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Cell Bio-Koster

Proteins-exam2

QuestionAnswer
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