cell BY ARIF MOHIDDIN MDS 1 ST YEAR DEPT OF ORAL PATHOLOGY
Dec 25, 2015
cell
BY
ARIF MOHIDDIN
MDS 1ST YEAR
DEPT OF ORAL PATHOLOGY
CONTENTS
Introduction
History
Cell components
Conclusion
References
INTRODUCTION
HISTORY Cell theory - 1839 by Schleiden & Schwann
states that all organisms are composed of similar units of
organization, called cells.
Robert Hooke - In the year 1665
- Examine thin slices of cork
- looks like small boxes
HOOKE called them - cells
Anton von leeuwenhoek- first to view organisms in living things
Cell
Prokaryotes Eukaryotes
Prokaryotes :
- cells that lack a nucleus or membrane
bound organelles .
- Eg : Bacteria
- simplest type of cell
- single circular chromosome
Eukaryotes :
-cell that have a nucleus and membrane
bond organelles
-Eg: plants and animals
CELL COMPONENTS
Cell
Cell membrane Protoplasm
Cytoplasm Nucleus
Cell organelles Cytosol
Cell membrane
PHOSPHOLIPID STRUCTURE
It is composed of two layers of phospholipids and embedded with protiens
It is thin and Semi-permeable
It is Amphipathic
Functions :
It separetes the contents of cell from its outside
Environement
It supports the cell and helps in maintaining the shape of
cell
It is semi- permeable
Protiens present in the membrane acts as Pumps ,
channels, Receptors , Enzymes .
ARRANGEMENT OF MEMBRANE PROTIENS
- INTEGRAL PROTIENS
- PERIPHERAL PROTIENS
INTEGRAL PROTIENS :
- External into / through the lipid bilayer
among fatty acid tails and are firmly
embedded in it.
- most are Transmembrane protiens .
Protrude into both cytosol and Extracellular
fluid .
- AMPHIPATHIC .
PERIPHERAL PROTIENS :
- They are attached to polar heads of membrane lipids
- The carbohydrate portion of glycolipid , glycoproteins form
an extensive surface coat called GLYCOCALYX .
- The pattern of carbohydrate in glycocalyx varies from cell to
cell .
- Glycocalyx enables cells adhere to one another In some
tissues.and protects cells from being digested by enzymes in
ECF .
FUNCTIONS OF MEMBRANE PROTIENS :
- INTEGRAL PROTIENS :
- Ion channels
- Carriers
- Receptors
- PERIPHERAL PROTIENS :
- Enzymes
- Linkers
- MEMBRANE FLUIDITY:
-It depends on number of doublebonds in the
fattyacid tails of lipids that make up the
bilayer and amount of cholestrol present
- Each double bond puts a KINK in fatty acid
tail , which increases membrane fluidity by
preventing lipid molecules from packing
tightly in membrane .
- fluidity allows lipid bilayer to self seal if
punctured
- MEMBRANE PERMIABILITY :
- Selective permeable
- permeable to non – polar , uncharged
molecules such as oxygen , carbondioxide
etc.
- Impermeable to ions and large uncharged
polar molecules such as glucose .
TRANSPORT ACROSS PLASMA MEMBRANE :
- PASSIVE PROCESS :
- Simple diffusion
- facilitated diffusion
- osmosis
- ACTIVE PROCESS :
- Endocytosis
- Exocytosis
- Transcytosis
NUCLEUS
Control centre of the cell
Spherical in shape
STRUCTURE
-Nuclear Membrane
-Nuclear pores
-Nuclear lamina
-Chromosomes
-Nucleolus
FUNCTIONS OF THE NUCLEUS
Storage of Hereditary material
Storage of protiens and DNA
Production of Ribosomes
Transport of Hereditary material to rest of cell
PROTIEN SYNTHESIS :
- First step is transcription of
mRNA from DNA in nucleous
- Starts at nucleus by formation
of mRNA through a process
called Transcription .
TRANSCRIPTION
-In the nucleus, enzymes make a RNA copy using a portion of DNA. The RNA is then transformed into a messenger RNA (mRNA). The mRNA leaves the nucleus through the pores and gets into the cytoplasm.- Here, the mRNA mixes with the ribosome, which begins the process of protein synthesis. So basically in this stage, RNA is created, so it can go and make instruct the making of protein.
TRANSFERAL
In this stage, an amino acid activating enzyme attaches
an amino acid to one end of transfer RNA (tRNA), also
called an adaptor molecule. On the other end of the
adaptor is a condon (a specific three-nucleotide code)
which will be used when the adaptor reaches the mRNA.
Once the condon is retrieved, the mRNA continues to the
ribosome. So basically, in this stage, an adaptor is
connected to an amino acid so it can be energized and
have enough strength to continue its journey.
TRANSLATION
At this point, one amino acid is attached to an adaptor.
Remember that it takes many amino acids to make up
one protein. Therefore, there must be a way to link
these amino acids into a single protein in order to
complete protein synthesis. This is where the ribosome
comes in which is so good at producing proteins that is
often termed a "protein factory." The ribosome "reads"
the start condon (AUG) and associates it with the
proper amino acid. Once all the amino acids have been
linked, mRNA signals STOP. The ribosome releases the
mRNA and the amino acid, and a protein has been
made.
- CYTOPLASM :
- CYTOSOL
- ORGANELLES
- INCLUSIONS
- CYTOSOL :
- 55% of total cell volume .
- It is 75% of water , ions , glucose , amino
acids,protiens, lipids , ATP , waste
products .
CYTOSKELETON :
It is a network of protein filaments that
extends throughout the cytosol .
- 3 types of filamentous protiens contribute
cytoskeleton .
- Microfilaments
- Intermediate filaments
- Microtubules
ORGANELLES :
- MITOCHONDRIA
- RIBOSOMES
- ENDOPLASMIC RETICULUM
- GOLGI APPARATUS
- LYSOSOMES
- CENTROSOME
- PEROXISOMES
MITOCHONDRIA
- Mitochondria (singular, mitochondrion) – are typically tubular or rod shaped organelles found in the cytoplasm of most cells and produces enzymes for the metabolic conversion of food to energy
- Power houses of cell
- Function – ATP production
STRUCTURE
- A mitochondrion contains outer and inner membranes
- composed of phospholipid bilayers and proteins.
- The two membranes have different properties.
Because of this double-membrane organization, there
are five distinct parts to a mitochondrion.
PARTS :
- Outer membrane
- Inner membrane
- Intermembrane space
- Crista
- Matrix
RIBOSOMES
Protien synthesizer consisting of two subunits .
Larger one 50 S and smaller 30 S .
ENDOPLASMIC RETICULUM
- Network of hollow membrane tubules
- Connects to nuclear envelope & cell membrane- Functions in Synthesis of cell products & Transport- Two types of ribosomes
- rough ER
- smooth ER
ROUGH ENDOPLASMIC RETICULUM
Has ribosomes on its surfacemakes membrane proteins and proteins for Export.
SMOOTH ENDOPASMIC RETICULUM
Lack ribosomes on its surface
It is attached to the ends of Rough ER.
It synthesizes fatty acids
GOLGI APPARATUS :- Golgi complex is a network of flattened smooth membranous sacs- cisternae and vesicles.
- These are responsible for the secretion of proteins from the cells(hormones, plasma proteins, and digestive enzymes).
- It works in combination with ER.
LYSOSOMES :- Lysosomes are roughly spherical bodies enclosed by a
single membrane. They are manufactured by the Golgi
apparatus
- They have a single limiting membrane.
- They have an acidic pH- 5
- They have a group of enzymes called Hydrolases
PEROXISOMES
Peroxisomes are about the size of lysosomes (0.5–1.5 µm) and like them are enclosed by a single membrane.
Peroxisomes are from the ER.
PEROXISOMES.
Some of the functions of the peroxisomes
breakdown of excess fatty acids
break down of hydrogen peroxide.
participates in the synthesis of cholestrol.
CONCLUSION
Every one should be thorough in the cell ,its functions and
their pathology to understand the pathogenesis of the
diseases.
REFERENCES
- TORTORA –Principles of Anotomy and Physiology
8th Edition
- Guyton - Text book of medical physiology
10th Edition
- Grays Anotomy – 38th Edition
- Wheaters oral Histology text book