Cell structure and function / dental implant courses by Indian dental academy

INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY
Leader in continuing Dental EducationLeader in continuing Dental Education
LIFE BEGINS WITH CELLLIFE BEGINS WITH CELL
Life is uninterrupted successionLife is uninterrupted succession
of cells. Like ourselves theof cells. Like ourselves the
individual cells that form our bodiesindividual cells that form our bodies
can grow, reproduce, processcan grow, reproduce, process
information, respond to stimuli andinformation, respond to stimuli and
carry out an amazing array ofcarry out an amazing array of
chemical reactions. These abilitieschemical reactions. These abilities
define life.define life.
Hence it is rightly told thatHence it is rightly told that
life begins with cell.life begins with cell.
www.indiandentalacademy.comwww.indiandentalacademy.com

CELL-STRUCTURE
AND
FUNCTION

DEFINITIONSDEFINITIONS
 CELL:CELL: It is defined as smallestIt is defined as smallest
structural and functional unit of astructural and functional unit of a
living organism, capable ofliving organism, capable of
independent existence, composed ofindependent existence, composed of
membrane enclosed mass ofmembrane enclosed mass of
protoplasm and containing nucleusprotoplasm and containing nucleus
or nucleoid.or nucleoid.

HISTORYHISTORY
The word cell was first coined by Robert hookThe word cell was first coined by Robert hook
in 1665.in 1665.
M.J.Schleiden and Theodar Schewenn putM.J.Schleiden and Theodar Schewenn put
forward cell theory.forward cell theory.
Virchow (1855), stated that all cells comeVirchow (1855), stated that all cells come
from pre existing cells (omnia cellular).from pre existing cells (omnia cellular).
In 1900 most of the cell structures visibleIn 1900 most of the cell structures visible
through light microscope were described,laterthrough light microscope were described,later
TEM followed by high voltage electronTEM followed by high voltage electron
microscope revealed a whole new realm ofmicroscope revealed a whole new realm of
cell and its architecture.cell and its architecture.

CELL THEORIESCELL THEORIES
CELL THEORYCELL THEORY- SCHEILDEN AND- SCHEILDEN AND
SCHEWAN(1838)SCHEWAN(1838)
It states that, “all living matter fromIt states that, “all living matter from
the simplest of unicellular organisms to verythe simplest of unicellular organisms to very
complex mammals is composed of cells.complex mammals is composed of cells.
Each cell acts independently but functions asEach cell acts independently but functions as
an integral part of the complete organism”.an integral part of the complete organism”.
Exception: VIRUSES that completelyException: VIRUSES that completely
lacked cellular morphology.lacked cellular morphology.

ORGANISMAL THEORYORGANISMAL THEORY- SACHS(1898)- SACHS(1898)
According to this theory, “cellsAccording to this theory, “cells
are not isolated units of structure andare not isolated units of structure and
function, instead each organism is a unitfunction, instead each organism is a unit
of itself.”of itself.”
The different cells of the bodyThe different cells of the body
function in a coordinated manner for thefunction in a coordinated manner for the
benefit of the whole organism.benefit of the whole organism.

DIVERSITY AND COMMONALITY OFDIVERSITY AND COMMONALITY OF
CELLSCELLS
Cells come in amazing variety of sizesCells come in amazing variety of sizes
and shapes ,some move rapidly and haveand shapes ,some move rapidly and have
fast changing structures,as seen infast changing structures,as seen in
Amoeba.Others are largely stationary andAmoeba.Others are largely stationary and
structurally stable.structurally stable.
 AEROBIC AND ANAEROBICAEROBIC AND ANAEROBIC
 PROKARYOTES AND EUKARYOTESPROKARYOTES AND EUKARYOTES
 UNICELLULAR AND MULTICELLULARUNICELLULAR AND MULTICELLULAR
 PLANT CELL AND ANIMAL CELLPLANT CELL AND ANIMAL CELL

PLANT CELLPLANT CELL

ANIMAL CELL

CELL ORGANISATION AND
ARCHITECTURE
 A Cell is bounded by a cell membrane(plasmaA Cell is bounded by a cell membrane(plasma
membrane), within which is enclosed a complex ofmembrane), within which is enclosed a complex of
cellular material called Protoplasm.cellular material called Protoplasm.
 Protoplasm consists of central more dense partProtoplasm consists of central more dense part
called the nucleus ,and outer less dense part calledcalled the nucleus ,and outer less dense part called
cytoplasm. The nucleus is separated from thecytoplasm. The nucleus is separated from the
cytoplasm by a nuclear membrane.cytoplasm by a nuclear membrane.
 The cytoplasm has a fluid base (matrix) called cytosolThe cytoplasm has a fluid base (matrix) called cytosol
or hyaloplasm. The cytosol contains a number ofor hyaloplasm. The cytosol contains a number of
organelles which have distinctive structure andorganelles which have distinctive structure and
function.function.

CELL SURFACE-PLASMA MEMBRANE
 Plasma membrane is one of the most fundamentalPlasma membrane is one of the most fundamental
structure of cellular evolution.structure of cellular evolution.
 Apart of the cell membrane,various organelles of theApart of the cell membrane,various organelles of the
cell are bounded by a membrane. All these have acell are bounded by a membrane. All these have a
common basic structure, though their propertiescommon basic structure, though their properties
considerably vary from one location to the other.considerably vary from one location to the other.
 They are:They are:
• The membranes are 7.5nm thick.The membranes are 7.5nm thick.
• They predominantly constitute Lipids, Proteins,& fewThey predominantly constitute Lipids, Proteins,& few
Carbohydrates..Carbohydrates..

STRUCTURESTRUCTURE
It mainly constitutes lipids and proteins.It mainly constitutes lipids and proteins.
Lipids (Lipids (Phospholipids and cholesterol)Phospholipids and cholesterol)
determine the structure anddetermine the structure and Proteins,Proteins, thethe
function of the plasma membrane.function of the plasma membrane.

PHOSPHOLIPID BILAYERPHOSPHOLIPID BILAYER
Railroad track or trilaminar appearance.Railroad track or trilaminar appearance.
Four types of phospholipids are :Four types of phospholipids are : phosphotidylphosphotidyl
choline, phosphotidyl serine,choline, phosphotidyl serine,
phosphotidylethanolamine and sphingomyelin.phosphotidylethanolamine and sphingomyelin.
CHOLESTEROLCHOLESTEROL provides membrane stability.provides membrane stability.

PHOSPHOLIPID BILAYERPHOSPHOLIPID BILAYER

IMPORTANCE OF PHOSPHOLIPIDIMPORTANCE OF PHOSPHOLIPID
BILAYERBILAYER
 It acts as a barrier between twoIt acts as a barrier between two
compartments-thus responsible for basiccompartments-thus responsible for basic
function of the membrane.function of the membrane.
 They are viscous fluids and not solids.They are viscous fluids and not solids.
 Lipid rafts move laterally within theLipid rafts move laterally within the
membrane.membrane.

MEMBRANE PROTIENSMEMBRANE PROTIENS
Fluid mosaic modelFluid mosaic model in 1972 by Jonathanin 1972 by Jonathan
singer and Garth Nicholson.singer and Garth Nicholson.
 It states that “membranes are twoIt states that “membranes are two
dimensional fluids in which proteins aredimensional fluids in which proteins are
inserted into lipid bilayers.I.e. mosaic likeinserted into lipid bilayers.I.e. mosaic like
proteins floating like icebergs in the sea ofproteins floating like icebergs in the sea of
lipids”.lipids”.
 Two types of proteins- peripheral and integralTwo types of proteins- peripheral and integral
membrane proteins(transmembrane proteins)membrane proteins(transmembrane proteins)

FLUID MOSAIC MODELFLUID MOSAIC MODEL

FUNCTIONS OF MEMBRANEFUNCTIONS OF MEMBRANE
PROTIENSPROTIENS
 Cell adhesion
 Structural proteins
 Transport across membranes
 As receptors
 As enzymes
 As marker molecules.

FUNCTION OF GLYCOLIPIDSFUNCTION OF GLYCOLIPIDS
 Special adhesion molecules in the layer enableSpecial adhesion molecules in the layer enable
for cell adhesion.for cell adhesion.
 They contain antigens that determine the type ofThey contain antigens that determine the type of
blood groups.blood groups.
 They maintain a minimum space of 20nmThey maintain a minimum space of 20nm
between the cells.between the cells.

NUCLEUSNUCLEUS

THE NUCLEUS
 Being the Largest organelle of the cell, it
constitutes the central most dense part of a
cell.
 By housing the cell’s genome, it serves
both as a repository to genetic information,
and as cell’s control center.

STRUCTURE
Nucleus is surrounded by a double layered
nuclear membrane, enclosing within itself,
nucleolus and the genetic material

Nuclear envelopeNuclear envelope
 Nuclear envelope consists of two nuclearNuclear envelope consists of two nuclear
membranes, an underlying nuclear laminamembranes, an underlying nuclear lamina
and pore complexes.and pore complexes.
 The outer membrane is continuous with theThe outer membrane is continuous with the
E.R. , being functionally similar to it.E.R. , being functionally similar to it.
 The inner membrane (karyoplasmic face) isThe inner membrane (karyoplasmic face) is
in contact with fibrous lamina.in contact with fibrous lamina.
 Space between two membranes is known asSpace between two membranes is known as
perinuclear space or cisternae.perinuclear space or cisternae.
 The inner and outer membrane are joined atThe inner and outer membrane are joined at
certain points called as nuclear pores.certain points called as nuclear pores.

Nuclear laminaNuclear lamina
 Underlying the inner nuclear membrane isUnderlying the inner nuclear membrane is
fibrous network known as Nuclear lamina.fibrous network known as Nuclear lamina.
 It provides structural support to the nucleus.It provides structural support to the nucleus.
 It contains proteins specific to nucleus calledIt contains proteins specific to nucleus called
lamins.lamins.
 Lamins:Lamins:
Serve as site for chromatin attachmentServe as site for chromatin attachment
Essential for DNA replication andEssential for DNA replication and
regulation of transcription.regulation of transcription.

Nuclear pore complex
 Sole channels through which small polarSole channels through which small polar
molecules, ions and macromolecules (proteinsmolecules, ions and macromolecules (proteins
and RNA) can travel between nucleus andand RNA) can travel between nucleus and
cytoplasm and vice versa.cytoplasm and vice versa.
 They actively transport proteins into the cell andThey actively transport proteins into the cell and
ribosomes out of the cell.ribosomes out of the cell.
 Proteins destined for import contain nuclearProteins destined for import contain nuclear
localization signals.localization signals.
 RNA’S are transported out as ribonucleoproteinRNA’S are transported out as ribonucleoprotein
complexes.complexes.

Internal organization of nucleusInternal organization of nucleus
 It is made up in large, by theIt is made up in large, by the
chromosomes.chromosomes.
 Each chromosome is made of DNA.Each chromosome is made of DNA.
 DNA is 2mm long, but it fits in the nucleusDNA is 2mm long, but it fits in the nucleus
as it is wrapped around core of his toneas it is wrapped around core of his tone
protein-nucleosome.protein-nucleosome.
 The whole complex of DNA and protein isThe whole complex of DNA and protein is
chromatin.chromatin.

Significance of chromosomesSignificance of chromosomes
 Each cell in body contains within itself aEach cell in body contains within itself a
store of information inherited from precursorstore of information inherited from precursor
cell. This information is necessary for propercell. This information is necessary for proper
functioning, and is stored in chromatin.functioning, and is stored in chromatin.
 Chromosomes determine type of protein toChromosomes determine type of protein to
be synthesized by the cell.be synthesized by the cell.

Nucleolus
 Patchwork of granules, rich in RNA, attachedPatchwork of granules, rich in RNA, attached
to internal face of nuclear membrane.to internal face of nuclear membrane.
 During cell division, it disappears andDuring cell division, it disappears and
reappears in nuclei of daughter cells.reappears in nuclei of daughter cells.
 Most prominent and numerous in growingMost prominent and numerous in growing
cells.cells.
 Site for synthesis of ribosome (ribonuclearSite for synthesis of ribosome (ribonuclear
proteinsproteins).).

THE CYTOPLASMTHE CYTOPLASM
 Cellular material outside the nucleus andCellular material outside the nucleus and
inside the plasma membrane.inside the plasma membrane.
 It constitutes approx half cytosol and halfIt constitutes approx half cytosol and half
organelles.organelles.
 They contain living sub cellular organellesThey contain living sub cellular organelles
and nonliving cytoplasmic inclusions.and nonliving cytoplasmic inclusions.

 They are suspended in amorphous matrixThey are suspended in amorphous matrix
referred to as hyaloplasm or cell sap.referred to as hyaloplasm or cell sap.
 Ectoplasm and endoplasm.Ectoplasm and endoplasm.
 Membranous and non membranousMembranous and non membranous
organelles.organelles.

PROTEIN SYNTHESIS AND TRANSPORTPROTEIN SYNTHESIS AND TRANSPORT
ENDOPLASMIC RETICULUMENDOPLASMIC RETICULUM
GOLGI APPARTUS &GOLGI APPARTUS &
LYSOSOMESLYSOSOMES

ENDOPLASMIC RETICULUM
 Network of interconnected membranousNetwork of interconnected membranous
structures within the cytoplasm of eukaryoticstructures within the cytoplasm of eukaryotic
cell, continuous with outer nucleus envelope.cell, continuous with outer nucleus envelope.
 They form flattened sacs and tubules thatThey form flattened sacs and tubules that
interconnect-cisternae.interconnect-cisternae.
 TypesTypes
 Rough endoplasmic reticulumRough endoplasmic reticulum
 Transitional endoplasmic reticulumTransitional endoplasmic reticulum
 Smooth endoplasmic reticulumSmooth endoplasmic reticulum

ENDOPLASMIC RETICULUMENDOPLASMIC RETICULUM

Functions of Rough endoplasmicFunctions of Rough endoplasmic
reticulumreticulum
 RER and transitional endoplasmic reticulumRER and transitional endoplasmic reticulum
Produces, Processes, and ships out proteins.Produces, Processes, and ships out proteins.
 The role of protein processing and sortingThe role of protein processing and sorting
was first demonstrated by George Palade inwas first demonstrated by George Palade in
1960.1960.
 RER—GOLGI—SECRETORY VESICLE—CELLRER—GOLGI—SECRETORY VESICLE—CELL
EXTERIOR /LYSOSOMES.EXTERIOR /LYSOSOMES.

 Proteins destined for secretion into thisProteins destined for secretion into this
pathway are targeted to RER and thenpathway are targeted to RER and then
translated to membrane bound ribosome.translated to membrane bound ribosome.
 In contrast, proteins that remain in cytosol orIn contrast, proteins that remain in cytosol or
secreted in other organelles are synthesizedsecreted in other organelles are synthesized
on free ribosome.on free ribosome.
 Half of proteins synthesized are degraded inHalf of proteins synthesized are degraded in
20 minutes, as they fail to fold correctly.20 minutes, as they fail to fold correctly.

PROTIEN SYNTHESISPROTIEN SYNTHESIS

Functions of Smooth endoplasmicFunctions of Smooth endoplasmic
reticulumreticulum
 Major site for synthesis for membrane lipids.Major site for synthesis for membrane lipids.
 Functions in detoxification process of manyFunctions in detoxification process of many
drugs.drugs.
 In skeletal muscle, acts as sarcoplasmicIn skeletal muscle, acts as sarcoplasmic
reticulum, stores calcium ions and functionsreticulum, stores calcium ions and functions
in muscle contractionin muscle contraction..

GOLGI APPARTUSGOLGI APPARTUS
 First described by Golgi, composed ofFirst described by Golgi, composed of
membranous sacs stacked on each other likemembranous sacs stacked on each other like
dinner plates.dinner plates.
 Membranous sacs (cisternae) form anMembranous sacs (cisternae) form an
independent system.independent system.
 Most numerous and highly developed in cellMost numerous and highly developed in cell
of salivary glands and pancreas.of salivary glands and pancreas.
 Functionally Golgi is divided into:Functionally Golgi is divided into:
Cis face (near nucleus)Cis face (near nucleus)
Trans face (near to cell membrane)Trans face (near to cell membrane)
Intermediate golgi /golgi stack (b/w cis andIntermediate golgi /golgi stack (b/w cis and
trans golgi)trans golgi) www.indiandentalacademy.comwww.indiandentalacademy.com

FunctionsFunctions
Modifies, sorts, packages andModifies, sorts, packages and
distributes proteins and lipidsdistributes proteins and lipids
manufactured by RER & SER.manufactured by RER & SER.
Forms secretory vesicles thatForms secretory vesicles that
discharges processed proteins viadischarges processed proteins via
exocytosis into extra cellular fluid.exocytosis into extra cellular fluid.
Forms membrane vesicles that ferry newForms membrane vesicles that ferry new
molecules to the plasma membrane.molecules to the plasma membrane.
Forms transport vesicles that carryForms transport vesicles that carry
proteins to other organelles such asproteins to other organelles such as
Lysosome.Lysosome.

Processing and packaging of proteins byProcessing and packaging of proteins by
GolgiGolgi
Modification of protein in trans golgi:Modification of protein in trans golgi:
 Proteolysis of some proteins convertingProteolysis of some proteins converting
them from inactive form to active form.them from inactive form to active form.
 Add sugar residues to proteins like medialAdd sugar residues to proteins like medial
Golgi.Golgi.

Two types of secretory pathwaysTwo types of secretory pathways
 Constitutive secretory pathway.Constitutive secretory pathway.
 Non constitutive secretory pathwayNon constitutive secretory pathway
e.g., endocrine hormones.e.g., endocrine hormones.

CAN DEFECTIVE PROTEINS BECAN DEFECTIVE PROTEINS BE
SYNTHESIZED?SYNTHESIZED?
The processes involved in proteinThe processes involved in protein
synthesis are so complex, yet lesssynthesis are so complex, yet less
defective proteins are produced –defective proteins are produced –
quality control.quality control.

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