chapter 3 non-membrane-bound cell organelles james f. thompson, ph.d
TRANSCRIPT
Chapter 3
Non-Membrane-Bound Cell Organelles
James F. Thompson, Ph.D.
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: substancesnot enclosed in membrane
– Centrioles*– Cilia– Flagella
[* not membrane-bound]
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.
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.
Ribosomes
Ribosome surface features ensure that the mRNA and tRNAsalign correctly for the translation of proteins.
The Cytoskeleton
The three main cytoskeletal elements are the fibrous proteins microtubules, intermediate filaments and microfilaments.
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.
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.
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
Microfilament- and Microtubule- Dependent Motility
The Nucleolus / Nucleoli
They are dark staining, oval/spherical bodies within the nucleus of cells which are synthesizing large quantities of proteins
hepatocytes
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
Centrosome & Centromeres• Centrosome– 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
Centrosome & Centromeres
Note: Cilia and flagella are membrane bound
Inclusion Bodies
Sporadic inclusion body myositis (IBM) is the most common muscle disease in old people.
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.
End Chapter 3
Non-Membrane-Bound Cell Organelles