PROCARYOTİC &EUCARYOTİC
CELLS
Prof. Dr. Gönül KANIGÜR
Microorganisms can be divided into 2 groups :
Single Cellular
Multi-cellular
Procaryote
Bacteria
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Eucaryote
Fungi
Protozoa
Algae
Fungi
Algae
CELLS
• The microscopic study of cells reveals 2 types
of cells: prokaryotic and eukaryotic.
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Two Main Classes of Cells
• Prokaryotic (Bacteria and Archaea)
– Pro = “Before”; Karyon = “Kernel”
– No nucleus, DNA coiled up inside cell
• Eukaryotic (Everything else)
– Eu = “True”
– DNA inside membrane bound organelle inside
cell, the nucleus
Prokaryotic Cells are relatively
simple
• 1. Bacteria are prokaryotic cells
• 2. 1-10 um in diameter, just visible with
light microscopes.
• 3. Metabolically diverse.
• 4. No True Nucleus
MORPHOLOGY OF PROKARYOTIC
CELLS
•Prokaryotes exhibit a variety of
shapes
– Most common
• Coccus
–Spherical
• Bacillus
–Rod or cylinder
shaped
Cellular Structure
• A typical bacterial (procaryotic) cell has the
following basic structures :
(1) Cell Wall,
(2) Cell Membrane,
(3) Ribosomes,
(4) Nuclear Region
CELL WALL
• Bacterial cell wall
– Rigid structure
– Surrounds cytoplasmic membrane
– Determines shape of bacteria
– Holds cell together
– Prevents cell from bursting
– Unique chemical structure
• Distinguishes Gram positive from Gram-negative
Cytoplasmic membrane
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A.Structure
-A phospholipid bilayer with proteins
-contains carbonhydrates
-contains sterols
B-Function
-transport:simple diffusion,facilitated
diffusion,osmosis and active transport
• -Endocytosis:phagocytosis and pinpcytosis
Cellular Structure
(3) Ribosomes
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Small particles composed of protein and ribonucleic
acid (RNA).
A single cell may have as many as 10,000 ribosomes.
Part of the translation apparatus, synthesis of cell
proteins take place upon these structures.
INTERNAL STRUCTURE
•Ribosome
– Involved in protein synthesis
– Composed of large and small
subunits
• Units made of protein 40% and
ribosomal RNA 60%
– Prokaryotic ribosomal subunits
• Large = 30S
• Small = 50S
– Small than eukaryotic ribosomes
• Difference often used as target
for antimicrobials
Cellular Structure
(4) Nuclear Region
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Nuclear region is primitive in procaryotic cell, i.e. bacteria.
Procaryotic cells DO NOT possess a true nucleus.
The functions of the nucleus are carried out by a single long
strand of deoxyribonucleic acid (DNA)
The nuclear region where the DNA is present is sometimes
known as a nucleoid, NOT a nucleus.
• Bacterial chromosome is not directly intereact
with the proteins such as histons
• DNA contents range from about 0.6 million to
five milion bp.5000 proteins are coded from
the chromosomal DNA
• Bacteria may also contain plasmids,double
stranded DNA molecules.they are not
essential for growth and reproduction.
• Plasmids carry functional genes that give
certain properties of the bacterial cell for
ex.drug rezistance .some bacteria are
rezistance to some antibiotics.
Movement
Many bacteria are motile, able to move
independently due to a special structure
known as Flagellum (plural : Flagella)
PILI
•Rigid tubular structure made of pilin
protein
•Found only in Gram negative cells
•Functions
– Sexual pili—joins bacterial cells for
DNA transfer (conjugation)
– Common pili—adhesion
EUCARYOTIC CELLS
I. Organisms and general properties
• A. Organisms
– 1. Microorganisms
• Fungi
• Protozoa
• Algae
– 2. Other
• Higher plants
• Animals
I. Organisms and general properties, cont.
• B. General properties
– More complex than procaryotes
– Larger than procaryotes
– Have a true nucleus
– Have membrane-bound organelles
III. The cell wall and glycocalyx
• A. Cell wall
– Rigid structure
– Found on plant cells
– Not made of peptidoglycan, but of long
polysaccharide, e.g., cellulose
• B. Glycocalyx A carbohydrate-containing structure on the
surface of a cell.
– May strengthen membrane of animal cells.
– Serves as an adhesin, i.e., holds adjacent cells
together
Eukaryotic Cells Components
Cell Wall
– contains cellulose
– support and protection
Cell membrane / Plasma membrane
– Phospholipid bilayer with embedded proteins
– boundary layer and transport
Nucleus
– nuclear envelope, nucleoplasm, chromatin, nucleoli
– storage and synthesis of genetic material.
Nucleolus
– Ribosome formation
IV. The cytoplasmic membrane
• A. Structure
– A phospholipid bilayer with proteins
– Contains carbohydrates
– Contains sterols
• B. Function
– Transport: simple diffusion; facilitated diffusion;
osmosis; and active transport
– Endocytosis: phagocytosis; and pinocytosis
VI. Organelles
• Organelle A membrane-enclosed structure.
• A. Nucleus
– Has a double membrane with pores
– Contains nucleoli where ribosomal RNA is
synthesized
– Contains chromatin: DNA + histones (basic
proteins)
– Chromosomes divide by mitosis.
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İts diameter is aprox. 5um
İt contains genetic material of the cell.
The Dna content is l.5 x10 – 7 to 5xl0 -9 bp
30.000 protein are coded.
The nucleus is the site of DNA replication and
RNA synthesis.
V. Cytoplasm
• The substance outside the nucleus and inside the plasma
membrane
• Similar in composition to that of procaryotes, but has a
cytoskeleton that provides shape, support, and transport
within cell
• Cytoskeleton consists of:
– Microfilaments
– Intermediate filaments
– Microtubules
VI. Organelles, cont.
• B. Endoplasmic reticulum (ER)
– Membrane network from nucleus to plasma
membrane
– Rough ER
• Has ribosomes attached
• Site of protein synthesis
– Smooth ER
• No ribosomes attached
• Site of lipid synthesis
VI. Organelles, cont.
• C. Golgi apparatus
– Stacks of membranes in cytoplasm
– Receives proteins & lipids from ER
– Ends pinch off forming secretory vesicles
– Transports proteins & lipids within cell
D. Ribosomes
– The site of protein synthesis
– In cytoplasm: 80S variety consisting of 60S &
40S subunits
– In mitochondria:70S variety consisting of 50S
& 30S subunits
G. Lysosomes
– Contains hydrolytic enzymes
– Especially important in phagocytes
. Organelles, cont.
• H. Vacuoles - membrane
bound cavities
– Diverse functions:
• Store proteins, sugars, etc.
• Store metabolic waste
• Store water (plant cells)
Organelles, cont.
• E. Mitochondria
– The site of respiration
– Has 2 membranes:
• Outer one has
sterols
• Inner one has no
sterols,
• Has DS circular DNA
– Has 70S ribosomes
– Replicates autonomously
VI. Organelles, cont.
• F. Chloroplasts
– The site of photosynthesis
– In algae and other plant cells
– Contain 70S ribosomes
– Contain DS DNA
– Replicate autonomously
• An endosymbiotic
orijin for these
organels
mitochondria,chlor
oplast) is now
generally accepted
I. Centrioles
– Near nucleus
– Functions: cell division, and formation of cilia
and flagella
II. Structures external to the cell wall
• A. Flagella
– Surrounded by the cytoplasmic membrane.
– Contains microtubules in a 2 + (2 x 9) arrangement
– Function: motility
– Found on some protozoa and algae
– Only a few per cell
VII. Comparisons
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EUCARYOTE
Larger
Simple wall structure
Sterols in membrane
2 + (9x2) flagella
True nucleus
Histones
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PROCARYOTE
Smaller
Peptidoglycan wall
No sterols in memb.
Flagellin in helix
No nucleus
No histones
VII. Comparisons, cont.
• EUCARYOTES
• Several chromosomes
• Membrane-bound
organelles
• 80S ribosomes
• PROCARYOTES
• One chromosome
• No membrane-bound
organelles
• 70S ribosomes
VII. Comparisons, cont.
• PROCARYOTES
• 1 chromosome
• No membrane-bound
organelles
• 70S ribosomes
• Replicates autonomously
• MITOCHONDRIA
• Multiple copies
• no membrane-bound
organelles
• 70S ribosomes
• Replicates autonomously
VII. Comparisons, cont.
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PROCARYOTES
About 1- 8 m
Peptidoglycan wall
No sterols in membrane
No nucleus
No histones
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MITOCHONDRIA
About 1 m
No wall
No sterols in inner
membrane
• No nucleus
• No histones