BIOL 11000 1st Edition Lecture 16Ribosome structure - Large complex of non-covalently associated ribosomal RNA and protein assembled in nucleolus o Found in cytoplasm o Some attached to membranes, other free in cytosol - 5 RNA components and > 50 protein components - Large and small subunits - Eukaryotic ribosomes are larger but similar to prokaryotic Ribosome Function - Found in all cells - Site where mRNA directs protein synthesis o Sequence determines sequence of amino acids in polypeptides made on the ribosome o Covalent bonds that link amino acids are made at ribosome  Dehydration synthesis reaction is catalyzed by rRNA 1. mRNA transcribed in nucleus 2. mRNA exits via nuclear pores 3. mRNA meets small subunit in cytoplasm 4. mRNA small subunit joined by large subunit 5. mRNA is translated into protein Endomembrane System - internal endomembrane system in eukaryotic cells - includes: endoplasmic reticulum o smooth: no ribosomes o rough: ribosomes attached to surface - Golgi apparatus These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Modifies and sorts material made in ER - Vesicles: small sacs of membrane for transport between compartments o Contain proteins, other molecules o Transport, secretory, lysosomal- depending on origin/destination Endoplasmic Reticulum - Network of interconnected tubules and interconnected flattened sacs - Interior called lumen o Interior of any organelle is called the lumen - Interconnected lumen of ER is continuous throughout cytoplasm 1. SER- no ribosomes a. Network of interconnected tubules only b. Dispersed through cytoplasm c. Site of phospholipid synthesis d. Site of cholesterol and other steroid synthesis e. Site of detox (especially in liver of animals) 2. RER- attached ribosomes a. Composed of interconnected flattened sacs b. Concentrated near the nucleus in cytoplasm c. Site for ribosomes that are synthesizing proteins for 3 set destinations i. Proteins incorporated in membrane ii. Proteins to be exported from cell iii. Proteins destined to stay inside other organelles - Newly synthesized proteins are segregated inside lumen o Chemically modifies these proteins while in lumen by adding arbs “glycosylation” - Sends vesicles away from RER to their final desination Golgi Apparatus - Stack of flattened sacs, generally near nucleus; one to several per cell- Cis face- side toward nucleuso Receives transport vesicles from ER “entrance door” - Trans face- side away from nucleus - Further modify proteins synthesized on RER - Sorts proteins be eventual destination Pathway for exported Proteins - Inside RER- Inside transport vesicle - Inside sacs of cis golgi - Inside sacs of trans golgi - Inside secretory vesicle - Secretory vesicle fuse with plasma membrane, release contents into extracellular space where they diffuse away- exocytosis Endocytosis/ Exocytosis - Cells carry out a bulk movement across membrane o Exocytosis – moving out of the cell o Vesicle fuse with membrane to release contents - Endocytosis- movement into the cell o Individual folding of membrane gets longer then pinches off - Phagocytosis- solid particles- cell eating - Pinocytosis- liquid particles- cell drinking - Receptor – mediated – uptake of specific particles containing molecules recognized by receptor proteins o LDL lipoprotein particles that carry cholesterol in blood o Molecules also move one at a time across cell called membrane transport Lysosomes - Specialized vesicles that digest material - Contain hydrolytic enzymes that accelerate degradation of macromolecules by hydrolysis o Must be segregated from cytoplasmFunction optimally at acidic pH- maintained inside