Term
| What three things are required for the definition of life? |
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Definition
| Metabolism, growth, and reproduction |
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Term
| How much of a cell is composed of protein? |
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Definition
| 50% of the dry weight of a cell |
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Term
| What enzymes are not proteins? |
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Definition
| A very small percentage are RNA that perform enzymatic functions |
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Term
| What is the theoretical limit for rate enhancement by enzymes? |
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Definition
| About 108 or 109 times the original speed, which is the diffusion limit |
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Term
| Do enzymes change equilibrium constant, free energy of activation, or equilibrium concentrations? |
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Definition
| Only free energy of activation, reduce time to reach equilibrium |
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Term
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Definition
Keq=[P]/[S]
Not affected by enzyme, enzyme just makes the reaction reach this point faster |
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Term
| Define oxidoreductases reaction type |
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Definition
| Transfer of electrons (H) |
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Term
| Define Transferase reaction type |
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Definition
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Term
| Define hydrolases reaction types |
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Definition
| Hydrolysis reactions (transfer of functional groups to water) |
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Term
| Define lysases reaction type |
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Definition
| Addition of groups to double bonds, or formation of double bonds by removal of groups |
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Term
| Define isomerases reaction type |
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Definition
| Transfer of groups within molecules to yield isomeric forms |
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Term
| Define ligases reaction type |
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Definition
| Formation of C-C, C-S, C-O, and C-N bonds by condensation reactions coupled to ATP cleavage |
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Term
| Describe the four digit code for enzyme classification |
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Definition
first digit- classification number (1-6)
2nd- cell family number
3 and 4- reaction and substrate info |
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Term
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Definition
| Enzymes composed of a protein plus a cofactor |
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Term
|
Definition
| A cofactor that is covalently bound |
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Term
|
Definition
| A cofactor that is NOT covalently bound |
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Term
|
Definition
| The complete complex enzyme, protein and cofactor |
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Term
|
Definition
| The protein component of a holoenzyme |
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Term
| Describe how vitamins and metals usually serve as cofactyors |
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Definition
| Usually vitamin derivatives serve as coenzymes while metal ions serve as prosthetic groups |
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Term
| What do high levels of CPK, LDH, and HBDH in the blood indicate? |
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Definition
| A heart attack; these enzymes are normally found in heart tissue, but heart attack damage allows escape to the blood |
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Term
| What are the four basic catalytic mechanisms used by enzymes? |
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Definition
1. Specific binding of substrate (ie, orientation)
2. Acid-base catalysis
3. Covalent catalysis
4. Metal ion catalysis (often in redox) |
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Term
| What does chymotrypsin do? |
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Definition
| It is a protease that cleaves the peptide bond between bulky AAs and the next residue |
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Term
| What does trypsin cleave? |
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Definition
|
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Term
| What does elastase cleave? |
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Definition
|
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Term
| How is chymotrypsin reaction rate often observed? |
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Definition
| By converting p-Nitrophenylacetate (yellow) to p-Nitrophenol |
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Term
|
Definition
| Catalytic power of an enzyme |
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Term
|
Definition
Binding affinity of an enzyme, the amount of unbound substrate at 1/2 Vmax
A smaller Km indicates tighter binding |
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Term
| What is the equation for vo of an enzyme? |
|
Definition
|
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Term
|
Definition
The turnover number
kcat=Vmax/[ET] |
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Term
| What is the equation to describe the efficiency of an enzyme? |
|
Definition
kcat/km
Turnover number / [S] at 1/2 Vmax |
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Term
| If V=Vmax, do we assume large [S] or large [E]? |
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Definition
Large [S], enzyme is saturated
You can do the math on the Michaelis-Menton equation to find this |
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Term
| What is the Diffusion-Controlled limit for kcat/km? |
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Definition
|
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Term
| How is the Lineweaver-Burk plot derived? |
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Definition
| By taking the inverse of the Michaelis Menton equation |
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Term
| What is the Lineweaver-Burk equation? |
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Definition
| 1/Vo= (Km/Vmax)(1/[S]) + 1/(Vmax) |
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Term
| In the Lineweaver-Burk Plot, what is the slope? |
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Definition
|
|
Term
| In the Lineweaver-Burk Plot, what is the y-intercept? |
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Definition
|
|
Term
| Define competitive inhibition |
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Definition
| An inhibitor competes for the binding site |
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|
Term
| Define uncompetitive inhibition |
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Definition
| An inhibitor binds allosterically but the substrate can still bind, just not be changed to product |
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Term
| Why are a lot of drugs inhibitors? |
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Definition
| Diseases are often caused by overactive enzymes |
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Term
| What is Thymidylate synthase? |
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Definition
| An enzyme in cancer cells, it is inhibited with Methotrexate to replace Tetrahydroflorate |
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Term
| How do irreversible inhibitors work? |
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Definition
|
|
Term
| How do competitive inhibitors affect the Michaelis-Menton equation? |
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Definition
|
|
Term
| How do noncompetitive inhibitors affect the Michaelis-Menton equation? |
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Definition
|
|
Term
| How do competitive inhibitors affect the Lineweaver-Burk graph? |
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Definition
| Since they raise Km, they increase the slope but do not change y-intercept |
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Term
| How do noncompetitive inhibitors affect the Lineweaver-Burk graph? |
|
Definition
Since they lower Vmax, they raise the y-intercept and increase slope
X-intercept is the same |
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Term
| Where is the x-intercept on a Lineweaver-Burke plot? |
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Definition
|
|
Term
| What are the two models for allosteric enzymes? |
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Definition
1. Concerted model (all subunits change at the same time)
2. Sequential Model (each subunit changes individually) |
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Term
| How do inhibitors/activators change the state of an allosteric enzyme? |
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Definition
| Inhibitos favor the T state and activators favor the R state |
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Term
| What step(s) of a reaction to allosteric enzymes control? |
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Definition
| They always control the first step of metabolic pathways |
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Term
| Define heterotropic enzyme |
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Definition
| An allosteric enzyme where the effector binding site (regulatory site) and the substrate binding site (active site) are different |
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Term
|
Definition
|
|
Term
| Why is adipose tissue gray? |
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Definition
| It is very concentrated, low water, low O2 |
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Term
| What is the name of the process by which AAs and glycerol turn to sugar? |
|
Definition
|
|
Term
|
Definition
| How glycogen turns to glucose |
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Term
|
Definition
| 6-membered carbon sugar ring |
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Term
|
Definition
| 5-membered carbon sugar ring |
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|
Term
| What enzymes make glycosidic linkages? |
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Definition
|
|
Term
| What is the characteristic of donor substrates in glycotransferase reactions? |
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Definition
| The donor substrate is usually a high end sugar nucleotide, whose hydrolysis makes the reaction more energetically favorable |
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Term
| How is galactose converted to free glucose during mammary milk production? |
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Definition
α-lactalbumin is expressed in the mammary gland, which promotes transfer of galactose to free glucose
Normally galactose is instead transfered to protein-bound N-acetyl glucosamine |
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Term
|
Definition
| When the free carbonyl of sugar is reactive enough that in high concentrations (ex. disease) a spontaneous reaction with AAs forms advanced glycation end products (AGEs) |
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Term
| Define advanced glycation end products (AGEs) |
|
Definition
The product when glucose, at disease high concentrations, has a spontaneous reaction with AA side chains.
Thought to mediate microvascular consequences of diabetes |
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Term
|
Definition
| An AGEs variant where sugar binds to hemoglobin, indicative of high average blood sugar over time |
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Term
|
Definition
| Enzymes that cleave glycosidic linkages |
|
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Term
| Define endoglycosideases and exoglycosidases |
|
Definition
Exoglycosidases: can only remove sugar at end of glycosidic linkages
Endoglycosidases: can cleave inside a glycosidic linkage forming polysaccharides |
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Term
|
Definition
| The third enzyme to break down glycogen, cleaves α(1-6)-linked bonds |
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Term
| List the three enzymes taken to break down glycogen, in order |
|
Definition
1. α-amylase
2. exoglucosidase maltase
3. Isomaltase |
|
|
Term
| Why can humans not break down cellulose? |
|
Definition
|
|
Term
| Define sucrase-isomaltase complex deficiency |
|
Definition
| A congenital sucrose intolerance defect that can be treated by dietary restriction or enzyme replacement therapy |
|
|
Term
|
Definition
| A sugar whose reactive hydroxyl group is not attached to another molecule |
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