. Cells are the structural, functional, and biological units of all living beings. A...

 What are the characteristics of living things?  What is a Cell ? “A cell is defined as the smallest, basic unit of life that is responsible for all of life’s processes. Cells are the structural, functional, and biological units of all living beings. A cell can replicate itself independently. Hence, they are known as the building blocks of life.  Discovery of cell Robert Hooke discovered the cell using compound light microscope in 1665. What is saw was like small boxes so he called the “Cells”  1674-Antnie Von Leeuwenhoek ,observed first living cell in pond water.1678 he observed globulus in cell which is choloplast 1833-studying orchid cell,Robert brown discovered that plant cells have nuclus 1838-Matthias schleiden and theodor schwann proposed cell theory based on microscope ovservation of plants and animals  Size and shape of cell Plant cells are often larger than animal cells. Whereas the size normal range for an animal cell is between 10 and 30 micrometers (µm), plant cells can measure anywhere between 10 and 100 µm. 1 meter =1000 millimeters 1 millimeters = 1000 micrometers Animal cells tend to be round with an irregular shape. This is different from plant cells, which have a fixed rectangular or box-like shape. Size and shape of cell Size and shape of cell  Cell Theory First proposed by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838 Three aspects of cell theory: 1.Cells are the basic unit of structure in all living things (smallest unit of life) 2.All living organisms are composed of cells. 3.New cells are formed from pre-existing cells  Types of cell On the basis of organization of nucleus: 1. Prokaryotic Cell 2.Eukaryotic cell On the basis of number of cell: 1. Unicellular Cell 2.Multicellular cell comparison between the eukaryotic nucleus and the prokaryotic nucleus :  Prokaryotic Cell Pro-Before , Karyon-Nucleus Prokaryotic cells are single-celled microorganisms known to be the earliest on earth. Prokaryotes include Bacteria and Archaea. The photosynthetic prokaryotes include cyanobacteria that perform photosynthesis. A prokaryotic cell consists of a single membrane and therefore, all the reactions occur within the cytoplasm.  Prokaryotic Cell They lack a nuclear membrane. Mitochondria, Golgi bodies, chloroplast, and lysosomes are absent. The genetic material is present on a single chromosome. The histone proteins, are lacking in them. The cell wall is made up of carbohydrates and amino acids. The plasma membrane acts as the mitochondrial membrane carrying respiratory enzymes. They divide asexually  Prokaryotic Cell Structure Capsule– It is an outer protective covering found in the bacterial cells Cell Wall– It is the outermost layer of the cell which gives shape to the cell. Cytoplasm– The cytoplasm is mainly composed of enzymes, salts, cell organelles and is a gel-like component. Cell Membrane– This layer surrounds the cytoplasm and regulates the entry and exit of substances in the cells. Pili– These are hair-like outgrowths that attach to the surface of other bacterial cells.  Prokaryotic Cell Structure Flagella– These are long structures in the form of a whip, that help in the locomotion of a cell. Ribosomes– These are involved in protein synthesis. Plasmids– Plasmids are non-chromosomal DNA structures. These are not involved in reproduction. Nucleoid Region– It is the region in the cytoplasm where the genetic material is present.  Eukaryotic Cell Eu-True , Karyon-Nucleus Eukaryotic cells have a nucleus enclosed within the nuclear membrane and form large and complex organisms. Protozoa, fungi, plants, and animals all have eukaryotic cells. They are called Eukaryota. They can maintain different environments in a single cell that allows them to carry out various metabolic reactions. This helps them grow many times larger than the prokaryotic cells Eukaryotic cell: 1.Plant cell 2.Animal cell  Eukaryotic Cell Eukaryotic cells have the nucleus enclosed within the nuclear membrane. Mitochondria, Golgi bodies, chloroplast, and lysosomes are present. A cell wall is the outermost layer of the eukaryotic cell(Absent in animal cell). The cells divide by a process called mitosis. The nucleus contains a single, linear DNA, which carries all the genetic information  Eukaryotic Cell Structure Plasma Membrane The plasma membrane separates the cell from the outside environment. It comprises specific embedded proteins, which help in the exchange of substances in and out of the cell.Made up of phospholipid Cell Wall A cell wall is a rigid structure present outside the plant cell. It is, however, absent in animal cells.It is a protective layer that protects the cell from any injury or pathogen attacks.  Eukaryotic Cell Structure Endoplasmic Reticulum It is a network of small, tubular structures ER is of two types: 1.Rough Endoplasmic Reticulum contains ribosomes. 2.Smooth Endoplasmic Reticulum that lacks ribosomes and is therefore smooth. Nucleus The nucleoplasm enclosed within the nucleus contains DNA and proteins. The nuclear envelop consists of two layers- the outer membrane and the inner membrane. Both the membranes are permeable to ions, molecules, and RNA material. Ribosome production also takes place inside the nucleus.  Eukaryotic Cell Structure Golgi Apparatus It is made up of flat disc-shaped structures called cisternae. Ribosomes These are the main site for protein synthesis and are composed of proteins and ribonucleic acids. Mitochondria These are also known as “powerhouse of cells” because they produce energy(regulation of cell metabolism).It consists of an outer membrane and an inner membrane. The inner membrane is divided into folds called cristae.  Eukaryotic Cell Structure Lysosomes They are known as “suicidal bags” because they possess hydrolytic enzymes to digest protein, lipids, carbohydrates, and nucleic acids. Plastids These are double-membraned structures and are found only in plant cells. Three Types: 1.Chloroplast that contains chlorophyll and is involved in photosynthesis. 2.Chromoplast that contains a pigment called carotene that provides the plants yellow, red, or orange colours. 3.Leucoplasts that are colourless and store oil, fats, carbohydrates, or proteins.  A jelly-like substance, which consists of water, Holds the cell organells Cytoplasm dissolved nutrients and and Responsible for the waste products of the cell’s metabolic activities. cell.  Forms the skeletal A network of framework of the cell, membranous tubules, Endoplasmic Reticulum involved in the present within the detoxification, production cytoplasm of a cell. of lipids and proteins.  Membrane-bound, sac- It is mainly involved in like organelles, present Golgi apparatus secretion and intracellular within the cytoplasm of transport. the eukaryotic cells.  Helps in the digestion and A tiny, circular-shaped, removes wastes and single membrane-bound digests dead and Lysosomes organelles, filled with damaged cells. Therefore, digestive enzymes. it is also called as the “suicidal bags”.  An oval-shaped, The main site of cellular membrane-bound respiration and also Mitochondria organelle, also called as involved in storing energy the “Powerhouse of The in the form of ATP Cell”. molecules.  Nucleus The largest, double membrane-bound organelles, which contains all the cell’s genetic information. Controls the activity of the cell, helps in cell division and controls the hereditary characters.  Double membrane-bound organelles. There are 3 types of plastids: Helps in the process of 1.Leucoplast –Colourless photosynthesis , imparts colour Plastids plastids. to leaves, flowers, fruits and 2.Chromoplast–Blue, red, and stores starch, proteins and fats. yellow colour plastids. 3.Chloroplast – Green coloured plastids.  Composed of It plays a major role in centrioles and found organizing the Centrosomes only in the animal microtubule and cell cells. division.  Non-membrane organelles, found floating freely in the Involved in the synthesis of Ribosomes cell’s cytoplasm or embedded proteins. within the endoplasmic reticulum.  Provide shape and rigidity A membrane-bound, to the plant cell and help fluid-filled organelle Vacuoles in digestion, excretion, found within the and storage of cytoplasm. food,wastes.