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Questions and Answers
What property of the amino acid is primarily determined by the 'R' group?
What property of the amino acid is primarily determined by the 'R' group?
- Color in solution
- Molecular weight
- Melting point
- Solubility in water (correct)
Which of the following amino acids is classified as a branched-chain amino acid (BCAA)?
Which of the following amino acids is classified as a branched-chain amino acid (BCAA)?
- Isoleucine (correct)
- Arginine
- Serine
- Lysine
In terms of polarity, which amino acid is classified as non-polar?
In terms of polarity, which amino acid is classified as non-polar?
- Isoleucine (correct)
- Serine
- Threonine
- Glycine
Which classification of amino acids is based on their metabolic fate?
Which classification of amino acids is based on their metabolic fate?
Where are hydrophobic (non-polar) amino acids typically located within a protein structure?
Where are hydrophobic (non-polar) amino acids typically located within a protein structure?
Which of the following amino acids is considered basic?
Which of the following amino acids is considered basic?
What type of side chain does aspartate possess?
What type of side chain does aspartate possess?
Which of the following amino acids is involved in maple syrup urine disease due to abnormal metabolism?
Which of the following amino acids is involved in maple syrup urine disease due to abnormal metabolism?
Which property of amino acids describes their ability to act as both acids and bases?
Which property of amino acids describes their ability to act as both acids and bases?
What configuration do all amino acids of physiological significance in the human body possess?
What configuration do all amino acids of physiological significance in the human body possess?
What is the pH at which an amino acid is in its zwitterionic form?
What is the pH at which an amino acid is in its zwitterionic form?
Which of the following amino acids is considered non-chiral?
Which of the following amino acids is considered non-chiral?
Which classification does NOT describe amino acids?
Which classification does NOT describe amino acids?
What is the main characteristic of the 20 proteinogenic amino acids?
What is the main characteristic of the 20 proteinogenic amino acids?
What happens to amino acids in an acidic solution?
What happens to amino acids in an acidic solution?
How many naturally occurring amino acids are there?
How many naturally occurring amino acids are there?
What results from the substitution of glutamate by valine in hemoglobin?
What results from the substitution of glutamate by valine in hemoglobin?
What characterizes a Zwitterion?
What characterizes a Zwitterion?
Which amino acid can form disulfide bonds to stabilize protein structure?
Which amino acid can form disulfide bonds to stabilize protein structure?
What is the effect of amino acids at their isoelectric point (pI)?
What is the effect of amino acids at their isoelectric point (pI)?
Which process is associated with the Golgi bodies?
Which process is associated with the Golgi bodies?
Which amino acid is likely to have a higher isoelectric point?
Which amino acid is likely to have a higher isoelectric point?
When does positive nitrogen balance occur?
When does positive nitrogen balance occur?
What is the main condition when nitrogen intake equals nitrogen excretion?
What is the main condition when nitrogen intake equals nitrogen excretion?
Which of the following has maximum buffering capacity?
Which of the following has maximum buffering capacity?
At what pH range do amino acids with hydrocarbon R groups typically attain their isoelectric points?
At what pH range do amino acids with hydrocarbon R groups typically attain their isoelectric points?
Which amino acids are considered semi-essential and required during positive nitrogen balance?
Which amino acids are considered semi-essential and required during positive nitrogen balance?
What can destroy disulfide bonds and denature proteins?
What can destroy disulfide bonds and denature proteins?
Why are proteins considered one of the major buffering systems in the body?
Why are proteins considered one of the major buffering systems in the body?
Which statement about acidic amino acids is true?
Which statement about acidic amino acids is true?
What is an example of a condition leading to negative nitrogen balance?
What is an example of a condition leading to negative nitrogen balance?
What happens to proteins at their isoelectric point?
What happens to proteins at their isoelectric point?
Which amino acid serves as a precursor for the production of nitric oxide?
Which amino acid serves as a precursor for the production of nitric oxide?
Which amino acid is classified as non-polar?
Which amino acid is classified as non-polar?
Which of the following amino acids is a derivative of Tryptophan?
Which of the following amino acids is a derivative of Tryptophan?
What is the status of proteins that are low in one or more essential amino acids?
What is the status of proteins that are low in one or more essential amino acids?
Which amino acid is directly involved in the synthesis of GABA?
Which amino acid is directly involved in the synthesis of GABA?
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Study Notes
Introduction to Amino Acids
- Organisms, including humans, are primarily composed of four basic biomolecules: carbohydrates, proteins, lipids, and nucleic acids.
- The study of amino acids covers their structure, properties, classification, nitrogen balance, and derivatives.
Basic Characteristics of Amino Acids
- Over 300 naturally occurring amino acids identified, with 20 being proteinogenic.
- Amino acids are crucial for bodily functions, including nerve transmission and hormone synthesis.
- Physiologically significant amino acids possess L-α configuration.
Structural Properties
- All amino acids are chiral except Glycine, which is symmetrical.
- Amphoteric properties allow amino acids to act as acids or bases depending on the pH of the solution.
- At low pH, they accept protons (positively charged); at high pH, they donate protons (negatively charged).
Isoelectric Point (pI)
- A Zwitterion forms when an amino acid has equal positive and negative charges, existing at its unique isoelectric point.
- pI varies among amino acids:
- Hydrocarbon R groups: pH 5.0-7.0 (e.g., Leucine pH 6.0)
- Basic amino acids: require high pH (e.g., Arginine pH 10.8)
- Acidic amino acids: require low pH (e.g., Aspartic acid pH 3.0).
Classification of Amino Acids
- Classified based on R group properties, determining hydrophobicity, polarity, and charge.
- Categories include:
- Non-polar (e.g., Glycine, Alanine, Valine)
- Polar and charged (e.g., Histidine, Aspartate)
- Essential (e.g., Phenylalanine, Valine, Threonine) and non-essential amino acids.
Nitrogen Balance
- Normal nitrogen balance occurs when nitrogen intake equals excretion.
- Negative nitrogen balance: Intake < excretion; caused by malnutrition, starvation, or infections.
- Positive nitrogen balance: Intake > excretion; linked to growth, pregnancy, or recovery from illness.
Amino Acid Derivatives
- Key derivatives include:
- Tryptophan transforms into Serotonin, Melatonin, and Niacin.
- Tyrosine converts into Dopamine, Norepinephrine, and Epinephrine.
- Histidine is the precursor for Histamine.
- Arginine is a precursor for Nitric Oxide; Ornithine is transformed into Spermine; GABA is synthesized from L-glutamate.
Additional Notes
- Hydrophobic amino acids (e.g., Valine, Leucine) tend to be located in the core of proteins, while hydrophilic amino acids reside on the surface.
- Unique characteristics, like the branched-chain nature of certain amino acids, affect metabolism and can lead to conditions like Maple Syrup Urine Disease or Sickle Cell Anemia.
- Glycosylation in proteins occurs at specific amino acids (Serine, Threonine for O-linked; Asparagine for N-linked).
Fun Fact
- Selenocysteine is recognized as the 21st amino acid.
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