BIOB10H3 Chapter Notes - Chapter 8: Macrophage, Gonad, Camillo Golgi

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18 Apr 2012
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BIOB10
CHAPTER 8 NOTES
Endomembrane system (CYTOPLASM):
Endoplasmic reticulum, golgi complex, endosomes, lysosomes, and vacuoles.
The organelles of the endomembrane system are part of a dynamic, integrated network in which materials
are shuttled back and forth from one part of the cell to another. For the most part, materials are shuttled
between organellesfrom the Golgi complex to the plasma membrane, for examplein small,
membrane-bounded transport vesicles that bud from a donor membrane compartment
A biosynthetic pathway can be discerned in which proteins are synthesized in the endoplasmic reticulum,
modified during passage through the Golgi complex, and transported from the Golgi complex to various
destinations, such as the plasma membrane, a lysosome, or the large vacuole of a plant cell. This route is
also referred to as the secretory pathway, as many of the proteins synthesized in the endoplasmic
reticulum
Secretory activities of cells can be divided into two types: constitutive and regulated
During constitutive secretion, materials are transported in secretory vesicles from their sites of synthesis
and discharged into the extracellular space in a continual manner. Most cells engage in constitutive
secretion, a process that contributes not only to the formation of the extracellular matrix, but to the
formation of the plasma membrane itself.
During regulated secretion, materials are stored as membrane-bound packages and discharged only in
response to an appropriate stimulus. Regulated secretion occurs, for example, in endocrine cells
that release hormones, in pancreatic acinar cells that release digestive enzymes, and in nerve cells that
release neurotransmitters. In some of these cells, materials to be secreted are stored in large, densely
packed, membrane-bound secretory granules
1. Compare and contrast the biosynthetic pathway with the
endocytic pathway.
2. How are particular proteins targeted to particular subcellular
Compartments traffic patterns
Autoradiography:
autoradiography provides a means to visualize biochemical processes by allowing an investigator to
determine the location of radioactively labeled materials within a cell. In this technique, tissue sections
containing radioactive isotopes are covered with a thin layer of photographic emulsion, which is exposed
by radiation emanating from radioisotopes within the tissue.
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Green Flourescent Protein:
This technology utilizes a gene isolated from a jellyfish that encodes a small protein, called the green
fluorescent protein (GFP), which emits a green fluorescent light. In this approach, DNA encoding GFP is
fused to DNA encoding the protein to be studied and the resulting chimeric (i.e., composite) DNA is
introduced into cells that can be observed under the microscope.
Once inside a cell, the chimeric DNA expresses a chimeric protein consisting of GFP fused to the end of
the protein to be studied. In most cases, the presence of GFP joined to the end of a protein has little or no
effect on the movement or function of that protein.
Subcellular Fractionation:
Techniques to break up (homogenize) cells and isolate particular types of organelles were pioneered in
the 1950s and 1960s by Albert Claude and Christian De Duve. When a cell is ruptured by
homogenization, the cytoplasmic membranes become fragmented and the fractured edges of the
membrane fragments fuse to form spherical vesicles less than 100 nm in diameter. Vesicles derived from
different organelles (nucleus, mitochondrion, plasma membrane, endoplasmic reticulum, and so forth)
have different properties, which allow them to be separated from one another, an approach that is called
subcellular fractionation
The endoplasmic reticulum:
The endoplasmic reticulum (ER) is divided into two subcompartments, the rough endoplasmic reticulum
(RER) and the smooth endoplasmic reticulum (SER).
the two types of ER share many of the same proteins and engage in certain common activities, such as the
synthesis of certain lipids and cholesterol.
The rough ER is defined by the presence of ribosomes bound to its cytosolic surface, whereas the smooth
ER lacks associated ribosomes.
The RER is typically composed of a network of flattened sacs (cisternae)
the membranous elements of the SER are highly curved and tubular, forming an interconnecting system
of pipelines curving through the cytoplasm.
Smooth endoplasmic reticulum:
the membranous elements of the SER are highly curved and tubular, forming an interconnecting system
of pipelines curving through the cytoplasm.
SER functions include:
Synthesis of steroid hormones in the endocrine cells of the gonad and adrenal cortex.
Detoxification in the liver of a wide variety of organic compounds, including barbiturates and
ethanol
Sequestering calcium ions within the cytoplasm of cells
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