Structure and Function of the Cell

Introduction

• Overview of cell structures and functions.
• Encouragement to support channel by liking, commenting, and subscribing.

Nucleus

• Nucleus as the Brain of the Cell:

  • Central organelle where cellular processes begin.

• Nuclear Envelope:

  • Double-layered structure with an outer and inner layer.
  • Outer Layer: Contains ribosomes; site where mRNA exits to bind ribosomes.
  • Inner Layer: Contains lamins; important for nuclear envelope structure and cell division.
    • Disorders like progeria linked to lamins mutations.

• Nuclear Pores:

  • Allow movement of ions, proteins, and nucleotides between cytoplasm and nucleus.

• Nucleolus:

  • Site of rRNA synthesis and ribosome production.

• Chromatin:

  • Composed of DNA and histone proteins.
  • Euchromatin: Loose form, involved in DNA expression and transcription.
  • Heterochromatin: Tight form, located near the nuclear envelope.

• Functions of the Nucleus:

  • DNA Replication: Making more DNA.
  • Transcription: Converting DNA to RNA.
  • Types of RNA: tRNA, mRNA, rRNA.

Endoplasmic Reticulum

• Rough ER:

  • Contains ribosomes; site of protein synthesis, folding, and glycosylation.
  • Synthesizes proteins for lysosomes, membranes, or excretion.
  • Packages proteins into vesicles for Golgi apparatus.

• Smooth ER:

  • Site of lipid synthesis (fatty acids, phospholipids, cholesterol).
  • Detoxification via enzymes like CYP450.
  • Glucose-6-phosphate metabolism.
  • Calcium storage.

Golgi Apparatus

• Structure:

  • Cis Golgi: Receives vesicles from ER.
  • Trans Golgi: Exports processed vesicles.

• Functions:

  • Modifies proteins and lipids via glycosylation and phosphorylation.
  • Packages molecules for lysosomes, membranes, or excretion.

Cell Membrane

• Components:

  • Phospholipid Bilayer: Polar heads (hydrophilic) and non-polar tails (hydrophobic).
  • Cholesterol: Regulates membrane fluidity.
  • Proteins: Integral and peripheral proteins involved in transport and enzymatic functions.

• Function:

  • Acts as a selective barrier for diffusion and transport.

Lysosomes

• Functions:
  • Contains hydrolytic enzymes for breaking down macromolecules.
  • Autophagy of organelles.
  • Autolysis of damaged cells.

Peroxisomes

• Functions:
  • Contains catalase and oxidase for breaking down hydrogen peroxide.
  • Involved in fatty acid oxidation and lipid synthesis.
  • Minor role in ethanol metabolism.

Mitochondria

• Structure:

  • Outer membrane (smooth, permeable).
  • Inner membrane (less permeable, folded into cristae).
  • Mitochondrial matrix (site of DNA and metabolic activities).

• Functions:

  • Site of ATP synthesis via oxidative phosphorylation.
  • Involved in Krebs cycle, heme synthesis, urea cycle, gluconeogenesis, and ketogenesis.
  • Contains mitochondrial DNA inherited maternally.

Ribosomes

• Structure:

  • Composed of large (60S) and small (40S) subunits.
  • Made of rRNA and proteins.

• Functions:

  • Site of protein synthesis (translation).
  • Membrane-bound ribosomes produce proteins for lysosomes, membranes, or export.
  • Free ribosomes synthesize cytosolic proteins.

Cytoskeleton

• Components:
  • Microfilaments (Actin): Involved in muscle contraction, cytokinesis, diapedesis, and phagocytosis.
  • Intermediate Filaments: Provide cell structure, anchorage to extracellular matrix, and organelles.
  • Microtubules: Involved in intracellular transport, cell division, and formation of cilia and flagella.

Conclusion

• Recap of the cell structure and functions discussed.
• Encouragement to apply similar study methods.
• Expressions of gratitude towards viewers.