3.4 Eukaryotic Cell Structure

3.4 Eukaryotic Cell Structure

1. Animal Cells

2. Plant Cells

3. Nucleus

   • Surrounded by nuclear envelope
     • contains nuclear pores
       • Allows substances (e.g RNA) to move between the nucleus and cytoplasm
   • contains chromosomes
   • contains nucleolus
     • Makes ribosomes
   • Controls the cells activities

4. Mitochondrion

   • Double membrane
     • Inner layer folded to form cristae.
   • Inside is the matrix
   • Site of Aerobic respiration where ATP is produced

5. Chloroplast

   • Found in plant cells
   • Surrounded by a double membrane
   • Has membranes inside called thylakoid membranes
     • Stacked up to form grana
       • Grana connected by lamellae - think, flat pieces of thlakoid membrane
       • Large S.A for attachment of chlorophyll, electron carriers and enzymes that carry out the 1st stage of photosynthesis (light absorption).
     • Contain a photosynthetic pigment called chlorophyll
   • Site where photosynthesis takes place
   • Stroma (a fluid-filled matrix found in chloroplasts)
     • contains the enzymes needed for 2nd stage of photosynthesis - synthesis of sugars

6. Endoplasmic Reticulum (ER)

   • Cells that manufacture and store large quantities of Carbs, proteins and lipids have a very expensive ER. Such cells include liver and secretory cell, for example the epithelial cells that line the intestine. :)
   • Rough ER (RER)
     • A system of membranes enclosing a fluid-filled space. The surface is covered with ribosomes
       • Provides a large surface area for the synthesis of proteins and glycoproteins
       • Provide a pathway for the transport of materials, especially proteins, throughout the cell
   • Smooth ER (SER)
     • Similar to the RER but with no ribosomes
       • Synthesis, store and transport Lipids and carbohydates

7. Golgi Apparatus

   • Consists of a stack of membranes that make up flattened sacs, or CISTERNAE.
   • Closely in contact with VESICLES. Small rounded hollow structures.
   • Add Carbohydrate to proteins to form glycoproteins
   • Produces secretory enzymes, such as those secreted by the pancreas
   • Secretes carbohydrates such as cellulose
   • Transports, modifies and stores lipids
   • Forms lysosomes

8. Lysosomes

   • Formed when the vesicles produced by the golgi apparatus contain enzymes such as proteases and lipases
   • A round organelles, surrounded by a membrane with no clear internal structure
   • Its basically a type of Golgi vesicle that releases lysozymes
   • Hydrolyse material ingested by phagocytic cells such as white blood cells and bacteria
   • Contains digestive enzymes called lysozymes
   • Release enzymes outside of cell in order to destroy material outside of the cell
   • Completely break down cells after they have died (autolysis)
   • Abundant in phagocytic cells and epithelial cells

9. Ribosomes

   • Small cytoplasmic granules found in all cells
   • They can float freely in the cytoplasm, or are attached to the Rough ER
   • 2 types depending on where they are found: 80S - found in eukaryotic cells, around 25nm in diametre and 70S - found in prokryotic cells, mitochondria and chloroplasts, these are slightly smaller
   • Site of Protein Synthesis

10. Cell Wall

    • A ridgid structure that surrounds cells in plants, algae and fungi
    • Consists of microfibrils of th epolysaccharide cellulose, embedded in a matrix
    • Thin layer called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells togeher
    • Provides mechanical strength in order to prevent cell lysis
    • Give mechanical strength to the plant as a whole
    • Allow water to pass along it and so contribute to the movement of water through the plant

11. Vacuoles

    • A fluid-filled sac bounded by a single membrane
      • Single membrane called the TONOPLAST
    • A plant vacuole contains a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
    • Support herbaceous plants by making cells turgid
    • The sugars and amino acids may act as a temporary food store
    • The pigments may colour petals to attract pollinating insects

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