The document discusses the key differences between prokaryotic and eukaryotic cells. Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have a nucleus enclosed in a nuclear membrane and membrane-bound organelles. The genetic material in prokaryotes is a single loop of DNA, whereas in eukaryotes it is organized into linear chromosomes within the nucleus. Prokaryotes tend to be unicellular while eukaryotes can be unicellular or multicellular. The document then provides more details on the structures and components of prokaryotic and eukaryotic cells.

1. Summer break
holiday
homework

2. Now that we have learned how living
things are organized what’s next?
. We will learn more about the lowest level of
organization: cells
What is the first thing that we need to know
about cells?
All cells fall into one of the two major
classifications of either prokaryotes or
eukaryotes.

4. Prokaryotes
• Prokaryotes are organisms made up of cells that lack a
cell nucleus or any membrane-encased organelles. This
means the genetic material DNA in prokaryotes is not
bound within a nucleus. Additionally, the DNA is less
structured in prokaryotes than in eukaryotes. In
prokaryotes, DNA is a single loop. In Eukaryotes, DNA is
organized into chromosomes. Most prokaryotes are
made up of just a single cell (unicellular) but there are
a few that are made of collections of cells
(multicellular). Scientists have divided the prokaryotes
into two groups, the Bacteria and the Archae.

5. What do prokaryotic cells look like?

6. • Prokaryotes are the simplest type of cell. (appeared
about four billion years ago) .
• Prokaryotes are the largest group of organisms
Prokaryotes unicellular organisms that are found in
all environments.
• Prokaryotes do not have a nuclear membrane .
Their genetic material dispersed throughout
cytoplasm. Prokaryotes do not have membrane-
bound organelles Prokaryotes have a simple
internal structure.

7. Shapes of Prokaryotes

8. • Eukaryotes are organisms made up of cells
that possess a membrane-bound nucleus (that
holds genetic material) as well as membrane-
bound organelles. Genetic material in
eukaryotes is contained within a nucleus
within the cell and DNA is organized into
chromosomes. Eukaryotic organisms may be
multicellular or single-celled organisms. All
animals are eukaryotes. Other eukaryotes
include plants, fungi, and protists.

9. What do eukaryotic cells
look like?

11. What Prokaryotic and Eukaryotic Cells
Have in Common
• Both have DNA as their genetic material (it’s DNA that tells
cells what kind of cells they should be).
• Both are covered by a cell membrane,.
• Both are made from the same basic chemicals:
carbohydrates, proteins, nucleic acid, minerals, fats and
vitamins.
• Both have ribosomes , Both contain RNA.
• Both have similar basic metabolism (life processes) like
photosynthesis and reproduction.
• Both are highly regulated by elaborate sensing systems
("chemical noses”) that make them aware of the reactions
within them and the environment around them.

12. DIFFERENCES BETWEEN PROKARYOTIC
AND EUKARYOTIC CELLS
parameters
Eukaryotic Cell Prokaryotic Cell
Nucleus: Present Absent
Number of chromosomes: More than one
One--but not true
chromosome: Plasmids
Cell Type: Usually multicellular
Usually unicellular (some
cyanobacteria may be
multicellular)
True Membrane bound
Nucleus:
Present Absent
Example: Animals and Plants Bacteria and Archaea
Genetic Recombination: Meiosis and fusion of gametes
Partial, undirectional transfers
DNA

13. Lysosomes and
peroxisomes:
Present Absent
Microtubules: Present Absent or rare
Endoplasmic reticulum: Present Absent
Mitochondria: Present Absent
Cytoskeleton: Present May be absent
DNA wrapping on
proteins.:
Eukaryotes wrap their
DNA around proteins
called histones.
Multiple proteins act
together to fold and
condense prokaryotic
DNA. Folded DNA is then
organized into a variety of
conformations that are
supercoiled and wound
around tetramers of the
HU protein.
Ribosomes: larger smaller
Vesicles: Present Present
Golgi apparatus: Present Absent
PARAMETERS EUKARYOTIC CELLS PROKARYOTIC CELL

14. Chloroplasts: Present (in plants)
Absent; chlorophyll
scattered in the cytoplasm
Flagella:
Microscopic in size;
membrane bound; usually
arranged as nine doublets
surrounding two singlets
Submicroscopic in size,
composed of only one fiber
Permeability of Nuclear
Membrane:
Selective not present
Plasma membrane with
steriod:
Yes Usually no
Cell wall:
Only in plant cells and
fungi (chemically simpler)
Usually chemically
complexed
Vacuoles: Present Present
Cell size: 10-100um 1-10um
PARAMETERS EUKARYOTIC CELLS PROKARYOTIC CELLS

15. •NOW LET US
LEARN MORE
ABOUT
CHROMOSOMES
AND CHROMATIN

16. CHROMOSOMES AND
CHROMATIN

17. CHROMOSOMES
• A chromosome is an organized structure
of DNA and protein that is found in cells. It is a
single piece of coiled DNA containing
many genes, regulatory elements and other
nucleotide sequences. Chromosomes also
contain DNA-bound proteins, which serve to
package the DNA and control its functions. The
word ''chromosome'' comes from the Greek
(''chroma'', color) and (''soma'', body) due to
their property of being very strongly stained by
particular dyes.

18. Human chromosomes
• Chromosomes in humans can be
divided into two types: autosomes
and sex chromosomes. Certain
genetic traits are linked to a person's
sex and are passed on through the
sex chromosomes. The autosomes
contain the rest of the genetic
hereditary information. All act in the
same way during cell division.
Human cells have 23 pairs of
chromosomes (22 pairs of
autosomes and one pair of sex
chromosomes), giving a total of 46
per cell

19. • Packed inside the nucleus of every human cell is nearly 6 feet of DNA, which
is subdivided into 46 individual molecules, one for each chromosome and each
about 1.5 inches long. Collecting all this material into a microscopic cell
nucleus is an extraordinary feat of packaging. For DNA to function when
necessary, it can't be haphazardly crammed into the nucleus or simply wound
up like a ball of string. Consequently, during interphase, DNA is combined
with proteins and organized into a precise, compact structure, a dense
string-like fiber called chromatin, which condenses even further into
chromosomes during cell division.
• Each DNA strand wraps around groups of small protein molecules called
histones, forming a series of bead-like structures, called nucleosomes,
connected by the DNA strand (as illustrated in Figure 1). Under the
microscope, uncondensed chromatin has a "beads on a string" appearance.
The string of nucleosomes, already compacted by a factor of six, is then
coiled into an even denser structure known as a solenoid that compacts the
DNA by a factor of 40. The solenoid structure then coils to form a hollow
tube. This complex compression and structuring of DNA serves several
functions. The overall negative charge of the DNA is neutralized by the
positive charge of the histone molecules, the DNA takes up much less space,
and inactive DNA can be folded into inaccessible locations until it is needed.

20. TYPES OF CHROMATIN
• There are two basic. Euchromatin is the genetically active
type of chromatin involved in transcribing RNA to produce
proteins used in cell function and growth. The predominant
type of chromatin found in cells during interphase,
euchromatin is more diffuse than the other kind of chromatin,
which is termed heterochromatin. The additional
compression of heterochromatin is thought to involve various
proteins in addition to the histones, and the DNA it contains is
thought to be genetically inactive. Heterochromatin tends to
be most concentrated along chromosomes at certain regions
of the structures, such as the centromeres and telomeres.
Genes typically located in euchromatin can be experimentally
silenced (not expressed) by relocating them to a
heterochromatin position.

21. CHROMATIN VS CHROMOSOME
• In the nucleus, the DNA double helix is
packaged by special proteins (histones) to form
a complex called chromatin. The chromatin
undergoes further condensation to form the
chromosome. So while the chromatin is a
lower order of DNA organization,
chromosomes are the higher order of DNA
organization. An organism’s genetic content is
counted in terms of the chromosome pairs
present. e.g. humans have 23 pairs of
chromosomes.

22. parameters Chromatin Chromosome
Definition:
In the nucleus, the DNA
double helix is packaged by
special proteins (histones) to
form a complex called
chromatin. The chromatin
undergoes further
condensation to form the
chromosome.
A threadlike structure of
nucleic acids and protein
found in the nucleus of most
living cells, carrying genetic
information in the form of
genes.
Structure:
Composed of nucleosomes-a
complex of DNA and proteins
(called histones). Represent
DNA folded on nucleoproteins
by a magnitude of 50. The
chromatin fiber is app. 10 nm
in diameter.
Chromosomes are condensed
Chromatin Fibers. They are a
higher order of DNA
organization, where DNA is
condensed at least by 10,000
times onto itself.
Appearance:
Chromatin Fibers are Long and
thin. They are coiled
structures found inside the
nucleus.
Chromosomes are compact,
thick and ribbon-like. These
are uncoiled structures found
inside the nucleus
DIFFERENCES BETWEEN CHROMOSOMES AND CHROMATIN

23. PARAMETERS CHROMATIN CHROMOSOMES
Pairs: Chromatin is unpaired. Chromosome is paired.
Metabolic activity:
Permissive to DNA
replication, RNA synthesis
(transcription) and
recombination events.
Refractory to these processes
Presence:
Found throughout the cell
cycle.
Distinctly visible at metaphase as
highly condensed structures in
nucleus upto several thousand nm.
Visualization:
Electron microscope
(beads on string
appearance)
Light microscope
Conformation:
May have open
(euchromatin) or compact
(heterochromatin)
conformations, which is
dynamically regulated
during the cell-cycle
stages.
Predominantly heterochromatic
state with a predetermined
position in the nucleus and a
specific shape such as metacentric,
acrocentric, telocentric.

24. • Prepared by : GEETU
IX – B