ch4 cell structure

• The nucleus is the control center of the cell, containing genetic material (DNA) that determines an organism's characteristics.
• Nucleolus - A small dense body within the nucleus where ribosomes are produced.
• Chromatin - The substance made up of DNA and proteins found inside the nucleus.
• Ribosome - Small structures involved in protein synthesis.
• Cell membrane - Also known as plasma membrane or plasmalemma, it separates the contents of the cell from its surroundings and regulates what enters and exits the cell.
• Cytoplasm - The fluid-like substance inside the cell that contains various structures such as mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, cytoskeleton, and ribosomes.
• Mitochondria - Organelles responsible for producing energy through respiration.
• Endoplasmic reticulum (ER): A network of membranes involved in protein production and lipid transport.
• Cytoplasm - The jelly-like fluid surrounding the nucleus and other organelles.
• Endoplasmic reticulum - Network of membranes involved in protein production and transport.
• Golgi Apparatus: Modifies and packages proteins produced by the ER for export outside the cell.
• Lysosomes: Membranous sacs containing digestive enzymes used to break down waste materials within cells.
• Cytoskeleton: Network of fibers that provides structural support and helps maintain cell shape.
• Cell Wall: Provides structural support and protection against pathogens.
• Vacuoles: Large, membrane-bound structures that store water, nutrients, or waste products.
• Microtubules: Long, hollow tubes made up of globular subunits called tubulin.
• Plasma Membrane: Regulates the movement of substances into and out of the cell.
• Centrioles: Pair of cylindrical structures composed of microtubules found near the nucleus.
• Chloroplasts: Organelles found only in plant cells that contain pigments called chlorophyll and are responsible for photosynthesis.
• Centrosome: Contains microtubule organizing centers (MTOC) responsible for organizing microtubules during mitosis.
• Flagella/Cilia: Whip-like appendages on some eukaryotic cells involved in movement.
• Chromatin: DNA wrapped around proteins to form chromosomes.
• Cell Theory:

  • Discovered in 1665 by Robert Hooke
  • Early studies conducted by Mathias Schleiden (1838) and Theodor Schwann (1839)
  • Proposed the Cell Theory:

  1. All organisms are composed of cells

  2. Cells are the smallest living things

  3. Cells arise only from pre-existing cells

  • All cells today represent a continuous line of descent from the first living cells
• Cell size limitations:

  • Most cells are relatively small due to reliance on diffusion of substances
  • Rate of diffusion affected by surface area available, temperature, concentration gradient, and distance
  • Cell surface area must be large enough to meet the metabolic needs of its volume
• Cell surface area and volume:

  • As a cell gets larger, its volume increases at a faster rate than its surface area
  • Cell's surface area must be large enough to meet the metabolic needs of its volume
  • Organisms made of many small cells have an advantage over those composed of fewer, larger cells
• Microscopes and cell visualization:

  • Not many cells are visible to the naked eye
  • Resolution is the minimum distance two points can be apart and still be distinguished as two separate points
  • Two types of microscopes: Light microscopes and Electron microscopes
• Prokaryotic Cell:

  • Basic structural similarities include nucleoid or nucleus, cytoplasm, ribosomes, and plasma membrane
  • Simplest organisms lacking a membrane-bound nucleus
  • Cell wall outside of plasma membrane
  • Two domains of prokaryotes: Archaea and Bacteria
• Prokaryotic cell structure:

  • Generalized cell organization of a prokaryote
  • Nucleoid visible as a dense central region segregated from the cytoplasm
  • Some prokaryotes have hairlike growths called pili on the outside of the cell
• Bacterial cell walls:

  • Most bacterial cells are encased by a strong cell wall composed of peptidoglycan
  • Protect the cell, maintain its shape, and prevent excessive uptake or loss of water
  • Susceptibility of bacteria to antibiotics often depends on the structure of their cell walls
• Prokaryotic flagella:

  • Present in some prokaryotic cells for locomotion
  • Rotary motion propels the cell forward
• Eukaryotic Cell:

  • Possess a membrane-bound nucleus
  • More complex than prokaryotic cells with compartmentalization achieved through membrane-bound organelles
  • Possess a cytoskeleton for support and to maintain cellular structure
• Animal vs. plant cells:

  • Both have plasma membrane and most organelles
  • Plant cells have extra components like a cell wall, chloroplasts, and specialized vacuoles
• Nucleus:

  • Repository of genetic information
  • Most eukaryotic cells possess a single nucleus with a nucleolus for ribosomal RNA synthesis
  • DNA organized into multiple linear chromosomes with proteins into chromatin
• Ribosomes are the cell's protein synthesis machinery found in all cell types in Archaea, Bacteria, and Eukarya
• Ribosomes consist of a large and a small subunit composed of rRNA and protein
• The individual subunits of ribosomes are synthesized in the nucleolus and then move through the nuclear pores to the cytoplasm, where they assemble to translate mRNA
• Ribosomes serve as sites of protein synthesis
• Endomembrane system is a series of membranes throughout the cytoplasm that divides the cell into compartments where different cellular functions occur
• One of the fundamental distinctions between eukaryotes and prokaryotes is the presence of the endomembrane system in eukaryotes
• Endoplasmic reticulum (ER) consists of rough ER (RER) and smooth ER (SER)