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Intro Biochem Lab > Experimental Techniques and Information > Flashcards

Experimental Techniques and Information Flashcards

1
Q

What is a buffer?

A

A solution containing a mixture of a weak acid (HA) and its conjugate base (A-) capable of resisting changes in pH upon the addition of additional acid or base.

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2
Q

What is the Henderson-Hasselbalch equation?

A

pH = pKa + log(base/acid)

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3
Q

What is the Henderson-Hasselbalch equation used for?

A

Calculating the pH of a buffer

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4
Q

Beyond what range of pH change can a buffer no longer work properly?

A

Plus or minus 1 pH

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5
Q

What does a pH meter measure?

A

It is a potentiometer that measures the potential difference between a glass electrode and a reference electrode (the calomel electrode)

Glass bulb only permeable to H ions, which are measured.

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6
Q

When titrating an amino acids, what substances are being titrated?

A
  • Amino acid

- Water in which it dissolves acts as a base

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7
Q

How can the pKa of ionizable groups on amino acids be found?

A

By titrating the amino acid and then creating a titration curve. Water should be titrated so that the effects of water can be corrected for.

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8
Q

What is the equivalence point on an amino acid titration curve?

A

An inflection point where added mmoles of acid are equivalent to the mmoles of acidic-amino group present in solution

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9
Q

Where are the two pka of neutral amino acids dissociable groups found on a titration curve?

A

Halfway between 0 mmoles HCL added and mmoles of HCL added at the equivalence point. nd an equal distance to the right of the equivalence point along the x-axis.

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10
Q

What are the axis of a titration curve?

A

x axis: mmoles of acid added

y axis: pH of solution

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11
Q

Is pKa higher for the amino group or the carboxyl group of amino acids?

A

Amino group (about 9.8)

Carboxyl group is about 2.4

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12
Q

How can you correct for the effect of water on amino acid titration? (Give formula)

A

mmol AA - (mmol H20)x(Total mL AA/total mmol H20)

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13
Q

When correcting for the effect of water on amino acid titration, are you converting mmols of of acid, mmols of AA or pH?

A

mmols of acid (eg. HCL)

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14
Q

Are most proteins soluble or insoluble in water?

A

Soluble, cells are mostly water

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15
Q

What three things can change the solubility of proteins?

A
  • Changing pH
  • Adding salts
  • Organic solvents
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16
Q

When proteins are precipitated out of a solution, do they retain their function?

A

They will usually retain their full function when the solution is diluted with water to dissolve them again

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17
Q

Does protein denaturation involve cutting covalent bonds?

A

No, denaturation does not result in a smaller protein

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18
Q

What are four ways to denature proteins?

A
  • Boiling
  • Urea
  • Organic solvents
  • Detergents
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19
Q

Is denaturation permanent?

A

Sometimes

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20
Q

What is the symbol of the dissociation constant? What is the negative logarithmic value of this constant?

A

Ka (very small number)

Negative logarithmic value is pKa

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21
Q

How many pH units above or below the pKa for a group results in an equilibrium essentially completely to the right or left?

A

2 pH units

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22
Q

What is the pKa of the carboxyl on the two acidic amino acids R group? What are these two amino acids?

A

Around 4

  • Glutamic acid
  • Aspartic acid
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23
Q

What is the pKa for the basic R groups of the three basic amino acids? What are the three basic amino acids?

A
  • Arginine and lysine: 11

- Histidine: 6

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24
Q

Every amino acid has an alpha-carboxyl group and an alpha-amino group. What are the pKas of these two groups?

A

Carboxyl: 2
Amino: 9

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25
Q

What is the isoelectric charge for a protein?

A

The pH at which the net charge of a protein is 0

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26
Q

How can the buffering capacity of a protein be observed?

A

By adding pH indicators that work in acidic or basic range and then adding acid/base. If the colour change is not very strong, then the protein is buffering against that treatment (acid or base).

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27
Q

At what UV absorption wavelength do the nitrogenous bases of DNA and RNA strongly absorb light?

A

260 nm

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28
Q

What is the hyperchromic effect in DNA?

A

Disruption of the secondary structure found in dsDNA increases UV absorption of stacked hydrogen-bonded bases. Disruption can be done by increasing the temperature, leading to an A260 closer to an equivalent number of free mononucleotides.

29
Q

What property of DNA allows the GC content to be determined?

A

Melting temperature

30
Q

DNase affects what two properties of DNA?

A
  • Viscosity

- A260

31
Q

The pores of a gel exclusion matrix become smaller as ____?

A

Pores become smaller as the number of cross-links between polymers increases.

32
Q

During column chromatography, will small molecules or big molecules be eluted first? Why?

A

Big molecules. Because smaller molecules are retained in the gel matrix in the internal fluid while large molecules remain in the external phase (void volume).

33
Q

What is a diffusate during dialysis?

A

The outside fluid that small molecules are diffusing to

34
Q

How do buffers of differing ionic strength effect electrophoresis outcomes?

A

A low ionic strength buffer allows charge molecules to travel faster, but with less resolution than a highly ionic buffer.

35
Q

What are three factors which increase electrophoretic separation?

A
  • Higher voltage
  • More time allowed
  • Shorter distance between electrodes
36
Q

What is the potential gradient of electrophoresis? What are the units?

A

The voltage drop divided by the distance between the electrodes. The units for this are V/cm

37
Q

What does salivary amylase digest (be specific)?

A

The α(1-4) glycosidic bonds between glucose residues in amylose (straight chain) and amylopectin (branched) of starch.

38
Q

What are the two products of amylose digestion?

A

Glucose and maltose

39
Q

What are products of amylopectin and glycogen (starch) digestion?

A
  • Glucose
  • Maltose
  • Isomaltose
  • Dextrins
40
Q

What is special about dextrins?

A

They contain both α(1 - 4) and α(1 - 6) glycosidic bonds

41
Q

How does iodine detect starch?

A

Winding of a left-handed helix of amylose around clusters of iodine atoms forms the dark blue iodine-starch complex

42
Q

What is an enzyme unit (U)?

A

The amount of enzyme that will catalyze the use of 1 umol of substrate (or the formation of 1 umol of product) per minute in a reaction under defined conditions.

43
Q

How is the enzyme unit (U) usually expressed?

A

U/mL

44
Q

What is the specific activity of enzymes?

A

THe number of enzyme units (U) per mg of total protein (U/mg)

SA = U/mg protein

45
Q

True or false? The more purified an enzyme preparation is, the greater its specific activity is.

A

True

46
Q

Why does the velocity value of enzyme level off over time? (5)

A
  • Denaturation of enzyme
  • Product inhibition
  • Substrate depletion
  • Inactivation of coenzyme
  • Increase of the reverse reaction at the product concentration builds
47
Q

When is the velocity of an enzyme reaction measured?

A

Only at the very beginning of a reaction

Enzyme studies only use initial velocity

48
Q

Why does iodine form a lighter coloured solution with glycogen than it does with starch?

A

Because glycogen is branched, meaning it cannot form as tight iodine-glycogen complexes as it does for iodine-starch complexes

49
Q

When lactic acid dehydrogenase converts pyruvate to lactate, is it oxidizing or reducing its cofactor NADH?

A

Oxidizing

50
Q

under anaerobic conditions, which direction is LDH working in?

A

Reducing pyruvate to lactate

51
Q

In the case of lactic acid dehydrogenase, how is Keq calculated? (give formula)

A

Keq = [lactate][NAD+] / [pyruvate][NADH]

52
Q

At what point of enzyme activity does free energy change apply to?

A

The equilibrium

53
Q

How can free energy change be calculated with the equilibrium constant? (give formula)

A

ΔG’ = -RT(lnKeq)

54
Q

A very large Keq value likely indicates? (in terms of spontaneity)

A

A negative change in free energy and therefore a spontaneous reaction

55
Q

What is the dilution formula?

A

(V total)(C final) = (V sample)(C initial)

56
Q

What is the alanine aminotransferase reaction?

A

Alanine + α-ketoglutarate = pyruvate + glutamate

57
Q

What is the katal (kat)?

A

The amount of enzyme that converts one mole of substrate per second

58
Q

1 cal is equal to how many:

  • kcal
  • kilojoules
A
  • 1 kcal

- 4.2 kJ

59
Q

What is the basal metabolic rate? (include units)

A

kcal consumed per day (kcal/day)

60
Q

Why is the BMR adjusted lower for females?

A

Because they have more adipose tissue and therefore a slower metabolism overall.

61
Q

What is ACT? How is it calculated?

A

Activity level

BMR/24)(hours multiplied by activity level, including factors like sleep

62
Q

What is the specific dynamic effect (SDE)?

A

Energy expenditure due to food digestion. Around 8-15 %

63
Q

What is the formula to calculate TEO (total energy output)?

A

TEO = (BMR + ACT)(SDE)

64
Q

What can be used to measure body frame size?

A

Getting calipers and measure sites with little overlying tissue, such as the wrists and elbows

65
Q

How is a waist to hip ratio (WHR) determined?

A

Divide waist measurement by hip measurement

66
Q

What does an apple shape look like for women?

A

Body fat located in upper body, greater risk of heart disease and harder for conception.

67
Q

How many kcal per gram of:

  • Fat
  • Carbohydrates
  • Protein
A
  • Fat (9)
  • Carbohydrates (4)
  • Protein (4)
68
Q

What type of body fat measurement is best for people under 15% bf?

A

Skin fold calipers

Intro Biochem Lab (5 decks)

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