handout cell structures

• Cell Theory Postulates

  • All living organisms are composed of cells
  • The cell is the basic unit of life
  • Cells arise from pre-existing cells
• Modern Postulates


  • Energy flow occurs within cell
  • Heredity information (DNA) is passed on from cell to cell
  • All cells have the same basic chemical composition
• Robert Hooke observed cells in cork in 1665
• Robert Hooke coined the term "cells"
• Anton van Leeuwenhoek created a powerful microscope in 1674
• Matthias Schleiden concluded that all plants are made of cells in 1838
• Theodor Schwann concluded that all animals are made of cells in 1838
• Rudolph Virchow concluded “Omnis cellula e cellula” in 1858
• Cell Functions

  • Smallest living unit/Basic unit of life
  • Protection and support
  • Movement
  • Communication
  • Cell metabolism and energy release
  • Inheritance
• Characteristics of All Cells

  • A surrounding membrane (Plasma Membrane)
  • Protoplasm/cytoplasm – cell contents in thick fluid
  • Organelles – structures for cell function
  • Control center with DNA
• Plasma Membrane/Cell Membrane


  Outermost component of a cell that encloses the cytoplasm and forms the boundary between materials outside it
• Major molecules that make up the cell membrane

  • Phospholipids
  • Proteins
• Phospholipid Bilayers


  The polar, phosphate-containing ends are hydrophilic and face water; the nonpolar, fatty acids ends are hydrophobic and face away from water
• Cytoskeleton


  • Consists of proteins that support the cell
  • Hold organelles in place
  • Enable the cell to change shape
• Cytoskeleton components

  • Microtubules
  • Microfilaments
  • Intermediate filaments
• Microtubules


  Hollow structures formed from protein subunits that provide support, assist in cell division, and form components of organelles
• Microfilaments


  Small fibrils formed from protein subunits that structurally support the cytoplasm and are involved with cell movement
• Intermediate Filaments


  Fibrils formed from protein subunits that provide mechanical support to the cell
• Membrane-bound Organelles

  • Nucleus
  • Smooth ER
  • Rough ER
  • Golgi Apparatus
  • Mitochondria
  • Chloroplast and other plastids
  • Lysosomes
  • Peroxisomes
• Non-Membrane-bound Organelles

  • Ribosomes
  • Centrioles
  • Cytoskeleton
• Nucleus


  Control center of cell, usually located near the center of the cell
• Nuclear Envelope


  • Consists of outer and inner membranes with nuclear pores for material passage
• Nucleoli/Nucleolus


  Rounded, dense nuclear bodies where ribosomal subunits are formed
• Production of Ribosomes

  1. Ribosomal proteins transported to nucleolus

  2. rRNA assembled with ribosomal proteins

  3. Subunits leave nucleolus and nucleus

  4. Subunits combine with mRNA in cytoplasm
• Ribosomes


  Organelles where proteins are synthesized
• Rough Endoplasmic Reticulum

  • ER with ribosomes attached
  • Responsible for protein production
• Smooth Endoplasmic Reticulum

  • ER without ribosomes
  • Site for lipid synthesis
  • Participates in detoxification
• Golgi Apparatus


  • Collects, modifies, packages, and distributes proteins and lipids
• Secretory Vesicles


  Pinch off from Golgi apparatus to release contents outside the cell
• Lysosomes


  Membrane-bound vesicles containing enzymes for intracellular digestion
• Peroxisomes


  Small vesicles containing enzymes that breakdown fatty acids and hydrogen peroxide
• Mitochondria

  Sites of cellular respiration, transforming energy from fuels into ATP
• Mitochondria structure

  • Outer membrane is selectively permeable
  • Inner membrane folds to increase surface area for metabolism
• Chloroplasts


  Sites of photosynthesis in plants and algae
• Three forms of Plastids

  • Chromoplasts
  • Leucoplasts
  • Chloroplast
• Chloroplast structure

  • Outer membrane is semi-porous
  • Inner membrane regulates material passage
  • Stroma contains chloroplast DNA and ribosomes
• Thylakoid System


  Collection of membranous sacks where light reactions of photosynthesis occur
• Types of Thylakoids

  • Granal thylakoids
  • Stromal thylakoids
• Centrioles


  Small cylindrical organelles that facilitate chromosome movement during cell division
• Centrosomes


  Main microtubule organizing center (MTOC) in the cytoplasm