Lecture Notes: Structure and Function of the Cell

Introduction

• Topic: Structure and Function of the Cell
• Presenter: Ninja Nerd
• Content Overview: Discussion on cell structures and their functions. Encouragement to like, comment, and subscribe.

Nucleus

• Role: Acts as the "brain" of the cell
• Components:
  • Nuclear Envelope: Double-layered membrane
    • Outer Layer: Contains ribosomes for mRNA transport and protein synthesis
    • Inner Layer: Contains lamins, important for nuclear structure, cell division, and chromatin interaction
  • Nuclear Pores: Facilitate transport between nucleus and cytoplasm
  • Nucleolus: Site of rRNA synthesis and ribosome production
  • Chromatin:
    • Composition: DNA and histone proteins
    • Forms: Euchromatin (loose, for expression) and Heterochromatin (tight, closer to inner membrane)

Rough Endoplasmic Reticulum (Rough ER)

• Structure: Membranous network with ribosomes
• Functions:
  • Protein synthesis, particularly for lysosomal, membrane, and secreted proteins
  • Protein folding and glycosylation (N-type)
  • Packaging proteins into vesicles for Golgi transport

Smooth Endoplasmic Reticulum (Smooth ER)

• Differences from Rough ER: Lacks ribosomes
• Functions:
  • Lipid synthesis (fatty acids, phospholipids, cholesterol)
  • Detoxification via CYP450 enzymes
  • Glucose-6-phosphate metabolism
  • Calcium storage

Golgi Apparatus

• Structure: Cis (entry) and Trans (exit) faces
• Functions:
  • Receives vesicles from ER
  • Modifies proteins and lipids (glycosylation and phosphorylation)
  • Packages molecules for lysosomal, membrane, or extracellular destinations

Cell Membrane

• Components:
  • Phospholipid bilayer (polar heads, non-polar tails)
  • Cholesterol (regulates fluidity)
  • Proteins (integral and peripheral)
• Functions: Acts as a selectively permeable barrier

Lysosomes

• Role: Break down macromolecules
• Functions:
  • Contains hydrolytic enzymes (proteases, nucleases, lipases, glucosidases)
  • Autophagy of old organelles
  • Autolysis of damaged cells

Peroxisomes

• Key Enzymes: Catalase and oxidase
• Functions:
  • Breakdown of hydrogen peroxide
  • Fatty acid oxidation
  • Lipid and cholesterol synthesis (plasmalogen)
  • Ethanol metabolism

Mitochondria

• Structure: Outer membrane (smooth, permeable), Inner membrane (folded cristae)
• Functions:
  • ATP synthesis via oxidative phosphorylation (electron transport chain)
  • Site of metabolic reactions: Krebs cycle, heme synthesis, urea cycle, gluconeogenesis, ketogenesis
  • Contains mitochondrial DNA (maternal)

Ribosomes

• Structure: Large (60S) and small (40S) subunits
• Composition: rRNA and proteins
• Functions:
  • Site of protein synthesis (translation)
  • Types: Membrane-bound (rough ER) and free (cytosolic)

Cytoskeleton

• Components:
  • Microfilaments (Actin): Involved in muscle contraction, cytokinesis, phagocytosis
  • Intermediate Filaments: Provide structural support, anchor cells and organelles
  • Microtubules: Intracellular transport, cell division, cell extensions (cilia, flagella)

Conclusion

• Summary: Detailed exploration of cell structures and their functions
• Final Note: Encouragement to develop a study process and continue supporting the Ninja Nerd channel.