Cell Structure and Organelles Lecture Notes

Overview

• Basic review of cell components
• Focus on organelles (tiny organs of the cell)

Nucleus

• Function: Command and control center
  • Dictates cell activities: growth, protein and lipid production
• Components:
  • DNA (Chromatin): Instruction manual, stores genetic information
  • Nucleolus: Produces ribosomal RNA (rRNA) for ribosome assembly

Ribosomes

• Function: Protein synthesis
• Composition: rRNA and proteins
• Location: Free-floating in cytosol and attached to rough ER

Endoplasmic Reticulum (ER)

• Types:
  • Rough ER: Contains ribosomes; assists in protein production
  • Smooth ER: Lacks ribosomes; produces lipids, cholesterol, hormones; detoxifies substances

Golgi Body

• Function: Modifies, processes, and exports proteins
• Process:
  • Adds lipids and carbohydrates to proteins
  • Shapes proteins
  • Exports modified proteins out of the cell

Mitochondria

• Function: Cellular respiration
• Unique Feature: Contains its own DNA
• Process: Converts energy stored in fats and carbohydrates into ATP

Lysosome

• Function: Breaks down food and pathogens
• Components: Contains digestive enzymes
• Role in Phagocytosis: Breaks down engulfed pathogens

Cytoplasm

• Description: Jelly-like fluid within the cell
• Contents: Organelles, salts, electrolytes, carbohydrates, lipids, ribosomes

Cytoskeleton

• Function: Maintains cell shape, provides structural support
• Components and Functions:
  • Microtubules: Largest fibers, made of tubulin, support and transport vesicles
  • Microfilaments: Smallest fibers, made of actin, assist in cell movement
  • Intermediate Filaments: Provide mechanical support, size between microtubules and microfilaments

Centrioles

• Function: Active during cell division
• Role: Forms mitotic spindle to separate chromosomes

Cilia and Flagella

• Function: Assist in cell movement
• Structure:
  • Cilia: Short, hair-like structures, numerous
  • Flagella: Long, whip-like structures, few
• Composition: Made of microtubules

Plant Cell-Specific Features

• Large Vacuole: Stores water/nutrients, provides structural support via hydrostatic pressure
• Chloroplast: Contains chlorophyll, site of photosynthesis
• Cell Wall: Provides additional structural support

Cell Membrane

• Structure: Phospholipid bilayer
• Property: Selective permeability
• Function: Regulates entry and exit of substances
  • Small molecules (e.g., O2, H2O) diffuse through
  • Large molecules (e.g., glucose) require protein channels

Additional Resources

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