Medical Biochemistry Exam
1
Medical Biochemistry Exam
1.Describe the physical and chemical properties of water Abnormally high boiling point (100
degrees Celsius)
Abnormally high freezing point (0 degrees Celsius)
Abnormally high melting point
Solid is less dense than liquid (ice floats in liquid water)
Heat capacity
H bonding
Dipolar character
Dissociation into charged particles
2.Describe the effects of hydrogen bonding in physiological solutions Rates of enzyme
reactions
Permeabiliyy of membranes to many molecules
Stability and conformation of proteins, etc.
Rates of transport through membranes
Absorption, etc. of drugs
Hydrophobicity or hydrophilicity of a compound
3.Explain the Henderson-Hasselbach equation pH = pKa + log ([A-]/[HA])
When log = 0, pH = pKa and amount of acid/base is equal
4.Describe the role of buffers in physiology and chemistry Buffers maintain the pH, to allow
reactions to occur without upsetting the balance of the system.
Phosphate and bicarbonate: bicarbonate buffer system is more important because there is more of
it (carbonic anhydrase is important for the body)
Buffers keep pH within 1 pH unit (either side)
5.Describe the differences in metabolic and respiratory acidosis and alkalosis Metabolic
acidosis - usage of "fuels" increase in lactic acid in body, kidney excretes sulfuric acid, lactic
acid, ammonia, and phosphoric acid
Respiratory acidosis - carbonic acid to be excreted by lungs, too much CO2 in body
, Medical Biochemistry Exam
2
Respiratory alkalosis - decreased in metabolism of fuels, too much O2 due to hyperventilation,
decrease pressure of CO2
6.Describe the categories of the 20 amino acids found in proteins Simple Aliphatic
Aliphatic with hydroxyl or sulfur side chains
Aromatic
Basic
Acidic with amides
7.Describe properties of the simple aliphatic amino acids Hydrophobic character increases
with chain size.
Glycine - precursor for hemes and purines
Alanine - precursor for glucose in glyconeogensis
Valine
Isoleucine
Leucine
Proline - secondary amine, constraints on shape
*Maple syrup disease - Valine, Isoleucine, Leucine
8.Describe properties of the aliphatic amino acids containing hydroxyl groups or sulfur
Hydroxyl - modified by phosphorylation, weakly polar and hydrophilic
Serine - precursor for purines, pyrimidines, and sphingosine
Threonine
Sulfur:
Cysteine - ionize own side chain, 2 cysteines can form disulfide linkages = cystine
Methionine - source of methyl groups in biochemical pathways
9.Describe properties of the aromatic amino acids Phenylalanine - precursor for artificial
sweetener, the most hydrophobic in this grouping, PKU - mental retardation and early death
Tyrosine - synthesis of thyroid hormone, tyrokinesis, albinism, and alcapyonuria (dark urine
disease)
Tryptophan - precursor for nicotinamide nucleotides, serotonin, - lack of causes: pellagra (deficit
in Vitamin B3)
1
Medical Biochemistry Exam
1.Describe the physical and chemical properties of water Abnormally high boiling point (100
degrees Celsius)
Abnormally high freezing point (0 degrees Celsius)
Abnormally high melting point
Solid is less dense than liquid (ice floats in liquid water)
Heat capacity
H bonding
Dipolar character
Dissociation into charged particles
2.Describe the effects of hydrogen bonding in physiological solutions Rates of enzyme
reactions
Permeabiliyy of membranes to many molecules
Stability and conformation of proteins, etc.
Rates of transport through membranes
Absorption, etc. of drugs
Hydrophobicity or hydrophilicity of a compound
3.Explain the Henderson-Hasselbach equation pH = pKa + log ([A-]/[HA])
When log = 0, pH = pKa and amount of acid/base is equal
4.Describe the role of buffers in physiology and chemistry Buffers maintain the pH, to allow
reactions to occur without upsetting the balance of the system.
Phosphate and bicarbonate: bicarbonate buffer system is more important because there is more of
it (carbonic anhydrase is important for the body)
Buffers keep pH within 1 pH unit (either side)
5.Describe the differences in metabolic and respiratory acidosis and alkalosis Metabolic
acidosis - usage of "fuels" increase in lactic acid in body, kidney excretes sulfuric acid, lactic
acid, ammonia, and phosphoric acid
Respiratory acidosis - carbonic acid to be excreted by lungs, too much CO2 in body
, Medical Biochemistry Exam
2
Respiratory alkalosis - decreased in metabolism of fuels, too much O2 due to hyperventilation,
decrease pressure of CO2
6.Describe the categories of the 20 amino acids found in proteins Simple Aliphatic
Aliphatic with hydroxyl or sulfur side chains
Aromatic
Basic
Acidic with amides
7.Describe properties of the simple aliphatic amino acids Hydrophobic character increases
with chain size.
Glycine - precursor for hemes and purines
Alanine - precursor for glucose in glyconeogensis
Valine
Isoleucine
Leucine
Proline - secondary amine, constraints on shape
*Maple syrup disease - Valine, Isoleucine, Leucine
8.Describe properties of the aliphatic amino acids containing hydroxyl groups or sulfur
Hydroxyl - modified by phosphorylation, weakly polar and hydrophilic
Serine - precursor for purines, pyrimidines, and sphingosine
Threonine
Sulfur:
Cysteine - ionize own side chain, 2 cysteines can form disulfide linkages = cystine
Methionine - source of methyl groups in biochemical pathways
9.Describe properties of the aromatic amino acids Phenylalanine - precursor for artificial
sweetener, the most hydrophobic in this grouping, PKU - mental retardation and early death
Tyrosine - synthesis of thyroid hormone, tyrokinesis, albinism, and alcapyonuria (dark urine
disease)
Tryptophan - precursor for nicotinamide nucleotides, serotonin, - lack of causes: pellagra (deficit
in Vitamin B3)
