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Lecture 3

BIOL 1000 Lecture Notes - Lecture 3: Sarcomere, Tubulin, Nuclear Dna


Department
Biology
Course Code
BIOL 1000
Professor
Y I Sheng
Lecture
3

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LEC 3
Eukaryotic Cell
1) distinct nucleus surrounded by nuclear envelope
2) endomembrane system: membrane-bound organelles (compartments with
specialized functions) & structures
3) energy generating units
Endomembrane System
= collection of interrelated internal membranous sacs that divide cell into functional
& structural compartments called organelles
-functions include:
1) synthesis, modification, & transport of proteins
2) synthesis of lipids & detoxification of toxins
3) eating/drinking & breakdown (digesting) large biomolecule containing
substances
membrane enclosed compartments with specialized functions (commonly found
in all textbook definitions)
Q: can ribosomes be considered organelles then?
A: it doesnt have a membrane, so according to this defn, no.
Q: does bacteria have organelles?
A: no
fig 2.16
-membrane-bound
organelles:
Rough ER,
Vesicles
Golgi Complex
Secretory Vesicles
Lysosomes
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Insulin Synthesis & Secretion
-insulin: a peptide hormone, produced by pancreas beta cells
-regulates glucose levels in the body by signaling cells to absorb glucose from the
blood (decrease blood-glucose level)
-diabetes mellitus: result of defective insulin production or function
-made of 2 chains (a & b), linked via disulfide bond
-biosyntthesis of insulin:
-precursor insulin (preproinsulin) is translated as a single oligopeptide
-intermediate insulin (proinsulin) is formed by cleaving the signal peptide
-insulin is formed by cleaving off the C peptide (a connecting peptide) from
the intermediate
Ribosomes
-function = site of protein synthesis
-structure = NO membrane, consists of protein, & RNA
-location = free in cytoplasm or associated with part of endomembrane system
-polysome: whole unit of active protein made with ribosome attached
-moves from   end of mRNA
know diff btwn cytoplasm vs cytosol***
Rough Endoplasmic Reticulum (RER)
-signaling peptide removed
-protein folded
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-disulfide bridge formed
The Golgi Complex
-tags proteins for sorting to their final destinations
-protein modification (glycoprotein, lipoprotein) makes sugar or lipid proteins
-cis side = side closest to nucleus (vesicle moves from ER towards cis-side)
-proinsulin insulin cleavage occurs inside golgi forms mature form of insulin
Exocytosis
-proteins to be secreted FROM the cell are transported to the membrane in
secretory vesicles which release their contents to the EXterior by exocytosis
Endocytosis
-vesicles also form by the reverse process, endocytosis which brings molecules
INTO the cell from the exterior cell engulfs things from outside cell
Eating & Digesting of the Cell
phagocytosis = eating
pinocytosis = drinking
endocytosis = taking in
autophagy = self-eating
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