The Cell Structure

• The cell was discovered by Robert Hooke in 1665
• Human body is composed of trillions of cells
• Cells


  • Carry out all chemical activities needed to sustain life
  • The building blocks of all living things
• Largest biological cell


  Ostrich egg, which measures 6 inches in length and 1.4 kg in terms of mass
• Cell


  Basic structural and functional unit of life
• Tissue


  Cells working together to perform an activity
• Organ


  Group of tissues
• Organ system


  Organs that work together to perform a certain task
• Organism


  Different organ systems are integrated to form an organism
• Cell theory formulated by Mathias Schleiden, Theodore Schwann, and Rudolf Virchow

  1839
• The cell theory states that all living things are made up of cells
• The cell theory predates Darwin's Theory of Evolution and Mendel's Laws of Inheritance
• Modern molecular biology has added many tenets to the cell theory, but it remains the preeminent theory of biology</b>
• Cell theory states


  • All organisms are composed of cells
  • The cell is the basic unit of organization of all living things
  • All cells arise from preexisting cells
• Cell membrane


  Outermost boundary of animal cells, directly in contact with the environment, composed of phospholipid bilayer
• Cytoplasm


  Covers the largest area within the cell, consists of semifluid portion (cytosol) where most organelles and other cellular inclusions are found
• Nucleus


  Suspended in the cytoplasm, control center of the cell, contains semifluid material called nucleoplasm
• Nucleus (Karyosome)


  Control center of the cell, contains the genetic material
• Nuclear membrane/envelope


  Separates the content of the nucleus from the cytoplasm
• Nucleolus


  Spherical body in the nucleus, responsible for the production of ribosomes
• Chromosomes


  Structure found in the nucleus of cells, made of DNA tightly coiled around proteins, serve as scaffold or support
• Chromatid


  One of the identical strands of a replicated chromosome
• Chromonemata


  Spirally coiled central threads inside the chromatid
• Centromere


  Links the sister chromatid of a chromosome, contains the assembled protein complex called kinetochore
• Telomere


  Part of a chromosome
• Cell wall


  Rough, flexible layer that surrounds the cell, provides structural support and protection
• Cell membrane


  Barrier for cell contents, made up of double phospholipid layer with hydrophilic heads and hydrophobic tails
• Functions of the cell membrane


  • Separates a cell from another cell
  • Gives shape to the cell and holds cellular parts together
  • Regulates the movement of materials in and out of the cell
  • Plays an important role for signal and reception, screens out substances that pass in and out of the cell (semi-permeability), essential for maintaining homeostasis
• Cytoplasm


  Material outside the nucleus and inside the plasma membrane, includes cytosol, organelles, and inclusions
• Ribosomes


  Made up of protein and RNA, site of protein synthesis
• RNA is produced in the nucleolus and enters the cytoplasm through the nuclear pore
• Ribosomes receive the genetic material from the nucleus and translate it into amino acids that make up a protein molecule
• Endoplasmic reticulum (ER)


  Fluid-filled tubules for carrying substances
• Rough endoplasmic reticulum (RER)


  Organelle to which most of the ribosomes are attached
• Smooth endoplasmic reticulum (SER)


  Branching canal without ribosomes that transports large molecules inside the cell
• Golgi apparatus


  Modifies and packages protein, flattened stacks of disc-like membranes, closely related to the ER in the cytoplasm, processes proteins from ribosomes and packages them into transfer or secretory vesicles
• Lysosomes


  Contains enzymes that digest non-usable materials within the cell
• Mitochondria


  Powerhouse of the cell, carry out reactions where oxygen is used to break down food, produce ATP
• Plastids


  Double-membraned organelles, including chloroplasts (contain green pigments called chlorophyll), chromoplasts (give yellow and orange colors), and leucoplasts (colorless, store carbohydrates, proteins, and fats)
• Vacuoles


  Serve as the space and compartments to store raw materials and finished products, most plant cells have a large fluid-filled vacuole at the center, some animal and protist cells have contractile vacuoles to pump excess water