prokaryotic cell with detail in biochemistry 2017
TRANSCRIPT
WELCOME TO BIO-CHEMISTRY CLASS
IntroductionAMIR HASSAN
CLASS BS-CHEMISTRYROLL NUMBER – 105
Presentation Topic Is Structure of Prokaryotic Cell
INTRODUCTION TO CELL Meaning:
The word cell comes from a Latin word called “cella” meaning a “small room”.
Definition No.1: Cell is the basic structural, functional and biological unit of all known living organism.
Definition No.2: Cell is the unit of life and is also called the building block of life.
The number of cell in plants & animals varies from species to species human contain about 100 trillion (1014) cell.
All the organisms have been classified as: UNICELLULAR: An organism consists of only one piece cell is called
unicellular. e.g. Bacteria, Archaea
MULTICELLULAR: An organism consist of more than one cell is called multicellular. e.g. Plants, Animals
CLASSIFICATION OF CELL A cell can be generally classified on the basis of unicellular or, multicellular organism.
1. Prokaryotic Cell: (include unicellular organism such as bacteria, Archaea) the simplest form of the cell having no membrane bound organelles.
2. Eukaryotic Cell: (include multicellular organism such as Plants & Animals) the most complex form of the cell having membrane bound organelles.
Plant cell Animal cell Bacteria Cell
1. PROKARYOTIC CELL:
• Prokaryotic cells were the first form of life on this planet.
• They are smaller and simpler than eukaryotic cells.
• Prokaryotic cells lack a well-defined nucleus and membrane-bound organelles such as the mitochondria.
• The DNA of a prokaryotic cell consists of a single chromosome which is in direct contact with the cytoplasm.
• There are 20 – times more prokaryotic cell on earth than eukaryotic cell, this is only minimum estimate about trillion of trillion are associated with eukaryotic cell and archaea are also prokaryotes but there number is not sure.
For example, bacteria and archaea.
DIAGRAM OF PROKARYOTIC CELL • Simple structure of prokaryotic cell (figure a)
STRUCTURE OF PROKARYOTIC CELL (TYPICALLY STUDY BACTERIA ) A prokaryotic cell structure have the following component:
Cell Membrane Cytoplasm Ribosomes
Genetic Material Plasmids Cell Wall
Cell capsule or, Envelope Flagella
Pili or, Fimbriae
ORGANALLES: (LITTLE ORGAN)• Organelles are parts of the cell which are specialized for
carrying out one or more vital functions.• Both eukaryotic and prokaryotic cells have organelles, but
prokaryotic organelles are generally simpler and are not membrane-bound.
• There are several types of organelles in a cell. , such as mitochondria, chloroplasts, peroxisomes and lysosomes (hundreds to thousands).
• The cell is filled with a gelatinous fluid which surrounds the organelles. This fluid is known as cytosol.
1) PLASMA MEMBRANEProkaryotic cells can have multiple plasma membranes . Plasma membrane in prokaryotic cells is responsible for exchange of materials between the cell and its surrounding environment. Plasma membranes also aids in sending and receiving chemical signals from other bacteria and interacting with the cells of eukaryotic organisms during the process of infection.Prokaryotes known as "gram-negative bacteria,"
• For example, often have two plasma membranes with a space between them known as the periplasm.
2) CYTOPLASM• The cytoplasm of the prokaryotic cells is a translucent or gel-like fluid substance
in which all of the other cellular components are suspended.
• It is very similar to the eukaryotic cytoplasm, except that it does not contain organelles.
• Recently, biologists have discovered that prokaryotic cells have a complex and functional cytoskeleton similar to that seen in eukaryotic cells.
• The cytoskeleton helps prokaryotic cells maintaining its shape.
3) RIBOSOME• Prokaryotic ribosomes are smaller and have a slightly different shape and
composition than those found in eukaryotic cells (shown in figure b).
• Bacterial ribosomes, are about half of the amount of ribosomal RNA (rRNA) and one third fewer ribosomal proteins (53 vs. ~ 83) than eukaryotic ribosomes.
• Along these differences, the function of the prokaryotic ribosome is totally same to that of eukaryotic cell.
• Just like in eukaryotic cells, prokaryotic ribosome is involved in the synthesis of proteins by translating messages sent from DNA in the shape of messenger RNA.
• Structure of Prokaryotic Cell
4) GENETIC MATERIAL• All prokaryotic cells contain large quantities of genetic material in the form of
DNA and RNA.
• As prokaryotic cells do not have a well-defined nucleus, the single large circular strand of DNA which contains most of the genes is found in the cytoplasm.
• These genes are required for the growth, survival, and reproduction of the cell.
• The DNA looks like a mesh of string in the middle of the cell.
• Generally, the DNA is spread throughout the entire cell, and is readily accessible for the transcription into messenger RNA (mRNA) which is immediately translated by ribosomes into protein.
• Sometimes, when biologist prepares prokaryotic cells for viewing under a microscope, the DNA will condense in one part of the cell producing a darkened area known as nucleoid.
5) PLASMIDS• Just eukaryotic cells, the prokaryotic chromosome is associated with
special proteins involved in maintaining the chromosomal structure and regulating gene expression.
• In addition to a single large piece of chromosomal DNA, many prokaryotic cells also contain small pieces of DNA called plasmids.
• These circular rings of DNA are replicated independently of the chromosome and can be transferred from one prokaryotic cell to another through pili.
• The transfer of plasmids between one cell and another is often referred to as "bacterial sex."
• Plasmids encode additional genes, such as antibiotic resistance genes.
• The genes for antibiotic resistance, or the gradual ineffectiveness of antibiotics in populations, are often carried on plasmids.
• For example, it was recently learned that the multidrug-resistant Staphylococcus aureus, received some of its drug-resistance genes on plasmids.
• Transmission Electro Micrograph Image Of Plasmid (Small DNA)
6) CELL WALL• The prokaryotic cells have a cell wall present outside the plasma membrane, with a
few exceptions such as Mycoplasma (bacteria) and Thermoplasma (archaea).
• The cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces.
• It also prevents the cell from expanding and bursting (cytolysis) from osmotic pressure due to a hypotonic environment.
7) CELL ENVELOPE OR CAPSULE• Some of the bacterial cells have an additional layer around the
cell wall called a cell envelop or cell capsule.
• The envelope gives rigidity to the cell and separates the interior of the cell from its environment, serving as a protective filter.
• The prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi).
• Though not forming a nucleus, the DNA is condensed in a nucleoid.
8) FLAGELLA• The bacterial flagella are long and thick thread or whip-like structures,
protein in nature which stretches from cytoplasm through the cell membrane(s) and extrudes through the cell wall.
• They are most commonly found in bacteria cells but are found in animal cells as well.
• They are involved in the movements.
9) FIMBRIAE (PILI)• They are short and thin hair-like filaments, made up of protein called pilin
(antigenic).
• They are responsible for attachment of bacteria to specific receptors of human cell (adherence).
• There are special types of pili called (sex pili) involved in conjunction.
THE END
Thank You !!