Chapter 6: A tour of the cell

• All cells share these basic features:

  • They are bounded by the plasma membrane, a selective barrier
  • They contain a semifluid jelly like substance called cytosol in which subcellular components are suspended
  • All cells contain chromosomes, which carry genes in the form of DNA
  • All cells have ribosomes, tiny complexes that make proteins according to the instructions from genes
• What is the significance of compartments in eukaryotic cells?

  They allow for specialized functions and maintenance of distinct conditions
• What is the function of lysosomes in eukaryotic cells?

  They act as recycling centers for the cell
• Why must lysosomes maintain an acidic pH?


  To effectively dispose of cellular waste
• What do peroxisomes produce during oxidation reactions?

  Hydrogen peroxide
• Why is it important for peroxisomes to store hydrogen peroxide safely?


  Because hydrogen peroxide can damage the cell if not contained
• How does the compartmentalization in eukaryotic cells benefit their metabolic processes compared to prokaryotic cells?

  It allows eukaryotic cells to carry out complex metabolic reactions that prokaryotes cannot
• What is a key reason eukaryotic cells can grow larger than prokaryotic cells?


  Their ability to maintain different environments inside the cell
• What are the key features that distinguish eukaryotic cells from prokaryotic cells?

  • Membrane-bound nucleus
  • Membrane-bound organelles
  • Multiple linear chromosomes
• What does the term "organelle" refer to in the context of eukaryotic cells?


  It refers to compartments with specialized functions within the cell
• How do eukaryotic cells compare in complexity to prokaryotic cells?


  Eukaryotic cells are much more complex than prokaryotic cells
• What roles do subcellular structures play in eukaryotic cells?


  • Important for energy balance
  • Essential for metabolism
  • Crucial for gene expression
• What is the endomembrane system?

  A group of membranes and organelles in eukaryotic cells that modifies, packages, and transports lipids and proteins
• What does the endomembrane system include?

  It includes the nuclear envelope, lysosomes, endoplasmic reticulum, and Golgi apparatus
• What is the function of the endomembrane system?


  To modify, package, and transport lipids and proteins
• What organelles are NOT included in the endomembrane system?


  Mitochondria, chloroplasts, and peroxisomes
• What is the role of the endoplasmic reticulum (ER)?


  To modify proteins and synthesize lipids
• What is the structure of the endoplasmic reticulum?

  A network of membranous tubules and flattened sacs
• What is the lumen in the endoplasmic reticulum?


  The hollow space inside the ER
• What gives the rough endoplasmic reticulum its name?

  The bumpy ribosomes attached to its cytoplasmic surface
• What happens to proteins inside the rough ER?


  They fold and undergo modifications, such as the addition of carbohydrate side chains
• What happens to modified proteins that are not destined to stay in the ER?

  They are packaged into vesicles and shipped to the Golgi apparatus
• What is the function of the smooth endoplasmic reticulum?

  It synthesizes carbohydrates, lipids, and steroid hormones, detoxifies medications, and stores calcium ions
• What is the special type of smooth ER in muscle cells called?

  Sarcoplasmic reticulum
• What is the role of the Golgi apparatus?


  To sort, package, and tag lipids and proteins for their final destination
• What are the two faces of the Golgi apparatus called?


  The cis face and the trans face
• What happens to proteins and lipids as they travel through the Golgi apparatus?

  They undergo further modifications, such as the addition or removal of sugar molecules
• How are modified proteins sorted in the Golgi apparatus?

  Based on markers such as amino acid sequences and chemical tags
• What do lysosomes do?


  They contain digestive enzymes and recycle old and unnecessary structures
• What is phagocytosis?

  A process where a cell engulfs a pathogen by folding its plasma membrane inward
• What is the function of vacuoles in plant cells?

  To store water and wastes, isolate hazardous materials, and break down macromolecules
• How do lysosomes differ from peroxisomes?

  Lysosomes contain digestive enzymes, while peroxisomes house enzymes for oxidation reactions
• What is the role of peroxisomes in the cell?


  To break down fatty acids and amino acids and detoxify substances
• Are peroxisomes part of the endomembrane system?


  No, peroxisomes are not part of the endomembrane system
• What are the main functions of the endomembrane system?


  • Modify lipids and proteins
  • Package lipids and proteins into vesicles
  • Transport lipids and proteins to their destinations
• Compare the functions of rough ER and smooth ER.

  Rough ER:

  • Contains ribosomes
  • Synthesizes and folds proteins in the lumen
  • Produces phospholipids for membranes
  • Abundant in cells that secrete proteins (e.x liver)

  Smooth ER:

  • Lacks ribosomes
  • Synthesizes carbohydrates, lipids, and steroid hormones
  • Detoxifies medications and poisons
  • Stores calcium ions
• Describe the process of protein transport from the rough ER to the Golgi apparatus.

  1. Proteins are synthesized in the rough ER.
  2. They are modified and packaged into vesicles.
  3. Vesicles bud off from the rough ER.
  4. Vesicles travel to the Golgi apparatus and fuse with the cis face.
  5. Proteins undergo further modifications in the Golgi.
  6. Modified proteins are sorted and packaged into vesicles at the trans face.
• What are the roles of lysosomes and vacuoles in cells?

  Lysosomes:

  • Digest old structures and foreign particles
  • Act as recycling facilities

  
  

  Vacuoles:

  • Store water and wastes
  • Isolate hazardous materials
  • Break down macromolecules
• What are the differences between lysosomes and peroxisomes?

  Lysosomes:

  • Contain digestive enzymes
  • Part of the endomembrane system

  
  

  Peroxisomes:

  • House enzymes for oxidation reactions
  • Not part of the endomembrane system
• What is the cytoskeleton?


  A network of fibers extending throughout the cytoplasm