Karteikarten
Proteins flashcards
Karten in diesem Stapel (26)
- 1What is the primary structure of a protein?The amino acid sequence alone. This determines every other aspect of the proteins shape and structure.
- 2What is the secondary structure of a protein?The alpha-helices and beta-strands, that form the local geometric protein backbone.
- 3What is the tertiary structure of a protein?The 3D relationship of the secondary elements, also called the protein fold.
- 4What is the quarternary structure of a protein?The relationship and interactions of the subunits of a particular protein. The structure of the subunits together.
- 5What is the term for a protein that is formed by two subunits?A dimer.
- 6In what direction is the polypeptide formed at the ribosome?From C-terminus to N-terminus.
- 7What is the topology of a polypeptide?The geometrical properties of the polypeptide unaffected by the continuous change in shape or size of the protein.
- 8What is the hierarchy for classification of domains using CATH?Class = predominantly alpha, beta, or mixed.
Architecture = the shape of the domain, tertiary structure.
Topology = the geometric properties.
Homology = protein families, common ancestry etc. - 9What are the five amino acids with a net charge at physiological pH? And which are basic and which are acidic?Acidic: Aspartic acid, Glutamic acid; (negative)
Basic: Lysine, Arginine, Histidine;
(positive) - 10When describing quarternary structure, what are some terms used to discern shape or arrangement of subunits?Cyclic, Dihedral, Tetrahedral, Octahedral (cubic), Isocahedral.
- 11What is the strongest force that stabilizes a protein?The covalent bond. Especially between carbon atoms.
- 12What is an important bond with a strength of around 10 kJ/mol and a length of ~3.2A'?The hydrogen bond.
- 13What effect does a chaotrope have on a protein?Chaotropic agents weaken the hydrophobic effect by disrupting the hydrogen bonds within the network.
- 14If the pH is lower than Arginine's pKa (12.5), what charge will the residue have?Positively charged, +1.
- 15The pKa of Glutamic Acid is 4.2, so how will the residue be charged at pH=5?At a superior pH to pKa, the acidic amino acids are negatively charged. (-1)
- 16How will Lysine be charged at pH=12? (Lysine pKa = 10.5)Lysine will be uncharged at a pH higher than the pKa.
- 17How does competitive inhibition work? What effect does this have on the kinetics?The inhibitor binds to the active site of the enzyme, thus disabling it's ability to bind the substrate. This increases the Km, because more substrate is needed to reach the same speed.
- 18How does un-competitive inhibition work? What effect does this have on the kinetics?The inhibitor binds to the enzyme-substrate complex, thus preventing it from forming the product complex. This decreases Vmax because there is less activated complex to form product, and also decreases Km because there is less enzyme-substrate so substrate affinity for the enzyme is heightened.
- 19How does non-competitive inhibition work? What effect does this have on the kinetics?The inhibitor binds to the enzyme somewhere other than the active site, allowing the substrate to bind but preventing the complex to form product. This decreases Vmax because the ES complex is inactivated, Km remains the same because the enzyme still binds the subsrate.
- 20What does the process of an unfolded protein forming into it's native state look like in regard to the forces involved?Hydrogen bonds form among the residue sequence to produce secondary structure. Then the hydrophobic collapse forms a molten globule, which is then formed into subdomains by ionic and van der Waals forces. Further formation of these forces induce the production of the native state.
- 21At what [S] will Vo = 0.95Vmax? (expressed as a multiple of Km)Using the Michaelis-Menten equation: Vo = Vmax[S] / Km+[S] we get 19Km to give a Vo = 0.95Vmax
- 22Explain the mechanism for non-sequential binding in a ping-pong fashion.The enzyme switches between two distinct states. The enzyme binds to substrate 1, and during catalysis the enzyme undergoes a conformational change, allowing it to bind substrate 2 after releaseing product 1. During catalysis of substrate 2 the enzyme reverts to it's former state and releases product 2. This process repeats.
- 23Explain the mechanism for ordered sequential binding.Enzyme binds to substrate 1 and the complex binds to substrate 2, then catalysis occurs, and product 1 is released prior to product 2.
- 24Explain the mechanism for random sequential binding.The enzyme binds either substrate, and then the complex then binds the other, and then after catalysis, either product is released, then the other. The substrate bound and product released is random, any order can occur.
- 25What does the Anfinsen experiment involve and what does it demonstrate?In the Anfinsen experiment, an RNase A is fully denatured by reducing the disulfide bonds with mercaptoethanol and denaturing with 8M urea. The protein is inacitve. If the urea is diluted out and the disulfide bonds allowed to reoxidise, the protein renatures and folds into it's native state, becoming fully inactive. This shows that all the information necessary to determine the three-dimensional fold is incorporated in the amino acid sequence.
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- 200 level Biochemistry (Proteins and Biotechnology - 222) Karteikarten am Proteins flashcards, erstellt von hanngeiss am 08/07/2015.
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