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Biochemistry MCAT > Enzymes > Flashcards

Enzymes Flashcards

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MCAT flashcards
1
Q

What are seven key features of enzymes

A
  • lower the activation energy
  • increase the rate of the reaction
  • do not affect the overall energy (delta G) of the rxn
  • are not changed or consumed in the reaction (will be in both the products and the reactants)
  • are pH and temperature sensitive, with optimal activity at specific pH and temperatures
  • are specific for particular reactions or class of rxns
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2
Q

A substrate is

A
  • molecule that the enzyme acts on
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3
Q

What is enzyme specificity

A
  • specific enzymes will only catalyze a single rxn or class of rxns with these substrates
  • example urease only catalyzes the breakdown of urea
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4
Q

Urease only catalyzes the breakdown of urea, why is this

A
  • bc of enzyme specificity
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5
Q

Chymotrypsin cleaves peptides from bonds around amino acids phenylalanine, tryptophan, and tyrosine in a variety of polypeptides, why would it not do this to every amino acid

A
  • bc of enzyme specificity to the aromatic rings of these certain amino acids
  • specific for a class of molecules
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6
Q

What is the mnemonic for enzyme classification

A

LI’L HOT

  • Ligase
  • Isomerase
  • Lyase
  • Hydrolase
  • Oxidoreductase
  • Transferase
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7
Q

Oxidoreductases

A
  • catalyze oxidation-reduction rxns that involve the transfer of electrons
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8
Q

Transferases

A
  • move a functional group from one molecule to another
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9
Q

Hydrolases

A
  • Catalyze cleavage with the addition of water
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10
Q

Lyases

A
  • catalyze cleavage without the addition of water and without the transfer of electrons - the reverse reaction (synthesis) is often more important biologically
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11
Q

Isomerases

A
  • catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers
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12
Q

Ligases

A
  • are responsible for joining two large biomolecules, often the same type
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13
Q

What class of enzyme catalyze oxidation-reduciton rxns that involve the transfer of electrons

A

oxidoreductases

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14
Q

What calls of enzyme moves a functional group from one molecule to another

A

transferases

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15
Q

What class of molecules catalyze cleavage with the addition of water

A

hydrolases

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16
Q

What class of enzyme catalyze without the addition of water and without the transfer of electrons

A

lyases

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17
Q

What class of enzyme catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers

A

isomerases

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18
Q

What class of enzyme are responsible for joining two large biomolecules often the same type

A

ligases

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19
Q

What do enzymes do to activation energy

A
  • lower the activation energy necessary for biological reactions
20
Q

Do enzymes alter free energy (delta G) or enthalpy (delta H)

A
  • Enzymes do not alter free energy or enthalpy or the final equilibrium position
  • enzymes change the rate (kinetics) at which equilibrium is reached
21
Q

What is the site of catalysis on the enzyme

A
  • active site
22
Q

What is the active site of an enzyme

A
  • site of catalysis
23
Q

What do the lock and key theory and the induced fit model represent

A
  • binding to the active site of the enzymes
24
Q

Explain the lock and key theory

A
  • enzyme and substrate are exactly complementary
25
Q

Explain the induced fit model

A
  • enzyme and substrate undergo conformational changes to interact fully
26
Q

Some enzymes require ____ or ____ to become active

A
  • cofactors

- coenzymes (small organic)

27
Q

What do enzymes stabilize

A
  • the transition state, providing a favorable microenvironment, or bonding with the substrate molecules
28
Q

What are saturation kinetics in a reaction with enzymes

A
  • enzymes experience saturation kinetics as substrate concentration increases the reaction rate does as well until a maximum value is reached
29
Q

What do the Michaelis-Menton and Lineweaver-Buck plots represent

A
  • represent the saturation kinetics of enzymes as a hyperbola and line respectively
30
Q

How can you compare enzymes

A
  • basis of their Km and vmax values
31
Q

What are cooperative enzymes

A
  • display a sigmoidal curve ceacuso of the change in activity with substrate binding
32
Q

How do temperature and pH impact enzymes

A
  • can cause the enzyme to denature - thus causing it to lose its function, secondary, tertiary, or quaternary structure is lost
  • can be the right temp or pH for the enzyme to become acitve
33
Q

Enzyme pathways are ___ regulated and subject to ____ and ____

A
  • regulated
  • inhibition
  • activation
34
Q

What is feedback inhibition

A
  • regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway
35
Q

What is reversible inhibition

A
  • ability to replace the inhibitor with a compound of greater affinity or to remove it using a mild laboratory treatment
36
Q

What is competitive inhibition

A
  • inhibitor is similar to the substrate and binds at the active site
  • can be overcome by adding more substrate
  • vmax is unchanged
  • km increases
37
Q

What is noncompetitive inhibition

A
  • inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex
  • vmax is decreased
  • km is unchanged
38
Q

What is mixed inhibition

A
  • inhibitor binds with unequal affinity to the enzyme and the enzyme-substrate complex
  • vmax is decreased
  • km is increased or decreased depending on if the inhibit has higher affinity for the enzyme or enzyme-substrate complex
39
Q

What is uncompetitive inhibition

A
  • results when the inhibitor binds only with the enzyme-substrate complex
  • vmax decreases
  • km decreases
40
Q

What is irreversible inhibition

A
  • alters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently
  • new enzyme molecules must be synthesized for the reaction to occur again
41
Q

Regulatory enzymes can experience ____ as well as ____

A
  • activation

- inhibition

42
Q

What is an allosteric site

A
  • can be occupied by activators, which increase either affinity or enzymatic turnover
43
Q

What is phosphorylation

A
  • covalent modification with phosphate
44
Q

What is glycosylation

A
  • covalent modification with carbohydrate
45
Q

How can phosphorylation and/or glycosylation impact enzymes

A
  • can alter the activity or selectivity of enzymes
46
Q

What are zymorgens

A
  • are secreted in an inactive form and are active by cleavage

Biochemistry MCAT (7 decks)

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