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ESA 1 - Medical Cell Biology & Genetics > Session 4.1c - Pre-Reading > Flashcards

Session 4.1c - Pre-Reading Flashcards

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1
Q

How can the Henderson-Hasselbalch equation be used physiologically?

A

To calculate how the pH of a physiologic solution responds to changes in the concentration of a weak acid and/or its corresponding “salt” form.

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2
Q

How can you calculate how the pH of a physiologic solution responds to changes in the concentration of a weak acid (and/or its corresponding “salt” form)?

A

Using the Henderson-Hasselbalch equation.

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3
Q

Give an example of the use of Henderson-Hasselbalch equation physiologically.

A

In the bicarbonate buffer system, the equation predicts how shifts in the bicarbonate ion concentration [HCO3-] and CO2 influence pH (Figure 1.12A).

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4
Q

What is the bicarbonate buffer system physiologically?

A

Shifts in the bicarbonate ion concentration [HCO3-] and CO2 influence pH, which can be determined via the Henderson-Hasselbalch equation.

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5
Q

How can the Henderson-Hasselbalch equation be used pharmacologically?

A

The equation is also useful for calculating the abundance of ionic forms of acidic and basic drugs.

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6
Q

How can the abundance of ionic forms of acidic and basic drugs be calculated pharmacologically?

A

Via the Henderson-Hasselbalch equation.

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7
Q

What are most drugs in the form of?

A

Weak acids or weak bases (Figure 1.12B).

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8
Q

Most drugs are either weak acids or weak bases.

True or False?

A

True

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9
Q

How do acidic drugs work?

A

Acidic drugs (HA) release a proton (H+), causing a charged anion (A-) to form.

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10
Q

What type of drugs release a proton (H+), causing a charged anion (A-) to form?

A

Acidic drugs

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11
Q

What is the equation for acidic drug dissociation?

A

HA H+ + A-

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12
Q

What does this depict pharmacologically?

HA H+ + A-

A

Acidic drug dissocation

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13
Q

Figure 1.12A

Label and caption the image

A

The Henderson-Hasselbalch equation is used to predict changes in pH as the concentrations of HCO3- or CO2 are altered

A - BICARBONATE AS A BUFFER
- pH = pK + log [HCO3-]/[CO2]
- An increase in HCO3- causes the pH to rise.
- Pulmonary obstruction causes an increase in carbon dioxide and causes the pH to fall, resulting in respiratory acidosis.
LUNG ALVEOLI

CO2 + H2O H2CO3 H+ + HCO3-

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14
Q

How does pulmonary obstruction cause respiratory acidosis?

A

Pulmonary obstruction causes an increase in carbon dioxide and causes the pH to fall, resulting in respiratory acidosis.

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15
Q

Is an increase in CO2 more acidic or alkaline?

A

Acidic (and therefore an increase in CO2 decreases pH, and therefore would cause acidosis)

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16
Q

What is the equation relating carbon dioxide and bicarbonate ions?

A

CO2 + H2O H2CO3 H+ + HCO3-

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17
Q

What is the Henderson-Hasselbalch equation for bicarbonate and carbon dioxide?

A

pH = pK + log [HCO3-]/[CO2]

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18
Q

What does an increase in HCO3- do to the pH?

A

Causes it to rise

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19
Q

Fig. 1.12B

Label and caption the image

A

The Henderson-Hasselbalch equation is used to predict the ionic forms of drugs.

DRUG ABSORPTION

  • pH = pK + log [Drug-]/[Drug-H]
  • At the pH of the stomach (1.5), a drug like aspirin (weak acid, pK = 3.5) will be largely protonated (COOH) and, thus, uncharged.
  • Uncharged drugs generally cross membranes more rapidly than charged molcules.

STOMACH
Lipid membrane
LUMEN OF STOMACH
BLOOD

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20
Q

What is the Henderson-Hasselbalch equation for drugs?

A

pH = pK + log [Drug-]/[Drug-H]

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21
Q

What is the pH of the stomach?

A

1.5

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22
Q

What type of drug is aspirin?

A

A weak acid, pK = 3.5

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23
Q

How will a drug like aspirin fare in the stomach?

A

At the pH of the stomach (1.5), a drug like aspirin (weak acid, pK = 3.5) will be largely protonated (COOH) and, thus, uncharged.

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24
Q

What is the significance of aspirin being uncharged in the stomach?

A

Uncharged drugs generally cross membrane more rapidly than charged molecules.

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25
Q

What can weak bases release?

A

Weak bases (BH+) can also release a H+.

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26
Q

As well as weak acids, H+ can also be released from __?

A

Weak bases (BH+).

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27
Q

What is the difference in the weak base and weak acid protonated form?

A

The protonated form of basic drugs is usually charged, and the loss of a proton produces the uncharged base (B).

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28
Q

When is a base charged and uncharged

A

Protonated form - charged (BH+)

Deprotonated form - uncharged (B)

(contrast to acids
protonated form HA uncharged; deprotonated form A- charged)

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29
Q

What is the equation for weak base dissociation?

A

BH+ B + H+

B for base; in acids HA H+ + A- A represents acid

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30
Q

What does this represent?

BH+ B + H+

A

Weak base dissociation

Weak base dissociation = HA H+ + A-, where A represents acid and B represents base.

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31
Q

Drugs pass through membranes more readily if they are ________.

A

Uncharged

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32
Q

Uncharged drugs pass through membranes more ______

A

Readily

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33
Q

How is aspirin able to pass through the membrane?

A

It is a weak acid, so the uncharged HA can permeate through membranes and A- cannot.

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34
Q

Why can HA (weak acid, e.g. aspirin) pass through membranes but A- (conjugate “salt” form) cannot?

A

HA is uncharged and can therefore permeate through membranes.

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35
Q

Give an example of a weak base.

A

Morphine

36
Q

Can morphine pass through membranes?

A

Morphine is a weak base, so its uncharged form (B) can but its charged form (BH+) cannot.

37
Q

Morphine is a weak ____

A

Base

38
Q

How does morphine travel in the cell?

A

Its uncharged form, B, can pass through membranes but BH+ cannot

39
Q

Charged or uncharged molecules can pass through membranes?

A

Uncharged

40
Q

How is the effective concentration of the permeable form of each drug at its absorption site (e.g. a membrane) determined by?

A

The relative concentrations of the charged and uncharged forms.

41
Q

What can knowing the relative charged and uncharged forms of each drug tell you?

A

The effective concentration of the permeable form of each drug at its absorption site

42
Q

How is the ratio between the two forms of molecule (charged or uncharged) determined?

A
  • By the pH at the site of absorption
    and
  • By the strength of the weak acid or base (which is represented by the pKa of the ionisable group).
43
Q

The pH and the pKa (strength) of a molecule determines what?

Use this information to apply it biologically and pharmacologically.

A

The ratio between the amount of charged and uncharged molecule, and therefore that determines the amount of drug that can permeate an absorption site, e.g. a membrane.

44
Q

How is the strength of a weak acid or base determined?

A

By the pKa of the ionisable group

45
Q

What does the pKa of an ionisable group give you?

A

The strength of a weak acid or base.

46
Q

How can the Henderson-Hasselbalch equation be used pharmacologically?

A

It determines how much drug is found on either side of a membrane that separates two compartments with differing pH, e.g.,

  • stomach (pH 1.0 - 1.5)
  • blood plasma (pH 7.4)
47
Q

How can you work out how much drug is found on either side of a membrane that has differing pH either side?

A

Via the Henderson-Hasselbalch equation

48
Q

What is the pH of the stomach?

A

1.0-1.5

Acidic

49
Q

What is the pH of blood plasma?

A

7.4

Normal

50
Q

Given an example of a body location with acidic pH, e.g. 1.0-1.5

A

Stomach

51
Q

Given an example of a body location with normal body pH, 7.4

A

Blood plasma

52
Q

(What is a concept map?)

A

A tool for visualising connections between concepts

They function as templates or guides for organisation information, so new information can be integrated into knowledge they already possess.

53
Q

(How are concept maps represented?)

A

In a hierarchic fashion, with the most inclusive, most general concepts at the top of the map, and the more specific, less general concepts arranged beneath.

The size of the type indicates the relative importance of each idea.

54
Q

(Define a concept.)

A

Perceived regularities in events or objects/.

55
Q

Give examples of concepts.

A

In biochemical maps, concepts include

  • abstractions (e.g. free energy)
  • processes (e.g. oxidative phosphorylation)
  • compounds (e.g. glucose 6-phosphate)
56
Q

(What is the layout of concept boxes?)

A

Broadly defined concepts are prioritised with the central idea positioned at the top. Concepts that follow from this central idea are then drawn in boxes (Figure 1.13A).

57
Q

(How are concept boxes formatted?)

A

The size of the type indicates the relative importance of each idea.

58
Q

(What do lines between concept boxes represent?)

A
  • Lines between concept boxes show which are related
  • The label on the line defines the relationship, i.e. makes it a valid statement
  • The arrowheads indicate which direction the connection should be read (Figure 1.14)
59
Q

Figure 1.13A (Symbols used in concept maps)

Draw a linked concept box for amino acids and protons.

A

Linked concept boxes

Amino acids (fully protonated)
–can–>
Release H+

60
Q

Figure 1.13B (Concepts cross-linked with a map)

Draw a cross-linked map to describe amino acid synthesis and protein degradation in the body.

A

Concepts cross-linked within a map

[Amino acid pool]
--is produced by-->
[Degradation of body protein] -->
[Simultaneous synthesis and degradation]
--leads to-->
[Protein turnover]
[Amino acid pool]
--is consumed by-->
[Synthesis of body protein]
-->
[Simultaneous synthesis and degradation]
--leads to-->
[Protein turnover]
61
Q

Figure 1.13C (Concepts cross-linked to other chapters and to other books in the Lippincott Series)

Describe the relationship of protein folding and to diseases.

A

Concepts cross-linked to other chapters and to other books in the Lippincott Series

…how the protein folds into its native conformation [Structure of Proteins, Chapter 2]

…how altered protein folding leads to prion disease, such as Creutzfeldt-Jakon disease [Lippincott’s Illustrated Reviews - Microbiology]

62
Q

Figure 1.14

Draw a key concept map for amino acids.

A

Amino acids
are composed of:
a-Carboxyl group (-COOH) is Deprotonated (COO-) at physiologic pH
a-Amino group (-NH2) is Protonated (NH3+) at physiologic pH
Side chains (20 different ones) group as:
Non polar side chains Alanine Glycine Isoleucine Leucine Methionine Phenylalanine Proline Tryptophan Valine found In the interior of proteins that function in an aqueous environment and on the surface of proteins (such as membrane proteins) that interact with lipids
Uncharged polar side chains Asparagine Cysteine Glutamine Serine Threonine Tyrosine found On the outside of proteins that function in an aqueous environment and in the interior of membrane-associated proteins
Acidic side chains Aspartic acid Glutamic acid characterised by Side chain dissociates to -COO- at physiologic pH found (map)
Basic side chains Arginine Histidine Lysine characterised by Side chain is protonated and generally has a positive charge at physiologic pH found (map)

when protonated can Release H+ and act as Weak acids described by Henderson-Hasselbalch equation ph+pKa + log[A-]/[HA] predicts Buffering capacity predicts Buffering occurs +/- 1 pH unit of pKa predicts Maximal buffer when pH = pKa predicts pH = pKa when [Ha] = [A-]

In proteins, most a-COO- and a-NH3+ of amino acids are combined through peptide bonds –> Therefore, these groups are not available for chemical reaction –> Thus, the chemical nature of the side chain determines the role that the amino acid plays in a protein, particularly … –> … how the protein folds into its native conformation [Structure of Proteins 2]

63
Q

(Why is it important to cross-link information?)

A

To help visualise complex relationships

Figure 1.13B or Figure 1.13C

64
Q

[Chapter Summary]

What does each amino acid have?

A

An A-CARBOXYL GROUP and a primary A-AMINO GROUP

65
Q

[Chapter Summary]

What is the exception of proline in amino acids?

A

Proline has a SECONDARY AMINO GROUP (rather than a primary a-amino group)

66
Q

[Chapter Summary]

What happens to the carboxyl group at physiologic pH?

A

The a-carboxyl group is dissociated, forming the negatively charged carboxylate ion (-COO-)

67
Q

[Chapter Summary]

What happens to the amino group at physiologic pH?

A

The a-amino group is protonated (-NH3+)

Positively charged

68
Q

[Chapter Summary]

How many different amino acids are theree?

A

20 distinctive amino acids due to their SIDE CHAINS

69
Q

[Chapter Summary]

How can amino acids be classified?

A

NONPOLAR
UNCHARGED POLAR
ACIDIC or
BASIC

based on their side chain

70
Q

[Chapter Summary]

What can serve as buffers?

A

All free amino acids, plus charged amino acids in peptide chains

71
Q

[Chapter Summary]

Free amino acids and charged amino acids in peptide chains can serve as what?

A

BUFFERS

72
Q

[Chapter Summary]

What is the relationship between the pH of a solution and the concentration of a weak acid (HA) and its conjugate base (A-)

A

HENDERSON-HASSELBALCH EQUATION

73
Q

[Chapter Summary]

What does the Henderson-Hasselbalch equation describe?

A

The quantitative relationship between the pH of a solution and the concentration of a weak acid (HA) and its conjugate base (A-)

74
Q

[Chapter Summary]

Describe the range of buffering.

A

Within +/- 1 pH unit of the pKa

75
Q

[Chapter Summary]

What do you find +/- 1 pH unit of the pKa?

A

The range of buffering that can occur

76
Q

[Chapter Summary]

When is buffering maximal?

A

When pH = pKa

77
Q

[Chapter Summary]

What is the relationship of pH = pKa to buffering?

A

Buffering is maximal

78
Q

[Chapter Summary]

When does pH = pKa?

A

when [A-] = [HA]

79
Q

[Chapter Summary]

What do you get when [A-] = [HA]

A

When pH = pKa

80
Q

[Chapter Summary]

Amino acids have their a-carbon attached to four different chemical groups. What is this known as?

A

A CHIRAL or OPTICALLY ACTIVE carbon atom

81
Q

[Chapter Summary]

What are chiral or optically active carbon atoms?

A

Carbon atoms that are bound to four different chemical groups.

82
Q

[Chapter Summary]

Which is the only amino acid that is not chiral?

A

Glycine (bound to two H)

83
Q

[Chapter Summary]

Which form of amino acid is found in proteins synthesised by the human body?

A

L-form

84
Q

[Chapter Summary]

Describe the relationship of the L-form of amino acids to the human body

A

It is the only amino acid found in proteins synthesised by the human body.

85
Q

[Study Questions]

Choose the ONE correct answer

1.1. The letters A through E designate certain regions on the titration curve for glycine (shown below). Which one of the following statements concerning this curve is correct?

See graph

A. Point A represents the region where glycine is deprotonated.
B. Point B represents a region of minimal buffering.
C. Point C represents the region where the net charge on glycine is zero.
D. Point D represents the pK of glycine’s carboxyl group.
E. Point E represents the pI for glycine.

A

Correct answer = C. C represents the isoelectric point or pi, and as such is midway between pK1 and pK2 for this monoamino monocarboxylic acid. Glycine is fully protonated at Point A. Point B represents a region of maximum buffering, as does Point D. Point E represents the region where glycine is fully deprotonated.

86
Q

[Study Questions]

Choose the ONE correct answer

1.2. Which one of the following statements concerning the peptide shown below is correct

Gly-Cys-Glu-Ser-Asp-Arg-Cys

A. The peptide contains glutamine.
B. The peptide contains a side chain with a secondary amino group.
C. The peptide contains a majority of amino acids with side chains that would be positively charged at pH 7.
D. The peptide is able to form an internal disulfide bond.

A

Correct answer = D. The two cysteine residues can, under oxidizing conditions, form a disulfide bond. Glutamine’s 3-letter abbreviation is Gln. Proline (Pro) contains a secondary amino group. Only one (Arg) of the seven would have a positively charged side chain at pH 7.

87
Q

[Study Questions]

Choose the ONE correct answer

1.3. Given that the pI for glycine is 6.1, to which electrode, positive or negative, will glycine move in an electric field at pH 2? Explain.

A

Correct answer = negative electrode. When the pH is less than the pI, the charge on glycine is positive because the α-amino group is fully protonated. (Recall that glycine has H as its R group).

ESA 1 - Medical Cell Biology & Genetics (21 decks)

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