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Biochemistry DO I > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Describe enzymes as catalysts

A

increase the reaction rate by decreasing the energy barrier

does not effect delta G or Keq

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2
Q

Characteristics of enzymes that differ from other proteins

A
  • higher reaction rate
  • Milder reaction conditions (standard atm pressure, neutral pH, temps less than 100 C)
  • High reaction specificity
  • Can be regulated (inhibitors, etc)
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3
Q

measurement of enzyme activity

A

measured in units:

amount of substrate converetd to product in a given amount of time (1 umol/min)

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4
Q

Specific activity

A

number of units per mg protein

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5
Q

optimum pH of human enzymes

A

37 C

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6
Q

Discuss pH optimum of enzymes

A
  • optimum pH dependent on where the enzyme is located
  • pepsin in stomach ~ pH 2
  • Trypsin in intestine ~ pH 8
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7
Q

Oxidoreductase

A

transfer protons (H) and electrons to go from C-C to C+C

catalyze oxidation-reduction reactions

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8
Q

Examples of oxidoreductase enzymes

A

Deydrogenase, Oxidase, reductase, peroxidase, catalase, oxygenase, hydrolases

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9
Q

Transferase

A

Transfer C-, N-, P- containing groups (glcosyl, methyl, phosphoryl)

usually transfer to a cofactor

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10
Q

Examples of transferases

A

kinase, phosphomutase, transaldolase, transketolase

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11
Q

Hydrolase

A
  • cleaves bonds by adding water

- cleavage of C-C, C-O, C-N and other bonds

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12
Q

Examples of hydrolases

A

esterases, glycosidases, peptidases, phosphatases

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13
Q

Lyases

A

cleaves C-C, C-S, C-O, and C-N

results in a C=C (double bond)

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14
Q

Examples of Lyases

A

Decarboxylases, aldolases, hydratases, dehydratases, synthases

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15
Q

Isomerases

A

Catalyze geometric rearrangement

** rearrange but dont change the molecular weight

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16
Q

Examples of Isomerases

A

Racemases, epimerases, isomerases, mutases

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17
Q

Ligases

A
  • adding two substrates together
  • Form bonds between C, O, S, N
  • coupled with hydrolysis of ATP (ATP –> ADP)
18
Q

Active site

A

area on the enzyme where catalysis occurs

19
Q

Catalysis by proximity

A

bring enzymes and substrate together so there is a higher chance of them meeting and interacting

20
Q

Acid Base Catalysis

A

Ionizable functional groups of amino acyl side chains move or accept protons by acting as acids/bases

21
Q

Catalysis by strain

A

enzymes that break bonds (hydrolase, lyases) may bind in such as way that they create strain to break the bond

“bend and snap!”

22
Q

Covalent Catalysis

A

covalent bond established between enzyme and substrate to make enzyme substrate complex

ESC then becomes the product for the rest of the reaction

23
Q

Prosthetic Group

A

Binds to enzyme
Tightly bound
Covalent
Most commonly metal ions (Co, Cu, Mg, Mn, Zn)

24
Q

Metaloenzymes

A

enzymes with a metal containing prosthetic group

25
Q

Cofactors

A

Binds to enzyme or substrate
Inorganic substances required for enzyme activity

Ex: Mg 2+ is required for enzymes that involve ATP

26
Q

Coenzymes

A

loosely bound
shuttles groups within the reaction

Ex: Coenzyme A transferes acyl group
Folates transfer Carbon group

27
Q

Isoenzymes

A

physically distinct enzymes which catalyze the same reaction

kinetic differences (Km, pH, temp)

28
Q

Kcat

A

how fast enzyme releases product/ unit of time

highter Kcat = better

29
Q

Km

A

binding affinity

Km= 1/2 Vmax

lower Km = better

30
Q

Catalytic efficienct

A

Kcat/Km

31
Q

Michaelis menton

[S]&raquo_space; Km

A

V= vmax

zero order reaction

32
Q

Michaelis menton

[S] &laquo_space;Km

A

first order reaction

33
Q

Lineweaver burke intercepts and slope

A

y-intercept = 1/vmx

x-intercept = -1/Km

Slope = Km/Vmax

34
Q

Competitive Inhibitor

A

structurally similar to substrate (competes)
Binds only to free enzyme
Increase Km
Vmax stays the same

overcome by addition of [S]

35
Q

Noncompetitive Inhibitor

A

Bind to E or to ES
DOES NOT BIND ACTIVE SITE –> doesnt compete with S for binding
Decreases Vmax

increasing [S] does NOT overcome inhibition

36
Q

Uncompetitive Inhibitor

A

Binds only to ES

Changes both Km and Vmax (slope stays the same)

As [S] increases so does the inhibition because it uses ES

37
Q

Enzyme coopertivity

A

binding of one substrate causes the binding of subsequent molecules

38
Q

Allosteric Enzyme

A

has more than one substrate binding site

usually more than one subunit

39
Q

Hill coefficient

A

measure of the degree of coopertivity

larger = greater coopertivity

n=1 no coopertivity and the equation is michaelis menton

40
Q

Conformational changes in allosteric enzymes

A

low [S] the enzyme is tensed

high [S] the enzyme is relaxed

41
Q

Homotrophic regulation

A

binding of S increases the activity of other catalytic sites

almost always positive (activator)

42
Q

Heterotrophic regulation

A

regulatory molecule distinct from the substrate

Biochemistry DO I (3 decks)

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