bio 178 lecture 8 cell structure copyright: j. elson-riggins
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Bio 178 Lecture 8Cell Structure
Copyright: J. Elson-Riggins
Reading
• Chapter 5
Quiz Material
• Questions on P 104
• Chapter 5 Quiz on Text Website (www.mhhe.com/raven7)
Outline
• Eukaryotic Cells (Cntd.)
The Golgi Apparatus
StructureFlattened membranous sacs (cisternae).
Functions
• Collection, packaging, sorting, and shipping of ER products.
• Modification (in particular glycosylation) of proteins and lipids.
Orientation• Cis - Receiving end.
• Trans - Discharging end.
Golgi Apparatus
Protein Transport from ER to Golgi
Golgi Apparatus
http://wilfred.berkeley.edu/TEM-Gallery1/pages/Golgi.htm
Golgi Apparatus
http://www.siena.edu/biology/faculty/cellbiology/golgi.jpg
Lysosomes
Structure• Membrane bound vesicles that contain hydrolytic emzymes. Enzymes only function at acidic pH.
• pH 5 in secondary lysosomes maintained by proton pumps in the membrane.
• Primary lysosomes not acidic.
Functions
• Organelle breakdown & recycling.
• Phagocytosis.
Lysosome Fusing
http://www.jdaross.mcmail.com/lysosome.htm
McGraw-Hill Video : Lysosomes
Organelles that Contain DNA
• Mitochondria
• Chloroplasts
Mitochondrion
Chloroplast
Organelles that Contain DNA Mitochondria & chloroplasts
Formation of DNA Containing Organelles:The Endosymbiont Theory
• The Theory
Mitochondria & chloroplasts were derived from prokaryotes that were engulfed by the ancestral eukaryote.
• Evidence1. 2 membranes - inner folded
2. Size
3. Own circular DNA
4. Ribosomes
5. Division
Endosymbiosis
Mitochondrion
The MitochondrionSize~ 0.5-1 µm diam
Membranes• Outer - smooth
• Inner - highly folded into cristae with embedded proteins that function in oxidative metabolism.
Compartments• Outer - intermembrane space
• Inner - matrix
FunctionsCellular respiration.
The Mitochondrion (Cntd)DNA• Own Circular DNA1. Contains several genes encoding proteins for oxidative
metabolism.
2. Synthesis of these proteins uses RNA and ribosomal components encoded by its own DNA.
• Use of Nuclear DNA
1. Nuclear DNA encodes the rest of the proteins required for oxidative metabolism.
2. Also encodes proteins required for mitochondrial division.
The Mitochondrion
Extracted DNA
DNA (arrow) & ribosomes (circle)
http://cellbio.utmb.edu/cellbio/mitoch2.htm
Chloroplast
The ChloroplastSize~ 2 µm X 5 µm
Membranes• Outer & inner membranes - smooth
• Thylakoid membrane - Forms flattened disks (thylakoids), which are stacked to form grana. Photosynthetic pigments in membrane.Compartments• Stroma - bathes thylakoids
• Thylakoid space - inside thylakoidsFunctionsPhotosynthesis
The Chloroplast (Cntd)DNA• Own Circular DNA
Some chloroplast proteins encoded here.
• Use of Nuclear DNA
Remaining chloroplast proteins encoded here.
The Cytoskeleton
The CytoskeletonComposition
• Network of protein fibers.
• Composed of actin (microfilaments), microtubules, & intermediate filaments.
Functions• Structure
• Transport
• Cell division
• Locomotion
• Anchoring of organelles
Distribution of The Cytoskeleton
Intermediate Filaments
Microtubules Actin Filaments
http://www.tmd.ac.jp/artsci/biol/textbook/cellmove.htm
The Cytoskeleton
Actin Microtubules Intermediate Filaments
http://cellix.imolbio.oeaw.ac.at/Videotour/video_tour_1.html
Dynamic Nature of the Cytoskeleton
Actin filaments and microtubules are constantly assembling (polymerization) and disassembling (depolymerization).
• Plus end - Fast growing end
• Minus end - Slow growing end
Actin (Microfilaments)
http://cellix.imolbio.oeaw.ac.at/Videotour/video_tour_1.html
Fibroblast labeled with fluorescent phalloidin.
Actin (Microfilaments)
http://www.microscopyu.com/articles/fluorescence/filtercubes/yfp/yfphyq/actin/yfpactinindex.html
Actin Filaments
Size
~ 7 nm diam
Composition
2 intertwined chains of the globular protein actin.
Functions of Actin filaments
• Muscle contraction
• Cellular extensions
• Cleavage furrow
• Anchoring
• Movement
Microtubules
Functions
• Movement of organelles
• Chromosome movement