cell & cell organelles dr naveen reddy
TRANSCRIPT
CELL AND CELL ORGANELLES
PRESENTED BY:
DR.NAVEEN PARVATHAREDDY, I MDS,NARAYANA DENTAL COLLEGE, NELLORE, AP.
CONTENTS INTRODUCTION
HISTORY
CLASSIFICATION
BASIC CELL STRUCTURE
CELL MEMBRANE
CYTOPLASM
CELL ORGANELLES - STRUCTURE & FUNCTIONS
CYTOSKELETON
PROJECTIONS FROM CELL SURFACE
CELL INCLUSIONS
REFERENCES
INTRODUCTION
Latin word ‘cella’Building blocksFunctionsCell biology
History
SCIENTIST YEAR DISCOVERYRobert Hooke 1655 CELLBrown 1831 NUCLEUSSchleiden 1838 CELL THEORY
Virchow 1858 “OMNIS CELLULA E
CELLULA”
Miescher 1871 DNA
James Watson & Francis
Crick1953 Double helix model of
DNA.
Singer & nicholson 1972 Fluid Mosaic model
CLASSIFICATION
Ex:animals, plants, protozoa, and fungi.
Ex :Bacteria, blue green algae
Size &shape• Spindle
shaped• Small &
disc shape• Long &
branched
number• Unicellular• multicellula
r
function• Movement• Synthesis &
secretion• Transport• Digestion• Absorption• Growth, repair
Based on cell
CELL STRUCTURE
CELL
CYTOPLASM NUCLEUSCELL MEMBRANE
CYTOSKELETON CYTOSOL CELL
ORGANELLES CELL INCLUSIONS
NUCLEAR MEMBRANE
NUCLEOLUS CHROMATIN NUCLEOPLASM
• Outer limiting membrane • Thickness• Functions as• Other names
HISTORY• Lipid bilayer• Sandwich model• Unit membrane
model• Fluid mosaic model
Cell membrane:
major constituents of plasma membrane are: lipids, proteins,
carbohydrates.
LIPIDS :
1. Phospholipids 2. Cholesterol. 3. Glycolipids.
Membrane ProteinsThey are mainly of two types:
Peripheral proteins
Integral proteins
Many Functions of Membrane ProteinsOutside
Plasmamembrane
InsideTransporter
Cell surfacereceptor
Enzymeactivity
Cell surface identity marker
Attachment to thecytoskeleton
Cell adhesion
Membrane carbohydrates Play a key role in cell-cell recognition
ability of a cell to distinguish one cell from another
important in organ & tissue development
basis for rejection of foreign cells by immune system
FUNCTIONS OF PLASMA MEMBRANE:
It maintains the shape of
cellHelps in
absorption of nutrients
Acts as Semipermeable membrane
Acts as Receptors for hormones &
enzymes
Regulates various
metabolic reactions
Helps in adhesion
between cells
Helps in exchange of
gases
Molecules move through plasma membrane by: Passive transporta) Diffusionb) Facilitated diffusionc) Osmosis
Active transport
Diffusion Move from HIGH to LOW concentration
No energy needed.
diffusion
Diffusion through phospholipid bilayermolecules that can get through directly are fats & other lipids
inside cell
outside cell
lipidsalt
aa H2Osugar
NH3
molecules can NOT get through
polar molecules H2O
Ions salts, ammonia large molecules starches, proteins
Channels through cell membrane
Membrane becomes semi-permeable with protein channels specific channels allow specific material across cell
membrane inside cell
outside cell
sugaraaH2O
saltNH3
Facilitated Diffusion Diffusion with the aid of protein channels
or carrier proteins. No energy is needed.
open channel = fast transporthigh
low
CARRIER PROTEINS:
The proteins move specific type of molecules through the membrane from one side to other side of membrane.
Active TransportCells may need to move molecules against concentration gradient.
Protein “pump”“costs” energy = ATP
conformational change
ATP
low
high
Transport summarysimplediffusion
facilitateddiffusion
activetransport
ATP
Transport of large molecules (bulk transport)
EndocytosisPhagocytosis Pinocytosis
Exocytosis
Phagocytosis: cell eating
Actin dependent endocytosis
Pinocytosis cell drinking endothelium clathrin independent endocytosis
EXOCYTOSIS
It is the process by which a vesicle moves from cytoplasm to the plasma membrane where it discharges its contents to the extracellular space.
CYTOPLASM
It is everything that is
present between the cell membrane and the nuclear envelope.
consists primarily of water. It includes:Factory area of cell site for
CYTOSOL
The cyoplasmic matrix is a concentrated aqueous gel consisting of molecules of different sizes and shapes.
Such as electrolytes, metabolites, RNA, and synthesised proteins.
Cytoplasmic cell Organelles Membranous organelles Mitochondria Golgi apparatus Rough surfaced endoplasmic reticulum Smooth surfaced endoplasmic reticulum
Coated vesicle Secretory vesicles Lysosomes Endosomes / Peroxisomes
Non Membranous organelles Ribosomes Microtubules Filaments
CELL ORGANELLES
MITOCHONDRIA-“powerhouse of the cell”
Bilayered organelle
“CRISTAE”.
“MATRIX”.
The outer membrane possess receptors
The inner membrane contains several enzymes, including phospholipase A2, monoamine oxidase and acetyl coenzyme A (coA) synthase.
Matrix contains
Elementary particles
The membrane forming the cristae contains proteins that have three major functions :
1.oxidative electron transfer.
2. Synthesis of ATP.
3.Regulating transport of metabolites .
CISTERNAE
Two types: r ER s ER
Present abundantly in
RER and Ribosomes are concerned with protein synthesis.
ENDOPLASMIC RETICULUM
Functions of rER: Segregation of proteins.
Helps in initial glycosylation of glycoproteins.
Synthesis of phospholipids.
The assembly of multi chain protein
Major reservoir of ca ions.
Functions of sER:Lipid and steroid
synthesis
Detoxification of drugs
Camillo Golgi.
Usually composed of 4 or more stacked layers of thin, flat, enclosed vesicles lying one side of nucleus.
Prominent in secretory cells.
It functions in association with ER,
GOLGI COMPLEX
STRUCTURE
Functionally Golgi complex is divided into 3 regions
1. The region nearest the nucleus is cis-face
2. The opposite face, nearest to cell membrane is trans-face
3. The intermediate part is medial Golgi.
Cis face: proteins are phosphorylated
Medial golgi : protein – carbohydrate complexes formed
Trans face : Inactive forms to active forms
Sugar residues are added and then
Sorting & packing into vesicles is done.
LYSOSOMES (Digestive bags, suicide sacks)
Lysosomes have unique membrane that is resistant to acidic internal PH.
They are fomed from region of golgi complex.
They are membrane limited vesicles and contain large variety of hydrolytic enzymes.
They are abundant in cells exhibiting phagocytic activity
Digestive organ of cell
Functions: Contains enzymes essential for for
intracellular digestion.
Kill and remove foreign bodies.
Acrosome
Autolysis.
PEROXISOMESsingle membrane bounded organelles with
oxidative enzymes Structure similar to lysosomesFormed by self replication or by budding
off from sERDetoxifying organs of cellLipid metabolism, myelin synthesisAbundant in hepatocytes
The enzymes in them react with other substances and produces H2O2 which is used to detoxify various substances by oxidising them.
ZELLWEGER SYNDROME
RIBOSOMES• Made up of a large and a
small subunit.
• Ribosomes are seen in 1.bound form 2.free form
• Mainly involved in protein synthesis
STRUCTURE
RNA molecules of both subunits are synthesized with in the nucleus
The individual ribosomes held together by strand of mRNA to form poly ribosomes.
The message carried by mRNA is a code for the amino acid sequence of proteins being synthesized by a cell and the ribosomes play a crucial role in decoding or translating this message during synthesis.
Centrosome is the area located near nucleus.
The two centrioles are located perpendicular to each other in the centrosome.
Each centrioles consists of nine bundles of tiny microtubules arranged in a circle.
Functions:
1. Basal body formation
2. Mitotic spindle formation
Centrosome:
CYTOSKELETON
The cytoplasm is permeated by a number of
fibrillar elements that collectively form a supporting network called the cytoskeleton.
Functions of cytoskeleton:-
Maintains the cellular architecture Cell motility Divides cytosol into functionally discrete areas Anchoring cells to each other.
25nm Protein is tubulin dimer(α and β
subunits). Polymerisation of microtubles in
centrioles constitute the microtubule organising centre (MTOC).
Act as conveyor belts
ROLE:
Intra-cellular vesicular transport.
Movement of cilia and flagella. Mitotic spindles Cell elongation and movement.
Microtubules
Microfilaments Diameter is 5 nm. It is composed of actin filaments.
Free actin = G –actin polymerised actin = F-actin.
FUNCTIONS: Anchorage and movement of
membrane protein Formation of core of microvilli. Cell division, locomotion. Extension of cell processes.
Intermediate filaments
Diameter: 10nm Connects adjacent cells through
desmosomes Made of fibrous proteins.
Proteins: Cytokeratin in epithelial cells Neurofilament proteins in neuronsDesmin in muscleGlial fibrillary acidic protein in astrocytesLaminin in nuclear laminaVimentin in various cells
PROJECTIONS FROM CELL SURFACE1. CILIA: These are minute
hair-like projections from free surface of some cells.
0.25μm in
diameter.
They are made up
of microtubules.
FUNCTIONS:Ciliary action moves :- -Secretions in the respiratory tract
-Ova through the uterine tube. -Spermatozoa through the male genital tract -Cells in embryogenesis
Abnomalities in cilia can lead to primary ciliary dyskinesia(PCD) or immotile cilia syndrome.
2) FLAGELLA
Similar in structure to cilia but longer.
Eg; tail of spermatozoan.
Movement starts at base of flagellum.
nearest segment--- one direction.
succeding segements--- opposite direction .
wave like motion passes down the flagellum.
3) MICROVILLI:
With EM: Finger like extensions of cell membrane. plasma memebrane and numerous actin filaments in it.
Increases the surface area for absorption of materials
CELL INCLUSIONS
Inclusions contain products of metabolic activity of the cell
Consists of pigment granules, lipid droplets and glycogen.
Considered as nonmoving and nonliving components of the cell.
characteristic staining properties
Commonly seen inclusions are Lipofuscin
Hemosiderin
Glycogen
Lipid inclusions
Crystalline inclusions
LIPOFUSCIN
Brownish gold pigment –H & E.
conglomerate of lipids, metals & organic molecules.
wear and tear pigment.
HEMOSIDERIN : Iron storage complex found in cytoplasm.
LM-deep brown granule.
GLYCOGEN:
Highly branched polymer.
may not be stained in H & E.
Liver and striated muscle cells shows unstained regions where glycogen is present.
In EM clusters of granules of 25 to 30nm.
LIPID INCLUSIONS: Are usually nutritive inclusions that provide energy for
cellular metabolism. May appear in cell for very short time but in Adipocytes they
constitute most of cytoplasmic volume and compress other organelles into thin rim at margin of the cell.
CRYSTALLINE INCLUSIONS: These contained in certain cells are recognised in light
microscope. In humans are found in sertoli and leydig cells of testis may contain storage material or cellular metabolite.
Significance is not clear.
REFERENCES: TEXT BOOK OF MEDICAL PHYSIOLOGY-
GUYTON & HALL 12TH EDITION CELL & MOLECULAR BIOLOGY- NALINI
CHENDAR & VISELLI BASIC HISTOLOGY- JUNQUERA HISTOLOGY 9TH EDITION- HAMS TEXT BOOK OF HUMAN HISTOLOGY, 4TH
EDITION – INDERBIR SINGH HISTOLOGY, A TEXT & ATLAS,5TH EDITION-
MICHAEL H.ROSS,WOJCIECH PAWLINA
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