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Questions and Answers
Which function describes proteins that facilitate chemical reactions, such as alcohol dehydrogenase?
Which function describes proteins that facilitate chemical reactions, such as alcohol dehydrogenase?
What is a function of proteins that involves providing structural support, as in tendons and hair?
What is a function of proteins that involves providing structural support, as in tendons and hair?
What type of disease is associated with misfolded proteins leading to neurodegenerative issues?
What type of disease is associated with misfolded proteins leading to neurodegenerative issues?
What determines the specific conformation of a polypeptide and thus its functionality?
What determines the specific conformation of a polypeptide and thus its functionality?
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Which type of protein is involved in muscle contraction and movement, such as actin and myosin?
Which type of protein is involved in muscle contraction and movement, such as actin and myosin?
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What does the 'CORN' rule indicate about amino acids?
What does the 'CORN' rule indicate about amino acids?
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What was the primary purpose of thalidomide when it was developed?
What was the primary purpose of thalidomide when it was developed?
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Why was separating the enantiomers of thalidomide ineffective?
Why was separating the enantiomers of thalidomide ineffective?
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Which classification of amino acids is based on the presence of a positive or negative charge at physiological pH?
Which classification of amino acids is based on the presence of a positive or negative charge at physiological pH?
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Which bond type is characterized by an unequal sharing of electrons between different electronegative atoms?
Which bond type is characterized by an unequal sharing of electrons between different electronegative atoms?
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Which amino acid classification includes those with nonpolar R groups?
Which amino acid classification includes those with nonpolar R groups?
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What was one significant consequence of the thalidomide tragedy?
What was one significant consequence of the thalidomide tragedy?
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Which pair of elements examples shows a polar covalent bond based on their electronegativities?
Which pair of elements examples shows a polar covalent bond based on their electronegativities?
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What determines the identity of a particular amino acid?
What determines the identity of a particular amino acid?
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Which of the following amino acids is not an L-isomer?
Which of the following amino acids is not an L-isomer?
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How many common amino acids are there in proteins?
How many common amino acids are there in proteins?
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What type of bond forms polypeptides?
What type of bond forms polypeptides?
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Which level of protein structure involves the overall 3D shape of a polypeptide?
Which level of protein structure involves the overall 3D shape of a polypeptide?
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Which of the following groups is not a common structural feature of all α-amino acids?
Which of the following groups is not a common structural feature of all α-amino acids?
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Which topic focuses on the relationship between protein structure and function?
Which topic focuses on the relationship between protein structure and function?
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What is the chiral center in most amino acids responsible for?
What is the chiral center in most amino acids responsible for?
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Which of the following amino acids is negatively charged at physiological pH?
Which of the following amino acids is negatively charged at physiological pH?
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What role does acetylation of histone lysine residues primarily play in cells?
What role does acetylation of histone lysine residues primarily play in cells?
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Which of the following statements about selenocysteine is correct?
Which of the following statements about selenocysteine is correct?
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Which of the following amino acids has a pKa value that suggests it is positively charged at physiological pH?
Which of the following amino acids has a pKa value that suggests it is positively charged at physiological pH?
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What is the effect of histone deacetylases (HDAC) on chromatin structure?
What is the effect of histone deacetylases (HDAC) on chromatin structure?
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Which amino acid is considered the simplest and nonpolar?
Which amino acid is considered the simplest and nonpolar?
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Which amino acids contain a hydroxyl group and are classified as polar?
Which amino acids contain a hydroxyl group and are classified as polar?
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What stabilizes protein structures through the formation of disulfide bonds?
What stabilizes protein structures through the formation of disulfide bonds?
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Which amino acid can accept a phosphoryl group during signal transduction?
Which amino acid can accept a phosphoryl group during signal transduction?
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What type of amino acids are Phenylalanine and Tryptophan due to their structure?
What type of amino acids are Phenylalanine and Tryptophan due to their structure?
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Which form of bond is critical for proper folding of insulin?
Which form of bond is critical for proper folding of insulin?
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Which property allows proteins containing aromatic amino acids to be quantified using spectrophotometry?
Which property allows proteins containing aromatic amino acids to be quantified using spectrophotometry?
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Which amino acids have carboxylamide groups in their side chains?
Which amino acids have carboxylamide groups in their side chains?
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Study Notes
Proteins - The Most Diverse Macromolecules
- Proteins are the most diverse macromolecules, exhibiting a vast array of sizes and shapes.
- Countless proteins are listed in the image, including: Cytochrome c, Glucagon, Insulin, ATP Synthase, Aquaporin, Potassium Channel, Mechanosensitive Channel, Gramicidin, Porin, Hemoglobin, Myoglobin, Ferritin, Serum Albumin, Phosphoglucose Isomerase, Aldolase, Triosephosphate Isomerase, Phosphofructokinase, Enolase, Pyruvate Kinase, Cytochrome b-c1 Complex, Cytochrome c Oxidase, Phosphoglycerate Kinase, Glyceraldehyde-3-phosphate Dehydrogenase, Tryptophan Synthase, Phosphoglycerate Mutase, Dihydrofolate Reductase, Human Growth Hormone, Interferon, Deoxyribonuclease, Trypsin, Lysozyme, Rhodopsin, Ribonuclease, Pepsin, Amylase, Phospholipase, Antibody, Alcohol Dehydrogenase, Thymidylate Synthase, Glutamine Synthetase, Cyclooxygenase, Aspartate Carbamoyltransferase, Ribulose Bisphosphate Carboxylase/Oxygenase, Nitrogenase, Photosynthetic Reaction Center, Light-Harvesting Complex, Valyl-tRNA Synthetase, Threonyl-tRNA Synthetase, Isoleucyl-tRNA Synthetase, Phenylalanyl-tRNA Synthetase, Glutaminyl-tRNA Synthetase, Elongation Factor Tu, Aspartyl-RNA Synthetase, Elongation Factor G, Elongation Factor Tu and Ts, Ribosome, Proline cis/trans Isomerase, Prefoldin, Transfer RNA, Chaperonin GroEL/ES
Protein Functions
- Proteins perform various essential functions, including:
- Catalysis: Examples include alcohol dehydrogenase
- Transport: Examples include hemoglobin
- Motor: Examples include actin and myosin in muscle cells, tendons, and hair
- Defense: Examples include antibodies
- Signaling: Examples include hormones and transcription factors
Protein Abnormalities and Diseases
- Sickle cell anemia: An abnormality in hemoglobin.
- Metabolic diseases: Dysfunction of protein enzymes.
- Neurodegenerative diseases: Misfolded proteins (e.g., Alzheimer's, Parkinson's, Huntington's diseases).Specific implicated proteins are highlighted (Amyloid-β peptide, tau, α-synuclein, mutated huntingtin protein).
Protein Structure and Function
- Polypeptides fold into specific shapes depending on their amino acid sequences.
The Nobel Prize in Chemistry 2024
- Prizes were divided concerning computational protein design and protein structure prediction.
Protein Composition and Structure
- Amino acids: The building blocks of proteins (20 common amino acids)
- Peptide bonds: Form polypeptides.
- Four levels of protein structure: Primary, secondary, tertiary, and quaternary structures.
Amino Acids
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Learning Objectives:
- Identify 20 common amino acids and their physical and chemical properties.
- Understand the biological importance of amino acids and small peptides.
- The 20 common amino acids are classified by chemical characteristics of their R groups (hydrophobic, polar, charged)
Common Structural Features of Amino Acids
- All α-amino acids have an α-carbon atom bonded to a carboxylate group, an amino group, and a side chain (R group).
- The R group dictates the unique identity and properties of each amino acid.
3D Shape (Stereochemistry) of Amino Acids
- All amino acids (except glycine) have a chiral carbon (α-carbon).
- Most naturally occurring amino acids in proteins are L-isomers.
- D-amino acids are found in bacterial cell walls
Distinguishing L- and D-amino acids
- CORN rule: An easy method to determine whether specific amino acid is L or D form.
Importance of Stereochemistry
- The thalidomide tragedy: Demonstrates the critical importance of stereochemistry in drug design and safety. Separation of isomers is not sufficient to preclude issues relating to enantiomers.
Classification of the 20 Amino Acids
- Classification based on the chemical characteristics of their R groups.
- Hydrophobic amino acids with nonpolar R groups
- Polar amino acids with neutral R groups
- Charged amino acids with R groups that have a positive or negative charge at physiological pH
Polar vs. Non-polar Covalent Bonds
- Polar covalent bonds result from unequal sharing of electrons between atoms with different electronegativities
- Electronegativity values for C, S, N, and O provided.
Aromatic Amino Acids
- Aromatic amino acids absorb ultraviolet light.
- Measurement of absorbance at 280 nm can be used to measure protein concentration.
Charged Amino Acids
- Negatively charged amino acids: Carboxylate groups of aspartate and glutamate have pKas of 3.7 and 4.0, respectively. They are ionized (negatively charged) at physiological pH.
- Positively charged amino acids: pKa values for lysine, arginine, and histidine side chains (~10.5, ~12.5, ~6.0). Lysine and arginine side chains are amphipathic.
Acetylation of Histone Lysine Residues
- DNA in chromatin is tightly associated with histone proteins via the packaging of DNA into nucleosomes.
- Acetylation of histone lysine residues opens up chromatin structure, allowing RNA polymerase access for transcription process. Deacetylation closes chromatin, hindering access.
Rare Amino Acid: Selenocysteine
- Selenocysteine, the 21st amino acid.
- Attached to a unique tRNA that recognizes the stop codon UGA.
- Found in 25 human selenoproteins.
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Description
Explore the fascinating world of proteins, the most diverse macromolecules in biology. This quiz challenges your knowledge about various proteins, their functions, and their significance in biological processes. Test your understanding of key proteins like Hemoglobin, Insulin, and many others listed in the quiz.
