Organelles & Subcellular Organization
May 21, 2015
Organelles & Subcellular Organization
Nucleus
• Nuclear envelope– Double memb enclosing the nucleus– Perforated by pores– Continuous w/ER
• Nucleolus– Non-mbo involved in prod’n of ribosomes– 1 or more/nucleus
• Chromatin– Material consisting of DNA & proteins– Visible as indiv chromosomes in a dividing cell
Plasma Membrane
• Memb enclosing cell
Ribosomes
• Non-mbo that make proteins• Found free in cytoplas,• Found bound to ER or nuclear envelope
Golgi Apparatus
• Active in synthesis, modification, sorting & secreting cell products
• Cis & trans face
Lysosome
• Digestive orgll where macromols are hydrolyzed
Peroxisome
• Orgll w/var sp’d metabolic functiosn• Prods H2O2
• Contains enz that transf H to O prod-ing H2O2 which is toxic
• Also contains enz that ∆s H2O2 H2O• Glyoxysome – sp’ed peroxysome– Fat storing tissue of seeds
Microvilli
• Projections that ↑ SA
Centrosome
• Region where cell microtubules are initiated– Animals: contain pr of centrosomes• Function unknown
– Plants : lack centrosomes
Cell Wall
• Outer layer • Maintains shape• Protects cell from mechanical damage• Made of cellulose, other polysaccharides &
proteins
Plasmodesmata
• Channels thru CWs that connect the cytoplasm of adj cells
Chloroplast
• PS-ic orgll• Converts nrg of sun to chem’l nrg stored in
sugar mol
ENDOMEMBRANE SYSTEM (EMS)
ER
• Network of membranous sacs & tubes• Active in membrane synthesis & other
synthetic & metabolic processes• Has rough & smooth regions
Smooth ER
• Synthesis of lipids• Metabolism of carbs• Detoxification of drugs & poisons• Cells rich in sER– Testes & ovaries (make & secrete sex hormones)– Liver cells (detox)– Muscle cells
Rough ER
• Secrete prot prod by ribosomes on rER• Memb factory of cell• Pacreas – secretes (prot) insulin
Vacuoles
• Food vacuoles – formed by phagocytosis• Contractile vacuole – pumps fw out• Central vacuole - plant
Central Vacuole
• Prominent orgll in older plant cells• Funct incl:– Storage– Breakdown of waste prods– Hydrolysis of mmols– Enlargement of vac is maj mech of plant growth
Tonoplast
• Memb around central vac
MITOCHONDRIA & CHLOROPLAST
•DNA•Ribosomes•Grow & reproduce inside of cell
Mitochondria
• Orgll where CR occurs & most ATP is generated • Outer memb• Intermemb space• Inner memb• Cristae – infolding of inner memb
• Mitochondrial matrix – Inside inner memb– Contains ribosomes & mRNA
Chloroplast
• Thylakoid – flattened sacs• Granum – stacks of thylakoids• Stroma – fluid outside thylakoid
Cytoskeleton
• Network of fibers extending thru cytoplasm• Plays maj role in organizing structures &
activities of cell
Roles of Cytoskeleton
• Mechanical support: maintains cell shape (dynamic ∆s)
• Motility– Flagella & cilia– Muscle cell contraction– Vesicles that bud off ER to Golgi travel tracks of
cytoskeleton elements– Cytoplasmic streaming– Regulation of biochem’l activities of cell
Components of cytoskeleton
• made of protein– Microfilaments– Intermediate filaments– Microtubules
Flagellum
• Locomotion orgll• Composed of membrane enclosed
microtubules• Move by gripping microtubules w/in those
orglls & propelling them past each other