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2) Biochemistry II > Lab 4: Amino Acid Detection > Flashcards

Lab 4: Amino Acid Detection Flashcards

1
Q

What is a stationary phase in chromatography?

A

Solid and/or a liquid supported on a solid

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2
Q

What is a mobile phase in chromatography?

A
  • A liquid or gas

- The mobile phase flows through the stationary phase and carries the components of the mixture or chemical with it

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3
Q

In paper chromatography, should the solvent level be above or below the line with the spots (amino acids)?

A

BELOW

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4
Q

Why do we cover the container in paper chromatography?

A
  • To make sure that the atmosphere in the beaker is saturated with solvent vapour
  • Stops the solvent from evaporating as it rises up the paper
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5
Q

What happens when the solvent has migrated almost to the end?

A

The paper is dried and sprayed by ninhydrin solution

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6
Q

What is the purpose of the ninhydrin solution spray?

A

At 100oC, ninhydrin reacts with a-amino acids to form a purple colour, allowing the amino acids to be visualized

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7
Q

What is the unit of the Rf value?

A

None

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8
Q

How do you calculate the Rf value?

A

Distance of the spot on the TLC-plate/Distance of the solvent front

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9
Q

Where should you measure the amino acids spots?

A

In the middle of the coloured spots

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10
Q

How many times were the amino acids spotted? What about the unknowns?

A
  • Amino acids: 3x

- Unknown: 6x

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11
Q

What is the stationary phase in paper chromatography?

A

White, uniform, absorbent chromatography paper, composed of cellulose fibers and water

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12
Q

Why do we use cellulose in paper chromatography?

A

The OH- groups can absorb H2O vapor, rendering the stationary phase polar

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13
Q

What is the polarity of the stationary phase?

A

Polar

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14
Q

What is the polarity of the mobile phase?

A

Non-polar

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15
Q

What is the mobile phase in paper chromatography?

A

Non-polar solvent (72% organic solution, 20% diluted H2O, 8% acetic acid)

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16
Q

What controls the distance at which amino acids travel?

A
  • The solvent carries the mixtures up the paper by capillary action
  • The interactions of the compounds with the non-polar solvent and polar paper control the distance at which they travel
17
Q

What do polar amino acids display in paper chromatography? How is the distance at which it travels? How is the Rf value?

A
  • Adsorption and attraction in the polar paper
  • Low solubility in the non-polar solvent
  • Low distance
  • Low Rf value
18
Q

What do non-polar amino acids display in paper chromatography? How is the distance at which it travels? How is the Rf value?

A
  • Low adsorption to the polar paper
  • High solubility in the non-polar solvent
  • Long distance
  • High Rf value
19
Q

Is phenylalanine polar or non-polar? Why?

A
  • Non-polar

- Hydrophobic aromatic side chain (benzene ring), composed solely of Cs and Hs, justifies its non-polar nature

20
Q

Are charged amino acids polar or non-polar? Why?

A
  • Polar
  • Due to a separation in electrical charge, creating a dipole moment, allowing them to form hydrogen bonds with the polar paper
21
Q

Is lysine polar or non-polar? Why?

A
  • Polar

- Contains a second primary amino group, creating a positive (basic) charge

22
Q

Are aspartic acid and glutamic acid polar or non-polar? Why?

A
  • Polar

- Both have a second carboxyl group, creating a negative (acidic) charge

23
Q

Why does glutamic acid travel farther up the paper than aspartic acid?

A

Since glutamic acid has a longer carbon chain, which decreases its polarity

24
Q

Why is Diet Pepsi composed of? What does that make?

A
  • Phenylalanine and aspartic acid

- Aspartame (methyl ester of the amino acids linked through a peptide bond)

25
Q

How does aspartame compare to sucrose?

A

It is 200 times sweeter than sucrose

26
Q

What are the 9 essential amino acids?

A
  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
27
Q

What are the 6 conditional amino acids?

A
  • Arginine
  • Cysteine
  • Glutamine
  • Glycine
  • Proline
  • Tyrosine

2) Biochemistry II (23 decks)

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