Prokaryotes
1- Bacteria
‫شبه نواة‬
‫الريبوزومات‬
‫غشاء بالزمى‬
‫الجدار الخلوى‬
‫الكبسولة‬
‫األسواط‬
Fig. 7.4 The prokaryotic cell is much simpler in structure, lacking a nucleus
and the other membrane-enclosed organelles of the eukaryotic cell.
Page 112
Prokaryotic Cell
Plasma
membrane
Ribosomes
Nucleoid
Cell Wall
Cytoplasm
(Cytosol)
Capsule
A) the bacterial capsule

Many prokaryotes (bacteria)
secrete a sticky
protective layer called
capsule outside
the cell wall, which has the
following functions ‫وظائف‬:
1.
2.
3.
4.
Adhere ‫ تثبيت‬bacteria cells to their substratum ‫السطح‬.
Increase bacteria resistance ‫ المقاومة‬to host defenses ‫مناعة العائل‬.
Stick )‫ )تلصق‬bacterial cells together when live as colonies.
Protect ‫ تحمى‬bacterial cell.
Fig. 27.6
B) The bacterial cell wall

In all prokaryotes, the functions of the cell wall are as
following:
1.
maintains ‫ تحافط‬the shape of the cell,
2.
affords physical protection ‫توفر الحماية الطبيعية‬
3.
prevents the cell from bursting (‫ )إنفجار‬in a hypotonic
environment ‫البيئة ذات الضغط األسموزى المنخفض‬.

Most bacterial cell walls contain peptidoglycan
(a polymer of modified sugars cross-linked by short polypeptides).

The walls of Archaea lack (‫ )تـفـتـقـد‬peptidoglycan.
The Gram’s stain: ‫صبغة جرام‬

It is a tool for identifying ‫ تعريف‬specific bacteria, based on
differences in their cell walls.

A)- Gram-positive (Gram +ve) bacteria:

Their cell walls have large amounts ‫ كمية كبيرة‬of peptidoglycans
that react with Gram’s stain (appear violet-stained ‫)تـُصبغ بنفسجيا‬.
Fig. 27.5a
Page 529
The Gram’s stain: ‫صبغة جرام‬

B)- Gram-negative (Gram -ve) bacteria:

their cell walls have no or small amount of
peptidoglycan. So, do not react or very weakly react with
Gram’s stain (do not appear stained ‫)ال تظهر الصبغة‬
Fig. 27.5b Page 529
Gram Staining of Bacteria

Gram +ve bacteria: have Large amount of peptidoglycan
that stained violet (non-pathogenic ‫)غير ممرضة‬.

Gram –ve bacteria: Have small amount or no peptidoglycan
(no staining) (pathogenic ‫)ممرضة‬.

Gram-negative species are pathogenic (‫ ) ممرضة‬more threatening
(‫ )أكثر خطورة‬than gram-positive species.

Gram-negative bacteria are commonly more resistant (‫)أكثر ممانعة‬
than gram-positive species to antibiotics ‫للمضادات الحياتية‬.
Reproduction of Bacteria
‫التكاثر فى البكتريا‬

Prokaryotes reproduce (‫ )تـتـكاثر‬only asexually (‫)ال جنسيا‬
by binary fission (‫)اإلنقسـام الثـنائى البسيط‬.

A single cell produce
a colony of offspring.
Fig. 27.9 Page 531
Nutrition of Prokaryotes
‫التغذية فى األحياء الدقيقة‬

Nutrition refers to how an organism obtains
energy and a carbon source from the environment
to build the organic molecules of its cells.
• Prokaryotes are grouped (‫صنٍفـَت‬
ُ ) into four
categories (‫ )أنواع‬according to how they obtain
energy and carbon
Nutrition of Prokaryotes
‫التغذية فى األحياء الدقيقة‬

Phototrophs (‫)ضوئية التغذية‬:

Chemotrophs (‫)كيميائية التغذية‬:
Organisms that obtain energy from light.
Organisms that obtain energy from
chemicals in their environment.

Autotrophs (‫)ذاتية التغذية‬:

Heterotrophs (‫)متعدد التغذية‬:
a carbon source.
Organisms that use CO2 as a carbon source.
Organisms that use organic nutrients as
There are four major modes of nutrition

Photoautotrophs (‫)ذاتية التغذية الضوئية‬:
use light energy as energy source, and CO2 as carbon source to synthesis
(‫ )تخلق‬organic compounds.

Chemoautotrophs )‫)ذاتية التغذية الكيميائية‬:
use chemical inorganic substances as energy source, and CO2 as a carbon
source.

Photoheterotrophs (‫)متعدد التغذية الضوئية‬:
use light as energy source, and organic substances as carbon source.

Chemoheterotrophs (‫)متعدد التغذية الكيميائية‬:
use organic substances as a source for both energy and carbon.
Prokaryotic modes of nutrition
Based on Carbon source and Energy source that can be used
by a prokaryote organism to synthesise organic compounds.
Prokaryotes
Page 532
Autotrophs
CO2 as Carbon Source
Photoautotroph
Chemoautotroph
Heterotrophs
Organic compounds as
Carbon Source
PhotoHeterotroph
ChemoHeterotroph
- Light as energy
source
- Chemicals as
energy source
- Light as
energy source
- Chemicals as
energy source
-CO2 as C source
-CO2 as C source
-Organic
compounds as
C source
- Organic
compounds as C
source