cell biology ppt
TRANSCRIPT
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BY: DR. JYOTISH KUMAR JHA
DEPARTMENT OF ORAL MEDICINE AND RADIOLOGY
CELL BIOLOGY
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CONTENTS : Definition: Characteristics of cells: Structure of cells Structure of cell membrane: Applied physiology of cell membrane: 1)Cytoplasm: 2)Rough Endoplasmic Reticulum: 3)Smooth Endoplasmic Reticulum: 4)Golgi apparatus: 5)Lysosomes: 6)Perioxisomes:
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7)Mitochondria : 8)Ribosomes: Nucleus Function of nucleus DNA RNA TRANSCRIPTION AND TRASNSLATION CELL DIVISION TYPES OF CELL DIVISION MITOSIS
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CELL CYCLE DIFFERENCE BETWEEN MITOSIS AND
MEIOSIS LIST OF CHROMOSOMAL
ABNORMALITIES CHROMOSOMAL ABERRATION APOPTOSIS CELL JUNCTON VIRUS ENTRY TO CELL
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TERM WAS COINED BY” ROBERT HOOK” (1635-1703)
DEFINED AS STRUCTURAL AND FUNCTIONAL UNIT OF LIFE
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GENERAL CHARACTERISTICS OF CELL• Needs nutrition & oxygen• Eliminates carbon dioxide & other
metabolic wastes• Shows immediate response to the
entrance of invaders• Reproduces by division
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STRUCTURE OF CELL
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Each cell is formed by a cell body and a membrane covering the cell body known as cell membrane or plasma membrane
The cell body has two parts namely the nucleus and the cytoplasm surrounding the nucleus.
Thus the structure of a cell is studied under 3 headings…
I. Cell membraneII. CytoplasmIII. nucleus
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CELL MEMBRANE
Protective sheath covering the cell body
Separates the fluid outside the cell called extracellular fluid(ECF) and the fluid inside the cell called intracellular fluid(ICF)
COMPOSITION OF CELL MEMBRANE 1. PROTEINS(55%)2. LIPIDS(40%)3. CARBOHYDRATES(5%)
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STRUCTURE OF CELL MEMBRANE
THREE PROPSED MODELSW ARE
1. Danielli-Davson model
2. Unit membrane model
3. The fluid mosaic model
THE CELL MEMBANE is a three layered membrane.
MICROSCOPIC STUDY REVEALS
Central electron-lucent layer called LIPID LAYER formed by lipid protein
• MAJOR LIPIDS PRESENT ARE
1. PHOSPHOLIPIDS
2. CHOLESTROL
functional significance of this layer is that it forms a semi permeable membrane and allows only fat soluble substances to pass through ie oxygen, carbon dioxide &alcohol
2 electron-dense layer one on either side of central layer called PROTEIN LAYER formed by protein substances.
MAJOR PROTEIN PRESENT ARE
3. Integral Protein
4. Peripheral Protein
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Functional significance of protein layer1. Integral protein provide the
structural integrity of cell membrane2. Channel protein- for diffusion of
water soluble substances like glucose and electrolyte
3. Carrier protein4. Receptor protein5. Antigen
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APPLIED PHYSIOLOGY ON CELL MEMBRANE
LIPID soluble material in the ECE, when come in contact with cell membrane get dissolved in the oily cell membrane then enter the cytoplasm. Thus lipid soluble drugs easily pass the blood-brain barrier(BBB)
In the cell membrane of fungus ergosterol is present instead of cholestrol, drugs are present which get attached with ergosterol and damage them and thus the fungal cell membrane is damaged and last death
such drugs are AMPHOTERECIN B. AMB used against fungal infection
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1. CYTOPLASM
ORGANELLES IN CYTOPLASM1. ENDOPLASMIC RETICULUM 2 TYPES rough endoplasmic reticulum smooth endoplasmic reticulum function of rough endoplasmic reticulum2. synthesis of protein3. degradation of worn out organelles function of smooth endoplasmic reticulum4. synthesis of lipids and steroids5. storage and metabolism of calcium6. degradation of toxic substances in liver
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GOLGI APPARATUS1. present in all cells except red blood
cells2. has two faces or ends cis face and
trans face, cis face is close to endoplasmic reticulum and trans face near the cell membrane
function of golgi apparatus• processing, labelling and delivery of
proteins and lipids in different parts of cell
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LYSOSOMES 1. membrane bound vesicular organelles
found throughout the cytoplasm 2. Formed by golgi apparatus3. Enzymes synthesized in RER are
processed and packed in the form of vesicles in the golgi apparatus
4. Then these vesicles are pinched off from golgi apparatus and become the lysosomes
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TYPES OF LYSOSOMES1. PRIMARY LYSOSOMES -- one that is
pinched off from the golgi apparatus and is inactive
2. SECONDARY LYSOSOMES – a active lysosome formed by fusion of primary lysosome with phagosome or endosome
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FUNCTION OF LYSOSOMES1. Degradation on macromolecules like
bacteria2. Degradation of worn out organelles 3. Secretory function
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PEROXISOMES
FUNCTION OF PEROXISOMES1. Degradation of toxic substances like
hydrogen peroxide – present in liver cells which is a major organ for detoxification
2. Oxygen utilization3. Breakdown of excess fatty acids4. Acceleration of gluconeogenesis from fats5. Degradation of purin to uric acid6. Role in the formation of myelin and bile
acids
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CENTROSOME AND CENTRIOLES
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Situated near the centre of the cell close to the nucleus
Responsible for the movement of chromosomes during cell division
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MITOCHONDRIA
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Rod like oval structure Bilayered membranous organelle Outer membrane smooth and encloses the
contents of mitocondria Inner membrane folded in the form of shelf
called cristae Cristae contains many enzymes and other
protein molecules which are involved in respiration and synthesis of ATP
Move freely in cytoplasm and capable of self reproduction
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FUNCTION OF MITOCONDRIA
Production of energy– called POWER HOUSE OF CELL – required for cellular function – produced during oxidation of digested food particles like proteins,crbohdrates and lipids
Synthesis of ATP apoptosis
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RIBOSOMES
Granular and small dot like structure Made up of proteins(35%) and RNA(65%) FUNCTION OF RIBOSOMES SYNTHESIS OF PROTEIN mRNA passes genetic code for protein synthesis
from nucleus to ribosomeRibosomes arrange the amino acids into small
units of proteinRibosomes attached with ER are involved in
protein synthesis like enzymatic protein,harmonal protein and proteina of cell membrane
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There are two types of cells:
1) Prokaryotic Cells
2) Eukaryotic Cells
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These are two distinct types of cells with STRUCTURAL differences.
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Traits of Prokaryotes: (pro-care-ee-ohts)
1. They do not have a nucleus, and their genetic material is not stored in the nucleus.
2. They have some organelles, but not many.
3. They are less complicated that eukaryotes.
4. All bacteria are prokaryotes.
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Eukaryote CellA more complex cell with
a nucleus and many
organelles.
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Traits of Eukaryotes: (you-care-ee-othts)
1. They all have a nucleus where the genetic material of the cell is stored.
2. They have many organelles that work together to help the cell function.
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COMPARISON OF PLANT AND ANIMAL CELL
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NUCLEUS
located near centre of cell and is mostly spherical in shape.
STRUCTURE OF NUCLEUS
Covered by nuclear membrane and it encloses the structures called nucleo plasm and nucleolus
NUCLEAR MEMBRANE
Double layered and porous in nature
Allows nucleoplasm to communicate with cytoplasm
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NUCLEOPLASMGel like ground substance of the
nucleusContains large quantities of the
genetic materials in the form of deoxyribonucleic acid(DNA) which form the gene
DNA made of thread like material known as chromatin
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NUCLEOLIo One or more nucleoli are present in
each nucleuso Nucleolus contains ribonucleic
acid(RNA) and some proteins similar to those found in ribosomes
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FUNCTION OF NUCLEUS1. Control of all the activities of the
cell2. Synthesis of RNA3. Sending genetic instruction to the
cytoplasm for protein synthesis through mRNA
4. Control of cell division through genes
5. Storage of hereditary information
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DNA Genetic information of an organism is stored
in genes of DNA DNA forms the chemical basis of hereditary
characters Carrier for genetic information to the
offspring Contains instruction for the synthesis of
proteins in the ribosome DNA present in nucleus is responsible for
synthesis of RNA
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RNA Formed from DNA Regulates the synthesis of proteins in
the ribosome TYPES
I. MESSENGER RNA (mRNA) carries genetic code of amino acid
sequence for synthesis of protein from the DNA to cytoplasm
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TRANSFER RNA(tRNA) Responsible for decoding the genetic
message present in mRNARIBOSOMAL RNA(rRNA) Present within ribosome and is
responsible for the assembly of proteins from amino acids in the ribosomes
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TRANSCRIPTION Copying of genetic material from DNA to
RNA Transcription of genetic codes in nucleus formation of m RNA copying of message from DNA to m
RNA
m RNA enter the cytoplasm and
activate the ribosome for protein synthesis
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TRANSLATION Process of protein synthesis in ribosomes ribosomes get attached to mRNA codons of mRNA recognized
by complimentary base of tRNA called anticodons
according to sequence of base of anticodon different amino acids transported from cytoplasm to ribosomes
rRNA assemble the proteins from amino acids and attach to RER
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BINARY FUSIONBINARY
FUSIONBINARY FUSION
MITOSIS
MEIOSIS
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The Cell Cycle
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LIST OF CHROSOMAL ABNORMALITIES
NUMERICAL ABNORMALITIESa) Aneuploidyb) Trisomic(2n+1)c) Monosomic(2n-1) STRUCTURAL ABNORMALITIESa. DOWN’S SYNDROMEb. EDWARDS SYNDROMEc. PATAU’S SYNDROME
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SEX CHROMOSOME DISORDER1) KLINEFELTER’S SYNDROME2) TURNER’S SYNDROME3) FRAGILE X SYNDROME
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CHROMOSOME ABERRATION
Useful marker for radiation injury Observed in irradiated cells at the time of
mitosis when the DNA condenses to form chromosome
If radiation exposure occurs after DNA synthesis(ie in G2 or mid or late S) only one arm of affected chromosome is broken
If radiation occurs before DNA replication(ie in G1 or early S) then break in both the arms
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APOPTOSIS
Defined as programmed cell death under genetic control
A normal phenomenon and in essential for normal development of the body
FUNCTIONAL SIGNIFICANCE Main function is to remove unwanted
cells without causing any stress or damage to the neighboring cells
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SIGNIFICANCE1) Vital role in cellular homeostasis2) Useful for removal of a cell that is
damaged by a virus of a toxin beyond repair
3) Essential event during the development and in adult stage
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ROLE OF MITOCONDRIA IN APOPTOSIS
external or internal stimuli initiate apoptosis by activating the proteases CASPASES
Normally caspases suppressed by apoptosis inhibiting factor(AIF)
WHEN CELL RECEIVE APOPTOSIS STIMULI… mitochondria release two proteins
1. CYTOCHROME C 2. SECOND MITOCONDRIA-DERIVED
ACTIVATOR OF CASPASES(SMAC)
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SMAC inactivates AIF SMAC +AIF to form apoptosome
activates CASPASES CYTOCHROME C also facilitate
caspase activation
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APOPTOTIC PROCESS
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CELL JUNCTION
It is the connection between the neighboring cells
THREE TYPES1. OCCLUDING JUNCTION- prevent intercellular
exchange of substances
2. COMMUNICATING JUNCTION-permits intercellular exchange of substances
3. ANCHORING JUNCTION-provide strength to the cells
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OCCLUDING JUNCTION prevent movement of ions and
molecule from one cell to another cell
TIGHT JUNCTION/ZONA OCCLUDENS belong to this category Present in the apical margin of
epithelial and endothelial cells in intestinal mucosa,walls of renal tubules,capillary wall
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STRUCTURE OF TIGHT JUNCTION
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FUNCTION OF TIGHT JUNCTION1. Holds the neighboring cell of tissues firmly
for strength and stability2. In epithelial and endothelial cells function
as selective diffusion barrier between neighboring cells
3. Prevents lateral movement of integral proteins and lipids in cell membrane
4. In brain capillaries form blood-brain barrier allowing only lipid soluble drugs and steroids to pass through
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