Recording-2025-03-07T16:25:32

Photosynthesis and Cellular Respiration in Bacteria

• Early bacteria, such as cyanobacteria, could perform photosynthesis and aerobic respiration before eukaryotic cells evolved.

• Organelle Functionality:

  • Mitochondria: Responsible for cellular respiration in eukaryotic cells.

  • Chloroplasts: Used for photosynthesis in eukaryotic cells.

  • However, bacteria can conduct these processes without these organelles due to their internal membrane systems.

Internal Membrane Systems

• Internal membrane systems in bacteria allow for processes similar to photosynthesis and respiration, compensating for the lack of organelles.

• The internal membrane is structured from folded phospholipid bilayers, creating spaces favorable for metabolic processes.

Flagella in Bacteria

• Flagella are whip-like structures used for locomotion in bacteria.

• Key Points:

  • Bacterial flagella differ from eukaryotic flagella in their structure and movement.

  • Prokaryotic flagella may have one or multiple flagella for motility.

  • Bacterial flagella are anchored by a complex rotary system and are made of the protein flagellin.

Pili and Their Functions

• Pili (also referred to as fimbriae) are hair-like structures that allow bacteria to adhere to surfaces and each other.

  • Significant in forming biofilms and contributing to dental plaque, which can lead to halitosis (bad breath) and tooth decay.

• Conjugation can occur through pili, allowing for gene transfer between bacteria, labeled as "bacterial sex."

Differences between Pili and Cilia

• Pili: Adhere and connect bacteria; vary in shape and size.

• Cilia: Hair-like structures found in eukaryotic cells, made of microtubules and assisting with motility.

Bacterial Cell Shapes

• Bacteria exhibit various shapes:

  • Cocci: Round-shaped bacteria (e.g., gonorrhea).

  • Bacilli: Rod-shaped bacteria (e.g., Escherichia coli).

  • Spiral-shaped bacteria (e.g., Treponema pallidum, which causes syphilis).

• Still unicellular despite sometimes adhering to each other.

Concept Map of Bacterial and Eukaryotic Cells

• The concept map summarizes core similarities and differences:

  • Common structures in both prokaryotic and eukaryotic cells include the plasma membrane, DNA, and ribosomes.

  • Distinct features of prokaryotic cells: lack of nucleus, circular genome, presence of pili.

  • Eukaryotic cells have a nucleus with linear DNA, organelles including mitochondria, and complex structures such as a cytoskeleton.

Eukaryotic Cell Characteristics

• Eukaryotic cells belong to multiple kingdoms: Animals, Plants, Fungi, and Protists.

• Eukaryotic organisms exhibit diverse forms from single-celled (e.g., protists) to multicellular (e.g., animals, plants).

• Eukaryotic cells have a cytoskeleton consisting of microfilaments, microtubules, and intermediate filaments.

Organelles of Eukaryotic Cells

• Nucleus: Largest organelle housing DNA in chromatin form and ribosomal subunits are produced in the nucleolus.

• Endoplasmic Reticulum (ER): Composed of rough (with ribosomes) and smooth (lipid synthesis) sections.

  • Rough ER synthesizes protein for excretion, lysosomes, and membrane integration.

  • Smooth ER synthesizes lipids and detoxifies chemicals.

• Golgi Apparatus: Processes, modifies, and packages proteins received from the ER.

• Lysosomes: Contain digestive enzymes that hydrolyze macromolecules and recycle cell materials.

Membrane Structure and Function

• The cell membrane is a fluid mosaic model made up of lipids, proteins, and carbohydrates.

  • Phospholipid Bilayer: Composed of hydrophilic heads and hydrophobic tails that provide membrane stability and fluidity.

  • Proteins: Integral (transmembrane) and peripheral proteins that play roles in transport and cell communication.

  • Cholesterol: Stabilizes membrane fluidity in animal cells, crucial for maintaining function at varying temperatures.

  • Carbohydrates: Oligosaccharides forming glycoproteins or glycolipids for cell recognition and adhesion.

Cytoskeletal Structures in Eukaryotic Cells

• Microfilaments: Composed of actin for cell shape and movement (e.g., microvilli).

• Intermediate Filaments: Provide mechanical strength and anchor organelles (e.g., keratin).

• Microtubules: Structural components for flagella and cilia, and facilitate intracellular transport (motor proteins).

Extracellular Structures

• Eukaryotic cells produce extracellular structures: cell walls in plants (cellulose) and fungi (chitin), vs. animal extracellular matrices (collagen).

  • Cell walls support and protect plant cells, facilitating communication through plasmodesmata.

Evolution of Eukaryotic Cells

• Eukaryotic cells likely evolved from prokaryotic ancestors through endosymbiosis.

  • Mitochondria originated from engulfed protobacteria.

  • Chloroplasts evolved from engulfed cyanobacteria.

• Shared features include circular DNA and similarities in ribosomal structures.