Recording-2025-02-24T19:05:54.446Z

Nutrients and Cell Membranes

• Cell membranes are crucial for concentrating nutrients and retaining them for:

  • Energy production

  • Building cellular molecules

• All cells must synthesize proteins, facilitated by ribosomes.

• Ribosome presence:

  • Varies by cell type (1 to thousands)

  • Essential for protein synthesis.

Cytoplasm

• Definition: Jelly-like substance inside cells (fluid-filled).

• Functions:

  • Surrounds all cellular structures not clearly visible.

  • Similar to the interstitial fluid in organisms.

  • Concentrates molecules from the environment for cellular needs.

Overview of Cellular Organelles

• Introduction to organelles: Tour through various organelles begins.

Nucleus

• Control center of the cell:

  • Contains DNA

  • Has a double membrane (nuclear envelope):

    • Composed of an inner and outer membrane with space in-between.

• Function of double membrane:

  • Slows diffusion to protect DNA and nuclear contents.

  • Pores in the membrane permit selective transport in/out.

  • Special pores can close if DNA approaches, protecting it from cytoplasmic enzymes.

• Importance of nucleus in cellular processes:

  • Prevents destruction of DNA from enzymes targeting rogue DNA (potential viruses).

• RNA can exit the nucleus through pores (different from DNA's restricted movement).

Nucleolus

• Nucleolus structure:

  • Region within the nucleus where DNA is concentrated.

  • Contains chromatin made from DNA wrapped around proteins for organization.

• Chromatin vs. chromosomes:

  • Chromatin: Loosely organized DNA during non-dividing periods.

  • Chromosomes: Tightly wound, visible during cell division (mitosis).

• Involvement in ribosome production:

  • Nucleolus synthesizes ribosomal RNA (rRNA) that forms ribosomes.

Ribosomes

• Composition:

  • Made of ribosomal RNA and proteins.

  • Consist of two subunits (small and large).

• Ribosome sizes in different cell types:

  • Prokaryotes:

    • Small subunit: 30S

    • Large subunit: 50S

    • Total functional ribosome: 70S

  • Eukaryotes:

    • Small subunit: 40S

    • Large subunit: 60S

    • Total functional ribosome: 80S

• Significance of difference in ribosome structure:

  • Allows antibiotic targeting (e.g., macrolide antibiotics target bacterial ribosomes without affecting eukaryotic ribosomes).

Protein Synthesis

• Importance for certain cells:

  • Cells like those in the pancreas producing insulin have many ribosomes (thousands) due to constant protein production.

  • Muscle fibers also contain numerous ribosomes for repairing proteins damaged by movement.