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Biochemistry PMY-3 > Enzymes 1 > Flashcards

Enzymes 1 Flashcards

1
Q

What are enzymes?

A

Biological catalysts that increases the rate of a chemical reaction of a chemical reaction without itself undergoing any permanent chemical change

  • enzymes are specific
  • they are located inside of cells, in the extracellular space or in the blood plasma
  • they can be regulated
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2
Q

What are the functions of enzymes?

A
  • Breakdown of nutrients
  • Production of high energy molecule
  • synthesis and assembly of cellular building blocks
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3
Q

What are substrates?

A

The reactants that are activated by the enzyme

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4
Q

What are apoenzymes?

A

Enzyme without its nonprotein component

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5
Q

What are holoenzymes?

A

An active enzyme with its nonprotein component

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6
Q

Differentiate Cofactors and Coenzymes?

A

Cofactors- a metallic nonprotein component e.g, Zinc (Zn2+)

Coenzymes- nonmetallic small organic molecule divided into co-substrates and prosthetic group

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7
Q

Define the category’s of Coenzymes

A

Co-substrates- transient association with the enzyme and dissociates into an altered form e.g. NAD+

Prosthetic groups- permanent association with an enzymes and the form is not changed at the end of the reaction

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8
Q

What is an active site?

A

Special pocket where substrate binds

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9
Q

What is the turnover number?

A

The number of substrate molecules converted to product per enzyme molecule per second

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10
Q

Describe the specifier of enzymes

A

Specificity:

  • Enzymes are specific for a single molecule or a structurally related group of substrates
  • Usually only 1 enzyme per reaction type
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11
Q

What are the c,asses of enzymes?

A
  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases
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12
Q

What type of enzyme are oxidoreductases?

A

Catalyze oxidation-reduction reactions

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13
Q

What type of enzyme are transferases?

A

Catalyze transfer of C-, N- or P- containing groups

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14
Q

What kind of enzymes are hydrolases?

A

Catalyze cleavage of bonds by addition of water

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15
Q

What kind of enzyme are lyases?

A

Catalyze cleavage of C-C, C-S and certain C-N bonds

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16
Q

What kind of enzymes are isomerases?

A

Catalyze racemization of optical or geometric isomers

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17
Q

What kind of enzymes are Ligases?

A

Catalyze formation of bonds between carbon and O, S, N, coupled to hydrolysis of high-energy phosphates

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18
Q

What are 2 minor enzyme Groups?

A

Kinases

Phosphatase

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19
Q

What are the steps in an enzymatic reaction?

A
  1. Enzyme and substrate combine to form a complex E+S = ES complex
  2. The complex goes through a transition state- not quite substrate or product. ES=ES*
  3. A complex of enzyme and product is produced
  4. The product is released
    EP= E+P
20
Q

What are the 2 basic components of the active site ?

A
  • catalytic site

- Binding site

21
Q

What is the catalytic site of an enzyme?

A

Where the reaction occurs

22
Q

What is the binding site of an enzyme?

A

Area that holds the substrate in proper place

23
Q

Describe the shape of enzymes

A

Shape are complementary to the substrate and determines the specificity of the enzyme

24
Q

Describe the interactions of enzymes

A

Enzymes use weak, non-covalent interactions to hold the substrate in place based on R groups of amino acids

25
Q

How are enzyme sutes shaped?

A

These are clefts or pockets on the enzyme surface

26
Q

Describe the lock and key model

A

The lock and key model-1890

Assumes only a substrate of the proper shape could fit with the enzyme

27
Q

Describe the induced fit model

A

Induced-fit model -1958

  • assumes continuous changes in active site structure as a substrate binds
  • more widely-accepted
28
Q

What are factors that influence enzyme activity?

A

Environmental factors
-temperature,pH

Cofactors
-metal ions

Effectors
-species that alter enzyme activity

29
Q

Explain the effect of temperature on enzyme activity

A
  • exceeding normal temperature ranges always reduces enzyme reaction rates
  • optimum temperature is usually 25-40 degrees celsius(but not always)
30
Q

What is enzyme regulation?

A

Proteolytic cleavage to activate : enzyme exists in inactive form(zymogen) that is activated by removal of a shirt peptide segment(truncation)

31
Q

What is covalent modification?

A

This is achieved by the addition(phosphorylation) or removal (dephosphorylation) of phosphate groups from specific serine, threonine and tyrosine residues of the enzyme

32
Q

What is the purpose of covalent modification?

A

Phosphorylation May make an enzyme more active or less active depending on the specific enzyme

33
Q

What is an example of covalent modification?

A

Glycogen phosphorylase increases increases with phosphorylation whereas that of glycogen synthase decreases

34
Q

What are the 5 types of covalent modification?

A

Phosphorylation

Adenylylation

Uridylylation

ADP-ribosylation

Methylation

35
Q

What is enzyme repression-downregulation?

A

Decrease gene expression, decrease synthesis of enzyme molecules

36
Q

What is enzyme degradation?t

A

Achieved by specific changes in the protein structure that is recognized for degradation by the ubiquitin-proteasome

37
Q

What is allosteric regulation?

A

“Other site” regulation, both. Positive and negative effectors(homotropic, heterotropic)

38
Q

What are homotropic effectors?

A

Substrate acts as the effector, most Often a positive effector.

Exhibits cooperativity analogous to the binding of oxygen to hemoglobin

39
Q

What are heterotropic effectors?

A

Effector may be different from the substrate. Feedback inhibition in some reactions can serve as an example (phosphofructokinase-1 and citrate in glycolysis)

40
Q

What is enzyme induction/upregulation?

A

Increase gene expression, synthesis of more enzyme molecules

Examples: steroid receptor mechanism of signal transduction

41
Q

Highlight the mechanism to form active Trypsin

A
  1. Chymotrypsin converted to pi-chymotrypsin by cleaving Arg, leaving Ile on the tail
  2. pi-chymotrypsin converted to a-chymotrypsin by adding another peptide chain to Ile and cleaving iff a poetics chain on the opposite end between Tyr and ALS
  3. trypsinogen is converted to trypsin(active form) by enteropeotidase
42
Q

What is a binary complex?

A

One substrate and one enzyme

43
Q

What is a tertiary complex?

A

Two substrates and one enzyme

44
Q

What is activation energy?

A

The energy difference between that of the reactants and a high-energy intermediate, the Transition state(T), which is form during the conversion of reactant to product

45
Q

What is the job of the kinase?

A

Uses ATP to add phosphate

46
Q

What is the job of a phosphatase?

A

To remove a phosphate group

Biochemistry PMY-3 (37 decks)

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