Cell Structure (Prokaryotic and Eukaryotic)

• What are prokaryotic cells?


  Single-celled organisms that lack a nucleus and membrane-bound organelles
• What are the characteristics of prokaryotic cells?


  • Lack a nuclear membrane
  • Absence of mitochondria, Golgi bodies, chloroplasts, and lysosomes
  • Genetic material on a single chromosome
  • Lack histone proteins
  • Cell wall made of carbohydrates and amino acids
  • Plasma membrane acts as mitochondrial membrane
  • Divide asexually by binary fission and sexually by conjugation
• Why do prokaryotic cells lack histone proteins?


  Histone proteins bind to DNA and help control gene activity
• What is the function of the capsule in prokaryotic cells?


  It helps in moisture retention and protects the cell
• What is the primary composition of the cell wall in eubacteria?


  It is primarily composed of peptidoglycan
• What is the role of ribosomes in prokaryotic cells?


  They are involved in protein synthesis
• What are the three basic shapes of prokaryotic cells?


  1. Cocci (Round)
  2. Bacilli (Rod)
  3. Helical (Spiral)

  
• What does a Gram stain indicate about bacteria?


  It identifies bacteria as either gram positive or gram negative
• What color do gram positive bacteria stain?


  Blue
• Why are gram negative bacteria harder to treat with antibiotics?


  They have a thin peptidoglycan layer
• What are the two modes of prokaryotic reproduction?


  • Asexual reproduction through binary fission
  • Sexual reproduction through recombination
• What are the steps of binary fission in prokaryotic cells?


  1. DNA replicates and attaches to the cell membrane
  2. Cell wall increases in size and moves inward
  3. A cell wall forms between each DNA, dividing the cell into two daughter cells
• What are the three ways recombination can occur in prokaryotic cells?


  1. Conjugation: Gene transfer through a pilus
  2. Transformation: Uptake of DNA from the surroundings
  3. Transduction: Transfer of genetic material via viruses
• What is the composition of the cell wall in bacterial cells?

  Peptidoglycan
• What is the function of plasmids in bacterial cells?


  They are extrachromosomal DNA structures that can replicate independently
• What is the ability of bacteria to form endospores?


  It helps them survive under unfavorable conditions
• What are the characteristics of archaeal cells?


  • Found in extreme environments
  • Have a cell wall and flagella
  • Cell wall does not contain peptidoglycan
  • Membranes have different lipids
  • Possess one circular chromosome and plasmids
• What defines eukaryotic cells?


  They have a clearly defined nucleus
• What are the characteristics of eukaryotic cells?


  1. Membrane-bound nucleus
  2. Membrane-bound organelles
  3. Multiple linear chromosomes
• How do eukaryotic cells differ from prokaryotic cells?


  Eukaryotic cells are more complex and have membrane-bound organelles
• What is the role of the cell membrane in eukaryotic cells?


  • Holds the cell together
  • Regulates transportation of substances
  • Maintains stable internal environment
• What are the characteristics of the cell membrane?


  • Selectively permeable
  • Amphipathic phospholipid bilayer
• What does it mean for the cell membrane to be selectively permeable?


  It actively transports certain materials into or out of the cell
• What is the structure of phospholipids in the cell membrane?


  They have a hydrophilic head and a hydrophobic tail
• What are the functions of proteins in the cell membrane?


  • Molecule transport
  • Enzymatic activity
• What are integral proteins in the cell membrane?


  Proteins that run completely through the bilayer
• What is the role of cholesterol in the cell membrane?


  It stabilizes phospholipid interactions and maintains membrane fluidity
• What is the Fluid Mosaic Model?


  • Describes the structure of the cell membrane
  • Composed of a phospholipid bilayer with embedded proteins
• What are the parts of the nucleus?

  • Nuclear envelope
  • DNA (chromatin and chromosome phases)
  • Nucleolus
• What is the function of the nuclear envelope?


  It separates the nucleus from the cytoplasm
• What happens to DNA during the chromatin phase?


  It is loose and spread out, allowing transcription
• What is the role of the nucleolus?


  It makes ribosomal RNA (rRNA) and proteins
• What are purines and pyrimidines?


  • Purines: Double carbon-nitrogen ring with four nitrogen atoms
  • Pyrimidines: Single carbon-nitrogen ring with two nitrogen atoms
• How do purines and pyrimidines interact in DNA?


  Purines form hydrogen bonds with corresponding pyrimidines
• What is the backbone of each DNA strand made of?


  A sugar-phosphate chain
• What is the chromatin phase of DNA?


  In the chromatin phase, the DNA is string-like and can be transcribed to make proteins.
• What happens to DNA during the chromosome phase?


  During the chromosome phase, the DNA coils around histones to organize itself.
• Why is the coiling of DNA important during cell division?


  The coiling helps to organize the DNA for correct distribution during nuclear and cell division.
• What is the function of the nucleolus?


  The nucleolus functions to make ribosomal RNA (rRNA) and proteins for ribosomes.
• What are purines and pyrimidines?


  Purines and pyrimidines are the two families of nitrogenous bases that make up nucleic acids.