Prokaryotic Cells Overview

Study Notes

Prokaryotic Cells

Definition: Simple, unicellular organisms without a defined nucleus or membrane-bound organelles.
Types:
- Bacteria
- Archaea
Structure:
- Cell Wall: Composed of peptidoglycan (in bacteria); provides shape and protection.
- Cell Membrane: Semi-permeable membrane controlling the movement of substances in and out.
- Cytoplasm: Jelly-like substance where metabolic processes occur; contains ribosomes and genetic material.
- Nucleoid: Region containing the cell's DNA; not membrane-bound.
- Ribosomes: Sites of protein synthesis; smaller than eukaryotic ribosomes.
- Flagella and Pili: Structures for mobility (flagella) and attachment (pili).
Reproduction:
- Asexual reproduction primarily through binary fission, leading to rapid population growth.
Metabolism:
- Diverse metabolic pathways; can be autotrophic (producing own food) or heterotrophic (consuming others).
- May exhibit anaerobic or aerobic respiration.
Genetic Material:
- Usually a single circular chromosome; may also contain plasmids (small circular DNA molecules).
Size:
- Typically smaller than eukaryotic cells, ranging from 0.1 to 5.0 micrometers in diameter.
Importance:
- Essential for nutrient cycling, biotechnology applications, and human health (both beneficial and pathogenic roles).

Definition and Types

Prokaryotic cells are simple, unicellular organisms without a defined nucleus or membrane-bound organelles.
Main types include Bacteria and Archaea.

Structure

Cell Wall: Made of peptidoglycan in bacteria; provides structural integrity and protection.
Cell Membrane: A semi-permeable barrier that regulates substance movement in and out of the cell.
Cytoplasm: Gel-like matrix where metabolic activities occur; contains ribosomes and DNA.
Nucleoid: A non-membrane bound area housing the cell's DNA, typically circular.
Ribosomes: Smaller than those in eukaryotes; sites for protein synthesis.
Flagella and Pili: Flagella enable motility; pili assist in attachment to surfaces.

Reproduction

Prokaryotes predominantly reproduce asexually via binary fission, facilitating rapid population growth.

Metabolism

Possess diverse metabolic pathways; can be:
- Autotrophic: Synthesizing their own food.
- Heterotrophic: Consuming organic material.
Capable of both anaerobic and aerobic respiration.

Genetic Material

Generally contain a single circular chromosome; may also have plasmids, which are small, extra-chromosomal DNA fragments.

Size

Prokaryotic cells are usually smaller than eukaryotic ones, measuring between 0.1 to 5.0 micrometers in diameter.

Importance

Play crucial roles in nutrient cycling, biotechnology, and human health, possessing both beneficial and pathogenic functions.

Overview of Prokaryotic Cells

Prokaryotic cells are unicellular organisms characterized by the absence of a membrane-bound nucleus and organelles.
Their size typically ranges from 0.1 to 5.0 micrometers in diameter, making them smaller than eukaryotic cells.

Characteristics

Prokaryotes possess a nucleoid region where their genetic material (DNA) is located, lacking a true nucleus.
DNA is usually structured as a single circular chromosome and may include plasmids, which are small circular DNA molecules that confer additional traits.
A majority of prokaryotes have a rigid cell wall composed of peptidoglycan in bacteria or other substances in archaea.
The cell membrane is a phospholipid bilayer that regulates substance transport into and out of the cell.
Ribosomes in prokaryotes are smaller (70S) than those in eukaryotes (80S) and are crucial for protein synthesis.

Types of Prokaryotic Cells

Bacteria are the most prevalent prokaryotic organisms, classified by shape: cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).
Bacteria can also be categorized as gram-positive or gram-negative based on their cell wall structure.
Archaea are distinct from bacteria and often thrive in extreme environments, possessing unique biochemical pathways and different membrane lipids.

Reproduction

Prokaryotes primarily reproduce asexually through binary fission, resulting in two identical daughter cells.
Genetic variation can arise through horizontal gene transfer, which includes transformation (uptake of DNA), transduction (virus-mediated DNA transfer), and conjugation (direct transfer between cells).

Metabolism

Prokaryotic cells exhibit diverse metabolic pathways, allowing them to thrive in various environments.
Autotrophic prokaryotes synthesize their own food through processes such as photosynthesis or chemosynthesis.
Heterotrophic prokaryotes obtain energy by consuming organic compounds from their surroundings.

Importance

Prokaryotes play vital ecological roles, functioning as decomposers, nitrogen fixers, and primary producers within ecosystems.
They can have beneficial effects, such as in gut microbiota and biotechnological applications, or harmful effects, as seen with pathogenic bacteria that cause diseases.

Special Features

Some bacteria can form endospores, which are highly resilient dormant structures capable of surviving extreme conditions.
Prokaryotic cells can develop biofilms, which are complex communities adhering to surfaces, exhibiting cooperative behaviors and enhanced survival strategies.

Description

Explore the fascinating world of prokaryotic cells, including their definitions, structures, types like bacteria and archaea, and methods of reproduction. Learn about their unique metabolic processes and how they differ from eukaryotic cells in terms of complexity and function.