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lect6 - Bio 1A February 2 2009 Lecture 6 Wilt Material Left...

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Bio 1A. February 2, 2009 Lecture 6. Wilt Material Left Over from Lect. 5 on Membrane function.n 3. Many ions and small metabolites may be actively conducted across the membrane by energy driven processes that move molecules against a concentration gradient through specialized of energy that modulates the conformation of the channel/pore proteins. The Na+/K+ channel, so important for maintaining ion balance and in nerve conduction, is such a transporter, requiring ATP to maintain the cycle of accumulation of K+ and expulsion proteins located in channels or pores in the membrane. This “ active” transport involves expenditure of Na+. Cystic fibrosis is due to a mutation of the chloride transporting channel of epithelial cells. The resulting inbalance in ion movement that results from chloride transport failure causes a cascade of problems, many of them related to excessive accumulation of mucus. 4. As mentioned before, large molecules and structure may enter the cell by endocytosis . This process may be fairly non-specific, as in phagocytosis ( particles) and pinocytosis ( fluids) that are enclosed in membrane vesicles. There is also a more specific version, called receptor-mediated endocytosis ; in this version specific receptors in the membrane interact with certain ligands in the molecule, thereby recognizing it, and setting in motion the formation of coated vesicles which are formed from the membrane. This is the mechanism by which cholesterol and proteins that transport them are taken into the cell. Proteins I. The Monomers A. The carboxyl and α amino group provide a backbone of peptide bonds. The R- groups provide the variety for bonding. There are 9 non-polar amino acids with hydrophobic R- groups. The Polar R groups are present on 6 amino acids, and have functional groups like amides (Asn, Gln), hydroxyls ( Ser, Threo, Tyr) or _SH. The -SH of cys is very reactive in oxidation-reduction reactions.These can form several different kinds of covalent bonds. Review the amino acids discussed in lecture 2.
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