Cell Theory and Discovery

Cell Theory

• Cell theory states that living organisms consist of cells.
• Cells are the structural and organizational units of organisms.
• Cells arise from pre-existing cells.
• Viruses are non-cellular, disagreeing with the first tenet that life consists of cells.

History of Cell Discovery

• Advancements in microscopes led to cell discovery in the 17th century, led by Robert Hooke.
• The scientific study of cells is known as cell biology.
• In 1839, cell theory was formulated, credited to Matthias Schleiden and Theodor Schwann; Rudolf Virchow also contributed.
• The independent discovery of cells was important to abandon spontaneous generation.

Microscopes

• Romans made glass, noticing magnification in the 1st century BC.
• Salvino D'Armate made lenses for one eye in Italy, 12th century.
• Compound microscopes (objective and eyepiece) appeared in Europe, around 1620, for higher magnification.
• Robert Hooke used a microscope with two convex lenses in 1665 for observations in Micrographia.
• Anton van Leeuwenhoek, a draper, made a simple microscope using a small glass sphere with 270x magnification in the 1600s.
• There was little microscope technology process after Leeuwenhoek until Carl Zeiss made lens changes in the 1850s.
• The optical quality was improved in the 1880s when Otto Schott and Ernst Abbe were hired, after Carl Zeiss made changes.
• Optical microscopes are limited to objects the size of a wavelength of visible light or larger.
• Electron microscopes in the 1920s allowed sub-optical wavelength object viewing.

Robert Hooke and "Cells"

• Robert Hooke discovered cells in 1665, and wrote about it in Micrographia, giving 60 'observations' in detail.
• "Cells" were first observed in thin slices of bottle cork under a compound microscope.
• Hooke named the pores "cells" after the Latin word 'Cella' (small room) or 'Cellulae' (six-sided cell of a honeycomb).
• Hooke did not know their true structure or function of cells; he saw empty cell walls of plant tissues, and concluded they weren't alive.
• There was no nucleus nor organelles indicated, and thus Hooke wasn't able to disprove Aristotelian theory that spontaneous generation was the cause.

Anton van Leeuwenhoek

• Anton van Leeuwenhoek observed cells with an improved microscope, magnifying objects 270x.
• Leeuwenhoek discovered motile objects, stating motility is a quality of life in a letter to The Royal Society in 1676.
• He used the name “animalcules” for microorganisms.
• Also identified bacteria, red blood cells, and sperm cells.
• Discovered the fertilization process requires sperm entry to the egg, ending the theory of spontaneous generation.

Further Historical Context

• Animal cells were recognized later because fragility made samples difficult to prepare.
• Henri Dutrochet connected the fundamental unit of life to cellular structure, indicating it was not only structural and organizational element.
• Karl Rudolphi and J.H.F. Link proved cells had independent cell walls in 1804, disproving they shared walls.

Credit for Cell Theory

• Theodor Schwann and Matthias Jakob Schleiden are credited for developing cell theory while Rudolf Virchow also contributed.
• In 1839, Schleiden suggested plant parts were made of cells or cell products, forming via crystallization.
• Theodor Schwann stated, in 1839, both plants and animals are composed of cells or cell product.
• Two of the three tenets of the theory were postulated from these conclusions.

Tenets of Credit for Cell Theory

• All living organisms are composed of one or more cells.
• Robert Remak, Rudolf Virchow, and Albert Kolliker discredited Schleiden's free cell formation theory in the 1850s.
• Rudolf Virchow added "Omnis cellula e cellula" (all cells arise only from pre-existing cells) to cell theory in 1855.
• The idea of cells arising from pre-existing cells was proposed by Robert Remak, whom Virchow might have plagiarized as the third tenet.
• Remak published how new animal cells were made via binary fission in 1852.

Modern Interpretation of Cell Theory

• All known living things are made up of one or more cells
• All living cells arise from pre-existing cells by division
• The cell is the fundamental unit of structure and function in all living organisms
• The activity of an organism depends on the total activity of independent cells
• Energy flow (metabolism and biochemistry) occurs within cells
• Cells contain DNA in the chromosome and RNA in the cell nucleus and cytoplasm
• All cells are basically the same in chemical composition in organisms of similar species.

Modern Version of Cell Theory

• Energy flow occurs within cells.
• Heredity information (DNA) is passed on from cell to cell.
• All cells have the same basic chemical composition.
• Viruses are not cells as they lack a plasma membrane and driving metabolic force.
• Viral genes express their genetic program of reproduction using the host organism's machinery and raw materials.
• Outside the host cell, a virus is inert.

Protoplasmic Theory

• Paramecium and amoeba divide by binary fission.
• Protozoans contain mass of indivisible cell filled with multi-nucleus and inner fluid (sarcode), identified by Felix Dujardin in 1835.
• Max Schultze propounded the protoplasm theory in 1861.
• H. von Mohl explained cell division in animal embryos.
• Purkinje named embryonic cell contents as protoplasm which applied to both animals and plants.

Main Points for Protoplasmic Theory

• Plants and animals are formed from a living matter known as protoplasm.
• Cells are accumulation of living matter or protoplasm enclosed within limited space.
• Cell protoplasm is composed of cytoplasm and nucleoplasm.
• Cytoplasm is the fluid filled part of protoplasm outside the nucleus; nucleoplasm is the fluid within.

Prokaryotic Cells

• Prokaryotic cells are simplest, smallest, and most primitive forms of cells.
• Most are unicellular organisms, bacteria and blue-green algae, enclosed by a cell membrane.
• Some also have a cell wall known as a capsule.
• Circular DNA material present, without membrane bound organelles without definite location in the cell.

More Detail for Prokaryotic Cells

• Ribosomes and RNA are not membrane bound floating in the cytoplasm.
• Exhibit an osmotic pressure.
• Exchanges gas with the outside via the cell membrane.
• Colonies (bacteria) mostly exist in diploid, tetra, staphy, and strepto-forms.
• Monoform is a single living cell e.g monococcus.
• Diploid is the attachment of two cells that have partially divided e.g. diplococcus.
• Tetracoccus features four partially attached cells that live separately.
• Staphy- cells are clustered but independent e.g. staphylococcus.
• Strepto- cells are chained but live differently e.g. streptococcus.

Characteristics

• No definite nucleus, meaning they lack membrane-bound nuclear materials
• Genetic materials (DNA/RNA) are found exposed in the cytosol , without definite location
• Contain single chromosome consists of double-stranded circular DNA
• Chromosomes lack histones, they are loosely situated in the cytosol
• Lack vital membrane bound organelles like the mitochondria, golgi-apparatus, ER, plastid etc
• Cells are smaller in size compared to cells of eukaryotic organisms

Eukaryotic Cells

• Eukaryotic cells are well-organized cells, with a defined nucleus, whose organelles are enclosed in the inner membrane.
• Eukaryotic cells comprise of higher plants and animals, fungi and protozoans.
• Organisms can be unicellular e.g; certain fungi (yeast), protozoans (amoeba, euglena, paramecium) or multicellular organisms.
• Characterized and composed of plasma membrane, cytoplasm and its embedded membrane-bound organelles.
• Organelles (mitochondria, Golgi bodies, endoplasmic reticulum, ribosomes, microtubules, lysomomes, nucleus etc) are surrounded by internal semi-permeable membrane.
• Nucleus and interior nucleolus are separated from the cytoplasm and nucleoplasm by perforated nuclear membrane.
• Have a nucleus that controls the workings of the cell because it contains the genes.
• Both animals and plants have eukaryotic cells

Eukaryotic Details

• Eukaryotic cells are large compared to prokaryotic as a result of organelles not found in prokaryotic cells.
• Varying cell sizes are sometimes visible to the naked eye (e.g. hen egg, ostrich) while others need a microscope.
• Unicellular cells (e.g. Amoeba, Euglena, paramecium) are larger than multicellular cells; organelles exert more osmotic pressure.
• Amoeba cells are 1000μm, Diatom is 200μm, unicellular algae called acetabularia can be up to 10cm.
• Human cells range from about 20 to 30μm while red blood cells are around 8μm
• The largest plant cells are fibre cells that can be over 100cm.
• Cell shape is based on functions and environmental adaptations, as multicellular cells face internal and external functions
• Plant cells are rigid due to cellulose cell wall, microtubules, and microfilaments.
• Animal cells are flexible and spherical.
• Microscopic unicellular organisms shape represent rectangular as bacterial, while plants are rectangular and animals are animal takes oval, cellular organelles are represented as bacteria, while animal cells feature membrane-bound organelles.
• The ratio of a cell's volume to surface area calculates its depth.
• Increased cell volume means less surface area in contact with the environment to slow down the rate of exchange of materials.
• Cell volume to surface area must be limited for efficient function
• Unicellular organism cells divide into daughter cells via binary fission when the limit range is passed

Cell Number

• Organisms can consist of a simple cell or multiple cells.
• Each species differs in cell number, hence, affecting height and size.
• The larger the organism, the more cells, for example, an elephant compared to the cell count of a goat is far denser.

Eukaryotic Structures in Animal and Plant Cells

• Cell Wall: Contains cellulose fibrils for support and protection, exclusively in plant cells.
• The plasma membrane consists of a phospholipid bilayer regulates the entrance and exit of molecules
• Nucleus: Storage is for genetic information; synthesis of DNA and RNA
• Nucleolus: A concentrated area of chromatin, RNA, and proteins; forms ribosomal subunits.
• Ribosomes: Protein and RNA protein synthesis.
• Membranous flattened channels and tubular canals synthesize other subtances and is involved in transport through vehicle formation
• Endoplasmic Reticulum (ER): Synthesis of proteins
• Rough ER: Studded with ribosome protein synthesis.
• Smooth ER: Lacks ribosome for lipid synthesis.
• Golgi Apparatus: It processes, packages and distributes proteins and lipids.
• Lysosome: Intracellular digestion
• Vacuole and Vesicle: Storage of substances for distribution
• Peroxisome: Various metabolic tasks
• Mitochondrion: Responsible for Cellular Respiration.
• Chloroplast: bounded by membranes for Photosynthesis, only found in plant cells.
• Cytoskeleton: Microtubules, intermediate filaments, and actin filaments offer Shape of cell movement of its parts.
• Cilia and Flagella: are made of +2 pattern, and allow Movement of cell
• Centriole: allows for the Formation of basal bodies in microtubules

Outer Boundaries of Animal and Plant Cells

• A plasma membrane (phospholipid bilayer with protein molecules embedded) surrounds animal and plant cells.
• It separates the living contents of the cell from the nonliving surrounding environment.
• Nucleus is the centre surrounded by semifluid cytoplasm which surrounds organelles.
• The plasma membrane regulates molecule entrance and exit to and from the cytoplasm.
• Plant cells (not animal cells) have a permeable but protective cell wall, in addition to a plasma membrane.
• Cell Walls contain cellulose molecules forming fibrils for strength

Cell Components: Composition and Functions

• Organelle types include membranous and well-defined subcellular structures.
• All organelles in a cell function simultaneously to process chemicals.

Plasma Membrane Details

• Attached to cell wall and separates it from the cytoplasm; semi-permeable, only allowing selective material flow into the cell.
• Known as plasmalemma and is a a three-dimensional layer is between lipid molecules and cholesterol.
• Lipid bilayers and proteins control the transport of small and large molecules.
• Phospholipids arrange with hydrophilic heads and hydrophobic tails for the transport of diffusion, osmosis or active - passive transport mechanisms

Plasma Membrane Function and

• Ultrathin, elastic, dynamic and selectively controls nutrients and control of internal enviroment with waste product removal
• Cell Composition consists of lipids, protein and carbohydrate
• Lipids: lipid bilayer of phospholipids for containing hydrophilic head and hydrophobic tail ends.
• Proteins: can be integral/intrinsic or peripheral/extrinsic according to function to create receptor, transport and enzymes
• Carbohydrates: Short or branched oligosaccharide chains create molecules that can give names to structures of Glycolipids

Plasma Structure and Function

• Exists fluid-mosaic structure of fluid consistency that allows lateral movements
• Unsaturated fats allows for fluidity and mosaic arrangement of protein molecules
• Acts as a thin barrier maintaining environment
• Controls Influx allowing the cell to respone to chemical properties
• Maintains Homeostasis
• Protects the interior

Cell Wall Composition

• the outermost coating and consists of a sugar unit, and contains a jelly coat and immunossensitivity factors for ABO

Cell Wall Structure

• It is the outmost component that composed long chain cellulose-based glucose and polymers

Cell Structure

• Linear strands with inter cellular D-Glucose forming microfibris and toughness

Cell Types

• The walls are segmented that prevent water loss, and provides mechanical support, containing cellulose, lignin and minerals
• Protoplasm: living matter of a cell

Cytoplasm

• contains organelles and has cell biosynthesis to produce elements and is the internal environment

Endoplasmic Reticulum

• Long flattened structure that synthesis Lipids, assembly protein with various form of membrane.

Golgi Apparatus

• stake membrane that sort proteins where secretion of wall components come from it

Lysosomes

• Intracellular Vesical for digestion

Lysomes

• These digest large particles contained in the process using Autology

Functions of Lysosmes

• membrane that digest material

Microbodies

• Enzymes oxidases catalase that use Hydrogen for photorespiration

###Mitochondria Inner membrane containing a protein that transports molecules and uses ATP to create chemical structure

###Functions

• It generates energy by oxidative phosphorylation Functionalities Functions in body with dna, biochemical properties

###Plastids

• DNA that replicates to store multiple pigments
• Luecoplast with protiens and phenols
• Chloroplast allow it to store sunlight

Plasmids

• A plasmid is a cellular genetic with pigments and chemical components

Function

• Prevent protiencd and help maintain it with micro tubes

Functions of cell

• micro tubes for protection against liquid

###Cillia Flagella

• Used in water, with a sensory organelle, that causes movement with differences in #

###Cell Fractionation

• Method of rupturing cells with components.
• Has three steps involving extraction, homogenization and centrifugation.
• extraction with cell-free system in order to study reaction interactions
• Disrupted by vibration and then reduced to a state which are then separated by a centrifuge.
• differential centrifugation exploits sediments

###Water Properties

• Diepotic used to dissolve variety of compounds and a solvent Physical proeprtis Water possss High level of visoocity and it contains cohesion to allow small animals to walk and has a high density to be resistant to heat

Structures

• Hydrophilic with dissolvable solution
• Hydrophobic with insoluble nature

Amphipathic Molicule

• It consist of hydro carbon such
• The pressure effects to dissolve and diffuse the liquid
• To cause Osmotic Pressure in Vant-hoff that needs to have a system

Osmotic pressure

• pressure system between diffusion
• Cells of organism for distribution system