BIO 1140 Chapter Notes - Chapter 2.1 abc, 3.1 - 3.4: Photon, Symbiosis, Transfer Rna

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Lecture 3 Reading Notes (Ch. 2.3-2.5, 3.5)
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2.3 Intro
oDomain Eukaryote divided into four major groups: protists, fungi, animals, plants
2.3 a – Eukaryotic Cells Have a True Nucleus and Cytoplasmic Organelles Enclosed within a Plasma Membrane
oCells of all eukaryotes have true nucleus enclosed by membranes
oHave endomembrane system (membranous organelles) each specialized to carry our special functions of
energy metabolism and molecular synthesis, storage, and transport
oCytosol = jelly-like substance that fills the cell and surrounds organelles, plays a role in energy
metabolism and molecular synthesis, specialized functions in support and motility
oPlasma membrane has embedded proteins --- some proteins are transport proteins and substances
across cell membrane and other proteins act like receptors for chemical signaling, in some eukaryotes
plasma membrane proteins recognize and stick to other cells, other plasma membrane proteins act as
cell markers (cells that don’t have these protein markers are recognized by the immune system as
foreign material)
oCell wall present in plant, fungal, and protist cells --- provides support and is an EXTRACELLULAR
component (not contained within plasma membrane), animal cells don’t have cell wall but they produce
other extracellular substances with supportive and other functions
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2.3 b – The Eukaryotic Nucleus Contains Much More DNA Than the Prokaryotic Nucleoid
oNucleus separated from cytoplasm by nuclear envelope, which consists of two concentric membranes
separated by a narrow space
oNetwork of protein filaments called lamins lines the inner face of the nuclear envelope to reinforce it (in
animal cells)
oNuclear envelope embedded with nuclear pore complexes --- octagonally symmetrical, cylindrical
protein structures that channel/ allow the exchange of substances between the nucleus and cytoplasm,
it prevents the transport of materials not meant to cross the nuclear membrance (like a filter), nuclear
pore complexes have channels called nuclear pores, large molecules (i.e RNA, proteins) travel through
the pores assisted by transport proteins while other smaller molecules pass through unassisted
oSome proteins must be imported into the nucleus (i.e enzymes for replicating and repairing DNA) must
be imported into the cell ---- the proteins to be imported are initially in the cytosol but are have special
amino acid markers (nuclear localization signal) that distinguish them, proteins in the cytosol recognize
the marked proteins and bind to the signal and then transport the proteins being carried o the nuclear
pore complex where they are then moved into the nucleus
oGel-like substance in nucleus called nucleoplasm
oMost space inside nucleus is chromatin = combo of DNA and protein
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oEukaryotes have genetic info. linear DNA not circular
oEach individual DNA molecule + its associated proteins = a eukaryotic chromosome
oNOTE: chromatin = a COLLECTION of DNA molecules and associated proteins while chromosome = ONE
complete DNA molecule and associated proteins
oEukaryotes have much more DNA than prokaryotic nucleoids
oNucleus contains nucleolus = irregular mass of fibers + granules
oWhat happens here: genes for rRNA >> rRNA molecules >>> rRNA + proteins = ribosomal subunits
produced, ribosomal subunits then leave nucleus and enter the cytoplasm to bind to mRNA and become
complete ribosomes
oMost protein production genes located in the chromatin as well as the genes for specialized RNA
molecules such as rRNA, expression of these genes is carefully controlled as required for the function of
the cell
2.3 c – Eukaryotic Ribosomes Are Either Free in the Cytosol or Attached to Membranes
oEukaryotic ribosomes appear similar to prokaryotic but not identical
oHas two subunits: large and small
oEukaryotic ribosomes much larger than prokaryotic
oFunction: bind and read mRNA molecules to stitch amino acids together to make proteins (translation)
oRibosomes can be freely suspended in cytosol or attached to membranes
oIn cytosol they may: remain in cytosol, travel to the nucleus, or become parts of the mitochondria,
chloroplasts ---- proteins that enter the nucleus become part of chromatin, line the nuclear envelope, or
remain in solution in the nucleoplasm
oIf attached to membranes, they may: most ribosomes are attached to ER, proteins made by these
ribosomes follow a special path to other organelles within the cell, some ribosomes are attached to the
nuclear envelope
2.3 d – An Endomembrane System Divides the Cytoplasm into Functional and Structural Compartments
oEukaryotic cells have endomembrane system = interrelated set of membranous sacs inside the cell that
divide the cytoplasm into structural and functional compartments
oFunctions: synthesize, modify, transport proteins; synthesize lipids; detoxify toxins
oMembranes of the system are interconnected physically or by vesicles
oComponents: nuclear envelope, endoplasmic reticulum, Golgi body, lysosomes, vesicles, plasma
membrane
Endoplasmic Reticulum
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