Ultra structure of plant cell
(PART II)
Pillai Aswathy Viswanath
Dept. of Botany
Assumption College Chenganacherry

Dictyosome
• Dictyosomes are stacks of flat, membrane-
bound cavities (cisternae) that together
comprise the Golgi apparatus.

• Dictyosomes in animal cells are stacked tightly
together called Golgi apparatus
• Plant cells contain smaller Golgi Apparatus
type vesicles, which are called dictyosomes.
• The dictyosomes in plant cells are dispersed in
the cytoplasm, making them difficult to
identify as the Golgi apparatus.
• Within the dictyosomes, proteins are stored,
modified, sorted, and packed into for further
transport.

function
• The proteins are synthesized on the rough
endoplasmic reticulum and arrived in the
vesicles of Golgi Apapratus.
• In the vesicles of Golgi apparatus, the proteins
are processed and sorted for future secretion,
storage, transport etc.

Lysosomes
• “Lysosomes are sphere-shaped sacs filled with
hydrolytic enzymes .
• Lysosomes are membrane-bound organelles
and the area within the membrane is called
the lumen, which contains the hydrolytic
enzymes and other cellular debris.
• The pH level of the lumen lies between 4.5
and 5.0, which makes it quite acidic.

Lysosome function
• lysosomes are membranous organelles whose
specific function is to breakdown cellular
wastes and debris by engulfing it with
hydrolytic enzymes.
• Cellular debris or foreign particles are pulled in
to the cell through the process of endocytosis.

• The process of endocytosis happens when the
cell membrane falls in on itself (invagination),
creating a vacuole or a pouch around the
external contents and then bringing those
contents into the cell.
• On the other hand, discarded wastes and other
substances originating from within the cell is
digested by the process of autophagocytosis or
autophagy.

Why are Lysosomes known as Suicidal
Bags?
• lysosomes work as the waste discarding structures
of the cell and degrading them, both from the
exterior of the cell and waste constituents inside
the cell.
• But sometimes, the digestive enzymes may end up
damaging the lysosomes themselves, and this can
cause the cell to die.
• This is termed as autolysis, where “auto” means
“self” and “lysis” means “the disintegration of the
cell by the destruction of its cell membrane“.
• Hence, lysosomes are known as “Suicidal Bags” of
the cell.

Microbodies
• A microbody is usually a vesicle with a spherical
shape, ranging from 0.2-1.5 micrometres in
diameter.
• The microbodies are found in the cytoplasm of a
cell
• They are surrounded by a single phospholipid
bilayer membrane and they contain a matrix of
intracellular material including enzymes and other
proteins,
• but they do not seem to contain any genetic
material to allow them to self-replicate.

• Microbodies facilitates the breakdown of fats,
alcohols and amino acids.
Different types of microbodies have different
functions:
• Peroxisome is a type of microbody that functions
to help the body break down large molecules and
detoxify hazardous substances.
• Glyoxysomes are specialized peroxisomes found
in plants , which help to convert stored lipids into
carbohydrates so that they can be used for plant
growth.

Vacuole and cell sap
• The vacuole is a type of organelle present in
eukaryotic cells.
• It is a sac surrounded by a single membrane
called a tonoplast.

• Both plant and animal cells can contain vacuoles,
but vacuoles are far more prevalent in plant cells.
• They are also much larger in plant cells and often
take up a great deal of space within the cell.
• Animal cells do not always have a vacuole, and
most never have a large vacuole, because it would
cause harm to the cell and disrupt the functioning
of the rest of the cell.
• Animal cells may instead have several very small
vacuoles.

• Vacuoles in animal cells are small and spend
most of their time providing transportation
into and out of the cell for various organic
materials.
• There are two kinds of transportation that the
vacuoles provide:
exocytosis
endocytosis

• Exocytosis is the method by which vacuoles
move materials out of the cell.
• These materials are often unwanted materials
such as waste, or molecules
• Endocytosis is the inverse process of
exocytosis, in which vacuoles help to bring
organic matter into the animal cell.

• Plant cells commonly contain one large vacuole that
fills more space within the cell than any other
organelle.
• The plant cell vacuole consists of tonoplast, which
forms a sac around a fluid called cell sap.
• Cell sap contains water and a number of other
substances. These can include:
Salts
Enzymes
Sugars and other carbohydrates
Lipids
Ions

• The concentration of ions in the cell sap is a useful
tool for moving water in and out of the vacuole via
osmosis.
• If the ion concentration is higher within the
vacuole, water moves through the tonoplast into
the vacuole.
• If the ion concentration is higher in the cytoplasm
outside of the vacuole, water moves out of the
vacuole.
• The vacuole enlarges or shrinks as water moves
into or out of it.

Nucleus
• The nucleus is a double-membraned organelle
that contains the genetic material.
• It is exclusively found in eukaryotic cells
• Parts Of The Nucleus:
Nuclear Envelope
Nuclear Pores
Nucleoplasm
Chromatin
Nucleolus

Structure Of Nucleus
• It is generally the most prominent organelle in
the cell.
• The nucleus is completely bound by
membranes.
• It is surrounded by a structure called the nuclear
envelope.
• The nuclear envelope is a double-layered
membrane that contains all the parts of the
nucleus and separates it from the cytoplasm of
the cell.

• The nuclear envelope is full of holes called
nuclear pores, which allow molecules to move in
and out of the nucleus.
• nucleopore allows proteins and nucleic acids to
pass through
• This membrane separates the contents of the
nucleus from the cytoplasm.
• The cell’s chromosomes are also enclosed within
it.
• DNA is present in the Chromosomes and they
provide the genetic information of life.

• The nucleoplasm is a jelly-like substance that is
found within the nuclear envelope, and its
function is similar to the cytoplasm found in
the main cell, supporting the nucleus and
protecting its contents.
• Finally, the nucleolus is the largest structure
found in the nucleus.
• It is very dense, has no membrane, and is
composed of chunks of protein and RNA.
• In nucleolus, ribosome biogenesis happens
here.

Function OF Nucleus
• The nucleus has been clearly explained as a
membrane-bound structure that comprises the
genetic material of a cell.
• It contains the cell’s hereditary information and
controls the cell’s growth and reproduction.
• It is not just a storage compartment for DNA
but also happens to be the home of some
essential cellular processes.
• First and foremost, it is possible to duplicate
one’s DNA in the nucleus

• This process has been named DNA Replication
and creates an identical copy of the DNA.
• Secondly, the nucleus is the spot of
transcription.
• Transcription is the process of creating different
types of RNA from DNA.

• Chromatin is a complex of DNA and protein
found in eukaryotic cells.
• Its primary function is packaging long DNA
molecules into more compact, denser
structures.
• This prevents the strands from becoming
tangled

DIFFERENCE
• Animal cells and plant cells are similar in that
they are both eukaryotic cells.
• These cells have a true nucleus, which
houses DNA and is separated from other
cellular structures by a nuclear membrane.

• Both of these cell types also contain cell
structures known as organelles, which are
specialized to perform functions necessary for
normal cellular operation.
• Animal and plant cells have some of the same
cell components in common including a
nucleus, Golgi complex, endoplasmic
reticulum, ribosomes, mitochondria, peroxisomes
, cytoskeleton, and cell (plasma) membrane.

Size
• Animal cells are generally smaller than plant cells.
• Animal cells range from 10 to 30 micrometers in
length,
• While plant cells range from 10 and 100
micrometers in length.
Shape
• Animal cells come in various sizes and tend to
have round or irregular shapes.
• Plant cells are more similar in size and are typically
rectangular or cube shaped.

Cell Wall
• Animal cells do not have a cell wall but have a cell
membrane.
• Plant cells have a cell wall composed of cellulose
as well as a cell membrane.
Glyoxysomes
• These structures are not found in animal cells but
are present in plant cells.
• Glyoxysomes help to degrade lipids, particularly
in germinating seeds.

Lysosomes
• Animal cells possess lysosomes which contain
enzymes that digest cellular macromolecules.
• Plant cells rarely contain lysosomes
Plastids
• Animal cells do not have plastids.
• Plant cells contain plastids such
as chloroplasts, which are needed
for photosynthesis

Plasmodesmata,
• Animal cells do not have plasmodesmata.
• Plant cells have which are pores between plant
cell walls that allow molecules and
communication signals to pass between individual
plant cells.
Vacuole
• Animal cells may have many small vacuoles.
• Plant cells have a large central vacuole that can
occupy up to 90% of the cell's volume.
• The plant vacuole handles molecule degradation

Energy Storage
• Animals cells store energy in the form of the
complex carbohydrate glycogen.
• Plant cells store energy as starch.
Proteins
• Of the 20 amino acids needed to produce proteins,
only 10 can be produced naturally in animal cells.
• The other so-called essential amino acids must be
acquired through diet.
• Plants are capable of synthesizing all 20 amino acids.

• Both of these cell types have similar processes
for reproduction, which
include mitosis and meiosis.
Centrioles
• Animal cells contain these cylindrical
structures that organize the assembly of
microtubules during cell division.
• Plant cells do not typically contain centrioles.