Structure of cell and its components

1. Structure of a basic cell, special
features of prokaryotes, plant and
animal cells

2. • All Living Organisms are Made Up of functional basic Unit of
life Called Cells
• There Are 2 Basic Types of Cells: Prokaryotic and Eukaryotic
– Prokaryotic cells are more primitive, small and without
nucleus and organelles
• Bacteria, blue-green algae
– Eukaryotic cells are more advanced, larger, contain nucleus
and organelles
• All higher species: animals, plants, fungi, protozoa
Cells

3. Prokaryotic Cells
• Small Prokaryotic Cells are Simple but Fast
– Size: bacteria 1-10 micron dia.
– Small cells such as bacteria divide fast (~ 20 min)
– Have no nucleus: DNA less protected, mutates
faster
– Prokaryotic cells consist of a single closed
compartment that is surrounded by the plasma
membrane,
– has a relatively simple internal organization

4. Bacteria Cell Structure

5. Eukaryotic Cells
• Large Eukaryotic Cells are Slow but
Versatile
– Size: typically 10-100 micron dia.; volumes
typically 1000 times larger than prokaryotes
– Have nucleus: DNA better protected, slow
mutation rate
– Organelles allow many activities to take place
within the same cell

6. • Eukaryotes comprise
• all members of the plant and animal
• and the fungal kingdoms, which exist in both multicellular
forms and and unicellular forms (yeasts),
• primitive; zoan, animal), which are exclusively
unicellular.

7. similarities between prokaryote and
eukaryote
• The major similarities between the two types of
cells (prokaryote and eukaryote) are:
• 1.They both have DNA as their genetic material.
2.They are both membrane bound.
3.They both have ribosomes.
4.They have similar basic metabolism
5.They are both amazingly diverse in forms.

8. Difference between prokaryotes and eukaryotes
• The major and extremely significant difference between prokaryotes
and eukaryotes is that eukaryotes have a nucleus and membrane-
bound organelles, while prokaryotes do not.
• The DNA of prokaryotes floats freely around the cell; the DNA of
eukaryotes is held within its nucleus.

9. The defining characteristic of eukaryotic cells is nucleus which is bounded by a
double membrane. The outer nuclear membrane is continuous with the rough
endoplasmic reticulum, a factory for assembling proteins. Golgi vesicles
process and modify proteins, mitochondria generate energy, lysosomes digest
cell materials to recycle them, peroxisomes process molecules using oxygen,
and secretory vesicles carry cell materials to the surface to release them.

10. Differences between
prokaryotes and eukaryotes
• Additional obvious differences between prokaryotes and
eukaryotes include:
• Size
Eukaryotic cells are, on average, ten times the size of
prokaryotic cells.
• Genomic composition and length
The DNA of eukaryotes is much more complex (in both
size and organisation) and than the DNA of prokaryotes.
• Cell Wall
Prokaryotes have a cell wall composed of peptidoglycan,
a single large polymer of amino acids and sugar. Many
types of eukaryotic cells also have cell walls, but none
made of peptidoglycan.

13. Structure of Eukaryotic cells

14. Basic cell structures
Plasma Membrane—A Cell's Protective Coat
Cytoskeleton—A Cell's Scaffold
Cytoplasm—A Cell's Inner Space
Genetic Material—DNA and RNA
Organelles
Nucleus—A Cell's Center
Ribosome—The Protein Production Machine
Mitochondria and Chloroplasts—The Power Generators
Endoplasmic Reticulum and the Golgi Apparatus—
Macromolecule Managers
Lysosomes and Peroxisomes—The Cellular Digestive
System

15. Cytosol
• Cytosol is the liquid matrix of the cell-
mostly water (cytosol + organelles except
nucleus = cytoplasm)
• Contains salts, dissolved molecules,
enzymes, etc.
• Glycolysis (energy metabolism: anaerobic)
takes place in cytoplasm

16. Organelles
• The largest organelle in a eukaryotic cell is generally the
nucleus, which houses most of the cellular DNA.
• In addition to the nucleus, several other organelles are
present innearly all eukaryotic cells:
• the mitochondria,
• the rough and smooth endoplasmic reticula,
• Golgi vesicles, peroxisomes,
• Animal cells, but not plant cells, contain lysosomes,
• Chloroplasts (plants)
• Both plant cells and some single-celled eukaryotes
contain one or more vacuoles,

17. Cell Membrane
• The Cell Membrane Separates the Cytoplasm
From the External World
– Cell membrane is made of phospholipid & protein
– Barrier to movement of things in and out of the cell-
hydrophobic molecules pass through it more readily
than hydrophilic ones
– Specialized transport mechanisms: selectively move
materials across the membrane
– Supported on inside by protein filaments
(cytoskeleton)

18. Nucleus
The nucleus, the largest organelle in animal cells, is surrounded
by two membranes
The inner nuclear membrane defines the nucleus itself.
The outer nuclear membrane is continuous with the rough endoplasmic
reticulum, and the space between the inner and outer nuclear membranes is
continuous with the lumen of the rough endoplasmic reticulum
The two nuclear membranes appear to fuse at nuclear pores, the ringlike
complexes composed of specific membrane proteins through which material
moves between the nucleus and the cytosol.
Nucleus is filled with chromatin composed of DNA and
proteins; in dividing cells is site of mRNA and tRNA synthesis.

19. Nucleolus
Is the dense region within the nucleus and it is a subcompartment of
the nucleus that is not bounded by a phospholipid membrane.
Most of the cell’s ribosomal RNA is synthesized in the nucleolus

20. Mitochondria
Principal sites of ATP production. It is bound by two membranes
The outer membrane, composed of about half lipid and half protein, contains
porins that render the membrane permeable to molecules having molecular
weights as high as 10 kDa
The inner membrane, which is much less permeable, is about 20 percent lipid
and 80 percent protein
The surface area of the inner membrane is greatly increased by a large number
of infoldings, or cristae, that protrude into the matrix, or central
Space.

21. The complete aerobic degradation of glucose to CO2 and H2O is
coupled to the synthesis of 30 molecules of ATP.
2 molecules of ATP at cytoplasm and 28 molecules at
Mitochodria.
Thus Mitochodria are called “power plants” of the cell.

22. chloroplasts
 in the cells of plants and green algae
 contains an extensive internal system of interconnected membrane-
bound sacs called thylakoids.
 The thylakoid membranes contain green pigments (chlorophylls) and
other pigments that absorb light.
 Thylakoids often form stacks called grana
 Tube like structure connecting thylakoid from granum to granum-
stroma lamellae.

23. endoplasmic reticulum
extensive network of closed, flattened membrane-bounded sacs and they are
fused to nuclear membrane.
The smooth endoplasmic reticulum is smooth because it lacks ribosomes.
Rough endoplasmic reticulum is studded with ribosomes.
smooth endoplasmic reticulum

24. Rough endoplasmic reticulum (ER) functions in the synthesis,
processing, and sorting of secreted proteins, lysosomal
proteins, and certain membrane
endoplasmic reticulum
Smooth endoplasmic reticulum (ER) synthesizes lipids and
detoxifies certain hydrophobic compounds (pesticides and
carcinogens).

25. Golgi apparatus
Golgi apparatus is a series of flattened membrane
vesicles or sacs (cisternae)
The stack of Golgi cisternae has three defined
regions—
the cis, the medial, and the trans.
Transport vesicles from the rough ER fuse with
the cis region of the Golgi complex, where they
deposit their protein contents. these proteins then
progress from the cis to the medial to the trans
region.
After proteins are modified in the Golgi complex,
they are transported out of the complex by a
second set of vesicles, which seem to bud from
the trans side of the Golgi complex.

26. Plant Vacuoles
Most plant cells contain at least one membrane bound vacuole.
The number and size of vacuoles depend on both the type of cell and its
stage of development;
single vacuole may occupy as much as 80 percent of a mature plant cell
Vacuoles store water, ions, and nutrients (e.g., sucrose, amino acids)

27. Lysosomes
• Lysosomes Digest Materials within the Cell
– Small vesicles surrounded by membranes
– Lysosomes contain digestive enzymes that degrade worn-out intracellular
organelles, as well as macromolecules (CHO, proteins and lipids) and particles
(bacteria) taken in from outside the cell by endocytosis.
– Involved in apoptosis (programmed cell death)
– Lysozomes are acidic organelles and require an acid pH inside (~4.5)

28. Peroxisomes
(degrades Fatty acids and toxic compounds)
• Peroxisomes Deal with Reactive Oxygen Molecules Such as
Peroxides
– Contain the enzyme, catalase
– Important in fat metabolism, oxidation of FA yields acetyl groups
which are used in synthesis of cholesterol and other metabolites.
– Various toxic molecules are degraded by peroxisomes expecially
in kidney and liver cells

29. • The Cytoskeleton Determines the Shape of the Cell
• Protein filaments that compose the cytoskeleton of the cell
– Give the cell shape
– Are used to transport structures within the cell (i.e., chromosomes in
mitosis)
– Are involved in movement of the whole cell
• Three basic types of filaments:
– Microfilaments (made of actin, 8-9 nm dia), and have a twisted two-
stranded structure
– Intermediate filaments (made of several proteins, 10-12 nm dia)
– Microtubules (made of tubulin, 25 nm dia), hallow tube like structure
Cytoskeleton

30. Microfilaments and Membrane-Binding
Proteins Form a Skeleton Underlying
the Plasma Membrane
Intermediate Filaments Support the
Nuclear
Membrane and Help Connect Cells
into Tissues
Microtubules Radiate from
Centrosomes
and Organize Certain Subcellular
Structures

31. Plant Cell Structure

32. Animal Cell Structure

33. Plant cells Animal cells
Relatively larger in size Relatively smaller in size
Cell walls almost present No cell walls present
structure is very rigid. more flexible membranes
Nucleus near cell wall Nucleus at the center
Plastids occur in cytoplasm No plastids are found
Lysosomes not usually evident Lysosomes occur in cytoplasm
Centrioles present only in cells of
lower plant forms
Centrioles always present
Large vacuoles filled with cell sap Vacuoles, if present, are small and
contractile or temporary vesicles
Plant cells have glyoxysomes Animal cells do not.
Starch as food storage Stores glycogen in the cytoplasm
Structural differences between Plant and Animal Cells