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Questions and Answers
Which amino acid contains a thiol group important for enzyme activity?
Which amino acid contains a thiol group important for enzyme activity?
At physiologic pH, which amino acid exists in an ionized state with a positive charge?
At physiologic pH, which amino acid exists in an ionized state with a positive charge?
Which of the following amino acids is classified as acidic due to its additional carboxyl group?
Which of the following amino acids is classified as acidic due to its additional carboxyl group?
What type of bond is formed when the –SH groups of two cysteines are oxidized?
What type of bond is formed when the –SH groups of two cysteines are oxidized?
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Which of the following amino acids does NOT have a polar side chain?
Which of the following amino acids does NOT have a polar side chain?
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What is the main function of collagens in living organisms?
What is the main function of collagens in living organisms?
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Which of the following substances serve as transporters in the human body?
Which of the following substances serve as transporters in the human body?
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What type of nitrogen balance occurs during periods of growth, such as in children?
What type of nitrogen balance occurs during periods of growth, such as in children?
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Which amino acid classification includes those with non-polar side chains?
Which amino acid classification includes those with non-polar side chains?
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What defines an amino acid as a standard amino acid in mammals?
What defines an amino acid as a standard amino acid in mammals?
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What component of amino acids distinguishes them from one another?
What component of amino acids distinguishes them from one another?
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Which of the following is a characteristic of amino acids with uncharged polar side chains?
Which of the following is a characteristic of amino acids with uncharged polar side chains?
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Which protein is responsible for catalyzing biochemical reactions?
Which protein is responsible for catalyzing biochemical reactions?
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What are the three amino acids that make up glutathione?
What are the three amino acids that make up glutathione?
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Which form of glutathione removes the toxicity of hydrogen peroxide?
Which form of glutathione removes the toxicity of hydrogen peroxide?
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What type of bond is responsible for the primary structure of proteins?
What type of bond is responsible for the primary structure of proteins?
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Which method uses FDNB to determine the primary structure of proteins?
Which method uses FDNB to determine the primary structure of proteins?
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What is the term for the three-dimensional structure of proteins?
What is the term for the three-dimensional structure of proteins?
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Which of the following is a function of glutathione?
Which of the following is a function of glutathione?
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What is the bond responsible for the secondary structure of proteins?
What is the bond responsible for the secondary structure of proteins?
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Which structure of protein organization involves a specific arrangement of polypeptide chains?
Which structure of protein organization involves a specific arrangement of polypeptide chains?
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Which amino acid is not optically active due to the absence of a chiral carbon atom?
Which amino acid is not optically active due to the absence of a chiral carbon atom?
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What is the primary factor that allows proteins to absorb ultraviolet light at 280 nm?
What is the primary factor that allows proteins to absorb ultraviolet light at 280 nm?
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At its isoelectric point (pI), an amino acid carries what kind of net charge?
At its isoelectric point (pI), an amino acid carries what kind of net charge?
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Which amino acids are unable to undergo transamination reactions?
Which amino acids are unable to undergo transamination reactions?
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What happens to an amino acid in an alkaline medium?
What happens to an amino acid in an alkaline medium?
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The isoelectric point of alanine is influenced by the pKa values of which groups?
The isoelectric point of alanine is influenced by the pKa values of which groups?
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What is a zwitterion?
What is a zwitterion?
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Which of the following statements is true regarding deamination reactions?
Which of the following statements is true regarding deamination reactions?
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What type of protein is soluble in alcohol and rich in proline?
What type of protein is soluble in alcohol and rich in proline?
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Which type of conjugated protein contains nucleic acids?
Which type of conjugated protein contains nucleic acids?
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What characteristic distinguishes α-keratins from β-keratins?
What characteristic distinguishes α-keratins from β-keratins?
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Which of the following is NOT a characteristic of collagen?
Which of the following is NOT a characteristic of collagen?
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What does the rigidity of keratin primarily depend on?
What does the rigidity of keratin primarily depend on?
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What type of proteins are characterized by their solubility in dilute acids and alkalies?
What type of proteins are characterized by their solubility in dilute acids and alkalies?
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How many types of collagens are recognized?
How many types of collagens are recognized?
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Which derived protein is formed from the coagulation of proteins like fibrinogen?
Which derived protein is formed from the coagulation of proteins like fibrinogen?
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What allows elastin to recoil to its original shape after being stretched?
What allows elastin to recoil to its original shape after being stretched?
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What is the major difference in cross-linking between collagen and elastin?
What is the major difference in cross-linking between collagen and elastin?
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What protein component is primarily found in lipoproteins?
What protein component is primarily found in lipoproteins?
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Which of the following correctly distinguishes glycoproteins from proteoglycans?
Which of the following correctly distinguishes glycoproteins from proteoglycans?
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Which of the following is an example of a nucleoprotein?
Which of the following is an example of a nucleoprotein?
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What is the primary component of phosphoproteins?
What is the primary component of phosphoproteins?
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Which property distinguishes collagen from elastin?
Which property distinguishes collagen from elastin?
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What component is absent in elastin that is present in collagen?
What component is absent in elastin that is present in collagen?
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Study Notes
Proteins and Amino Acids
- Proteins are large polymers of L-amino acids
- Proteins are the most abundant and functionally important molecules in living systems.
- Main functions include structural components (collagen in bones, elastin in lungs), enzymes (pepsin, lipase, urease), hormones (growth hormone), transporters (lipoproteins, hemoglobin), blood clotting factors, receptors (insulin receptor), etc.
- Proteins also act as defense molecules (immunoglobulins), storage molecules (myoglobin), and contractile proteins (actin, tubulin).
Nitrogen Balance
- Nitrogen intake equals nitrogen loss for a healthy individual
- Nitrogen loss e.g., fasting, starvation, diabetes, diarrhea, fever, burns
- Nitrogen intake is more than loss e.g., growing children or pregnancy, body building
- 100 grams of protein contains roughly 16 grams of nitrogen
Amino Acid Classification
- Amino acids are classified based on chemical structure.
- 9 amino acids have non-polar side chains and are hydrophobic. These include Glycine, Alanine, Valine, Leucine, Isoleucine, Phenylalanine, Tryptophan, Methionine, and Proline.
- 6 amino acids have uncharged polar side chains, these are Serine, Threonine, Tyrosine, Asparagine, Glutamine, and Cysteine.
- 2 have acidic side chains (Aspartic acid, Glutamic acid).
- 3 have basic side chains (Lysine, Arginine and Histidine).
- Additional classifications include aromatic, sulfur-containing, and amide-containing.
- Twenty amino acids are commonly found in mammals. These are coded for by DNA.
Additional Information
- Non-standard amino acids which occur in human body, but are not commonly found in proteins include, D-amino acids, and derivatives like hydroxylysine, hydroxyproline, and other amino-acid derivatives
- Proteins can be hydrolyzed by heating with strong acids (e.g., HCl, H2SO4) to yield amino acids.
- Denaturation can change the structure of a protein but not the polypeptide chain
Protein Structure
- There are four organizational levels for protein structure (primary, secondary, tertiary, and quaternary).
- Primary structure is the sequence of amino acids.
- Secondary structures include alpha-helices and beta-sheets stabilized by hydrogen bonds.
- Tertiary structure describes the overall 3-D shape of the protein (e.g. globular proteins).
- Quaternary structure involves multiple polypeptide chains interacting.
- Protein structure impacts its function.
Methods of Protein Separation
- Methods such as chromatography, electrophoresis, precipitation, ultracentrifugation, dialysis are used to separate proteins.
Protein Properties
- Some proteins are water-soluble (e.g., albumin), while others are not (e.g., collagen).
- Salting in and salting out, are common methods to change the solubility of proteins.
- Proteins are amphoteric because they have both acidic and basic properties. Proteins have an isoelectric point that affects solubility and migration.
- Denaturation processes affect the overall protein structure and functions.
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Description
Test your knowledge about amino acids, their properties, and functions in biochemistry. This quiz covers various classifications, structural features, and roles of amino acids and proteins in living organisms. Perfect for students studying biochemistry or related fields.
