Chapter 5 - Cells: The Working Units of Life

• What are the key concepts covered in Chapter 5?

  • Cells are the fundamental units of life
  • Prokaryotic cells are the simplest cells
  • Eukaryotic cells contain organelles
  • Extracellular materials provide structure
  • Eukaryotic cells evolved in several steps
• What is the significance of melanin in animal cells?

  Melanin absorbs UV light, protecting DNA from damage.
• Where is melanin made in the cell?

  In a cell compartment called the melanosome.
• What does cell theory state?

  Cells are the fundamental units of life, all organisms are composed of cells, and all cells come from preexisting cells.
• What is the role of microscopes in studying cells?

  To see most cells, we use microscopes to increase apparent size and clarity.
• What is the difference between magnification and resolution in microscopy?

  Magnification increases apparent size, while resolution is the clarity of the magnified object.
• What are the two basic types of microscopes mentioned?

  Light microscopes and electron microscopes.
• What is the resolution of light microscopes?

  0.2 μm
• What is the resolution of electron microscopes?

  0.2 nm
• What are the main components of a cell?

  • Cell membrane: outer boundary of every cell
  • Cytoplasm: everything in the cell except the nucleus
  • Cytosol: fluid cytoplasm not contained inside another compartment
• What are the functions of the cell membrane?

  It is a selectively permeable barrier, maintains a constant internal environment, and is important in communication and receiving signals.
• What are the two types of cells mentioned in the study material?

  Prokaryotic cells and eukaryotic cells.
• What distinguishes prokaryotic cells from eukaryotic cells?

  Prokaryotic cells have no membrane-enclosed internal compartments, while eukaryotic cells have membrane-enclosed organelles.
• What are the features of prokaryotic cells?

  • Enclosed by a cell membrane
  • DNA located in a region called the nucleoid
  • Cytoplasm: the rest of the cell contents
  • Ribosomes: sites of protein synthesis
• What is the function of the rigid cell wall in most prokaryotes?

  It provides structural support and protection outside the cell membrane.
• What is peptidoglycan?


  A component of the rigid cell wall found in most prokaryotes.
• What are flagella and their function in prokaryotes?

  Flagella are made of the protein flagellin and help prokaryotes swim.
• What are pili and fimbriae in prokaryotic cells?

  Pili are hairlike structures that help bacteria adhere to other cells, while fimbriae are shorter and help cells adhere to surfaces.
• What is the structure of ribosomes in prokaryotic cells?

  • Sites of protein synthesis
  • Consist of two subunits: ribosomal RNA (rRNA) and more than 50 different protein molecules
• What is the nucleus in eukaryotic cells?

  The nucleus is usually the largest organelle and contains most of the DNA.
• What is the role of the nucleolus?

  The nucleolus is the site of ribosome assembly within the nucleus.
• What is chromatin?


  Chromatin is DNA combined with proteins, forming long, thin threads called chromosomes.
• What happens to chromatin before cell division?

  Chromatin condenses, and individual chromosomes become visible under a light microscope.
• What is the endomembrane system in eukaryotic cells?

  • Interconnected system of membrane-enclosed compartments
  • Tiny, membrane-surrounded vesicles shuttle substances between components
• What is the rough endoplasmic reticulum (RER)?

  The RER is a network of membranes in the cytoplasm with ribosomes attached, where newly made proteins are modified and transported.
• What is the smooth endoplasmic reticulum (SER)?

  The SER has no ribosomes and is involved in the modification of small molecules, lipid synthesis, and calcium ion storage.
• What is the function of the Golgi apparatus?

  The Golgi apparatus modifies, concentrates, packages, and sorts proteins received from the RER.
• What are lysosomes and their function?


  Lysosomes contain digestive enzymes that hydrolyze macromolecules into monomers and are involved in waste disposal.
• How do secondary lysosomes form?

  Secondary lysosomes form when phagosomes fuse with primary lysosomes.
• What is the role of mitochondria in cells?

  Mitochondria transform glucose into energy-rich ATP through cellular respiration.
• How do mitochondria reproduce?

  Mitochondria can reproduce and divide independently of the central nucleus.
• What is the structure of mitochondria?

  Mitochondria have two membranes, with the inner membrane folding inward to form cristae, creating a large surface area for proteins involved in cellular respiration.
• What do chloroplasts do?

  Chloroplasts are the site of photosynthesis and have a double membrane.
• What are plastids and their types?

  Plastids are found only in plants and some protists; types include chloroplasts, chromoplasts, and leucoplasts.
• What is the function of peroxisomes?

  Peroxisomes collect and break down toxic byproducts of metabolism using specialized enzymes.
• What are glyoxysomes and their function?

  Glyoxysomes are found only in plants and convert lipids to carbohydrates for growth.
• What is the role of vacuoles in plant cells?

  Vacuoles provide structure for plant cells and store pigments and nutrients.
• What is the cytoskeleton and its functions?

  The cytoskeleton supports and maintains cell shape, holds organelles in position, and is involved in cell movement.
• What are the three types of filaments that compose the cytoskeleton?

  • Microfilaments
  • Intermediate filaments
  • Microtubules
• What are microfilaments and their functions?

  Microfilaments help a cell or parts of a cell to move and determine cell shape, made from the protein actin.