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Enzymes
Biosci 106
| Question | Answer |
|---|---|
| Composition | can be only proteins -or + nonprotein group |
| Apoenzyme | only protein without the non-protein group required to do the catalytic activity |
| Holoenzyme | contains both protein+ non-protein group = complete enzyme |
| Prosthetic Group | group attached to protein -always bound |
| Co-enzyme | binds & dissociates during catalytic cycle |
| Characteristics of enzymes | specific efficient Regulation |
| Specificity of and enzyme | -particular type of reaction -with unique molecules |
| Efficiency of enzyme | -catalyst -speeds up reaction 10^6/7 |
| Enzymes >Regulation | pro-enzyme-(on only) Co-valent modification-(on&off) Allostery- (graded response) |
| Function of Enzymes | -lower Ea -no change in G or equalibrium position or amount of product -speeds up rate of reaction |
| Structure of enzymes | -100/1000sAA -reactions use 3/4 of AA |
| what other 1/4 AA are necessary for | -hold active site AA in place -provide correct microenvironment -site for recognition & control |
| Simple chemical reaction S----->P | -straightline -constant gradient Rate=k[S] |
| Reaction of Substrate & Enzyme | E+S--> ES --> E + P |
| Concentration dependence of typical Enzyme reaction | -Hyperbole -never reaches Vmax |
| Km? | [substrate] at 1/2Vmax |
| who's equations are used for the reaction scheme? | Michaelis-menten |
| Lineweaver-Burk plot | 1/V vs 1/[S] y intercept= 1/Vmax x intercept= -1/Km |
| Eadie-hofstee plot | V vs V/[S] y intercept= Vmax slope= Km |
| Inhibitor | -substance that binds to an Enzyme -not chemically altered -prevents reactions |
| Competitive inhibitor | -competes for active site |
| competitive inhibitor GRAPH | -Vmax same=Y intercept same -Km changes= X intercept & slope changes |
| Uncompetitive inhibitor | reacts with another site on enzyme ONLY after S has bonded to enzyme |
| uncompetetive inhibition -GRAPH | -Vmax & Km changes -y & x intercept & slope change |
| Non-competetive inhibition | binds to another site whenever |
| Non-competetive inhibition -GRAPH | -Vmax changes= yintercept changes |
| Ki? | defines the effective [] of inhibitor |
| Effect of temperature on enzyme reactions | -inr exponentially -reaches optimum -denatures |
| Effect of pH on Enzyme reactions | -requires more than 1AA at site -titration curve of 2 AA |
| Allostery (co-operation) | -more than one active site -Very sensitive to change [S] |
| homotropic effect | -sites become free once one site is taken |
| Heterotropic effect | -effectors that are chemically unrelated to enzyme change rate of reaction (-ve or +ve) |
| Feedback inhibition | heterotropic effect allows inhibition or activation of rate limiting steps |
| Membrane structure | - 50-100A thick -proteins & lipids (4:1/1:4) -non covalent bonding -RP 8-10mV |
| Membrane properties | -Boundaries -selective permeanbility -specific Receptor &transporters |
| Lipids | -phospho=amphipathic -Glyco=signals outside -cholesterol=rigid |
| ATP Hydrolysis | -terminal P=High E realease -reasonance -(7-10kcal/mol) |
| Molecular recognition of proteins | -specific binding clefts -correct size&shape |
| Trypsin | -protease -cleavesproteins -vepocket |
| BPTI | -bovine pancreatic trypsin inhibitor -insert+ve lys -block activity of site |
| Drug design | -identify proteins -determine 3d structure -design molecules that bind to active site |
| HIV virus | CD4 receptor allows entry into cell*RNA to DNA*DNA integrated*produce more virus*assemble |
| Reverse transcriptase | changes Viruses RNA to DNA |
| HIV protease | essential for new virus to mature*coat protein*chops into small polypeptides |
| Influenza proteins | -Haemaglutinin -Neuraminidase |
| haemaglutinin(HA) | -spikes -bind sialic acid -give entry to cell |
| Nueraminidase (NA) | -removes sialic acid from newly formed virus -stops sticking&allows escape |
Created by:
meglet
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