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Lecture 4
Protein structure
| Question | Answer |
|---|---|
| types of secondary structures | α-helix β-pleated sheet β-turn |
| secondary structures are held together by | hydrogen bonds |
| linear primary structures are held together by | peptide bonds |
| quaternary structure is | 3D shape of multiple interacting polypeptides |
| tertiary structure is | 3D shape of polypeptides |
| secondary structure is | folded 2D structure of primary structures |
| primary structure is | linear sequence of amino acid held by peptide bonds |
| R groups location in α-helix | point outward away from the seemingly hollow core |
| how many aa's per turn in α-helix | 3.6 amino acids |
| why is proline rarely found in helices? | because it has cyclic structure, amine group is rigid and can't form H bonds with carbonyl oxygen |
| what causes the transition or stops an α helix? | proline |
| in α helices, the carbonyl oxygen h bonds to the ________ amide hydrogen down the line | 4th |
| in α helices, hydrophobic and hydrophilic amino acids are ___________ | on opposite sides, due to amphipathic nature of αhelices |
| β strands can | parallel or antiparallel |
| in antiparallel β strands, atoms involved in H bonding are _____________ of eachother and in parallel atoms are __________________ | directly opposite, slightly skewered |
| antiparallel strands have ________________ while parallel tend to have ___________________ | hydrophobic side and hydrophilic side, hydrophobic residues on both sides |
| function of β turns | connects 2 β strands in an antiparallel β sheet |
| β turns vs loop | tight changes in direction- turn slow, gradual change in direction- loop |
| why do we see a lot of glycine and proline when making β turns? | because they have small R groups that can turn more easily than a big group |
| silk is composed of | antiparallel β-pleated sheet |
| keratin is composed of | two αhelical polypeptides covalently linked by disulfide bridges |
| collagen consists of | three intertwined αhelices |
| what secondary structure provides tough, insoluble protective structures of varying hardness and flexibility? example? | α helices cross linked by disulfide bonds ex: keratin of hair, feathers, nails |
| what secondary structure provides soft, flexible filaments? example? | β conformation ex: silk fibroin |
| what secondary structure provides high tensile strength without stretch? example? | collagen triple helix ex: collagen of tendons, bone matrix |
| what allows collagen to twist the way it does? or what gives it its elastic properties? | high percentage of proline and glycine (small side groups) almost 2/3 glycine+proline |
| define motif give example | combinations of αhelices, βstrands, and loops (secondary structures) found in multiple proteins, can have different functions in different proteins ex: helix-loop-helix |
| leucine zipper function where is it found? | mediates transcription factor dimerization found straddling DNA at major groove |
| zinc finger domains have similar structure but differ in ______________ | amino acid sequence |
| define domains | conserved, discrete parts of a protein sequence that are folded, compact combination of motifs (sometimes tertiary structures). |
| features of domains | - predict a specific protein function - exist independently of the protein chain |
| most proteins consists of several __________ (motifs/domains) | domains |
| immunoglobulin domains can be seen in ______________ | antibodies |
| function of PDZ domain | anchors receptor proteins in the membrane to cytoskeletal components |
| what bonds do tertiary structures require to tell protein how to fold in 3D space? | all noncovalent (hydrophobic forces, salt bridges, h bonds, van der waals) and disulfide bonds |
| what maintains the secondary structure of a protein? | hydrogen bonds |
| which of the following does not influence protein shape? disulfide,peptide,hydrogen bonds,ionic bonds, none of the above | peptide bonds (interaction of R groups influences shape) |
| heme group in myoglobin is a | prosthetic group |
| heme is tucked into an area to protect it from environment called | hydrophobic cleft |
| similarity between tertiary and quaternary? difference? | use same bonds difference is quaternary is composed of multiple polypeptides |
| T/F polypeptides that form quaternary structures have to be similar | FALSE, they can be similar or different |
| in what protein quaternary structures are disulfide bonds found | fibrous/structural proteins. rarely in globular |
| hemoglobin is a ____________ | tetramer (has 4 monomers) |
| hemoglobin can carry ______ oxygens, one per _____________ | 4, heme group |
| amino acid R groups are most important for stabilizing what level(s) of protein structure? | tertiary and quaternary |
Created by:
rusulali97
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