This document provides an overview of cell biology. It defines the cell as the structural and functional unit of life. It describes the key differences between prokaryotic and eukaryotic cells. The structure and functions of major cell organelles like the cell membrane, nucleus, mitochondria and ribosomes are explained. The processes of cell division, transcription and translation are summarized. Different types of cell junctions and their roles are also outlined.

2. CELL
BIOLOGY
BY:
DR. JYOTISH KUMAR JHA
DEPARTMENT OF ORAL MEDICINE AND
RADIOLOGY

3. 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:

4. 









7)Mitochondria :
8)Ribosomes:
Nucleus
Function of nucleus
DNA
RNA
TRANSCRIPTION AND TRASNSLATION
CELL DIVISION
TYPES OF CELL DIVISION
MITOSIS

5.  CELL CYCLE
 DIFFERENCE BETWEEN MITOSIS AND





MEIOSIS
LIST OF CHROMOSOMAL
ABNORMALITIES
CHROMOSOMAL ABERRATION
APOPTOSIS
CELL JUNCTON
VIRUS ENTRY TO CELL

6.  TERM WAS COINED BY” ROBERT HOOK”
(1635-1703)
 DEFINED AS STRUCTURAL AND
FUNCTIONAL UNIT OF LIFE

7. GENERAL CHARACTERISTICS OF CELL
• Needs nutrition & oxygen
• Eliminates carbon dioxide & other metabolic
wastes
• Shows immediate response to the entrance
of invaders
• Reproduces by division

8. STRUCTURE OF CELL

9.  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 membrane
II. Cytoplasm
III. nucleus

10. 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%)

11. 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
1.
Integral Protein
2.
Peripheral Protein

12. Functional significance of protein layer
1. Integral protein provide the structural
integrity of cell membrane
2. Channel protein- for diffusion of water
soluble substances like glucose and
electrolyte
3. Carrier protein
4. Receptor protein
5. Antigen

13. 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 bloodbrain 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

14. 1. CYTOPLASM
 ORGANELLES IN CYTOPLASM
1. ENDOPLASMIC RETICULUM
2 TYPES rough endoplasmic reticulum
smooth endoplasmic reticulum
function of rough endoplasmic reticulum
1.
synthesis of protein
2.
degradation of worn out organelles
function of smooth endoplasmic reticulum
1.
synthesis of lipids and steroids
2.
storage and metabolism of calcium
3.
degradation of toxic substances in liver

16.  GOLGI APPARATUS
present in all cells except red blood cells
2. 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
1.

18.  LYSOSOMES
membrane bound vesicular organelles
found throughout the cytoplasm
2. Formed by golgi apparatus
3. 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
1.

19.  TYPES OF LYSOSOMES
1. 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

21. FUNCTION OF LYSOSOMES
1. Degradation on macromolecules like
bacteria
2. Degradation of worn out organelles
3. Secretory function

22. PEROXISOMES
 FUNCTION OF PEROXISOMES
1. Degradation of toxic substances like hydrogen
2.
3.
4.
5.
6.
peroxide – present in liver cells which is a major
organ for detoxification
Oxygen utilization
Breakdown of excess fatty acids
Acceleration of gluconeogenesis from fats
Degradation of purin to uric acid
Role in the formation of myelin and bile acids

23. CENTROSOME AND CENTRIOLES

24.  Situated near the centre of the cell close to
the nucleus
 Responsible for the movement of
chromosomes during cell division

25. MITOCHONDRIA

26.  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

27. 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

28. 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 ribosome
Ribosomes arrange the amino acids into small units of
protein
Ribosomes attached with ER are involved in protein
synthesis like enzymatic protein,harmonal protein
and proteina of cell membrane

30. There are two types of cells:
1) Prokaryotic Cells
2) Eukaryotic Cells

31. These are two distinct types of cells with
STRUCTURAL differences.
Prokaryotes
Bacteria
Eukaryotes
Animal
Plant

33. 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.

34. Eukaryote Cell
A more complex cell with a
nucleus and many organelles.

35. 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.

37. COMPARISON OF PLANT AND ANIMAL CELL

38. 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

39.  NUCLEOPLASM
 Gel like ground substance of the nucleus
 Contains 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

40.  NUCLEOLI
o One or more nucleoli are present in each
nucleus
o Nucleolus contains ribonucleic acid(RNA) and
some proteins similar to those found in
ribosomes

41. FUNCTION OF NUCLEUS
1. Control of all the activities of the cell
2. Synthesis of RNA
3. Sending genetic instruction to the
cytoplasm for protein synthesis through
mRNA
4. Control of cell division through genes
5. Storage of hereditary information

42.  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

44.  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

45.  TRANSFER RNA(tRNA)
Responsible for decoding the genetic message
present in mRNA
RIBOSOMAL RNA(rRNA)
 Present within ribosome and is responsible
for the assembly of proteins from amino acids
in the ribosomes

47. 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

49. 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

53. BINARY FUSION
BINARY FUSION
BINARY FUSION
MITOSIS
MEIOSIS

54. The Cell Cycle

58. LIST OF CHROSOMAL ABNORMALITIES

a)
b)
c)

a.
b.
c.
NUMERICAL ABNORMALITIES
Aneuploidy
Trisomic(2n+1)
Monosomic(2n-1)
STRUCTURAL ABNORMALITIES
DOWN’S SYNDROME
EDWARDS SYNDROME
PATAU’S SYNDROME

59.  SEX CHROMOSOME DISORDER
1) KLINEFELTER’S SYNDROME
2) TURNER’S SYNDROME
3) FRAGILE X SYNDROME

60. 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

62. 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

63. SIGNIFICANCE
1) Vital role in cellular homeostasis
2) 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

64. 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)

65.  SMAC inactivates AIF
 SMAC +AIF to form apoptosome activates
CASPASES
 CYTOCHROME C also facilitate caspase
activation

66. APOPTOTIC PROCESS

67. CELL JUNCTION
 It is the connection between the neighboring
cells
 THREE TYPES
1. OCCLUDING JUNCTION- prevent intercellular exchange
of substances
2. COMMUNICATING JUNCTION-permits intercellular
exchange of substances
3. ANCHORING JUNCTION-provide strength to the cells

68.  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

69. STRUCTURE OF TIGHT JUNCTION

70.  FUNCTION OF TIGHT JUNCTION
1. Holds the neighboring cell of tissues firmly for
strength and stability
2. 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