lecture 1 CBNS 101: Fundamentals of Cell Biology

Central Dogma of Molecular Biology

• Processes:

  • DNA replication

  • Transcription (DNA to RNA)

  • Reverse transcription

  • RNA replication

  • Translation (RNA to protein)

Protein Synthesis (Translation)

• Key Components:

  • Amino acid sequence determines protein structure

  • Examples of amino acids: Leu, Tyr, Ser, Gly, etc.

  • tRNA involved in translation process.

Protein Structure

• Levels of Organization:

  • Primary: Amino acid sequence

  • Secondary: α-helices and β-sheets

  • Tertiary: 3D folding based on interactions among side chains

  • Quaternary: Assembly of multiple polypeptide chains

Cell Theory

• Principles:

  1. All organisms are made of cells.

  2. The cell is the fundamental unit of life.

  3. All cells arise from pre-existing cells.

Cell Structure and Function

• Common Features of Cells:

  • Bounded by a plasma membrane.

  • Utilize metabolic pathways to convert substrates into ATP.

  • Governed by genetic principles (based on the Central Dogma).

  • Cells proliferate through cell division (including DNA replication and chromosome segregation).

Types of Cells

• Prokaryotic Cells:

  • Example: Escherichia coli (typical prokaryote)

  • Characteristics: Lack a true nucleus, smaller size (about 1 µm).

• Eukaryotic Cells:

  • Characteristics: Include various membrane-bound organelles (e.g., nucleus, mitochondria).

  • Important for compartmentalization to optimize biochemical reactions.

Membrane-Bound Organelles

• Describe roles of distinct organelles:

  • Nucleus: Site of DNA/RNA synthesis.

  • Endoplasmic Reticulum (ER): Synthesizes lipids and proteins.

  • Golgi Apparatus: Modifies, sorts, and packages proteins/lipids.

  • Lysosomes: Digestive enzymes for organelle and macromolecule degradation.

  • Mitochondria/Chloroplasts: ATP production; plastids contribute to photosynthesis and storage.

Membrane-less Organelles

• Formed by dynamic, reversible assemblies of proteins and RNA.

• Nucleolus as a key example of biomolecular condensates, facilitating rRNA processing.

Model Organisms in Cell Biology

• Examples:

  • Arabidopsis thaliana (plant)

  • Drosophila melanogaster (fruit fly)

  • Saccharomyces cerevisiae (yeast)

  • Caenorhabditis elegans (nematode)

  • Mus musculus (mouse)

• Used for various experimental approaches to understand cellular processes.

Visualizing Cell Structures

• Structures such as membranes, organelles, and compartments can be depicted with ribbon models and space-filling models.