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Enzymes Flashcards

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1
Q

What enzymes are secreted in salivary glands?

A

Alpha-amylase
Lingual Lipase

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2
Q

What is the product of Amylose (a polysaccharide) digestion?

A

Disaccharide

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3
Q

What is the product of lipid digestion?

A

DAG, MAG, FFA, Glycerol

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4
Q

What enzymes are secreted in the stomach?

A

Pepsin (protease)
Gastric lipase

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5
Q

What is the product of protein digestion?

A

Peptides

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6
Q

What enzymes are secreted in the pancreas?

A

Pancreatic amylase
Trypsin (protease)
Chymotrypsin (protease)
Acid Lipases

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7
Q

What are the pancreatic enzymes that digest proteins into peptides?

A

Trypsin and Chymotrypsin

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8
Q

What are the pancreatic enzymes that digest lipids into DAG, MAG, FFA, glycerol?

A

Acid lipases

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9
Q

What are the pancreatic enzymes that digest polysaccharides into disaccharides?

A

Pancreatic amylase

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10
Q

What enzymes in the small intestine brush border digest disaccharides into monosaccharides?

A

Lactase, maltase, sucrase

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11
Q

What enzymes in small intestine brush border digest DNA and RNA into nucleotides and ribose?

A

Nucelotidases and nucleases

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12
Q

What enzymes in the small intestine brush border digest polypeptides into amino acids?

A

Peptidases

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13
Q

What plays the role of the key in the key and lock behavior of enzymes?

A

Ligand/substrate

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14
Q

What plays the role of the lock in the key and lock behavior of enzymes?

A

Protein

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15
Q

The ability of a protein to change shape, resulting in a change in binding affinity at a different binding site

A

Allostery

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16
Q

What enzymes have an active site as well as an additional allosteric site?

A

Allosteric enzymes

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17
Q

What enzymes degrade proteins for use of detergents?

A

Protease

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18
Q

What enzymes degrade cellulose for use of detergents?

A

Cellulase

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19
Q

What enzymes degrade lipids for use of detergents?

A

Lipase

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20
Q

What form does the substrate take before it becomes the product?

A

Transition state

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21
Q

What is the highest energy point of a reaction?

A

Transition state

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22
Q

What does stabilizing the transition state in an enzyme do?

A

It can greatly decrease the concentration of the reactive intermediate, accelerating the reaction.

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23
Q

What stabilizes the transition state?

A

Enzymes

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24
Q

What is the substrate and product of the enzyme pepsin?

A

Substrate - Protein
Product - Short polypeptides

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25
Q

What is the substrate and product of the enzyme rennin?

A

Substrate - Soluble casein (milk protein)
Product - Insoluble casein (curdled milk)

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26
Q

What class of enzymes catalyze reactions in which one molecule is oxidized while the other is reduced?

A

Oxidoreductases

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27
Q

What class of enzymes transfer carbon, nitrogen or phosphate groups?

A

Transferases

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28
Q

What class of enzymes catalyze a hydrolytic cleaveage reaction (uses water to break a chemical bond)?

A

Hydrolases

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29
Q

What class of enzymes catalyze the cleavage of C-C, C-S, and C-N bonds? (Often form a new double bond or ring structure)

A

Lyases

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30
Q

What class of enzymes catalyze the rearrangement of bonds within a single molecule, yielding isometric forms?

A

Isomerases

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31
Q

What class of enzymes join two molecules in an energy-dependent process?

A

Ligases

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32
Q

Which of the following requires ATP? Synthase or synthetase?

A

Synthetase requires ATP
Synthase does NOT require ATP
Hint to remember: Synthetase has T in it and synthase does not

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33
Q

What is the difference between phosphatase and phosphorylase?

A

Phosphatase removes phosphates
Phosphorylase ADDS phosphates

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34
Q

What enzyme catalyzes the incorporation of molecular O2 to a substrate?

A

Oxygenase

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35
Q

What enzyme is an O2 acceptor of electrons or hydrogen (the oxygen atoms are NOT incorporated into substrate)?

A

Oxidase

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36
Q

What enzyme catalyzes ox/redox reactions transferring hydrogen to NAD/NADPH?

A

Dehydrogenase

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37
Q

What does polymerase do?

A

It catalyzes polymerization reactions such as synthesis of DNA and RNA

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38
Q

What does Protease do?

A

Breaks down proteins by hydrolyzing bonds between amino acids

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39
Q

What do kinases do?

A

Catalyze the addition of phosphate groups to molecules

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40
Q

What do ATPases do?

A

Hydrolyze ATP

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41
Q

What do synthases do?

A

They synthesize molecules in anabolic reactions by condensing two smaller molecules together - WITHOUT ATP

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42
Q

What does phosphatase do?

A

Catalyzes the hydrolytic removal of a phosphate group from a molecule

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43
Q

TCA Cycle, Fatty acid oxidation and oxidation of pyruvate occur where in the cell?

A

Mitochondria

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44
Q

Where does glycolysis, PP pathway and fatty acid synthesis take place?

A

Cytosol

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45
Q

Where does DNA and RNA synthesis take place?

A

Nucleus

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46
Q

What happens in the lysosome?

A

Degradation of complex macromolecules

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47
Q

Km is equal to the substrate concentration at which the reaction velocity is…

A

1/2 Vmax

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48
Q

True or False
Km varies with the enzyme concentration

A

FALSE it does not vary

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49
Q

If an enzyme has high affinity, will the Km be low or high?

A

High affinity = low Km

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50
Q

If the velocity of a reaction is nearly proportional to the substrate concentration what order reaction would we have?

A

First order

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51
Q

If the velocity of the reaction is constant or equal to Vmax what order reaction would we have?

A

Zero order

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52
Q

If the rate of the reaction is independent of the substrate concentration what order reaction do we see?

A

Zero order

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53
Q

In what order reaction would adding substrate have no effect on the reaction?

A

Adding substrate to Zero Order would have no effect because all of the enzymes are already bound/saturated

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54
Q

What kind of curve is seen by the Michaelis-Menten Constant?

A

Hyperbolic curve

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55
Q

What kind of curve would be seen with Allosteric enzymes?

A

Singmoidal

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56
Q

What kind of curve would hemoglobin binding to O2 show?

A

Allosteric/Sigmoidal

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57
Q

Does Myoglobin show Michaelis-Menten or Sigmoidal?

A

Michaelis-Menten (Hyperbolic curve)

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58
Q

What has a higher affinity for oxygen, hemoglobin or myoglobin?

A

Myoglobin has a higher affinity for oxygen.

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59
Q

Why is it beneficial for hemoglobin to have a low affinity for oxygen?

A

Because it needs to be readily unbound from hemoglobin so that it can be delivered and released to other areas of the body.

60
Q

What is the purpose of the Lineweaver-Burk plot?

A

To more accurately visualize Km and Vmax

61
Q

What is the optimal temperature for most mammalian enzymes?

A

35-40C (95-104F)

62
Q

What are the two forms of reversible inhibition?

A

Competitive and Non-competitive

63
Q

What mode of inhibition is seen with covalent bonds?

A

Irreversible

64
Q

What mode of inhibition is seen with non-covalent bonds?

A

Reversible

65
Q

What kind of inhibitor would bind to the same site the substrate normally would bind?

A

Competitive Inhibitor

66
Q

How is competitive inhibition reversed?

A

Increasing substrate

67
Q

How does Competitive Inhibition effect Km and affinity?

A

It increases Km, reducing affinity because more substrate is needed to reach 1/2 Vmax

68
Q

When looking at a Lineweaver-Burk Plot, if 1/Vmax is unchanged, but 1/Km is higher, what kind of inhibition is indicated?

A

Competitive Inhibition

69
Q

What type of inhibitor binds at the allosteric site?

A

Noncompetitive Inhibitor

70
Q

How do Non-Competitive Inhibitors cause inhibition?

A

They bind to the allosteric site, causing conformational changes in the enzyme or active site.

71
Q

When looking at a Lineweaver Burk Plot, if 1/Vmax is increased, what type of inhibitor is present?

A

Non-Competitive inhibitor

72
Q

If the Km is unchanged, what kind of inhibition is seen?

A

Non-competitive

73
Q

Why does Km remain unchanged with Non-Competitive Inhibition?

A

Because the inhibitors do not interfere with the binding of substrate to enzyme since they are binding to an allosteric site.

74
Q

How do B-Lactam antibiotics, such as penicillin and amoxicillin, help to treat infections?

A

They act by inhibiting enzymes that synthesize bacterial cell walls.

75
Q

How do ACE inhibitors work?

A

They block the enzyme that cleaves angiotensin I into the potent vasoconstrictor antiotensin II, this causes vasodilation which lowers the BP

76
Q

What irreversibly inhibits prostaglandin and thromboxane synthesis?

A

Aspirin

77
Q

What type of inhibitor does Statin act as?

A

Competitive

78
Q

Drug that acts to lower plasma cholesterol levels by preventing De Novo Synthesis, acts as an analog to the enzyme’s natural substance

A

Statin

79
Q

The catalytic activity of many enzymes depends on the presence of these small, non-protein molecules, also called “helpers”

A

Cofactors

80
Q

What are the two groups of cofactors?

A

Inorganic metals
Small organic molecules (coenzymes)

81
Q

What are the tightly bound (covalently bonded) cozenzymes?

A

Prosthetic groups

82
Q

Heme is an example of what type of coenzyme?

A

Prosthetic group (tightly bound)

83
Q

What are the loosely bound coenzymes?

A

Co-substrates

84
Q

Coenzymes are associated with the enzyme’s ______ _______ that assist with their catalytic function

A

Active Site

85
Q

Why is biotin an important coenzyme?

A

Attaches to a distinct lysine residue in histones, affecting chromatin structure and mediating gene regulation (epigenetic modification)

86
Q

What is the inactive precursor in an enzymatic reaction?

A

Zymogen/Proenzyme

87
Q

What activates zymogen?

A

Proteolytic cleavage of peptide bonds

88
Q

Where does proteolytic cleave generally take place in the body?

A

Golgi apparatus, when inside secretory vesicles, or at the site of action of the enzyme (i.e. digestive enzymes)

89
Q

Why does the pancreas secrete zymogen?

A

To prevent enzymes from digesting proteins in the cells in which they are synthesized.

90
Q

True or False
ATP is needed for proteolytic cleavage

A

FALSE
No ATP is needed

91
Q

Is proteolytic cleavage reversible or irreversible?

A

Irreversible and occurs only once.

92
Q

What is an example of accidental zymogen activation?

A

When the secretion duct in the pancreas is blocked by a gallstone, resulting in acute pancreatitis

93
Q

True or False
Only proteins located inside cells can be activated by proteolytic cleavage

A

False - those located OUTside of the cells can be activated.

94
Q

What are 4 zymogens synthesized in the pancreas?

A

Chymotrypsinogen
Trypsinogen
Procarboxypeptidase
Proelastase

95
Q

What zymogen is synthesized in the stomach?

A

Pepsinogen

96
Q

Where are pepsinogens converted into pepsins?

A

Gastric lumen

97
Q

What are two steps that can regulate enzyme activation in the gastric glands?

A

Parietal cells secreting HCl
Chief cells secreting Pepsinogen (zymogen)

98
Q

If the goal was to increase blood coagulation, would vitamin K or Warfarin be used and why?

A

Vitamin K because it is the coenzyme for synthesis of blood coagulation factors (II, VII, IX, X)

99
Q

What drug reduces blood clot formation and competes irreversibly with the liver enzyme, epoxy reductase complex?

A

Warfarin

100
Q

How is Warfarin related to Vitamin K?

A

It reduces the activation of vitamin K

101
Q

What do the proteolytic enzymes, caspases, do?

A

Mediate apoptosis (programmed cell death)

102
Q

What is the precursor (zymogen) form of caspase?

A

Procaspase

103
Q

How is apoptosis different from necrosis?

A

Apoptosis does not cause cell inflammation and is highly regulated

104
Q

What is the function of caspase?

A

To cause cell death in multicellular organisms, producing special cell fragments (apoptotic bodies) which are cleared by macrophages

105
Q

What do executioner caspases do?

A

Kill the cell by degrading proteins indiscriminately

106
Q

True or False
Once apoptosis has been started it can not be stopped

A

True

107
Q

What are the pathways that can initiate apoptosis?

A

Intrinsic and Extrinsic

108
Q

What are some other roles of zymogens in biology?

A

Developmental processes (i.e. metamorphosis of a tadpole into a frog)
Conversion of procollagenase into collagenase in the remodeling process (i.e. formation of hands/fingers)

109
Q

What are three mechanisms for regulating enzyme activity and which are reversible vs irreversible?

A

Cofactors/Cosubstrates - Reversible
Zymogens/Proenzymes - Irreversible activation
Enzyme activation cascades - Irreversible once started

110
Q

In allosteric activation, when does the active site become available to the substrate?

A

When a regulatory molecule binds to a different site on the enzyme

111
Q

In allosteric deactivation, when does the active site become unavailable to the substrate?

A

When a regulatory molecule binds to a different site on the enzyme

112
Q

Allosteric enzymes change their shape based on what?

A

The binding of an effector

113
Q

Effectors bind ________ at a site other than the active site

A

Non-covalently

114
Q

What will a positive effector do to enzyme activity?

A

It will increase enzyme activity

115
Q

What will a negative effector do to enzyme activity?

A

It will decrease enzyme activity

116
Q

True or False
Effectors have no influence on affinity of an enzyme for its substrate

A

False. Effectors CAN influence affinity

117
Q

What is an example of a homotropic allosteric protein?

A

Hemoglobin

118
Q

What is a homotropic effector?

A

When the substrate itself serves as an effector

119
Q

What is an effector?

A

Modifier/regulator

120
Q

What is a heterotropic effector?

A

When an effector is different from the substrate

121
Q

Feedback inhibition of a metabolic pathway (end-product inhibition) is a classical example of what?

A

Heterotropic effector

122
Q

Covalent modifications usually involve the addition or removal of what?

A

Phosphate groups from specific amino acids of enzymes (Ser, Try, Thr)

123
Q

How are phosphorylation reactions catalyzed?

A

By kinases using ATP as a phosphate donor

124
Q

True or False
Covalent modifications are irreversible

A

False - they are reversible

125
Q

Induction or repression of protein synthesis are ______ compared with allosteric or covalent regulations

A

Slow (hours to days)

126
Q

What regulator events occur immediately in enzyme regulation?

A

Substrate inhibition
Product inhibition
Allosteric regulation (control enzyme kinetics)
Covalent modification (turn enzyme on or off)

127
Q

What regulator event results in changes to velocity (Vo)?

A

Substrate inhibition

128
Q

What regulator event results in changes in Vmax and/or Km?

A

Product inhibition and Covalent modifications

129
Q

What regulator event results in changes in Vmax and/or K(0.5)?

A

Allosteric control

130
Q

What regulator event results in change in amount of enzyme?

A

Synthesis or degradation of enzyme

131
Q

All of the following are characteristics of enzymes except
a) High degree of specificity
b) Mediators for almost all chemical reactions
c) Can bind to several substrates
d) Proteins can act as catalysts of reactions

A

C) Can bind to several substrates
–> No because they are highly specific

132
Q

True or False
Allosteric enzymes have only an active site for substrate binding

A

False
They have an allosteric site for binding as well

133
Q

Which of the following is NOT true of transition states:
a) Stabilized by enzymes
b) It is the form the substrate takes before it becomes a product
c) Highest energy point
d) Form enzyme must take to lower activation energy

A

D) Form enzyme must take to lower activation energy
—> No it is the form the SUBSTRATE must take to lower activation energy

134
Q

What do proteases degrade?
a) Cellulose
b) Proteins
c) Lipids
d) All of the above

A

b) Proteins

135
Q

True or False
The ligase class of enzymes do not require energy

A

FALSE- they DO require energy

136
Q

Which classes of enzymes are responsible for adding phosphate groups? (There are two correct answers)
a) Polymerase
b) Phosphorylase
c)Hydrolase
d) Kinase

A

B, D

137
Q

True or False
For first order reactions the velocity of the reaction is constant and equal to Vmax

A

False

138
Q

True or False
Hemoglobin follows allosteric enzyme kinetics while myoglobin follows Michaelis-Menten?

A

True

139
Q

True or False
Myoglobin has higher affinity for oxygen than hemoglobin because it has a lower Km value?

A

True

140
Q

Why do allosteric enzymes display a sigmoidal curve?

A

Because binding of one substrate increases the enzymes affinity for more substrates

141
Q

True or False
Vmax is lowered in non-competitive inhibition

A

True

142
Q

Which of the following factors does NOT affect reaction velocity?
a) Temperature
b) Concentration of substrate
c) pH
d) Chemical bonds
e) All of them affect velocity

A

d) Chemical bonds

143
Q

True or False
Adding more substrate will reverse the effects of noncompetitive inhibition

A

False

144
Q

Which of the following are derived from vitamins?
a) Essential ions
b) Cofactor
c) Coenzyme
d) Zymogen

A

C) Coenzyme

145
Q

Which of the following does NOT apply to Zymogens?
a) Cleavage requires ATP
b) Pancreas secretes zymogen granules
c) Activated by proteolytic cleavage
d) Inactive precursors for enzymes

A

a) Cleave requires ATP
–> it does NOT require ATP

146
Q

True or False
Apoptosis is involved in development of fingers?

A

True

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