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Cell Bio-Koster
Proteins-exam2
| Question | Answer |
|---|---|
| What are proteins' functions? | 1. Structure (ecm-collagen, icm-cytoskeleton) 2. communication (receptors, antibodies, hormones, transport) 3. catalytic (enzymes) 4. regulation (gene expression, other proteins) 5. adhesion (glycoproteins) 6. storage and transport (albumin, seed storage) |
| what extracellular protein structure is present in ECM especially in animals ? | collagen |
| what is the intracellular protein structure ? | cytoskeleton |
| transmembrane glycoproteins are _____________ whose function is to _____________ | receptors, communicate |
| what sort of communication proteins are there? | 1. receptors: transmembrane glycoproteins, 2. antibodies (animals) 3. hormones (insulin, glucagon, growth hormone, etc) 4. transport:across membrane (channels, pumps) along cytoskeleton (myosin, kinesin) |
| enzymes are _______________proteins | catalytic |
| In what 2 ways do proteins regulate gene expression? | 1. Physically-by histones 2. Physiologically-enzymes that control transcription |
| give an example of a protein that regulates other proteins | Calmodulin |
| what causes adhesion at cell surface? | Glycoproteins |
| Give examples of storage and transport proteins | Seed storage proteins, albumins, hemoglobin |
| What is a protein monomer? | an amino acid |
| how many amino acids are used in protein synthesis? | 20, may be chemically modified after they are linked in a peptide |
| at least _____ amino acids are known | 150 |
| what is the structure of a generic amino acid? | alpha carbon with NH3, carboxyl, H, and R group attached |
| T or F 3 nucleotides form an amino acid? | TRUE |
| What are 2 types of amino acids? | 1. non polar 2. polar |
| what is the difference between polar and non polar amino acids? | Non polar aa's R group is mostly hydrocarbon, no charge or polarity. While polar aa's, at neutral pH, R group may be 1. uncharged, 2. negatively charged (acidic), or 3. positively charged (basic) |
| what is a feature of non polar amino acids? | they are structural residues, not directly involved in reactions. |
| what does the term residue mean | term used to indicated a monomer within a polymer. inert, not many reactions. |
| Which amino acid when part of polypeptide is expected to have a negative charge? | Glutamate |
| Which amino acid when part of polypeptide is expected to have a positive charge? | Lysine |
| what contributes to the partial double bond characteristic in peptide bonds? | mobility of electrons from the carbonyl group. |
| what is the effect of the partial double bond in peptide bonds? | limits rotation around the bond |
| in living organisms, amino acids are only added to _______________ of a peptide | C-terminus |
| what is another term for polymers of proteins? | polypeptides |
| what main levels of hierarchical organization in polypeptides? | 1. primary 2. secondary 3. tertiary 4. quaternary |
| what is primary structure of polypeptides? | linear sequence of amino acids in a chains from N (amino) to C (Carboxyl) terminus |
| each amino acid within a polypeptide is termed _________ | residue |
| where do secondary conformations of proteins result from? | rotation of bonds in chains |
| what are the three common patterns in secondary protein conformations? | 1. alpha helix, 2. beta strand, 3. random coil |
| alpha helix is a right handed __________ held together by __________ bonds and _______ forces | spiral, hydrogen, van der waal |
| where are side chains located? | they point out from helix axis. Bottle brush bristles |
| how many amino acids per turn in an alpha helix? | 3.6 amino acids |
| what makes rod like, semi rigid section of protein? | alpha helix, due to no space in the alpha helix |
| what are beta strands? | stretched chains |
| how do beta strands link? | they link to neighboring strands, parallel or antiparallel. NO H BONDS. |
| where are side chains located in beta strands? | side chains point up and down-perpendicular-from strand |
| what 2 shapes do beta strands form? | beta sheets or beta barrels |
| random coils are ________ but not random | irregular |
| why are random coils important? | bending and folding of polypeptides |
| what are random coils caused by? | 1. proline 2. charged side chains |
| what abundant proteins are random coil primarily but can gain structure when environment changes? | intrinsically unstructured proteins e.g. alpha synuclein forms alpha helices near membranes |
| _____________ forms alpha helices near membranes | alpha synuclein |
| __________ can unfold and aggregate to form ________ that are associated with neurodegenerative disease | alpha synuclein, fibrils |
| what conformation do amino acids isoleucine, valine, and phenylalanine tend to form? | Beta sheets |
| what conformation do amino acids leucine, methionine, and glutamate tend to form? | alpha helices |
| how does proline disrupt the structure and why? | it introduces a bend in the helix because it cannot form hydrogen bonds |
| what are tertiary structures? | 3-D arrangement of secondary structures |
| what do tertiary structures depend on | 1. primary and secondary structures 2. solution especially that affect H bonding, ionic bonding, van der waals (pH, salt concentration, temperature) |
| why do H bonds stabilize structures? | because if disrupted, the structure will be disrupted |
| what are disulfide bridges? | covalent link between two cystine (bc has SH) residues, may be in different polypeptides |
| what do disulfide bridges provide? | structural stability, in keratin that's why burnt hair smells like sulfur |
| oxidation _____________ disulfide bridges | disrupts |
| unfolding is ________________ | change in 3D structure of tertiary proteins |
| what is denaturation | unfolding that disrupts function, may be reversible or not |
| what causes denaturation? | alcohol, heat, acids, bases, heavy metals, reducing agents, detergents,... |
| what is a domain? | discrete, locally folded, stable region within tertiary protein structure, may be functionally distinct. Region that folds and functions independently. |
| proteins may have single domain or multiple, depending on what? | size and function of the protein |
| a domain is typically ___to ____ amino acids long with regions of ____________ and ____________ packed together | 50 to 350, alpha helices, beta sheets |
| proteins with similar functions often share a common____________ | domain |
| proteins with _________________ usually have a different domain | multiple functions |
| what is a modular unit? what is it an example of? | a domain for different proteins that construct globular proteins. It is an example of multiple domains linked together to form final protein |
| what is quaternary structure? example | multi-subunit protein. (more than 1 polypeptide chain in final protein). ex: hemoglobin which has 4 polypeptides, each has their iron |
| how are subunits held together in quaternary structures? | H bonds, ionic bonds, disulfide bridges, hydrophobic interactions, van der waals. Just like tertiary structures. |
| how does hair perming work? | bonds in hair are wrapped around a roller, treated with a reducing agent which breaks the bonds. After oxidation the hair bonds are realigned in a different order, which leads to permanent change in hair's shape producing a curl |
| Range of subunits a quaternary protein can have? what is common? | few to thousands. 10-12 subunits is common. |
| ____________ refers to similar subunits, ____________ refers to different subunits | homopolymer, heteropolymer |
| give example of homopolymer and a heteropolymer | homopolymer--> microfilaments (100s-1000s actin monomers) heteropolymer--> 20 monomers 9 different types |
| what is a motif? | Referring to secondary structures, it is a commonly seen orientation. A pattern that is shared among different proteins |
| what is the difference between a motif and a domain? | domain is stable and functional on its own, a motif isn't. Proteins are constructed from different combinations of domains. |
Created by:
rusulali97
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