Cell Biology: Prokaryotic and Eukaryotic Cells

Basic Structure of a Cell

• Cells are the fundamental units of all living things.
• All cells share common features, though they are diverse.
• Cells are typically microscopic, needing microscopes to be seen.
• Cells have specialized parts called organelles, each with a specific job.
• Two major types exist: prokaryotic and eukaryotic.

Prokaryotic Cells

• Prokaryotic cells are simpler and smaller than eukaryotic cells.
• They lack a nucleus or other membrane-bound organelles.
• Examples include bacteria and archaea.
• Genetic material (DNA) is stored in a region called a nucleoid.
• A cell wall provides support and protection.
• Some have flagella for movement or pili for attachment.

Eukaryotic Cells

• Eukaryotic cells are more complex and larger than prokaryotic cells.
• They have a nucleus, which holds the DNA.
• Membrane-bound organelles divide up cell functions, increasing effectiveness.
• Animal and plant cells are examples of eukaryotic cells.
• Multiple organelles work together, like mitochondria for energy and endoplasmic reticulum for protein production.
• Cell membranes control what enters and exits the cell.

Cell Membrane

• The cell membrane separates the cell from its surroundings.
• It is mainly a phospholipid bilayer with embedded proteins.
• The interior of the phospholipid bilayer is hydrophobic.
• Proteins on the membrane help move molecules.
• Receptors on the membrane allow communication with other cells.

Cytoplasm

• The jelly-like substance inside the cell.
• Contains and suspends the organelles.
• Site of many important cellular reactions.
• Supports and cushions organelles.
• Includes water, nutrients, and ions.

Nucleus

• The control center of the eukaryotic cell.
• Contains DNA organized into chromosomes.
• Enclosed by a double-layered membrane (nuclear envelope).
• DNA replication and transcription (DNA to RNA) happen here.
• The nucleolus is a region for ribosome production.

Organelles

• Specialized structures within a cell with particular functions.
• Examples: mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, vacuoles.
• These work together for cellular processes.

Mitochondria

• Mitochondria are the cell's powerhouses.
• They do cellular respiration, creating energy (ATP).
• Mitochondria have their own DNA and ribosomes, reflecting an ancient bacterial origin.
• They have a double membrane.

Endoplasmic Reticulum (ER)

• A network of membranes inside the cell.
• Two types:
  • Rough ER: studded with ribosomes, involved in protein synthesis.
  • Smooth ER: lacks ribosomes, plays a role in lipid synthesis.

Golgi Apparatus

• Modifies, sorts, and packages proteins and lipids.
• Composed of flattened sacs called cisternae.

Ribosomes

• Sites of protein synthesis.
• Can be free in the cytoplasm or attached to the rough ER.
• Made of two subunits (large and small).

Vacuoles

• Membrane-bound sacs for storing water, nutrients, or waste.
• Plant cells have a large central vacuole that contributes to structural support.

Cell Wall

• Found in plant cells and some others.
• Provides support and protection.
• Mostly made of cellulose in plant cells.

Cell Division

• Mitosis and meiosis result in cell reproduction.
• They ensure accurate distribution of genetic material.
• Crucial for growth and repair in multicellular organisms.