3/5/2019 Membrane-bound organelles Materials were extracted from Alberts et al., 2015. Molecular Biology of the Cell, 6th edition unless cited otherwise The major intracellular compartments of an animal cell 1 3/5/2019 Relative amounts of membrane types Topologically equivalent compartments 2 3/5/2019 Endomembrane system Mader and Windelspecht 2015 The nucleus Contains DNA Synthesizes RNA Assembles ribosomal subunits Reece et al., 2015 3 3/5/2019 Macromolecular transport into and out of the nucleus Hardin et al., 2012 Endoplasmic reticulum Hoefnagels, 2014 4 3/5/2019 ER and plasma membranes of rat liver cells Hardin et al., 2012 Rough and smooth endoplasmic reticulum Hardin et al., 2012 5 3/5/2019 Rough endoplasmic reticulum • Synthesizing both membrane-bound and soluble proteins for the endomembrane system • Posttranslational modification: • initial steps of addition and processing of carbohydrate groups to glycoproteins (glycosylation) • folding of polypeptides (disulfide bond formation) • the recognition and removal of misfolded polypeptides (ER-associated degradation) • assembly of multimeric proteins Biosynthesis of the oligosaccharide precursor Lodish et al., 2016 6 3/5/2019 Addition and initial processing of oligosaccharides Asn-X-Ser Asn-X-Thr Lodish et al., 2016 Oligosaccharides are used to monitor folding Calnexin Calreticulin Lodish et al., 2016 7 3/5/2019 Formation of a disulfide bond protein disulfide isomerase Lodish et al., 2016 Hemagglutinin folding and assembly protein disulfide isomerase Lodish et al., 2016 8 3/5/2019 Smooth endoplasmic reticulum Steroid Biosynthesis: cholesterol and steroid hormones such as cortisol, testosterone, and estrogen Liver Adrenal gland Follicular cells Leydig cells Hardin et al., 2012 Smooth endoplasmic reticulum Carbohydrate metabolism Hardin et al., 2012 9 3/5/2019 Smooth endoplasmic reticulum Detoxification: cytochrome P450 proteins hydroxylate hydrophobic drugs → more soluble and easier to excrete by kidneys RH + NAD(P)H + H+ + O2 ----> ROH + NAD(P)+ + H2O • sedative phenobarbital: increased proliferation of smooth ER; higher dose of sedative; reduction of effectiveness of antibiotics, anticoagulants, and steroids • polycyclic hydrocarbons: converted into more toxic compound, potential carcinogens into carcinogens Smooth endoplasmic reticulum Calcium Storage: sarcoplasmic reticulum in muscle cells Hardin et al., 2012 10 3/5/2019 Golgi apparatus • cis-Golgi network: close to ER, receives transport vesicles containing proteins and lipids from ER • trans-Golgi network: generates transport vesicles carry lipids and proteins to secretory granules, endosomes, lysosomes, and the plasma membrane Raven et al., 2011 Flow of lipids and proteins through the Golgi apparatus • Stationary cisternae model: each Golgi cisternae is a stable structure, transport vesicles bud from one cisterna and fuse with the next cisterna in the cis-to-trans sequence • Cisternal maturation model: the Golgi cisternae are transient compartments that gradually change from CGN cisternae through medial cisternae to TGN cisternae Raven et al., 2011 11 3/5/2019 Flow of lipids and proteins through the Golgi apparatus Alberts et al., 2015 Golgi apparatus functions • Modifies glycoproteins and lipids (glycolypids) • Sorts the modified molecules and packages them into transport vesicles • Synthesizes cell wall components (noncellulose polysaccharides) Alberts et al., 2015 12 3/5/2019 Lysosome • >40 different enzymes • pH ~ 5 • Digest old organelles (autophagy) or engulfed particles (phagocytosis) in animals • Tay-sachs disease: defective hexosaminidase-A leads to accumulation of GM2 ganglioside lipid in nerve cells, causing mental retardation, blindness, and death before age 4 Sadava et al., 2012 Alberts et al., 2015 Four pathways to degradation in lysosomes Alberts et al., 2015 13 3/5/2019 Vacuole • Storage: water, suger, salts, stored food, pigments, toxins, waste products… • Maintaining osmotic pressure, pH • Structural support • Digest foods Fat cell vacuole Contractile vacuoles Plant cell vacuole Mader and Windelspecht, 2015 Peroxisome • Breaks down fatty acid • Glyoxysome (only in plants) converts fatty acid to sugar • Metabolizes H2O2 • Detoxifies harmful compounds: methanol, ethanol, formic acid, formaldehyde, nitrites, and phenols • Synthesizes certain phospholipids to protect nerve cells • Zellweger syndrome: no peroxisome, children do not survive beyond 1 year Hoefnagels, 2014 14 3/5/2019 Peroxisome formation and proliferation Alberts et al., 2015 Mitochondrion Hoefnagels, 2014 Pollard et al., 2016 15 3/5/2019 The electron transport system and ATP synthase Pollard et al., 2016 Contributions of nuclear and mitochondrial genes Pollard et al., 2016 16 3/5/2019 Metabolic functions within the mitochondrion Hardin et al., 2012 Integration of metabolic pathways in mitochondrium Pollard et al., 2016 17 3/5/2019 Chloroplast Hardin et al., 2012 Chloroplast structure of timothy grass Hardin et al., 2012 18 3/5/2019 Morphology of chloroplasts and cyanobacteria Pollard et al., 2016 Photosystems II and I in cyanobacteria, algae, plants Pollard et al., 2016 19 3/5/2019 Mitochondria and chloroplasts convert energy Solomon et al., 2011 Origins of mitochondria and chloroplasts Urryl et al., 2017 20 3/5/2019 Evolution of eukaryotic cell 21
