Prokaryotic and Eukaryotic Cells Quiz

Prokaryotic Vs. Eukaryotic Cells

• Chemically similar - both contain nucleic acids, protein, lipids, and carbohydrates
• Both have ribosomes, but prokaryotic ribosomes are smaller (70S) and eukaryotic ribosomes are larger (80S)
• Prokaryotes lack membrane-bound organelles (e.g., mitochondria, Golgi apparatus, endoplasmic reticulum)
• Prokaryotic genome consists of a single, circular chromosome, while eukaryotic genome is organized into multiple linear chromosomes within a nucleus
• Prokaryotes divide by binary fission, while eukaryotes divide by mitosis or meiosis
• Prokaryotic cell walls contain peptidoglycan, which is absent in eukaryotic cell walls

Bacterial Morphology

• Bacteria vary in size, morphology, cell-to-cell arrangement, and chemical composition and structure of the cell wall
• Bacterial cell wall differences form the basis for the Gram stain
• Most clinically relevant bacterial species range in size from 0.25 t0 1um in width and 1 to 3um in length
• Bacteria are 100 times larger than a virus and 10 times smaller than a eukaryotic cell

Bacterial Structures

• Cell wall: provides structural support and shape, and protects the cell from osmotic lysis. Composed of peptidoglycan.
• Plasma membrane: regulates the transport of nutrients and waste products. Composed of phospholipids and proteins.
• Cytoplasm: the gel-like substance within the cell membrane that contains the cell's genetic material, ribosomes, and other essential components.
• Ribosomes: responsible for protein synthesis.
• Nucleoid: the region of the cytoplasm where the bacterial chromosome is located. Not enclosed by a membrane.
• Flagella: long, whip-like appendages that allow bacteria to move.
• Pili (fimbriae): short, hair-like structures that help bacteria adhere to surfaces.
• Capsule: a gelatinous layer that surrounds some bacteria, protecting them from phagocytosis by white blood cells.
• Spores: dormant, highly resistant forms of bacteria that can survive harsh conditions.

Endospores

• Responsible for perpetuation
• Not involved in multiplication
• Examples: Bacillus, Clostridium
• Types of spores based on location:
  • Terminal spore (Clostridium tetani)
  • Subterminal spore (Clostridium botulinum)
  • Central spore (Bacillus anthracis)
• Properties of Endospores:
  • Core: spore protoplast, containing a complete chromosome, protein-synthesizing apparatus, and a glycolysis-based energy-generating system.
  • Spore wall: the innermost layer surrounding the inner spore membrane, composed of peptidoglycan.
  • Exosporium: the outermost layer of the endospore, composed of protein.

Capsule

• Composed of polysaccharide or polypeptide
• Protects the bacteria from the attacks of the human defense system
• Resists phagocytosis
• Resists desiccation
• Capsules sometimes must be removed for detecting the somatic (cell wall) antigens
• Capsule removal achieved by boiling a suspension of the microorganism
• Capsules do not stain with common laboratory stains (Gram or India ink)

Slime Layer

• Unorganized material loosely attached to the cell wall
• Diffuses between the cell wall and the surrounding medium

Spirochetes

• A group of bacteria with unique structure and motility
• Movement achieved by axial filaments or endoflagella
• True motility and Brownian movement are best observed through the Hanging Drop Method
• Flagellar staining, serological tests, fluorescent antibody techniques, and swarming phenomena can also be used to demonstrate motility

Taxis

• Movement of bacteria toward or away from a particular stimulus

• Types of Taxis:

  • Chemotaxis - movement in response to chemical stimuli.
  • Phototaxis - movement in response to light stimuli.
  • Aerotaxis - movement in response to oxygen stimuli.
  • Magnetotaxis - movement in response to magnetic stimuli.

Pili (Fimbriae)

• Hairlike, proteinaceous structures extending from the cell membrane into the external environment
• Approximately 2 μm long
• Hair-like microfibrils usually produced by flagellated Gram-negative bacteria.
• Observable by electron microscopy
• Assist with attachment to surfaces.

Test your understanding of the differences between prokaryotic and eukaryotic cells, including their structures, functions, and reproduction methods. This quiz will also cover bacterial morphology and how it relates to classification, such as the Gram stain technique. Dive into the fascinating world of cellular biology!