Chapter4
Eukaryotes 2 groups: protists and fungi
Have membranes with large surface area to increase respiratory and photosynthetic activity
Compartmentation – partition intearior to separate the different biochemical and physiological functions

Most lack cell wall, those organisms with a cell wall have chemically distinct ones. Most eukaryotes use plasma membrane. The plasma membrane is a lipid bilayer, made up of tightly packed sphingolipids and sterols (eg cholesterol) that reists osmotic pressure. Lipids distribuition is asymmetrical. Microdomains, affect movement, cell division and signal transduction. When cell walls are present: protists have cell walls composed of cellulose and pectin, as well as silica and/or calcium carbonate; fungi have rigid cell walls composed of chtin, cellulose or glucan; both are chemically simpler than peptidoglycan.

Cytoplasm. Liquid portion is cytosol, contains organelles.
Cytoskeleton, 3 types of filaments
Microfilament aka actin, functions in endocytosis and cytokinesis
Intermediate filaments – function is unclear, only studied in aminals. Found in nuclear lamina and forms tissues
Microtubules – largest (25nm) 2 protein subunits a and b tubulin. Forms spindle apparatus and is found in cilia and flagella.

ER – network of tubules and flat membrane bound sacs called cisternae
RER – ribosomes on surface, makes proteins
SER – no ribosomes, makes lipids

Golgi apparatus – stack of flat sacs dictyosome. Modification

Lysosome – intracellular digestion. Contains hydrolases which catalyze molecule hydrolysis. Maintains acidic conditions by pumping protons

Secretory pathway – move materials throughout and outside of cell. Proteins involved are made on RER, released in small vesicles. As they pass through ER, glycolysation – sugar added. Vesicles go to cis face of golgi, bud of trans face of golgi. Sent either to endosome and lysosomes or sent to plasma membrane (2 types of vesicles to membrane: unregulated or secretory [ protein stored until signaled otherwise]). If protein fails, its marked by ubiquitin and killed by proteasomes.

Endocytic pathways – bring materials into cell. Solutes (pinocytosis) and particles (phagocytosis) are brough into the cell using vesicles from the membrane)
Phagocytosis – vesicle forms around particle, called phagosome. Fuses directly with lysosome, called phagolysome.
Clathrin dependent – pits coated w/ clathrin, creates clathrin coated vesicles. Bind specifically with macromolecules. Vesicle sent to endosome (has hydrolytic enzymes) which binds to lysosomes.
Caveolin dependent – little caves. Vesicles go to caveosome which go to endosome which bind to lysosome
Autophagy – degrade cells own components, necessary for homeostasis. Macroautophagy – cell components selectively digestd. Surrounded by double membrane called autophagosome, bind with lysosome.

Nucleus – genetic info, bounded by envelope, penetrated by pores. Nucleosome, non membrane bounded part inside nucleus, makes rRNA.
Chromatin – DNA + histones, unreplicated uncondensed form. Euchromatin is loosely coiled, has actively expressed genes. Heterochromatin is more tighly coiled, has nonactively expressed (barr bodies, centromeres, telomeres). Acetylation is more loose, methylation is tighter. Basic element of chromatin is nucleosome (dna + H1)

Endosymbiotic hypothesis – mitochondria, chloroplast and hydrogenosomes all come from bacteria that were engulfed and evolved. Evidence: m and c have their own chromosome and are similar to extant bacteria

Mitochondria. 2 membranes – outer has porins similar to outer membrane of gram – bacteria. Inner has infoldings called cristae to increase surface area, location of enzymes and electron carriers. In bacteria ETC is in plasma membrane

Hydrogenosome – makes ATP through fermentation, pyruvate is catabolized, CO2 H2 and acetate are products

Chloroplasts – 2 membranes stroma (matrix) is inner membrane – contains DNA,