1. Non-Membrane-Bound Cell Organelles James F. Thompson, Ph.D.
Chapter 3
Non-Membrane-Bound Cell Organelles
James F. Thompson, Ph.D.

2. The Organelles of Typical Cells
Cytoplasmic organelles you should know
Mitochondria
Ribosomes*
Rough endoplasmic reticulum (Rough ER)
Smooth endoplasmic reticulum (Smooth ER)
Golgi apparatus
Lysosomes & Peroxisomes
Cytoskeleton*
Nucleus
Nucleoli*
Inclusion bodies: substances
not enclosed in membrane
Centrioles*
Cilia
Flagella
[* not membrane-bound]

3. Ribosomes Ribosomes self assemble from rRNA molecules and proteins.
They form two subunits which come together to form the functional whole, the ribosome, which is where translation, the synthesis of protein molecules occur.

4. Ribosomes
Ribosomes are located in the general cytoplasm or may shift to become attached to the cytoplasmic side of the rough endoplasmic reticulum (RER); another set of ribosomes are located inside mitochondria.

5. Ribosomes Ribosome surface features ensure that the mRNA and tRNAs
align correctly for the translation of proteins.

6. The Cytoskeleton
The three main cytoskeletal elements are the fibrous proteins microtubules, intermediate filaments and microfilaments.

7. Microtubules
Large diameter, hollow tubes made of coiled tubulin subunits.
They assemble or disassemble as needed, using ATP energy.
They anchor and move organelles in the cytoplasm.
They form the spindle fibers seen in nuclear divisions (mitosis and meiosis) which move the chromosomes to the cell poles.

8. Intermediate Filaments
Four families of intermediate filaments are known.
Some give shape to cells like a scaffolding.
Some bind to cytoskeletal anchors and to cell junctions such as desmosomes.
They are less involved in cell movements.

9. Microfilaments The smallest filament are composed of actin
They are involved in cell motility and cell shape
They are responsible for muscle contraction when actin interacts with myosin

10. Microfilament- and Microtubule- Dependent Motility

11. The Nucleolus / Nucleoli
hepatocytes
They are dark staining, oval/spherical bodies within the nucleus of cells which are synthesizing large quantities of proteins

12. The Nucleolus / Nucleoli
They are composed of clusters of DNA, RNA, and proteins
They are the sites of ribosomal RNA synthesis and ribosomal subunit assembly
They disappear during nuclear divisions and reappear later

13. Centrosome & Centromeres
Microtubule organizing center
Contains centrioles
Centrioles
Involved in mitosis and orient the spindle fibers to the poles of the dividing cell
Give rise to cilia and flagella

14. Centrosome & Centromeres
Note: Cilia and flagella are membrane bound

15. Inclusion Bodies
Reticulocytes are immature red blood cells which do not have a cell nucleus. They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA that becomes visible with certain special stains.
Sporadic inclusion body myositis (IBM) is the most common muscle disease in old people.

16. Non-Membrane-Bound Cell Organelles
End Chapter 3
Non-Membrane-Bound Cell Organelles