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Questions and Answers
What is the primary function of haemoglobin in the body?
What is the primary function of haemoglobin in the body?
What structural feature allows haemoglobin to exhibit positive cooperativity?
What structural feature allows haemoglobin to exhibit positive cooperativity?
What results from the failure of proteins to fold into their native structure?
What results from the failure of proteins to fold into their native structure?
What characterizes the difference in oxygen binding between haemoglobin and myoglobin?
What characterizes the difference in oxygen binding between haemoglobin and myoglobin?
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What effect do amyloid fibrils have on protein functionality?
What effect do amyloid fibrils have on protein functionality?
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Which of the following statements about amino acids at their isoelectric point is true?
Which of the following statements about amino acids at their isoelectric point is true?
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Which group of amino acids is synthesized by the body and thus considered non-essential?
Which group of amino acids is synthesized by the body and thus considered non-essential?
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What is the correct result of a condensation reaction between two amino acids?
What is the correct result of a condensation reaction between two amino acids?
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What characterizes the peptide bonds in proteins?
What characterizes the peptide bonds in proteins?
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Which amino acid is not classified as essential?
Which amino acid is not classified as essential?
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When three amino acids link together, what is the product called?
When three amino acids link together, what is the product called?
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In terms of charge, which amino acid is classified as basic?
In terms of charge, which amino acid is classified as basic?
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What is the minimum number of amino acids required for a chain to be considered a polypeptide?
What is the minimum number of amino acids required for a chain to be considered a polypeptide?
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What term is used to describe each amino acid in a chain?
What term is used to describe each amino acid in a chain?
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Which terminal of a polypeptide is referred to as the N-terminal?
Which terminal of a polypeptide is referred to as the N-terminal?
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Which of the following statements is true regarding the formation of amide bonds in peptides?
Which of the following statements is true regarding the formation of amide bonds in peptides?
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Which of the following is a biological role of peptides?
Which of the following is a biological role of peptides?
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What distinguishes the naming convention of peptides?
What distinguishes the naming convention of peptides?
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What is one indicator of psychological/neurological disorders related to peptide levels?
What is one indicator of psychological/neurological disorders related to peptide levels?
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How is glutathione categorized in biological terms?
How is glutathione categorized in biological terms?
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Which of the following amino acid combinations represents a correctly named peptide?
Which of the following amino acid combinations represents a correctly named peptide?
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What is the primary function of glutathione in biological systems?
What is the primary function of glutathione in biological systems?
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Which peptide is biologically inactive and acts solely as a precursor?
Which peptide is biologically inactive and acts solely as a precursor?
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What enzyme converts angiotensin I to angiotensin II?
What enzyme converts angiotensin I to angiotensin II?
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What is a major application of inhibitory peptides in clinical research?
What is a major application of inhibitory peptides in clinical research?
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Which of the following correctly describes globular proteins?
Which of the following correctly describes globular proteins?
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Which protein type is primarily responsible for the high tensile strength of the skin and bone?
Which protein type is primarily responsible for the high tensile strength of the skin and bone?
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What is the primary role of receptor proteins in biological systems?
What is the primary role of receptor proteins in biological systems?
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In terms of food sources, which protein type is typically considered higher quality?
In terms of food sources, which protein type is typically considered higher quality?
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Which type of peptide is used in skin care to stimulate collagen production?
Which type of peptide is used in skin care to stimulate collagen production?
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What distinguishes fibrous proteins from globular proteins?
What distinguishes fibrous proteins from globular proteins?
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What is the primary structure of a protein characterized by?
What is the primary structure of a protein characterized by?
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What effect does reduced oxygen concentration have on red blood cells carrying hemoglobin S (HbS)?
What effect does reduced oxygen concentration have on red blood cells carrying hemoglobin S (HbS)?
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Which secondary structure is characterized by hydrogen bonding and forms a helix?
Which secondary structure is characterized by hydrogen bonding and forms a helix?
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What is the main role of chaperones in protein structure?
What is the main role of chaperones in protein structure?
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Which type of hemoglobin is produced more when treated with Hydroxyurea?
Which type of hemoglobin is produced more when treated with Hydroxyurea?
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What characterizes the tertiary structure of a protein?
What characterizes the tertiary structure of a protein?
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In sickle cell anemia, what is the consequence of sickled cells clogging capillaries?
In sickle cell anemia, what is the consequence of sickled cells clogging capillaries?
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Which of the following best describes quaternary structure in proteins?
Which of the following best describes quaternary structure in proteins?
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How does a small mutation in amino acids potentially affect a protein's function?
How does a small mutation in amino acids potentially affect a protein's function?
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What is the main type of bond stabilizing the secondary structure of proteins?
What is the main type of bond stabilizing the secondary structure of proteins?
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Study Notes
Amino Acid Chemistry
- Amino acids are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and small amounts of sulfur (S) – often abbreviated as CHONS.
- The alpha-carbon in amino acids is asymmetric (except glycine).
- This asymmetry leads to two optically active forms: D-form and L-form.
- Only L-amino acids are used to make proteins.
- Glycine lacks an asymmetric carbon.
- Amino acids are dipolar ions (zwitterions) in solution.
- The amino group (NH2) gains a positive charge, and the carboxyl group (COOH) gains a negative charge.
- Dipolar ions have zero mobility in electrophoresis.
- Amino acids exhibit amphoteric behavior.
- There is no pH where a.a have no ionic character.
- The isoelectric point (pI) is the pH at which the number of cations equals anions.
- Each amino acid has a specific pI depending on its structure.
- Acidic amino acids have lower pI values (e.g., aspartic acid 2.8, glutamic acid 3.2).
- Neutral amino acids have pI values between 5.0 and 6.3.
- Basic amino acids have higher pI values (e.g., lysine 9.7, arginine 10.8, histidine 7.6).
- Electrophoresis separates amino acids based on their isoelectric points.
- A mixture of amino acids is placed on a gel or paper.
- An electric field is applied.
- Positively charged amino acids move towards the negative electrode (cathode), negatively charged amino acids towards the positive electrode (anode).
- Amino acids with no net charge at a given pH stay in place.
- Twenty amino acids make up proteins.
- Nine are essential amino acids; the body doesn't produce them, so they must be obtained through diet.
- Eleven are nonessential; the body can synthesize them.
- Amino acids are grouped based on the R-group properties:
- Nonpolar
- Polar uncharged
- Acidic (negatively charged)
- Basic (positively charged).
- Peptides are formed from amino acids linked via peptide bonds (condensation reactions).
- A molecule of water is removed when forming a peptide bond.
- The terminal ends of peptides are identified as N-terminal and C-terminal.
- Peptides are important in biological processes, as intermediates in protein synthesis, antibacterial agents (e.g., penicillin), growth factors (e.g., folic acid), hormones (e.g., insulin, angiotensin), antioxidants (e.g., glutathione) and in diseases (neurological disorders).
- Glutathione (γ-Glu-Cys-Gly) is a natural antioxidant.
- Angiotensin is a potent vasodilator/constrictor.
- Peptides have industrial uses, particularly in pharmaceutical, cosmetic and medical applications.
- Peptide-based drugs.
- Cancer-detection agents.
- Skin care products.
- Food additives/sweeteners.
- Proteins are large polypeptides.
- Proteins have important biological functions including catalysis (enzymes), transport (hemoglobin), structural support (collagen), regulation of the immune response, transmission of nerve signals (receptors).
- Proteins are classified based on source (animal or plant), and shape (globular or fibrous).
- Globular proteins generally have spherical shapes and tertiary/quaternary structures.
Protein Structure
- Proteins are composed of amino acids linked together by peptide bonds.
- Proteins have four levels of structure:
- Primary structure: linear sequence of amino acids.
- Determines a protein's overall structure and function.
- Example of how small changes in amino acid sequence can affect function is Sickle Cell Anemia.
- Secondary structure: local folding patterns (α-helices, β-sheets, β-bends) stabilized by hydrogen bonds.
- Tertiary structure: 3D shape of the entire polypeptide chain, stabilized by various bonds (hydrogen bonds, disulfide bonds, ionic bonds, hydrophobic interactions). This determines the protein's specific shape and function.
- Quaternary structure: arrangement of multiple polypeptide chains in a protein, stabilized by the same bonds as tertiary structures.
- Haemoglobin is an example of a protein that has a quaternary structure and made up of both α and β chains.
- Myoglobin is another example of a protein that has a tertiary structure composed of a polypeptide chain.
- Primary structure: linear sequence of amino acids.
Protein Chemical Bonds
- Disulfide bridges form between cysteine residues in specific cases.
- Hydrogen bonds stabilize secondary and tertiary structures.
- Nonpolar/hydrophobic interactions are important in tertiary structures.
- Ionic/electrostatic interactions occur between charged amino acid side chains.
Protein Methods
- Electrophoresis and Western Blotting are used to separate and identify proteins.
Protein Quantification
- Methods used to determine protein amounts include immunological techniques (ELISA, Western Blotting) and protein-specific tools like mass spectrometry.
Protein Denaturation
- Denaturation disrupts the three-dimensional structure of a protein, causing it to lose its biological activity.
- It results from physical agents (heat, shaking, radiation etc) and chemical agents (organic solvents, detergents, etc).
- Denaturation often results from changes caused by alterations in pH levels, change in temperature, or the addition of chemicals.
- Denaturation is commonly a reversible process.
Industrial Importance of Proteins
- These important roles extend to pharmaceutical, cosmetic and agricultural applications.
- Proteins and peptides in these industries range from the formation of gelatin for food products, to uses in medical treatment.
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Description
Test your knowledge on amino acid structures and properties, including their composition, asymmetry, and ionic behavior. Understand the significance of the alpha-carbon and the concept of the isoelectric point (pI) in this essential chemistry quiz.
