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B M B 212 > Test One > Flashcards

Test One Flashcards

1
Q

Water

A

The basis of the chemical environment of all living systems

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2
Q

pH

A

It is the negative log concentration of protons

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3
Q

The affect of pH on biomolecules

A

Acidic and basic groups of a molecule can change charge as a function of pH

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4
Q

Bronsted-Lowry Acid

A

A proton donor

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5
Q

Bronsted-Lowry Base

A

A proton acceptor

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6
Q

Strong Acids

A

Completely dissociate in water

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7
Q

Weak Acids

A

Partially dissociate and some concentration of its protonated form

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8
Q

Weak Acid Equilibrium Constant

A

Ka = [H+][A-]/[HA]

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9
Q

Buffer

A

A compound or mixture which when added to a solution helps maintain the pH of that solution at a desired value

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10
Q

Buffer System

A

Composed of a weak acid and its conjugate base - generally effective in the pH range +/- 1 unit of the pKa value for weak acid - greatest buffer capacity is obtained when the weak acid and conjugate base are found in equimolar concentration

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11
Q

Henderson-Hasselbach Equation

A

An equation that is useful for calculating the pH or determining the equilibrium constant of a weak acid buffer system
pH = pka + log[A-]/[HA]

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12
Q

Multiprotic Acids

A

Require multiple pKa’s

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13
Q

Titrant

A

Strong acid/base

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14
Q

Analyte

A

The solution the titrant is being added to

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15
Q

Titration Curve

A

A graph plotting the pH of the solution as a function of the volume of titrant added

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16
Q

Equivalence Point

A

A vertical inflection point on a titration curve - denotes the complete dissociation of components in one reaction step (moles of acid = moles of base)

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17
Q

Half Equivalence Point

A

A horizontal inflection point on a titration curve - denotes when the pH = pKa (moles of conjugate base = moles of conjugate acid)

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18
Q

Concentration

A

The amount of desired material divided by the total of the amount of that desired material plus whatever it is dissolved in or mixed with

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19
Q

Would adding 95 mL of water to known solutions changed the number of moles of NaOH required to completely titrate them?

A

No, the number of moles does not change. Adding the water dilutes the solution which causes the volume to increase and the molarity to decrease

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20
Q

Can NaCl act as a buffer? Why or why not?

A

No, NaCl cannot act as a buffer because the pH increases dramatically as soon as the NaOH was added - the pH was not maintained because NaCl dissociates so readily in water

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21
Q

Spectrophotometry

A

A technique that involves the use of a substance’s selective absorbency for identification and determination of the concentration of the substance

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22
Q

Selective Absorbance

A

The property of a substance that occurs when a light is passed through a solution of an absorbing substance certain wavelengths of light will be absorbed by the substance

23
Q

Why is the wavelength of maximum absorbency used to detect a substance?

A

The maximum wavelength is used because it helps identify the substance - if the maximum is not used there could be other values not considered that could lead to incorrect idenitification

24
Q

Beer’s Law

A

A law that states the amount of light absorbed by a solution of a substance is proportional to the concentration of the substance

25
Q

What is the importance of a blank?

A

A blank allows you to account for all of the components that you are not measuring for - it lets you directly read the absorbance values of the component of interest

26
Q

How would the slope of your standard curve change if you had used a 3 cm spectroscopy cuvette?

A

The slope would increase by a factor of 3

27
Q

What is the importance of an enzyme?

A

Enzymes are biological catalysts that help cell’s use their energy more efficiently

28
Q

What are things that can adversely affect an enzyme?

A

Changes in pH, changes in temperature, proteases, and oxidizing agents can adversely affect activity

29
Q

What are the units of enzyme activity?

A

Micromoles/min or units - it indicates that functional enzyme is present but it does not indicate how much is available or its purity

30
Q

Enzyme Activity

A

The enzyme’s ability to catalyze a reaction that is unique to that enzyme

31
Q

What are the units of protein content?

A

Milligrams

32
Q

Specific Activity

A

The units of enzyme per mg of protein

33
Q

What are the units for specific activity?

A

Units/mg

34
Q

What is the enzyme of interest in experiment 3?

A

The enzyme of interest in experiment 3 is wheat germ acid phosphatase

35
Q

What is the function of acid phosphatase?

A

Acid phosphatase catalyzes the reaction of the release of a phosphate group from many substrates (ATP, G-6-P,etc.)

36
Q

What is the first step of purification?

A

The first step of purification is soaking the wheat germ in cold distilled water - this creates a hypotonic solution so the cells will lyse and release acid phosphatase into the water - it also separates the water insoluble and soluble components

37
Q

Why does the water have to be cold and distilled?

A

It is important for the water to be cold because it will slow down the interactions between the acid phosphatase and the cellular components that could damage the enzyme

38
Q

Why are most of the solutions distilled?

A

Most of the solutions are distilled because it minimizes the interaction between the enzyme and the harmful cellular components

39
Q

Salt Fractionation

A

For this experiment we are using methanol and ammonium sulfate - salting out is a purification technique that separates proteins, lipids, carbohydrates, and DNA -

40
Q

What is the importance of 35% ammonium sulfate?

A

35% ammonium sulfate precipitates the hydrophobic proteins out of the supernatant because the ammonium sulfate ions attract the water molecules

41
Q

What is the importance of 57% ammonium sulfate?

A

57% ammonium sulfate precipitates the hydrophilic proteins our of the supernatant (including acid phosphatase)

42
Q

What is the importance of the heat treatment?

A

The heat treatment reversibly denatures acid phosphatase and irreversibly denatures the other unwanted proteins

43
Q

Dialysis

A

The process of separating smaller molecules from larger ones in solution by the use of a semipermeable membrane

44
Q

Centrifugation

A

The process if separating molecules based on their density in a solution using rotation

45
Q

Describe the acid phosphatase activity assay

A

To test the activity of acid phosphatase the substrate p-nitrophenylphosphate (PNPP) is used - acid phosphatase will cleave off a phosphate group to form p-nitrophenol (PNP) - potassium hydroxide is then added which turns PNP yellow - the resulting solution’s absorbance is then measured using a spectrophotometer - the stronger the yellow the more acid phosphatase activity

46
Q

Describe the Biuret method

A

To determine protein concentration a standard curve using bovine serum albumin is conducted - biruet reagent is then added to the aliquots and the absorbance is measured - the protein concentration can then be calculated by using the linear equation made from the standard curve

47
Q

Concentration of PNP formed

A

Concentration = absorbance/ (extinction coefficient*path length of light)

48
Q

Concentration of PNP formed per minute

A

Molarity of PNP/minutes for assay reaction

49
Q

Moles of PNP formed per minute

A

Molarity of PNP/minutes x liters in assay reaction tube

50
Q

Enzyme activity

A

Moles of PNP/minutes x 1x10^6 micromoles/moles = Units

51
Q

Level of activity attributed to the amount of enzyme used to initiate the reaction

A

Units/mL of enzyme added to assay reaction tube x dilution factor

52
Q

Total Enzyme Activity

A

Units/mL x mL of collected fraction

53
Q

Percent Recovery

A

Total enzyme activity (Sx)/Total enzyme activity (SI)

54
Q

Fold Purification

A

Specific Activity (Sx)/Specific Activity (SI)

B M B 212 (2 decks)

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