Lecture 7

• Structural Components of Bacterial cells

  Bacterial cells (prokaryotic cells):

  • Lack a true nucleus and membrane-bound organelles.
  • Have no real cytoskeleton.
  • Belong to two domains: Archaea and Bacteria.

  Features include a nucleoid (housing a single chromosome), ribosomes, plasma membrane, cell wall, capsule, fimbriae, and flagella (used for movement).
• Structural Components of Eukaryotic Cells

  • A true nucleus and membrane-bound organelles.
  • A cytoskeleton for structure.
  • Belong to the domain Eukarya.

  Found in animals and plants, they include mitochondria, vesicles, Golgi apparatus, endoplasmic reticulum (ER), ribosomes, nucleus, cytoplasm, and plasma membrane.

  Additionally, animal cells have lysosomes and a central vacuole, while plant cells have a cell wall and chloroplasts.
• Mitochondria (Eukaryotic cells) 


  Power house of the cell

  Produce energy

  Responsible for regulating the metabolic activity of the cell

  Promotes cell multiplication and cell growth
• Vesicles (Eukaryotic Cells)

  Helps transport materials that an organism need to survive and recycle waster materials

  Absorb and destroy toxic substances and pathogens to prevent cell damage and infection
• Lysosome ( Eukaryotic Cells) 


  Only in animal cells

  Degrade material taken up from outside the cell and digest obsolete components of the cell itself

  Breaks down food, toxic compounds

  Autophagy- Digest old organelles, recycling defective components inside the cell
• Cell Membrane (Eukaryotic cells) 


  Only in animal cells

  Regulates the transport of materials entering and exiting the cell
• Cell Wall (Eukaryotic cells)


  Only in plant cells

  Separates the interior contents of the cell from the exterior environment

  Provides shape, support and protection to the cell and its organelles
• Golgi (Eukaryotic cells)


  Transport

  Sorting and modification of both protein and lipids into vesicles

  Completes Glycosylation

  Makes polysaccharides
• ER ( Endoplasmic Reticulum ) (Eukaryotic cells)


  Rough ER:(RER)

  • Protein synthesis
  • Surface covered in ribosomes
  • Formed from continuous fold of membrane continuous with the nuclear envelope
  • Processes proteins made by the ribosomes

  Smooth ER: (ER)

  • Doesn't have ribosomes on the surface, its function is distinct to the RER.
  • Involved in the production, processing and storage of lipids, carbohydrates and steroids.
• Ribosomes (Eukaryotic cells)


  Synthesize proteins by translating mRNA.

  Read mRNA sequences and assemble amino acids into polypeptide chains.

  Found free in the cytoplasm or attached to the endoplasmic reticulum (ER).

  Produce proteins vital for cell structure, function, and regulation.
• Central Vacuole (Eukaryotic cells)

  Only in plant cells

  Holds materials and waste
• Chloroplasts (Eukaryotic cells)

  Only in plant cells

  Produce energy through photosynthesis
• Cytoplasm (Eukaryotic cells)

  Holes components of the cell and protects them from damage

  Stores the molecules required for cellular processes

  Responsible for giving the cell its shape
• Plasma Membrane (Eukaryotic cells)


  Regulates the transport of materials entering and exiting the cell
• Cytoskeleton (Eukaryotic cells)

  Major roles in movement and structural support

  • Spatially organise the components of the cell
  • Connects the cell physically and biochemically to the external environment
  • Generates coordinated forces that enable the cell to move and change shape
• Structure and function of Microtubules

  Structure:

  • Part of the cell's cytoskeleton, they are the thickest type.
  • Made of tubulin proteins that form small diameter tubes.
  • Dynamic structures that lengthen and shorten by adding or removing tubulin subunits at ends.

  Function:

  • Maintain cell shape.
  • Facilitate cell movement, division, and transportation of materials within the cell.
• Components of the Nucleus- Chromatin


  Structure:

  • DNA wound around histone proteins.

  Function:

  • Packs DNA into a compact unit.
• Components of the Nucleus- Nucleolus 


  Structure:

  • Spherical body at the center of the nucleus.

  Function:

  • Produces and assembles ribosomes.
• Components of the Nucleus- Nuclear envelope

  Structure:

  • Double membrane around the nucleus.

  Function:

  • Separates nucleus from cytoplasm, provides structural support.
• Components of the Nucleus- Nuclear pore


  Structure:

  • Large protein complex.

  Function:

  • Allows small molecules and ions to enter and exit nucleus.
• Components of the Nucleus - Nuclear lamina


  Structure:

  • Made of lamins.

  Function:

  • Supports various nuclear processes like DNA replication, RNA transcription, and cell cycle regulation
• Endosymbiont Theory


  The nucleus developed from a prokaryotic cell engulfed by an amoeba-like cell similar to eukaryotic cytoplasm.

  Large cells engulfed smaller bacteria:

  • Some bacteria remained intact and lived symbiotically.

  Bacteria capable of self-energy production evolved into mitochondria, with mitochondria evolving first.

  Not all eukaryotic cells have chloroplasts, which originated from bacteria using sunlight for food.

  Mitochondria and chloroplasts have their own DNA separate from the nucleus.

  They are typically similar in size to bacteria and divide similarly.