CELLS NUCLEAS AND RIBOSOMES

Overview of Cell Biology Methods

  • Cell Biology methods involve various techniques for studying cells.

    • Microscopy: crucial for visualizing cells.

    • Techniques include Thin Layer Chromatography (TLC), Mass Spectrometry (MS), and sequencing.

Cell Types Comparison

  • Focus on two major cell types: Prokaryotic and Eukaryotic.

    • Differences include nucleus and ribosome structure.

    • Study the commonalities and differences between both cell types.

    • Understand why cells are generally small and microscopic.

Prokaryotic Cells

  • Definition: "Pro" means prior to nucleus.

  • Features:

    • Simple structure, typically smaller than eukaryotic cells (1–2 micrometers).

    • DNA located in the nucleoid region, not enclosed in a nucleus.

    • No membrane-bound organelles.

    • Common structures: ribosomes, plasma membrane, and cell wall.

  • Classification:

    • Formerly grouped under Monera (bacteria and archaea); now classified into three domains: Bacteria, Archaea, and Eukarya.

    • Archaea are extremophiles, survive in extreme conditions (temperature, pH, salt).

Eukaryotic Cells

  • Definition: True nucleated cells; "eu" means true.

  • Characteristics:

    • Larger than prokaryotic cells (at least 10 micrometers).

    • Complex structures with organelles (nucleus, ribosomes, Golgi apparatus, mitochondria).

    • Presence of a true nucleus with a double membrane and nucleolus for ribosome synthesis.

  • Types:

    • Animals: have cell membranes and lysosomes.

    • Plants: have cell walls (cellulose), chloroplasts, central vacuoles.

  • Functions of organelles relate to their structures.

Common Features of Cells

  • Plasma membrane and ribosomes are present in all living cells.

  • Cell walls present in most organisms except for animal cells and some protists (e.g., paramecium, amoeba).

  • Eukaryotic cells have compartmentalization to increase surface area for metabolic functions.

Cell Size and Function Relationship

  • Cell size is constrained due to surface area-to-volume ratio.

  • Calculations show that as cells grow larger, their volume increases faster than surface area.

  • Importance of maintaining a high surface area for effective transport and metabolic processes.

Specialization and Compartmentalization in Eukaryotes

  • Eukaryotic cells adapt to size limits through:

    • Internal membranes for specialization.

    • Folding of cell structures to increase surface area (e.g., endoplasmic reticulum).

  • Organelles assist in compartmentalization: nucleus, Golgi apparatus, mitochondria, cytoskeleton components (microfilaments, intermediate filaments, microtubules).

Nucleus Structure

  • Double membrane structure with a nuclear envelope containing pores for material exchange.

    • Nuclear lamina (protein skeleton) supports nuclear shape.

    • Nucleoplasm contains DNA and ribonucleotide triphosphates (NTPs).

    • Nucleolus: site for ribosomal RNA (rRNA) synthesis and ribosome assembly.

  • Chromatin: loose DNA structure during interphase, compacts into chromosomes during cell division.

Ribosomes

  • Ribosomes: RNA-containing structures essential for protein synthesis.

    • Composed of a small and large subunit; can be found freely in cytoplasm or attached to membranes.

  • Prokaryotic vs. Eukaryotic ribosomes differ in size and protein/RNA composition:

    • Eukaryotic ribosomes: approximately 40% RNA, 60% protein.

    • Prokaryotic ribosomes: similar proportions, but smaller sizes.

Summary of Key Points

  • Understanding commonalities and differences between prokaryotic and eukaryotic cells is crucial.

  • Classification improves understanding of evolutionary relationships and functional capabilities.

  • Methodological approaches in cell biology enhance the study and understanding of cell structures and functions.