Lecture on chapter 3 Cellular structure (mostly on eukaryotic cells)

Cell Wall

  • Function of the Cell Wall

    • Protects the cell from external damage.

    • Maintains the overall shape of the cell.

    • Prevents excessive water uptake and loss.

  • Effect on Antibiotics

    • The structure of the bacterial cell wall influences its susceptibility to antibiotics.

    • Overuse of antibiotics reduces their effectiveness; it's crucial to finish prescribed courses.

Differences Between Bacteria and Archaea

  • Composition of Cell Walls

    • Bacterial cell walls contain peptidoglycan.

    • Archaeal cell walls do not contain peptidoglycan and exhibit great diversity in composition.

  • Membrane Structure

    • Archaeal membranes contain saturated hydrocarbons attached to glycerol at both ends.

Flagella in Prokaryotic Cells

  • Functionality of Flagella

    • Present in some prokaryotic cells, potentially having multiple flagella.

    • Used for locomotion, moving the cell through rotary motion (like a propeller).

  • Structure of Flagella

    • Composed of a hook, filament, and covered with peptidoglycan.

    • The motor uses hydrogen ions (H+) to generate energy to spin the flagellum.

  • Flagella in Archaea

    • Known as archaealum, and may have an S-layer as a protective structure.

    • The motor uses ATP for energy instead of protons.

Eukaryotic Cells Overview

  • Characteristics of Eukaryotic Cells

    • Can be unicellular or multicellular.

    • Have a membrane-bound nucleus that contains genetic material.

    • Exhibit compartmentalization through membrane-bound organelles (e.g. mitochondria, endoplasmic reticulum).

    • Contain a cytoskeleton, providing support and maintaining cell shape.

Comparison of Plant and Animal Cells

  • Common Structures

    • Both have plasma membranes, nuclei, mitochondria.

    • Eukaryotic characteristics include membrane-bound organelles and cytoskeleton.

  • Unique Structures in Plant Cells

    • Cell Wall: A rigid outer layer providing support.

    • Chloroplasts: Organelles for photosynthesis.

    • Central Vacuoles: Large storage spaces for water, nutrients, and waste.

Detailed Structure of the Nucleus in Eukaryotic Cells

  • Functions

    • Controls cell activities, stores genetic material (DNA).

  • Components

    • Nuclear Envelope: A double phospholipid membrane surrounding the nucleus that regulates material entry and exit.

    • Nucleolus: Region within the nucleus where ribosomal RNA is synthesized.

    • Nuclear Pores: Openings allowing materials to pass in and out of the nucleus.

Ribosomes and Protein Synthesis

  • Roles

    • Ribosomes are the protein factories of cells, synthesizing proteins from amino acids.

    • Found in all cell types across three domains: Bacteria, Archaea, and Eukaryotes.

  • Types of RNA Involved

    • mRNA: Carries instructions from DNA to ribosomes.

    • tRNA: Assembles the correct amino acids into proteins.

Endomembrane System

  • Functionality

    • A system of membranes within eukaryotic cells that compartmentalizes various cell functions (e.g. protein synthesis, lipid production).

    • Differentiates between eukaryotic and prokaryotic cells due to its presence in eukaryotes only.

Endoplasmic Reticulum (ER)

  • Types of ER

    • Rough ER: Has ribosomes; involved in protein synthesis and processes proteins for secretion, lysosomes, or plasma membranes.

    • Smooth ER: Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.

  • Rough vs Smooth ER Functionality

    • Rough ER is more abundant in cells producing digestive enzymes (e.g. pancreatic cells).

    • Smooth ER is more abundant in cells detoxifying substances (e.g. liver cells).

Cellular Quiz Preparation

  • Focus Areas for Study

    • Familiarize with bolded terms and relevant tests or experiments from the lab manual.

    • Pay special attention to the structure and function differences between plant and animal cells.

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