Prokaryotic cells lack membrane-bound organelles and have no nucleus. They contain genetic material in the form of a single circular chromosome located in the nucleoid region. Prokaryotic cells are much smaller than eukaryotic cells, ranging from 0.2 to 0.5 micrometers in diameter. The plasma membrane is a selectively permeable barrier that encloses prokaryotic cells and is composed of phospholipids and proteins arranged in a fluid mosaic structure. Ribosomes are the sites of protein synthesis in prokaryotes and are composed of RNA and protein. Inclusion bodies are insoluble protein aggregates that form in bacteria when they are forced to overproduce foreign proteins.

1. Prokaryotic cell
BY:
SARAH HAMMAD

3. INTRODUCTION
 The word prokaryotes is derived from Greek words
Pro means before or primitive and Karyon means nucleus.
 Cells containing false nucleus or lack an organized nucleus are
called as Prokaryotes. The organisms containing prokaryotic cells
are called as Prokaryotes.
 Prokaryotic cells are mainly classified into
1. Bacteria
2. Archae
 Ancient type of cells.
 Prokaryotic cells are almost similar in morphology with eukaryotic
cells but the major difference is in genetics.

5. STRUCTURE OF PROKARYOTIC CELLS
 Lacks membrane bound organelles.
 Chloroplast, Golgi bodies, Mitochondria,
Endoplasmic reticulum and Lysosomes are absent.
 Respiratory system is present in plasma membrane.
 Mesosomes, endospores and magnetosomes may or
may not be present in prokaryotic cells.
 Ribosomes are of 70S size and are dispersed in
cytoplasm.
 Protein synthesis is carried out in cytoplasm.
 Plasma membrane lack sterols.

7. THE NUCLEUS
 Lack of nuclear membrane, histone proteins and
nucleolus is also absent.
 Genetic material is located in nuclear region or
nucleoid.
 Nucleoid contains single chromosome and piece of
circular double stranded DNA. The chromosome is
circular as well.
 Genes are present in form of clusters.
 The G+C content is about 20 to 70%.
 Mitosis and meosis mechanism is absent
 Reproduction through binary fission mechanism.

9.  Have ability to fix atmospheric nitrogen.
 Shows wide variety of anaerobic energy yielding
mechanism.
 The cell wall composed of:
1. Peptidoglycan
2. Polysaccharide
3. Glycoprotein
 Divided into gram +ve and gram –ve
 Contains flagella, pili, capsule on its surface.

11. Size of prokaryotic cell
 Average size of prokaryotic cells ranges from 0.2 to 0.5 micro
meters in diameter.
 Size ranges in nano and ultra micro meters as well.
 The small size of prokaryotic cells allows ions and organic
molecules that enter them to quickly spread to other parts of cell.
 The largest prokaryote discovered till now is Thiomargarita
namibiensis which is gram –ve bacteria ranges from 0.1 to
0.33mm (100-300 micrometrer) sometimes ataining size upto
0.75mm.

14. Plasma Membrane

15. CONTENTS
 What is plasma membrane ?
 How could youe define plasma membrane ?
 Structure
 Fluide mosaic model
 Overview
 Membrane protein
 Chemical composition
 Functions and Movement

16. What is plasma membrane ?
1. Outermost layer of animal cell
2. Thickness is 5-8 Nm
3. Selectively permeable membrane
4. Serve as outer boundary
5. Allow some substances to cross more easily than others
6. Made of phospholipids, proteins and conjugated molecules
7. Protect cell from external environment
8. Also called cell membrane

17. How could you define plasma
membrane ?
“An outermost envelope surrounding the cell that
separate
and protects the cell from external environment and
provides
a connecting system between the cell and its
environment.”

18. Structure of Plasma Membrane
The plasma membrane is
Composed of two layers Of
“phospholipids back to back”.
Phospholipids are lipids attached
to them.

19. Phospholipids
 Fatty acid tails hydrophobic
 Phosphate group head hydrophilic
 Arranged as bilayer
“Phospholipids, cholesterol and glycolipids
are amphiphatic lipids composed of Hydrophobic and
Hydrophilic ends.”

20. Phospholipid Bilayer :

21. Fluid Mosaic Model
 In 1972 S.J. Singer and G. Nicolson proposed Fluid Mosaic model

22. What is Fluid Mosaic Model ?
“Cell membrane is lipid bilayer in which
proteins are partially embeded like
floating Iceburge in sea.
“The fluid mosaic model desribes the
plasma membrane as a flexible boundary
of a cell. The phospholipid moves within
the cells “

23. Membrane Proteins
Membrane proteins are categorized into following
1. Extrinsic (peripheral ) membrane
2. Intrinsic (internal) membrane

24. Extrinsic Membrane protein
 Membrane loosely associated with membrane Surface
 Located entirely outside of the lipid bilayer
 Either on the extracellular or Cytoplasmic surface
 Examples
1. Cytochrome C of Mitochondria
2. Cell surface identity marker (antigens )

25. Intrinsic Membrane Protein
 Directly incorporated within the lipid bilayer
 Tightly bound to the lipid bilayer
 Provide channel for water soluble substances
Examples
1. Transmembrane proteins
2. Transport proteins
3. Channels , pumps

26. Plasma Membrane protein
(Transmembrane)

27. Chemical Composition
 Composed of lipid , protein and carbohydrates
 Actual component differs from tissue to tissue
Lipids of cell membrane are :
1. Phospholipids
2. Glycolipids
3. Sterols
4. Cholesterol

28. Functions

29. Movement
 Moving large molecules in
And out of the cell through vesicles
And vacuoles.
Endocytosis
1. Phagocytosis
2. Pinocytosis
Exocytosis

30. RIBOSOMES

31. DEFINITION:
RIBOSOMES COMPRISE A COMPLEX MACROMOLECULAR MACHINE
FOUND WITHIN ALL LIVING CELLS THAT SERVES AS A SITE OF
BIOLOGICAL PROTEIN SYNTHESIS.
 RIBOSOMES LINK AMINO ACIDS TOGETHER IN THE ORDER
SPECIFIED BY MESSENGER RNA.
DISCOVERY:
 RIBOSOMES WERE FIRST OBSERVED IN MID 1950S BY
ROMANIAN-AMERICAN CELL BIOLOGIST GEORGE EMIL PALADE
USING AN ELECTRON MICROSCOPE ; AS DENSE PARTICLES OR
GRANULES.
 TERM “RIBOSOMES” WAS PROPOSED BY RICHARD B . ROBERTS
IN END OF 1950S.

32. STRUCTURE:
 HIGHLY COMPLEXED STRUCTURE CELLULAR MACHINE.
 IT IS LARGELY MADE UP OF TWO MAIN COMPONENTS :-
 PROTEINS = 25-40%
 RRNA =37-62%
 TWO MAIN SUBUNITS ARE PRESENT.
A SMALLER SUBUNIT (CONSISTS OF SINGLE RNA STRAND).
A LARGER SUBUNIT (CONSISTS OF TWO STRANDS, A LONGER
AND A SHORTER STRAND WRAP UPON EACH OTHER).
 EUKARYOTIC SUBUNIT CONTAINS LARGER SUBUNIT 60S
AND SMALLER SUBUNITS 40S , TOTAL RIBOSOMAL
COMPLEX=80S
 PROKARYOTIC SUBUNIT CONTAINS LARGER SUBUNIT 50S
AND SMALLER SUBUNIT 30S AND TOTAL RIBOSOMAL
COMPLEX =70S

33. LOCATION:
RIBOSOMES CAN BE FOUND EITHER :-
 DISPERSED FREELY IN THE CYTOSOL.
 ATTACHED TO THE SURFACE
ENDOPLASMIC RETICULUM.
FUNCTION:
 MAIN FUNCTIONS OF RIBOSOMES IS THE
TRANSLATION OF GENETIC
INFORMATION ENCODED IN
NUCLEOTIDE BASIS OF DNA INTO
AMINO ACID SEQUENCE OF PROTEINS.
 THIS IS ALSO KNOWN AS “ GENE
EXPRESSION”.

34. RIBOSOME ASSOCIATED DISEASES:-
 DURING STRESS CONDITIONS , RIBOSOMES ON
ENDOPLASMIC RETICULUM FUNCTION IMPROPERLY.
 IMPROPER FUNCTIONING IS CHARACTERIZED BY
IMPROPER FOLDING OF PROTEINS.
SOME OF SUCH DISEASES ARE :-
 DIABETES
 CYSTIC FIBROSIS

35. INCLUSION BODIES IN BACTERIA

36. INTRODUCTION
 Inclusion bodies , sometimes called
elementary bodies, are nuclear or
cytoplasmic aggregates of stable
substances, usually proteins.
 Inclusion bodies are insoluble protein
aggregates usually found in
recombinant bacteria when they are
forced to produce heterologous protein
species.

37. INCLUSION BODIES
 Inclusion bodies are basically used to store variety of carbon
compounds, inorganic substances and energy.
 They also reduce osmotic pressure by tying up molecules in
particular manner.
EXAPMLES:
 Poly-hydroxybutyrate granules.
 Gas vacuoles.
 Sulphur Granules.
 Carboxysomes.
 Glycogens

39. TYPES OF INCLUSION BODIES IN
BACTERIA
Cyanophycins Granules:
 Present in Cyanobacteria.
 Are of large polypeptides.
 Contain equal amount of Amino acids i.e. Arginine
and Aspartic Acid.

40. Carboxysomes:
 Present in Cyanobacteria, Nitrifying bacteria,
Thiobacilli.
 Contain enzyme Ribulose-1,5-bisphosphate
carboxylase.
 Serve as reserve of this enzyme and site for C02
Fixation.

41. Gas Vacuoles:
 They are organic inclusion bodies.
 Present in Cyanobacteria, Purple and
Green photosynthetic bacteria.
 They are aggregates of enormous
number of small hollow, cylindrical gas
vesicles.
 They are composed of single small
protein.
 It is impermeable to water but freely
permeable to atmospheric gases.