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Biochem lab > Midterm > Flashcards

Midterm Flashcards

1
Q

catalysts for biological reactions

A

enzymes

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2
Q

Enzymes can become inactive when they coagulate during:

A 
Heating
Treatment with: 
alcohol
salts of heavy metals
acids and bases
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3
Q

inorganic or organic substance which speeds up the rate of a chemical reaction without itself entering the reaction

A

Catalyst

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4
Q

organic catalysts made of protein

A

Enzymes

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5
Q

How do enzymes catalyze?

A

They lower the activation energy needed to start the chemical reaction

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6
Q

Enzymes begin to be destroyed at:

A

above 45 degrees Celsius

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7
Q

The enzyme must form a _________ with the substance or substances whose reaction rate it affects

A

temporary association

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8
Q

The association between enzyme and substrate is thought to form a close physical association between the molecules and is called-

A

enzyme-substrate complex

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9
Q

While the enzyme-substrate complex is formed,

A

enzyme action takes place

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10
Q

Upon completion of the reaction, the enzyme and product(s)-

A

separate

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11
Q

molecules upon which an enzyme acts

A

substrate

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12
Q

The enzyme is shaped so that it can only lock up with-

A

a specific substrate molecule.

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13
Q

Each enzyme is specific for

A

one and only one substrate

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14
Q

Source of catalase

A

potato

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15
Q

Role of catalase

A

Decomposition of hydrogen peroxide

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16
Q

Source of glutatione

A

animal cells

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17
Q

Role of glutathione

A

Protects red cells from oxidation damage

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18
Q

Source of oxidase

A

living cells

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19
Q

Role of oxidase

A

Oxidizes carbohydrates, fats and proteins

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20
Q

Enzymes end in

A

-ase

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21
Q

Enzymes that identify reacting substance:

A

sucrase-reacts sucrose

lipase - reacts lipid

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22
Q

Enzymes that describe function of enzyme

A

oxidase-catalyze oxidation

hydrolase - catalyze hydrolysis

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23
Q

Common names of digestion enzymes use:

A

-in

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24
Q

Examples of digestion enzymes

A

pepsin, trypsin, chymotrypsin

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25
Q

Classifications of Enzymes

A 
Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligases
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26
Q

Reaction catalyzed by oxidoreductases

A

oxidation-reduction

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27
Q

Reaction catalyzed by Transferases

A

transfer group of atoms

movement of a functional group from one molecule to another

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28
Q

Reaction catalyzed by Hydrolases

A

hydrolysis

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29
Q

Reaction catalyzed by Lyases

A

add/remove atoms to/from a double bond

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30
Q

Reaction catalyzed by Isomerases

A

rearrange atoms

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31
Q

Reaction catalyzed by Ligases

A

combine molecules using ATP

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32
Q

LER

A

reducing agent (redox)

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33
Q

GEO

A

oxidizing agent

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34
Q

basic reaction of Transferases

A

AX + B ——> A + BX

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35
Q

Lyases catalyze the cleavage of:

A

C-C, C-O,C-S and C-N bonds by any other means than hydrolysis or oxidation

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36
Q
  • the reduction of methylene blue to methylene white by formaldehyde is rapidly catalyzed by fresh milk but not by boiled milk
  • an example of oxidation in the absence of O2 with an organic hydrogen acceptor
A

Schardinger Reaction

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37
Q

catalyzing enzyme present in Schardinger reaction

A

xanthine oxidase

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38
Q

organic hydrogen acceptor in Schardinger reaction

A

methylene blue

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39
Q

Reactants in TT1

A

Boil –> Methylene Blue –> mix –> paraffin oil –> water bath

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40
Q

Reactants in TT2

A

Methylene Blue –> formalin –> mix –> paraffin oil –> water bath

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41
Q

Reactants in TT3 (Control)

A

Methylene blue –> mix –> paraffin oil –> water bath

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42
Q

Reaction in TT1

A

Light blue

did not decolorize after heating

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43
Q

Reaction in TT2

A

Light blue

decolorizes after to white heating

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44
Q

Reaction in TT3 (Control)

A

Light blue

decolorizes to white after heating

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45
Q
  • is a compound containing three amino acids
  • an antioxidant in the body
  • vital component in the destruction of free radicals
  • detoxification of harmful substances within the body
A

glutatione

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46
Q

three amino acids in glutathione

A

glutamate
cysteine
glycine

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47
Q
  • Test used for detecting the presence of free thiol groups of cysteine in proteins
  • used for the identification of ketones in urine testing
A

Nitroprusside Reaction

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48
Q

The color that indicates positive result in Nitroprusside Test

A

red

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49
Q

Factors that affect the speed of decomposition of hydrogen peroxide by catalase:

A

concentration of catalase
concentration of hydrogen peroxide
hydrogen ion concentration
temperature

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50
Q

reaction involved in liver catalase

A

absorption of hydrogen peroxide at the catalase surface

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51
Q

The optimum pH of catalytic decomposition of H2O2

A

6.8 - 7.0

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52
Q

Reaction in liver catalase

A

Liver + H2O ——> H2O + O2 (bubbles)

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53
Q

Roles of catalase in liver

A
  • common antioxidant enzyme
  • helps body break down H2O2, thus prevents accumulation of CO2 bubbles in the blood
  • very potent enzyme; can decompose millions of H2O2
  • uses H2O2 to oxidize harmful toxins
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54
Q

Potentially harmful toxins oxidized by H2O2

A

formaldehyde
formic acid
alcohol
phenol

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55
Q

chemicals used in Nitroprusside test

A

sodium nitroprusside

ammonium hydroxide

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56
Q

the substance added to the mixture of milk and methylene blue to prevent oxygen from reacting with oxidase

A

paraffin oil

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57
Q

The compound responsible for the rapid reduction of methylene blue to methylene white in the presence of the enzyme present in milk

A

formaldehyde

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58
Q

It is a group present in proteins that is being liberated in Nitroprusside Reaction for Glutathione to indicate a positive result

A

thiol

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59
Q

It is an enzyme from potato responsible for the decomposition of hydrogen peroxide

60
Q

Source of catalase in animal enzyme activity

61
Q

Source of specimen for vegetable/fruit oxidase and catalase:

A

potato
guava
chico
apples

62
Q

oxidizes carbohydrates, fats and proteins (main source of body energy)
found in living cells

63
Q
  • a biochemical process in which fruit or vegetable tissues turn brown when exposed to oxygen
  • one of the most important color reactions that affects fruits, vegetables and seafood
  • can adversely affect flavor and nutritional value
A

Enzymatic browning

64
Q

Enzymatic browning is catalyzed by:

A

polyphenol oxidase or phenolase

65
Q

Enzymatic browning takes place at:

A

warm temperature

pH 5.0 - 7.0

66
Q

Enzymatic browning can economically benefit:

A

tea, coffee, cocoa, chico

67
Q

Enzymatic browning can economically jeopardize:

A

fruits and vegetables

68
Q

in the presence of oxygen from the air, this enzyme catalyzes the formation of brown pigments called melanin

69
Q

Ways to reduce enzymatic browning

A
  1. Treatment of slices with organic substances such as ascorbic acid, citric acid or acetic acid
  2. Soaking in plain water
  3. Heating
70
Q
  • acts as an antioxidant
  • oxygen preferentially reacts with this rather than phenolic compounds in the fruit or vegetable
  • browning does not proceed until all of it is used up in the reaction
  • reacts with melanin to bleach them
A

ascorbic acid

71
Q

lower the pH of the fruit tissue to retard the action of phenolase

A

Citric and acetic acid

72
Q

pH where phenolase will be deactivated

73
Q

restricts the amount of oxygen in contact with apple tissue

A

soaking in plain watter

74
Q

cannot be used as treatment for fruits which will be served fresh

75
Q

TT1 Potato Oxidase (Phenol)

A

During Exp: Cloudy

Next Lab Period: Red/brown

76
Q

TT2 Potato Oxidase ( Pyrogallol)

A

During Exp: colorless

Next lab period: From colorless to purple because it absorbed oxygen from air

77
Q

toxic white with slightly pink shade crystalline solid

78
Q

phenol is also known as

A

carbolic acid

79
Q

formula of phenol

80
Q

white crystalline powder

powerful reducing agen

A

Pyrogallol

81
Q

formula of pyrogallol

82
Q

uses of pyrogallol

A

hair drying

developing agent in black and white photos

83
Q

an enzyme that catalyzes the reduction of H2O2 liberating O and H2O

84
Q

Reagents in TT1 Vegetable catalase

A

potato extract

H2O2

85
Q

Reagents in TT2 Vegetable Catalase

A

boiled potato extract

H2O2

86
Q

Reagents in TT3 (control) vegetable catalase

A

Water

H2O2

87
Q

Reaction in TT1 Vegetable catalase

A

produced bubbles

88
Q

Reaction in TT2 Vegetable catalase

A

did not produce bubbles

89
Q

Reaction in TT3 Vegetable catalase

A

does not produce bubbles

90
Q

Factors that influence enzyme activity

A 
concentration of enzyme
concentration of substrate
pH
Inorganic salts of heavy metals
Presence of activators (co-enzymes) and inhibitors (anti-enzymes)
91
Q

Tests for Carbohydrates

A 
Iodine Test
Fehling's Test
Benedict's Test
Barfoed's Test
Picric acid Test
Seliwanoff's Test
Moore's Test
Molisch's Test
Trommer's Test
Mucic Acid Test
92
Q
  • specific test for starch

- test for dextrin

A

Iodine test

93
Q

Reagent composition and color of Iodine test

A

Iodine

brown

94
Q

Positive result in Iodine Test

A

Starch - dark blue

Dextrin - purple

95
Q
  • test for sugar

- tests the presence of aldehydes but not ketones

A

Fehling’s test

96
Q

Reagent composition and color of Fehling’s test

A

A - CuSO4
B- NaOH + Na K Tartrate

Dark blue

97
Q

Positive result of Fehling’s test

A

Brick red precipitate

98
Q
  • sensitive test for the presence of sugar in urine

- test determine whether a monosaccharide or disaccharide is a reducing sugar

A

Benedict’s test

99
Q

Reagent composition and color of Benedict’s test

A

CuSO4 + Na Citrate + Na2CO3

Light blue

100
Q

Positive result of Benedict’s test

A

Brick red precipitate

101
Q
  • differentiates mono and disaccharides

- similar to Fehling’s test, except that different types of sugars react at different rates

A

Barfoed’s test

102
Q

Reagent composition and color of Barfoed’s Test

A 
Copper acetate (CuAc)
Acetic acid (HAc)

light blue

103
Q

Positive result of Barfoed’s test

A

Brick red precipitate

104
Q
  • test for the formation of sodium picramic acid/ picramate
A

Picric acid test

105
Q

Reagent composition and color of Picric acid test

A

Picric acid

yellow

106
Q

Positive result of Picric acid test

A

Mahogany red solution

107
Q
  • distinguishes aldose (-) from ketose (-)

- specific test for fructose

A

Seliwanoff’s test

108
Q

Reagent composition and color of Seliwanoff’s test

A

Resorcinol + HCl

yellow

109
Q

Positive result of Seliwanoff’s test

A

Cherry red compound/complex

110
Q

test based on the liberation of aldehyde

A

Moore’s test

111
Q

Reagent composition and color of Moore’s test

A

NaOH

Colorless

112
Q

Positive result of Moore’s test

A

Brown color with caramel-like odor

113
Q

general test for carbohydrates

A

Molisch’s test

114
Q

Reagent composition and color of Molisch’s test

A

alphanaphthol in alcohol layered with H2SO4

red orange

115
Q

Positive result of Molisch’s test

A

violet ring

116
Q

specific test for glucose

A

Trommer’s test

117
Q

Reagent composition and color of Trommer’s test

A

CuSO4 + NaOH

blue

118
Q

Positive result of Trommer’s test

A

glucose - red precipitate

water - black

119
Q

specific test for galactose

A

Mucic Acid test

120
Q

Reagent composition and color of Mucic Acid test

A

HNO3

colorless

121
Q

Positive result of Mucic Acid test

A

galactose - white flaked crystals

lactose - glucose interferes making fine elongated crystals

122
Q

Positive and negative results in Fehling’s test

A

Positive: glucose, maltose, fructose, lactose, galactose
negative: sucrose

123
Q

Positive and negative results in Benedict’s test

A

Positive: glucose, maltose, fructose, lactose, galactose
negative: sucrose

124
Q

Positive and negative results in Barfoed’s test

A

Positive: glucose, fructose, galactose
negative: sucrose, maltose, lactose

125
Q

Positive and negative results in Picric Acid test

A

Positive: glucose, maltose, fructose, lactose, galactose
negative: sucrose

126
Q

Positive and negative results in Seliwanoff’s test

A

Positive: sucrose, fructose
Negative: Glucose, Maltose, galactose, lactose

127
Q

Positive and negative results in Moore’s test

A

Positive: glucose, maltose, fructose, lactose, galactose
negative: sucrose

128
Q

Positive and negative results in Molisch’s test

A

all positive

129
Q
  • an intermediate product before the final change of starch into sugar
  • has same chemical formula as starch but possesses different properties
  • smaller and less complex structure to starch that is formed during hydrolysis of starch
130
Q

formula of dextrin

A

(C6H10O5)n

131
Q
  • are polyhydroxyaldehydes or polyhydroxy ketones

- substances that yield these compounds upon hydrolysis

A

carbohydrates

132
Q

means “containing several alcohol groups”

A

Polyhydroxy

133
Q

are alcohols and are also either aldehydes or ketones

A

simple carbohydrates

134
Q

Difference of Reducing sugars from non-reducing sugars

A

Reducing:

  • possess a free aldehyde or ketone
  • can reduce cupric ions to cuprous ions in Fehling’s or Benedict’s solution that precipitate out as Cu2O cuprous oxide
  • oxidized by mild oxidizing agents
135
Q

Difference of Non reducing sugars from reducing sugars

A

Non-reducing:

  • free aldehyde or ketone is lacking
  • no brick red precipitate
  • not oxidized by mild oxidizing agents
136
Q

exist in solution as an equilibrium of open chain and closed ring structures

137
Q

carbon atom that contains the C=O bond in the open chain form

A

carbonyl carbon

138
Q

the carbonyl carbon is the one which is attached to the O of the ring and an OH group

A

closed ring (cyclic)

139
Q

type of sugar that is a reducing sugar

A

all common monosaccharides

140
Q

reducing disaccharides

A

lactose and maltose

141
Q

disaccharide that is a non-reducing sugar

142
Q

common oxidizing agents used to test for the presence of a reducing sugar

A

Benedict’s solution

Fehling’s solution

143
Q

result when closed ring opens to form a chain

A

alkanal

alkanone

144
Q

sugars that are aldehydes

145
Q

sugars that are ketones

146
Q

Advantages of Benedict’s solution over Fehling’s

A
  1. Sensitive test for glucose thus used in urine test
  2. More sensitive to reducing sugars
  3. Not affected by uric acid, creatinine, chloroform, formalin which are sometimes employed as preservatives in urine

Biochem lab (3 decks)

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