CELL BIOLOGY AND GENETICS-Prokaryotic Cell.pptx

A prokaryotic cell is a simple, single-celled organism that lacks a true nucleus and membrane-bound organelles. Here are some key features:

1. Nucleus: Prokaryotic cells do not have a true nucleus. Instead, their genetic material (DNA) is located in a region called the nucleoid.
2. Size: These cells are generally smaller than eukaryotic cells, typically ranging from 0.1 to 5.0 micrometers in diameter¹.
what is a cell memebrane?
3. Cell Membrane: The cell is enclosed by a plasma membrane that controls the movement of substances in and out of the cell.
how does acell wall work in pro?
4. Cell Wall: Many prokaryotes have a rigid cell wall that provides structural support and protection. In bacteria, this wall is made of peptidoglycan.
5. **Cytoplasm**: The interior of the cell is filled with cytoplasm, a jelly-like substance where cellular processes occur.
6. **Ribosomes**: These are the sites of protein synthesis. Unlike eukaryotic ribosomes, prokaryotic ribosomes are smaller and less complex.
7. **Reproduction**: Prokaryotic cells reproduce asexually through a process called binary fission, where the cell divides into two identical cells².

Prokaryotic cells are found in two domains of life: Bacteria and Archaea. They play essential roles in various ecosystems, including decomposition and nitrogen fixation

1. ULTRA STRUCTURE OF PROKARYOTIC CELL

2. THE CELL WALL Cell wall is the dense layer surrounding the plasmamembrane and functions to give shape and rigidity. The main constituent or backbone of bacterial cell wall is peptidoglycan(also known as murein, muramic acid or mucopeptide) Peptidoglycan- Glycan or peptide portion Glycan portion- NAG & NAM, bonded by……………………….? Peptide portion- 4 amino acids linked by peptide bond. Presence of Cross linkage

3. THE PLASMA MEMBRANE Absolute requirement, chief point of contact with the cell’s environment and outside world. Membrane is broken, the integrity of the cell is destroyed. Structure approx. 7.5nm thick, forms the boundary of the cell Made up of phospholipids and proteins FLUID MOSAIC MODEL- by Singer & Nicolson

4. Bi- layer made up of phospholipids. Polar and non polar ends. Hydrophilic- outer surface of membrane and hydrophobic buried interior. Extrinsic proteins And Intrinsic proteins Hopanoids – sterol like molecules, provide stability to plasma membrane.

5. FUNCTIONS Regulates the flow of materials in and out of the cell. Contains enzymes that mediate in the synthesis of membrane lipids and various other macromolecules that compose the bacterial cell It is the site of enzymes and carriers of ETS that generates ATP from ……….? It Plays an active role in replication and during cell division.

6. NUCLEOID The nucleoid is an irregularly-shaped region within a prokaryotic cell where the cell's genetic material ( DNA ) is located. Unlike the nucleus in eukaryotic cells, the nucleoid is not enclosed by a membrane. DNA Composition: The nucleoid contains a single, circular DNA molecule, although some bacteria may have additional small, circular DNA molecules called plasmids.

7. Organization: The DNA is supercoiled and associated with various proteins that help in packaging and compacting it into the cell. Function: The nucleoid is involved in controlling the cell’s activities and reproduction by regulating gene expression, replication, and segregation during cell division. Location: It typically occupies a central position within the cell but can be found throughout the cytoplasm. Visualization: Under an electron microscope, the nucleoid appears as a dense, fibrous region, but it lacks the distinct membrane-bound structure seen in eukaryotic nuclei.

8. PLASMIDS Plasmids are small, circular DNA molecules that are separate from the chromosomal DNA in bacteria. They are typically found in the cytoplasm of the cell and can replicate independently of the chromosomal DNA. EPISOMES

9. Resistance Plasmids : These plasmids carry genes that provide resistance to antibiotics or other toxic compounds. They are often found in clinical settings where they contribute to antibiotic resistance in bacteria. Virulence Plasmids: Virulence plasmids contain genes that enhance the ability of bacteria to cause disease by producing toxins or other virulence factors. Conjugative Plasmids: These plasmids have genes that enable them to transfer between bacteria through conjugation, a process where genetic material is transferred directly from one bacterium to another.

10. Fertility Plasmids : Fertility plasmids are a type of conjugative plasmid that carries genes responsible for the formation of sex pili and the transfer of plasmid DNA during conjugation. Col Plasmids: Col plasmids encode colicins, which are bacteriocins that kill other bacteria. They provide a competitive advantage to the host bacterium in environments with limited resources.

11. CYTOPLASM Contains enzymes and molecules necessary for cellular metabolism and growth. It also houses the genetic material (chromosome or nucleoid) and ribosomes. Ribosomes FLAGELLA- Appendages used for movement (locomotion). Flagella rotate like propellers, allowing the bacterium to move toward or away from stimuli (chemotaxis). PILI- Hair-like appendages that extend from the cell surface. Pili can help bacteria adhere to surfaces or other cells (adhesion) and are also involved in conjugation, which is the transfer of DNA between bacterial cells.

12. Storage Granules : Function : Some prokaryotes can store excess nutrients or energy in the form of granules within the cytoplasm. Examples include glycogen granules (carbon storage) and polyphosphate granules (phosphorus storage). Gas Vesicles : Function : Found in some aquatic bacteria, gas vesicles are small, gas-filled structures that help the cell regulate its buoyancy in water.