Cell Structure

Cell Structure



Cell Structure

Notes Chapter 7.2 “Cell Structure”
Eukaryotic cells can be divided into two regions:  the nucleus and the cytoplasm

  • Cytoplasm:  the region of the cell outside the nucleus
    • Prokaryotic cells have cytoplasm but no nucleus.
  • The nucleus contains nearly all the cell’s genetic information (DNA), and therefore, the code for making proteins and other molecules that the cell needs.
    • Surrounded by a porous nuclear envelope which allows substances to move into and out of the nucleus
    • Contains chromosomes which carry DNA
    • Most contain a nucleolus – responsible for the production of ribosomes



  • Organelles:  “tiny organ”, specialized structures inside the cytoplasm
  • Vacuoles:  storage areas in a cell (for carbohydrates, waste, water, & proteins)
    • in plants the vacuole is usually singular and large (the pressure of the water in the vacuole helps support the leaves and flowers of the plant)
    • in single celled organisms (paramecium, euglena) there is a contractile vacuole which expels excess water from the cell
    • vesicles – membrane bound organelles in eukaryotic cells that moves materials between organelles and out of the cell




  • Lysosomes:  “the clean-up crew” of a cell
    • Filled with enzymes
    • Break down old organelles, as well as carbohydrates, proteins, and lipids into molecules that can be used by the cell




  • Cytoskeleton:  protein filaments that give a cell its shape and help transport materials within a cell
    • Microfilaments – made of a protein called actin
      • Enable amoebas to move using pseudopods – “false feet” – structures that enable them to “crawl” across a surface
    • Microtubules – made of proteins called tubulins
      • Make centrioles in animal cells, mitotic spindle, cilia, and flagella
      • In cilia and flagella microtubules are arranged in a “9 + 2” pattern that allow the cells to move through their environment
      • Cilia and flagella are extensions of the cell surface


  • Ribosomes:  structures made of RNA and protein
    • responsible for the assembly of protein molecules from DNA’s coded instructions



  • Endoplasmic Reticulum: (ER) assembly of lipids, proteins, and other molecules within the cell
    • rough ER has ribosomes on the surface that complete the assembly of proteins
      • proteins made here are released (secreted) from the cell
      • proteins that are made here are membrane proteins and those needed at the lysosomes and in other specialized structures within the cell
    • smooth ER has no ribosomes on the surface
      • contain enzymes that help create lipids for membrane and detoxify drugs


  • Golgi Apparatus:  take proteins made in the rough ER and modifies, sorts, and packages them
    • These proteins will be stored or released from the cell

Protein made in the rough ER


Protein packaged in vesicles are transported to Golgi Apparatus


In Golgi apparatus proteins are modified, sorted, and packaged


Proteins are transported in vesicles to be stored or secreted


  • Chloroplasts:  capture energy from the sun and converts it to food for the organism (in the form of chemical energy)
    • This process is called photosynthesis.
    • Chloroplasts are surrounded by two membranes.
    • Contain the pigment chlorophyll
    • Has its own DNA


  • Mitochondria:  convert chemical energy of food into compounds that the cells can use
    • two membranes – inner one is folded up
    • in humans nearly all mitochondria comes from the egg cell
    • has its own DNA



  • Cell Membrane – controls what enters and leaves the cell, supports and protects the cell
    • all cells have a cell membrane
    • double-layer called a lipid bilayer allows for flexibility
      • fatty acid tails are hydrophobic – “water hating”
      • opposite side is hydrophilic – “water loving”
      • when mixed with water the fatty acid tails clump together on the inside of the bilayer and the water loving heads attract to the water


    • described as a fluid mosaic model – the cell membrane has proteins and carbohydrates embedded in it that float around among the lipids
      • proteins are involved in movement of molecules across the membrane (some have channels, others act as pumps)
      • carbohydrates act as identification tags so cells recognize each other
    • semipermeable (selectively permeable):  describes the cell membrane
      • some substances are too large or too strongly charged to pass through the membrane
      • other substances can pass into and out of the cell
  • Cell wall:  supports, shapes, and protects the cells of certain organisms
    • Found in most prokaryotes and all plants
    • Provide the strength plants need to withstand gravity
    • Porous – allows water, oxygen, carbon dioxide, and some other materials to cross easily
    • Cells with a cell wall also have a cell membrane.

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Cell Structure


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Cell Structure



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Cell Structure