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Biochem/ metab > lecture 8 > Flashcards

lecture 8 Flashcards

1
Q

what do kinetics measure?

how does it do this (2 things)

A

the rate of an enzyme-catalyzed rxn

done by:

  1. stabilizing the transition state
  2. there is a specific enzyme for each step in the metabolic process
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2
Q

how to enzymes catalyze chemical reactions?

A
  1. lower the activation energy by stabilizing the transition state and allow for products to form more easily
  2. active sites: binding surfaces where chemistry takes place
    * bonds are broken and then formed again Sā€“>P
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3
Q

what is a ribozyme?

A

the first enzyme that was discovered that was not a protein enzyme

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4
Q

describe a lock and key (model for substrate binding)

A
  1. inflexible

2. highly specific only binds to the complementary strands

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5
Q

describe induced fit

and an example

A
  1. flexible enzyme
  2. conform to the shape of substrates
  3. lower specificity

ex: hexokinase: glucose, and fructose

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6
Q

what are conjugate proteins?

A

protein + nonprotein components

cofactor: metal ions, or organic molecules-vit/coenzymes

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7
Q

what is a Holoenzyme

A

apoenzyme + cofactor

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8
Q

describe the function of oxidoreductase

A
  1. transfer electrons/ redox rxn
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9
Q

what are the 6 major groups of enzymes?

A
  1. oxidoreductase
  2. transferase
  3. hydrolase
  4. lyases
  5. isomerases
  6. ligases
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10
Q

describe the function of transferases

A

transfer groups from one molecule to another

  • usually cofactors
  • prefix: trans
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11
Q

describe the function of hydrolase

A

uses water to cleave a bond

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12
Q

describe the function of lyases

A

chemistry dealing with double bonds, either adding double bonds or removing double bonds

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13
Q

describe the function of isomerases

A

intramolecular rearrangement, isomerization

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14
Q

describe the function of ligases

A

makes bonds, glues things together

*requires ATP

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15
Q

describe the central concept of the Michaelis-Menten Kinetics

A

enzyme substrate complex (ES)- intermediate formed at the transition state
substrates vs. products

E +Sā€“> ES complex -chemistry-> enzyme free + product

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16
Q

what equation is used for the Michaelis-Menten kinetics

A

v= Vmax x [S] / [S] - Vmax

S: 3 of substrates floating around in the environment

17
Q

describe the Km value

A

value on the x-axis
is used to indicate he slope
it is calculated after Vmax is calculated

1/2 of the Vmax on the yaxis and then use the calculated y-value to tell the x-value

18
Q

describe the Vmax value

A

where the rate pf the enzyme begins to taper off, a point at which the enzyme can no longer increase the rate at which its produces products (value on the y axis)

19
Q

how would you graph a Iineweaver-Burk Plot? and how would you label it?

A
  1. take the reciprocals of the x and y axis values giving a straight line (the slope)

1/Vo
line: Km/ Vmax

       1/[S]

Km: point at the bottom of the graph
Vmax: where it intersects with the y-axis

20
Q

Describe irreversible inactivators

A

covalently modified enzymes: prevent enzyme activity/ shuts it down

21
Q

what are example of irreversible inactivators?

A

heavy metals: able to bind with Ca binding sites

  1. lead: prevents oxygen from binding to heme
  2. arsenic: binds between sulfur and shuts down ATP synthesis
22
Q

describe reversible inhibitors

A

can bind but disassociate from the enzyme

23
Q

what are the 3 types of reversible inhibitors?

A
  1. competitive
  2. uncompetitive
  3. noncompetitive
24
Q

describe the reversible inhibitor: competitive

A

cannot bind to the ES complex
forms EI complex
inhibitor is similar in structure to S

25
Q

describe the reversible inhibitor: uncompetitive

A

binds only to the ES complex

* most common in the enzymes that bind more than one substrate

26
Q

describe the reversible inhibitor: noncompetitive

A
  1. can bind to both E and ES
  2. different structure than S
  3. Bind to a different site other than the active side
  4. MODIFIES ENZYME CONFORMATION AND PREVENTS PRODUCTION OF FORMATION
27
Q

describe the kinetics of: competitive inhibitors

like on a graph (Vmax and Km)

A

Vmax: stays the same
Km: increases

28
Q

describe the kinetics of Noncompetitive inhibitors

A

Vmax: decreases
Km: stays the same

29
Q

describe the kinetics of: uncompetitive inhibitors

A

Vmax: decreases
Km: decreases

30
Q

why is inhibitors important to understand?

A
  1. chemotherapy: methotrexate prevents synthesis of cancer cells (irreversible)
  2. metabolic control: ATP inhibition of glycolysis
  3. pesticides: can shut down the enzyme that are needed for amino acids production
  4. antibiotics: destroy cell walls

Biochem/ metab (4 decks)

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