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17 Cards in this Set
- Front
- Back
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models of cell membrane structure
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Davson and Danieli - 1935 bilayer with a layer of protein on each surface
Singer and Nicholson - fluid mosaic model - a mosaic of proteins floating in a phospholipid bilayer |
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phospholipid bilayer dimensions
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7-8nm thick
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amphiphatic
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both hydrophillic and hydrophobic components
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fluidity of membrane
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sideways switching is common but opposite switching is not common
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passive transport across membrane
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membranes move from a high concentration to a low concentration (down a concentration gradient).
There are two types: diffusion: small polar and non-polar molecules facilitated diffusion: hydrophillic molecules can move passively through membrane when assisted by transport proteins |
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two types of transport proteins
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- channel protein
- carrier protein |
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active membrane transport
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molecules moving across a membrane against a concentration gradient. Requires ATP and all carrier proteins
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membrane proteins advantages and disadvantages
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can be recycled
speed up transport of molecules rate of transport limited by number of carrier proteins specific membrane proteins |
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exocytosis
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transport of large molecules across a cell plasma membrane
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endocytosis
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phagocytosis: "cell eating" - transport of large molecules across cell membrane
pinocytosis: cell drinking - transport of large molecules across membrane receptor mediated endocytosis: coated proteins and vesicle |
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how much dry weight in a cell is made up of proteins
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more than 50% of dry mass
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types of proteins
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-enzymes
-defensive -storage -transport -hormones -receptors -motor proteins -cytoskeleton |
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secondary structure of protein
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beta pleated sheets (made up of two or more polypeptide chains lying side by side and make up core of globular proteins) or alpha helices (hydrogen bonding between every 4th amino acid) with hydrogen bonding
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tertiary structure
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descries the overall 3D conformation of the polypeptide chain
- stabilized by interactions between side chains - disulfide bridge (strongest) - hydrogen bonding - hydrophobic collapse and van der Waals interactions ionic bonding |
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quaternary structure
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two or more polypeptides
held together by interactions between amino acid side chains entire protein structure |
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chaperonin
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assists the folding of proteins (protects polypeptide from degradation, polypetide folds spontaneously)
some chaperonin's check that protein folding has been done correctly and mark them for destruction or refold creates hydrophillic environment |
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denaturation of proteins
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breakage of hydrogen bonds, hydrophillic, hydrophobic and sulfide bridges.
It is caused by heat (break weak bonds) , pH (changes ionisation patterns of R groups), reducing agents (reducing S=S to S-H), organic solvents disturb hydrophobic and hydrophillic interactions and detergents (disrupt hydrophobic interactions) some denatured proteins can return to original shape if denaturing agent is removed |
