Biology chap. 4 pt 2

Eukaryotic Cells and Organelles

• Overview of Eukaryotic Cells
  • All eukaryotic cells share common organelles.

Mitochondria

• Function of Mitochondria
  • Known as the "powerhouse of the cell."
  • Primary site for aerobic respiration, where cells extract energy from food.
• Aerobic Respiration Process
  • Organism takes in food (large biological molecules) and oxygen.
  • Food is oxidized, yielding carbon dioxide, water, and energy (in forms yet to be determined).
• Structure of Mitochondria
  • Two membranes:
  • Outer membrane: A phospholipid bilayer.
  • Inner membrane: Highly folded, increasing surface area for reactions.
  • Inner Membrane Space: Area between the inner and outer membranes.
  • Contains its own DNA (circular chromosome), similar to bacterial DNA.
  • Has unique mitochondrial ribosomes for protein production relevant to its functions.

Lysosomes

• Function of Lysosomes
  • Break down large biological molecules and organelles.
  • Degrades damaged or non-functional mitochondria into simpler components like amino acids and carbohydrates.

Chloroplasts

• Function of Chloroplasts
  • Site of photosynthesis, converting light energy into food.
  • Uses carbon dioxide, water, and sunlight to produce oxygen and sugars.
• Structure of Chloroplasts
  • Contains three membranes:
  • Outer membrane
  • Inner membrane
  • Thylakoids: Third membrane stacked, where chlorophyll is found.
• Has its own circular DNA and ribosomes similar to mitochondria.

Endosymbiotic Theory

• Concept Overview
  • Proposes that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by early eukaryotic cells.
  • Supported by similarities such as double membranes, circular DNA, and ribosome structures.
• Functionality
  • Over time, these bacteria became integral to the eukaryotic cells for aerobic respiration and photosynthesis, losing the ability to survive independently.

Vacuoles

• Definition
  • Large membrane-bound organelles typically found in plant cells.
  • Function to store water, nutrients, and waste products.

Cytoskeleton

• Purpose
  • A network of proteins that provides shape and support to the cell.
  • Consists of three main components:

Microtubules

• Description
  • Hollow tubes made of tubulin proteins.
  • Grow from the centrosome, providing structural support and facilitating movement of cell components.
• Functions
  • Maintain cell shape
  • Aid in intracellular transport (e.g., vesicle movement along microtubules)
  • Form structures such as cilia and flagella for cell movement.

Actin Filaments (Microfilaments)

• Description
  • Made of the protein actin, located beneath the cell membrane in animal cells.
• Functions
  • Support cell membrane and maintain cell shape
  • Contribute to changes in cell shape, especially in amoebae.

Intermediate Filaments

• Description
  • Various structural proteins, including keratins (found in skin), which provide mechanical support to cells.
• Functions
  • Anchor organelles and reinforce the structure of cells.

Cell Junctions

• Types of Cell Junctions
  • Anchoring Junctions: Resist tear or mechanical stress.
  • Gap Junctions: Allow rapid communication between cells.
  • Tight Junctions: Prevent leakage of materials between cells.
  • Plasmodesmata: Large holes in plant cells, allowing transport of materials between cells.

Exam Preparation

• Students should review organelle functions, structures, and the endosymbiotic theory for their exam one week from today. Study guides will be available to help focus on key concepts and preparation strategies.