CYTOPLASM AND ITS CONTENTS

1. CYTOPLASM
-DEVIKA K V
I MDS

2. SYNOPSIS
 INTRODUCTION
 CYTOPLASMIC MATRIX
 CELL MEMBERANE
 CELL JUNCTION
 MITOCHONDRIA
 ROUGH AND SMOOTH ENDOPLASMIC RETICULUM.
 RIBOSOMES
 GOLGI APPARATUS
 LYSOSOMES
 PEROXISOMES
 MICROTUBULES
 CILIA
 FILAMENTS
 CONCLUSION
 REFERENCES

3. INTRODUCTION
 The cell was first discovered by Robert Hooke
in 1665, which can be found to be described in his book,
Micrographia
 The cytoplasm is the part of the cell designed to perform principal
metabolic activities. To carry out a broad range of different
functions, the cytoplasm is equipped with several different kinds
of cytoplasmic organelles, cytoplasmic matrix and cytoskeleton.

5. COMPONENTS OF THE CELL
CYTOPLASM
MEMBERANEOUS
ORGANELLES
1. CELL MEMBERANE
2. MITOCHONDRIA
3. ROUGH SURFACED
ENDOPLASMIC
RETICULUM
4. SMOOTH
ENDOPLASMIC
RETICULUM
5. GOLGI APPARATUS
6. SECRETORY
VESICLES
7. LYSOSOMES
8. ENDOSOMES
9. PEROXISOMES
NON MEMBERANEOUS
ORGANELLES
1. RIBOSOMES
2. MICROTUBULES
3. CILIAAND FLAGELLA
4. CENTRIOLES
5. FILAMENTS
CYTOPLASMIC
INCLUSION
1. STORED FOOD
Glycogen
Fat
2. PIGMENTS
i. EXOGENOUS
Carotene,
Carbon particles
ii. ENDOGENOUS
Haemoglobin
Hemosiderin
Bilirubin
Melanin
Lipofuscin

6. CYTOPLASMIC MATRIX/ CYTOSOL
 Non organelle component of the cytoplasm.
 Liquid component?
 Microtrabecular lattice (6nm thick) represent part of the gel
structure of the matrix.
 This network hold the organelle in position.
cytoplasm
EM H & E

7. Cell memberane / plasma memberane /
PLASMALEMMA
 Outer memberane of the cell
 Cannot be seen in the LM because
the memberane is only 8-10nm thick
 In EM – trilaminar structure
 The cell memberane posess
a unique outer region made up of
(glycocalyx or cell coat)

8. FUNCTIONS
 Cell memberane is the part of the cell that determines which
constituent are able to enter or leave the cytoplasm
 Cell memberane plays a role in receiving chemical messages
from other cells
(A receptor is defined as a protein molecule with in a cell
or on the cell surface to which a substance like hormone, a
drug, or an antigen can bind to it , and cause a change in
the cell activity)

9. MOLECULAR STRUCTURE OF THE
CELL MEMBERANE

10. CELL MEMBERANE PROTEINS
 Memberane proteins furnish transmemberane channels for the
passage of ions and molecules present in aqueous solution.
 Intrinsic or integral memberane proteins and peripheral or
extrinsic memberane proteins
FLUID MOSAIC MODEL by Singer and Nicholson(1972)
 Lipids are organised in a double layer or bilayer. Membrane lipids
are amphipathic.
 Memberane proteins can be associated either to the lipid bilayer
polar head groups (peripheral proteins) or to the hydrophobic
matrix (integral proteins)
 Both the lipids and the proteins are in the constant motion. Three
main modes of motion are rotational, translational and
transbilayer.

11. ASYMMETRY OF THE CELL MEMBERANE
 Glycocalyx present only on the outer side
 Two constituent layer of the lipid bilayer have substatially
different lipid compositions
 Different proteins can be present in inner and outer parts

12. CELL JUNCTIONS
Tight/occluding
junction
Anchoring/ adhering
junction
Gap junction

13. MITOCHONDRIA

14.  “Mitos, thread;
chondrion, granule”
 Ovoid elongated thread like
structures present in the
cytoplasm
 0.5-1 um in diameter and
5-10um in length
 It contain both DNA(mt DNA)
and RNA
 Site of the cell involved in the
oxidation process- “power
House of the cell”
 Contains the enzymes
responsible for respiratory
metabolism-(ATP)

15. In Electron microscopy
i)outer memberane
(permeable)
ii) inner memberane (7
nm thick,
selectively permeable)
ii)Intermemberaneos
space
iv) Cristae
v)Mitochondrial matrix
vi)Matrix granules
STRUCTURE OF MITOCHONDRIA

16. FUNCTIONS
Mitochondrial structure is related to various enzymatic
and electrochemical reactions that bring about oxidative
phosphorylation
Mitochondial enzymes catalyse a number of different
reactions involved in the breakdown of various end
products of glycolysis, fatty acid metabolism, aminoacid
metabolism

17. ENZYMATIC REACTIONS IN MITOCHONDRIA
 In the cytosol, mammalian cells utilize an oxygen independent
pathway to degrade glucose in the cytosol
 The aerobic pathway comes into effect once pyruvate has been
produced through glycolysis
 Pyruvate is taken in through both the memberanes to the
mitochondrial matrix, which is where the enzymes of the citric
acid cycle are situated
 The enzymes catalyse a number of different reactions involved in
the break down of various end products of
 1) glycolysis,
 2) fatty acid metabolism
 3)amino acid metabolism

18.  Within the mitochondrial matrix, glycolytic end products are
gradually oxidised to carbon dioxide by the enzymes of the citric
acid cycle
 During these process there is release of hydrogen atoms, some of
which become transferred to NAD, and others to FAD
 The electrons of the hydrogen are then passed along the series of
respiratory enzymes called flavoproteins and cytochromes
 The energy obtained from the transfer of electron carriers is used
to generate ATP from ADP and inorganic phosphate
 The various enzymes involved in the electron transport chain and
oxidative phosphorylation form integrated complexes on the
inner mitochondrial memberane and its cristae

20. mi
MITOCHONDRIA APPEAR TO BE DESCENDED FROM
AEROBIC BACTERIA
 It contains both DNA and RNA
 They also contain ribosomes
 Thus mitochondria posess the basic requirement of an
independent existence
 Mitochondrial DNA, RNA and ribosomes are similar to their
counterparts in the bacteria
 Mitochondrial DNA directs the synthesis of proteins
 The mitochondrial genes have become integrated in the cell’s own
genome

21. MITOCHONDRIAL DISORDERS

25.  Rounded ribonucleoprotein particles
 20-30nm in diameter
 Present as unbound particles and also as bound state attached to
the endoplasmic reticulum
 They are composed of rRNA and ribosomal proteins and the don’t
posess a memberane (non memberaneous organelle)
 LM
 In H & E staining the cytoplasm are either tinged with blue or is
definitely blue in cells that are actively producing proteins
 Cytoplasmic basophiia- strong affinity of rRNA for hematoxylin.
DIFFUSE LOCALIZED

26. ELECTRON MICROSCOPIC VIEW

27. FUNCTIONS
 It provides the intracellular sites where aminoacid molecules are
linked together to form polypeptides
 Translation

28. RIBOSOMIOPATHIES
• Treacher Collins syndrome (TCS)
• Diamond-blackfan anemia (DBA)
• Robert syndrome (RBS)
• Shwachman-diamond syndrome (SDS)
• Bowen-conradi syndrome (BWCNS)
• North American Indian childhood cirrhosis (NAIC)

29. ROUGH
ENDOPLASMIC
RETICULUM

30. o Endo:within the cytoplasm;
Reticulum:network by PORTER
o Largest organelle in the cell and is the major
site of protein synthesis and transport, protein
folding, lipid biogenesis, calcium storage
o Endoplasmic reticulum with ribosomes attached
o Regions of cytoplasm that exhibits intense local
basophilia
o Memberaneous organelle
o Seen in cells that elaborate secretory proteins or
glycoprotein

32. ELECTRON MICROSCOPIC VIEW

33. SEGREGATION OF LYSOSOMAL ENZYMES AND SECRETORY
PROTEINS
rER is required by all the cells eventhough they are not secretory, for
the synthesis and segregation of lysosomal enzymes.
SIGNAL HYPOTHESIS BY BLOBEL AND SABATANI

34. +
SITE OF INCORPORATION OF INTEGRAL
MEMBERANE PROTEINS AND MEMBERANE LIPIDS.
 Integral protein and glycoprotein molecules extend partially
through the rER
SITE OF MODIFICATION OF SEGREGATED
PROTEINS
 Once protein are synthesised, protein destined for secretion must
undergo proper folding and modifications, with the aid of
chaperons
 Following the removal of the signal sequence, the molecule fold up
because of the formation of S-S bonds, a configurational change
that helps to keep segregation unidirectional
 From the rER memberane segregated proteins are delivered by
means of small vesicles to the golgi apparatus

35. PROCESS OF PROTEIN
SYNTHESIS
 RNA is transcribed from DNA
RNA transcript mRNA is
spliced and modified to mRNA
which is moved from nucleus to
the cytoplasm
 The mRNA attaches to the
ribosome
 Each aminoacids attaches to
the proper tRNA with the help
of enzymes & ATP
 A succession of tRNAs add
their aminoacids to the
polypeptide chains as the
MRNA is moved through the
ribosome one codon at a time

36. LIPID BIOGENESIS
 ER is a site of bulk memberane lipid biogenesis
 Proteins and phospholipids are transferred and biochemically
modified in the region of the ER and Golgi apparatus
 This region is known as ERGIC
CALCIUM METABOLISM
 Ca 2+ concentration in the lumen of the ER is 100-800uM.
 ER contains several calcium channels, ryanodine receptors and
inositol 1,4,5 tri phosphate receptors that are responsible for
releasing calcium from the ER into the cytoplasm when the
intracellular levels are low

37. 1. Lack of protein due to ER retention
 Cystic fibrosis and associated diseases
 Congenital goiter and hypothyroidism due to thyroglobulin deficiency
 Osteogenesis imperfecta
 Procollagen type I, II, IV deficiency
 Albinism/tyrosinase deficiency
2.Toxic protein or protein aggregates
 Diabetes insipidus
 Liver disease in a1-antitrypsin deficiency
3. Defective transport machinery
 Abetalipoproteinemia
ENDOPLASMIC RETICULUM DISORDERS

38. SMOOTH ENDOPLASMIC RETICULUM
• Devoid of ribosomes, hence it cannot synthesise proteins.
• It consists of tubules that branch and anastomose in an irregular
manner
FUNCTIONS
 sER is the site of intracellular synthesis of lipids and cholestrol.
 Steroid hormone secretion
 It is believed to detoxify many drugs including alcohol
 It is involved in hepatic glycogen metabolism (glycogen synthase
phosphatase & phosphorylase phosphatase)
 Regulation of intracellular distribution of calcium ions.

39. EM

41.  Named after Camillo Golgi, Italian neurologist
 A pale staining area seen near the nucleus
 The main structural unit of the golgi apparatus
is flattened memberaneous vesicle described
as a Golgi saccule
 Golgi saccules are arranged in golgi stacks
that contains 3-10 saccules
 The saccules are fenestrated known as a network
of anastomosing tubules
 Saccules in each stacks are interconnected with those of other
stacks by complex of anastomosing tubules. This network is termed
as golgi complex

42. Structure of

43. ELECTRON MICROSCOPIC VIEW

44. FUNCTIONS
 Modify the secretory products
ROUTE TAKEN BY THE SEGREGATORY PROTEINS
 Golgi stack contain 3 compartment
cis medial trans
( mannose) (N- glucosamine) (galactose & sialic acid)
Glycosylation by glucosyl transferase
Sulfation by sulfotransferase
Golgi
memberane

45. Golgi sorts and packages its segregated proteins into two distinct
intracellular compartments
 golgi apparatus sort out the secretory products and package them as secretory
granules
 It manages to segregate the acid hydrolases and sequester these in lysosomes
The golgi apparatus is the main center for memberane traffic
within the cell
 It serves as a major distribution centre for newly synthesised memberane
constituents and it redirects much of the recycled memberane that returns to it in
the form of coated vesicles
The golgi apparatus plays a role in both lipoprotein secretion and
prohormone processing

46. MAKING PROTEINS; A REVIEW

47. AFFECTED GENE DISEASE PRIMARY CLINICAL
MANIFESTATION
CELLULAR EFFECT
RAB1, RAB2, RAB8,
STX5
Parkinson’s disease Neurological disease Altered expression of
the proteins leads to
Golgi fragmentation
ABCB6 Dyschromatosis
universalis
hereditaria
Skin disorder Mutation leads to
retention of the protein
ATP6V0A2 Cutis laxa Connective tissue
disorder
Mutations lead to
abnormal glycosylation
of serum proteins and
impairment of Golgi
trafficking
ATP7B Wilson disease Hepatic and
neurological disorders
Protein is localized to
the TGN and is
essential for copper
metabolism.
UBE3A Angelman syndrome Neurodevelopmental
Disorder
Loss of protein
expression leads to an
altered Golgi
morphology and pH

48. Golgi Endoplasmic Reticulum Lysosomal complex
(GERL) by Novikoff.
GERL may provide a more direct route for certain
enzymes synthesised in the rER to reach the sites from
which lysosomes and the secretory vesicles arise.
When a GERL is present it receives the luminal contents
of Golgi saccules before they are delivered to the
secretory vesicles or lysosomes.

49. SECRETORY VESICLES
 They are vesicles bounded by a unit memberane
 Large secretory granules are called zymogen granules. It contain
enzymes in the precursor forms
 It is stained vivid red in H&E staining due to their high protein
concentration
 The mechanism by which the secretory products are releases to the
cell surface is termed as exocytosis

50. LYSOSOMES
 Described in 1950 by Christian de Duve
 Spherical memberaneous organelle
 0.2-0.4um diameter
 They are centre for degradation and recycling of macromolecules delivered by
endocytosis, phagocytosis and autophagy
STRUCTURE OF LYSOSOMES
 7-10 nm phospholypid bilayer
 high carbohydrate
content (glycosylated lysosomal
memberane protein
 Lysosomal memberane proteins include
LAMP-1,2, lysosomal integral memberane
Proteins(LIMP) &CD63
 Intralysosomal memberane is rich in
phospholipids
 Lysosome contain upto 600uM calcium

51. ELECTON MICROSCOPIC VIEW

52. FUNCTIONS
Degradation of macromolecules
 60 resident hydrolases including proteases, peptidases,
phosphatases, nucleases, glycosidases, sulfatases and lipases have
different target substrates and their collective action permits the
degradation of macromolecules
 The best known lysosomal hydrolases are cathepsin family of
proteases
 The characteristic acidic pH of lysosomes are the result of action of
the vacuolar H+-ATPase

53. Endocytosis
 Process by which cells internalize the plasma memberane along
with the cell surface receptors and soluble molecules
 Cells have multiple mechanism for endocytosis, including
clatherin dependent and independent routes
phagocytosis pinocytosis

54. Autophagy
 Chaperon mediated autophagy, microautophagy and
macroautophagy
 Chaperon mediated autophagy is a process by which cytosolic
proteins harboring specific recognition motifs are delivered to the
lysomes via the action of a chaperon and the lysosomal receptor
LAMP-2A
 Micro autophagy involves the direct engulfment of the
cytoplasmic cargo at the limiting lysosomal memberane
 During macroautophagy, sequestration of small portion of the
cytoplasm including soluble materials and organelles, within a
newly generated double memberane called the isolation
memberane(phagophore) result in the formation of
autophagosomes
 Autophagosomes fuse with the lysosomes for the degradation and
recycling of their contents

55. Exocytosis
Damage to the plasma memberane
resulting in calcium influx
Lysosomes are translocated to the
periphery, and fuse with the plasma
memberane
Calcium binds to the synaptotagmin
VII and facilitates interaction with
the SNAREs
Lysosomal
exocytosis plays
an important role
in immune
responses, bone
resorption, cell
signalling and
plasma
memberane repair

56. CHOLESTROL HOMEOSTASIS
 The majority of cholestrol (80%) is found in the plasma
memberane, where it constitutes 40% of all lipids
 In addition to the cholestrol synthesis in the ER, the uptake of low
density lipoprotein via receptor mediated endocytosis is an
important route for cholestrol entry into the cell
LDL derived cholestrol esters are
transported to the lysosomes
Action of acid lipase liberates free
esterified cholestrol

57. Lysosomal participation in cell death signalling
 Lysosomes were referred to as ‘suicide bags’
 Partial permiabilization of the memberane induces apoptosis, and
massive lysosomal rupture induces necrosis
 The executors of lysosomal mediated apoptosis are not the lysosomes
themselves but their hydrolases, more specifically the cathepsins
release of cathepsin to the cytosol by
Lysosomal memberane permeablization
(LMP)
Cathepsin B induces typical apoptosis
associated changes includes chromatin
condensation, DNA fragmentation,
phosphatidyl serine exposure, and
plasma memberane blebbing

58. lys
LYSOSOMES IN DISEASE
 Lysosomes have a central role in lysosomal storage disorders but an
increasing evidence indicates that lysosomes are involved in
alzhiemer’s disease and amyotropic lateral sclerosis
 Lysosomal storage disorders frequently involve the central nervous
system
 Cathepsins contribute to the development and progression of
cardiovascular diseases, including atherosclerosis and aneurysm
formation

59. DISEASE ENZYME
DEFICIENCY
AGE AT ONSET CLINICAL SIGNS PATHOLOGY
TAY- SACH’S
DISEASE
Hexosaminidase
A, Gangliosides
3-8 months Psychomotor
arrest, startle
reflex, seizures,
cherry red spots
Storage in
central and
peripheral
neurons
NIEMANN
PICK’S DISEASE
TYPE A
Sphyngoyelinase
, shyngomyelin
1-6 months Psychomotor
arrest, spleen
enlargement,
retinal cherry
red spot
sometimes
Storage in
neurons and
spleen
METACHROMATIC
LEUKODYSTROPHY
Cerebroside
sulfatase
Early childhood Progressive
mental and
motor
deterioration
Myelin deficits
in CNS and often
PNS, storage in
glia
KRABBE’S
DISEASE
Galactocerebrosi
de8-
galactosidase,
galactocerebrosi
dase
3-6 months Irritability,
crying, mental
and motor
deterioration,
seizures
Myelin deficits,
gobloid cells
(large
mulinucleated
macrophages

60. PEROXISOMES
 Memberane bound organelles
 Less than 1um, hence called as microbodies
 They contains peroxide forming enzymes and catalase and are
involved in the formation and degradation of intracellular
hydrogen peroxides
FUNCTIONS
 Peroxisomes play a direct role in lipid metabolism (glucose from
lipids)
 Hepatocyte peroxisomes can breakdown fatty acids by beta
oxidation
 The oxidase enzymes in peroxisomes (urate oxidase, D-amino
oxidase and alpha hydroxy acid oxidase) produce hydrogen
peroxide wherase catalase converts products into water and
oxygen

61. ELECTRON MICROSCOPIC VIEW

62. MICROTUBULES
 Tubular or cylindrical structures
 Outer diameter is 25nm
 It contains a protein tubulin, that are arranged in rings stacked end
to end
FUNCTIONS
 It provide internal support for the cell and present its main
skeletal element
 Facilitate the intracellular transport of organelles, particles and
macromolecules along the specific routes through the cytoplasm
 Microtubules are essential for the process of segregation of
daughter chromosomes at mitosis

63. ELECTON MICROSCOPIC VIEW OF MICROTUBULES

64. CILIA

65. CILIA
 Motile hair like processes almost10 um length with a diameter of
0.2um
 They extend from the luminal border of most of the surface
epithelial lining of certain internal passages and cavities
 Every cilium has a tiny associated structure known as basal body
at the base
 The basal bodies of cilia and flagella are derived from the
centrioles
cilia

66. IN H&E STAINING IN ELECTRON MICROSCOPE

67. FILAMENTS
 Non memberaneous organelle
 Elongated thread like structures seen in decreasing diameters
 If they are seen under LM, they are called as fibres
 Those resolved under high power of LM is called as fibrils
 Those resolved by EM having smaller diameter are called as
filaments
 Three different categories of
filaments are
1. Thin filaments/microfilaments
2. Thick filaments
3. Intermediate filaments

68. MICROFILAMENTS
 Slender rods with a diameter of 6-7nm.
 They are composed of actin associated with tropomyosin.
 In the thin filaments of skeletal and cardiac muscle contain
troponin as well as actin and tropomyosin.
THICK FILAMENTS
 12-16 nm in diameter.
 It is composed of myosin.
INTERMEDIATE FILAMENTS
 7-11nm,also called as10nm filaments.
 They supplement microtubles in providing support and
maintaining the shape of the various part of the cell.
 Ex: tonofilaments, desmin, neurofilament, glial filament, vimentin

69. MAIN CLASS OF INTERMEDIATE FILAMENTS
CLASSES OF FILAMENTS CELL TYPES
cytokeratin Epithelial cells
desmin Muscle cells
neurofilament neurons
Glial filament Astrocytes, ependymal cells, schwann
cells, pituicytes
vimentin Mesenchymal derivative including
endothelial cells, muscle cells, neuro
ectodermal derivative including early
differentiating neurons and most kind
of glial cells, immature cells

70. THIN AND THICK FILAMENTS INTERMEDIATE FILAMENTS

71. REFERENCES
1.Ham’s Histology
2.”The Endoplasmic Reticulum: structure, function and response to
cell signaling”; Dianne S. Schwarz, Michael D.Blower;Cell.Mol.Life
Sci(2016) 73:79-74
3.’’The Golgi apparatus: an organelle with multiple complex
functions’’; Cathal WILSON, Rosella VENDITT, Laura R. REGA,
Antonino COLANZI, Giovanni D’ANGELO and M.Antonietta DE
MATTEIS; Biochem. J, (2011) 433, 1-9
4.’’Lysosome: The story Beyond the Storage’’; Ursula Matte, Gabriela
Pasqualim; Journal of Inborn Errors of Metabolism and screening,
2016, volume 4: 1-7

72. THANK YOU