molecular biology

1. PROKARYOTES AND
EUKARYOTES

2. Introduction:
 Eukaryotic cells contain a nucleus and organelles bound by plasma
membranes. Fungi, plants, and animals are made of eukaryotic cells
(eukaryotes). Prokaryotic cells do not have a membrane-bound nucleus or
organelles. All bacteria and members of Archaea are made of prokaryotic cells
(prokaryotes).

3. Difference Between Eukaryotic And
Prokaryotic Cells
The most obvious difference between them is that prokaryotes have no
nuclei, but there are four major differences between a eukaryotic and
prokaryotic cell:
1.No prokaryotic cell has a nucleus; every eukaryotic cell has a nucleus.
2.Prokaryotic cells have no mitochondria, nearly every eukaryotic cell
has mitochondria.
3.Prokaryotic cells have no organelles enclosed in plasma membranes;
every eukaryotic cell has a nucleus and organelles, each enclosed in
plasma membranes.
4.Prokaryotic cells have circular strands of DNA; eukaryotic cells have
multiple molecules of double-stranded, linear DNA.

4. PROKARYOTIC VS. EUKARYOTIC
CELLS

5. Similarities Between Prokaryotic And
Eukaryotic Cells
For all their differences, prokaryotes and eukaryotes have
a few similarities share some common structures (due to
physics and evolution), and though their DNA is different,
they even share some genetic features.

6. Both types of cells have five similarities:
 Both types of cells carry on all the necessary functions of life (adaptation
through evolution, cellular organization, growth and development, heredity,
homeostasis, reproduction, metabolism, and response to stimuli). However,
they do these things in different ways.
 Both cells carry DNA and rDNA (ribosomal DNA)
 Both prokaryotic cells and eukaryotic cells have vesicles.
 Both prokaryotes and eukaryotes may be single-celled organisms. Amoebas,
paramecia, and yeast are all single-cell eukaryotes.
 Both types of cells have vacuoles, storage units for food and liquid.
Similarities Between Prokaryotic And Eukaryotic
Cells

7. Structures Found In Prokaryotic And
Eukaryotic Cells
All living organisms use cellular organization to create structures to conduct
life processes. Cells organize into tissues, which organize into organs,
which organize into amazing life forms like plants, fungi, dogs, ducks, and
people.
Intracellular structures are common to both types of cells. Both prokaryotic
and eukaryotic cells have:
•DNA
•Ribosomes
•Cytoplasm
•Plasma membrane

8. Prokaryotes
An organism with prokaryotic cells is a prokaryote. Prokaryotic
organisms get their names from the Greek roots, pro (before)
and karyon (nut or kernel). This roughly means they are cells with
structures so simple that they came from a time before a cell's
nucleus existed.

9. The three domains of life, Eukaryota, Bacteria, and Archaea, include
two branches that are prokaryotes:
1.Bacteria – The first prokaryotes were discovered in 1676. Bacteria
have bacterial rRNA (Ribosomal RNA), no nuclear membrane, and cell
membranes composed primarily of diacylglycerol diester lipids (ester-
linked lipids).
2.Archaea – Single-cell organisms. They have no nuclear membrane
and share some qualities with bacteria (rDNA, circular chromosomes,
asexual reproduction) but are set apart from bacteria by their unique
rDNA and ether-linked lipids in their cell membranes.
Prokaryotes

10. Prokaryotic Organelles
 Prokaryotes help recycle nutrients by decomposing dead organisms
 Bacteria in the intestines and mouths of all higher animals help with
the digestion of food
 The DNA of a prokaryotic cell is tightly coiled in a ‘nucleoid,’ which is
not a true nucleus since it has no membrane
 Prokaryotic rDNA is a single ring of DNA and is only
about 0.10.1 percent of the amount of DNA in a eukaryotic cell
 Prokaryotic cells have many more ways to obtain and use energy
than eukaryotic cells, performing photosynthesis, respiration in
common with eukaryotes but also using nitrogen fixation,
denitrification, sulfate reduction, and methanogenesis

11.  Prokaryotic cells have many more ways to obtain and use energy
than eukaryotic cells, performing photosynthesis, respiration in
common with eukaryotes but also using nitrogen fixation,
denitrification, sulfate reduction, and methanogenesis
 Roughly half of all bacteria have flagella, little whip-like external
structures that all them to move
 Prokaryotic cells can use pili and fimbriae, also types of external
growths, to stick to other cells or surfaces they make their home
 Prokaryotic cells can perform binary fission roughly
every 2424 hours, meaning they can reproduce exponentially fast
 All adult humans have about 0.2 kg0.2 kg of bacteria in their
digestive systems and on their skin;
 Prokaryotic cells are the oldest life forms on earth, dating
back 3.53.5 million years

12. Eukaryotes
Fungi, plants, protista, and all animals (including
humans) are eukaryotes. We are all built with
eukaryotic cells. The word eukaryote comes from
two Greek roots, eu (good, well), and karyon (nut,
kernel), so a eukaryote has a well-defined or “good”
nucleus (kernel) in its cells.
Eukaryotes Cells
Eukaryotic cells have nuclei and organelles, which
immediately sets them apart from prokaryotic cells.

13. Some of these eukaryotic cell organelles are:
 Mitochondria (cell powerhouses)
 Chloroplasts (in plants and some algae, for
photosynthesis)
 Endoplasmic reticulum (the cell transport system)
 Golgi apparatus (protein packagers)
 Ribosomes (protein synthesis)
 Vacuoles (water and food storage)
 Lysosomes (digestive processes)
 Peroxisomes (metabolic processes)
 Nucleus (the mind and brain of the cell)

14. Size Of Eukaryotic Cells
In general, eukaryotic cells are much bigger than
prokaryotic cells. One eukaryotic cell could be
double to 1,000 times the size of a prokaryotic cell.
Eukaryotic cells measure between 10 µm and 100
µm, which means you could barely see them with a
standard school light microscope.

15. Eukaryote Characteristics
 Eukaryotes can be single-celled organisms (like protozoa or paramecia) or
multicellular organisms (like you or an elephant)
 The largest organism on earth is a eukaryote nicknamed the Humongous
Fungus, a specimen of Armillaria ostoyae that covers almost four square miles
under the ground of Malheur National Forest in Oregon
 Eukaryotes have linear chromosomes, contrasting with the single ring of rDNA
in prokaryotes
 Eukaryotes include animal and plant cells, differentiated in many ways but
most obviously by the plasma membrane of animal cells and synthesis cell
walls in plants

16.  Eukaryotic cells store chromatin (DNA and proteins) in a gel-like fluid
called the nucleoplasm, inside the nucleus
 Mitochondria, found only in eukaryotic cells, have their own DNA
chromosome, which may indicate they were once freely existing,
independent prokaryotic cells “captured” by eukaryotic cells
 In contrast with the mind-blowing miniature prokaryotic cells,
eukaryotic cells are so large, even some of their organelles are
visible under the light microscope of a high school science laboratory
 The oldest eukaryote, Grypania, dates back around 1.874 billion
years ago; fossils of this eukaryote were discovered in a Michigan
iron mine
 Eukaryotes mostly reproduce sexually, though some do use cell
division
 Adult humans have around 3 ·1013 human (eukaryotic) cells in their
bodies and a roughly equal number of bacteria (prokaryotes).