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Questions and Answers
What happens to the zwitterion form of an amino acid when the pH of the solution increases?
Which of the following amino acids does not have a chiral α-carbon atom?
What term is used for compounds that have the same molecular formula but differ in the arrangement of atoms in space?
Which classification describes amino acids with a positive side chain due to the presence of two amino groups and one carboxyl group?
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In terms of hydropathy, what does a larger hydropathy value indicate?
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What classification of amino acids yields ketone bodies upon metabolism?
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Which of the following amino acids can exist in mirror image pairs designated as L and D?
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What characterizes an amino acid with a polar neutral side chain?
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Which amino acids are classified as purely ketogenic?
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Which of the following amino acids can yield both ketone bodies and glucose?
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What characterizes glucogenic amino acids?
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What distinguishes proteins from peptides based on the number of amino acids?
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Which of the following is a rare amino acid found in collagen?
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What is the primary cause of the formation of Lewy bodies in Parkinson's disease?
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What effect does cooking have on protein structure?
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Which factor is NOT listed as affecting protein denaturation?
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What happens to proteins when a person experiences a high fever (above 104 ºF)?
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What is the consequence of protein denaturation?
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What is the primary cause of Scurvy?
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What is Osteogenesis Imperfecta primarily associated with?
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Which protein is primarily affected in emphysema due to α1-antitrypsin deficiency?
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Which of the following describes the structure of elastin?
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What is a characteristic feature of glycoproteins?
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How do lipoproteins function in the body?
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Which type of protein is casein classified as?
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What is a primary role of α1-antitrypsin in the lungs?
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What is the primary structural characteristic of collagen?
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Which type of protein is insulin classified as?
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Which of the following proteins is classified as an α-globulin?
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What is the main function of γ-globulins?
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What occurs when collagen is heat-treated or mixed with dilute hydrochloric acid?
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What distinguishes scleroproteins from other types of proteins?
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What percentage of total body proteins do collagens constitute in mammals?
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What is the key feature of globins (Histones)?
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What is the primary function of amino acids in proteins?
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Which statement accurately reflects the synthesis of amino acids?
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What bond links amino acids together in a protein?
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How do protein structures differ among organisms?
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How many different amino acids are used to make proteins?
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Study Notes
Amino Acid Structure
- The structure of an amino acid depends on the pH
- Lower pH leads to zwitterion picking up a proton
- Higher pH leads to zwitterion losing a proton
Chirality of Amino Acids
- 19 out of 20 common amino acids have a chiral α-carbon atom.
- Glycine does not have a chiral carbon atom.
- Chiral carbons have four different groups attached.
- Threonine and isoleucine have two chiral carbons each, leading to four possible stereoisomers.
- Stereoisomers are compounds with the same molecular formula but different spatial arrangements of atoms.
Stereochemistry of Amino Acids
- Mirror image pairs of amino acids are designated as L (levo) and D (dextro) and are called enantiomers.
- Proteins are built from L-amino acids.
- Some D-amino acids occur in nature.
Classifications of Amino Acids
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Side Chain:
- Non-polar: Contains uncharged hydrocarbon groups or benzene rings. Hydrophobic and insoluble in water.
- Polar neutral: Contains side chains with positive or negative charge. Hydrophilic and soluble in water.
- Polar acidic: Contains one amino group and two carboxyl groups. Side chain is negative, referred to as "-ic acid."
- Polar basic: Contains two amino groups and one carboxyl group. Side chain is positive.
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Hydrophobicity:
- Hydropathy: the relative hydrophobicity of each amino acid.
- Higher hydropathy indicates a greater tendency to prefer hydrophobic environments.
- Hydropathy affects protein folding, with hydrophobic residues tending to be in the interior and hydrophilic residues on the surface.
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Nutrition: Essential amino acids cannot be synthesized by the body and must be obtained from the diet. Non-essential amino acids can be synthesized by the body.
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Metabolic Products:
- Ketogenic: Metabolized into ketone bodies. Lysine and Leucine are the only pure ketogenic amino acids.
- Glucogenic: Metabolized into glucose.
- Mixed Ketogenic and Glucogenic: Can produce both ketone bodies and glucose.
Rare Amino Acids
- 4-Hydroxyproline: Found in plant cell wall proteins (extensins) and collagen.
- 4-Hydroxylysine: Found in collagen.
- β-alanine: Component of pantothenic acid (vitamin B5).
- Homocysteine: Intermediate in amino acid metabolism.
- Homoserine: Intermediate in amino acid metabolism.
Protein Structure
- Peptides: Chains containing less than 50 amino acids.
- Proteins: Chains containing more than 50 amino acids.
Classification of Proteins
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Simple Proteins: Yield only amino acids upon hydrolysis.
- Albumin and globulins: Present in egg, milk, and blood.
- Globins (Histones): Basic proteins rich in histidine. Found combined with DNA and heme (hemoglobin).
- Gliadines: Proteins found in cereals.
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Scleroproteins: Structural proteins, not digested.
- α-Keratin: Found in hair, nails, teeth enamel, and skin. α-helical polypeptide chain, rich in cysteine.
- Collagens: Found in connective tissues. Most common type is collagen I. Composed of three helical polypeptide chains (trimeric).
- Elastin: Found in blood vessels, lungs, ligaments, and skin. Composed of four polypeptide chains (tetrameric).
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Conjugated Proteins: Yield protein and non-protein components upon hydrolysis.
- Phosphoproteins: Contain phosphate groups attached to serine or threonine. (e.g. casein in milk, vitellin in yolk)
- Lipoproteins: Contain lipids. Assist in lipid transport and cell membrane structure.
- Glycoproteins: Contain carbohydrates. Found in mucin, some hormones, and cell membranes.
- Nucleoproteins: Contain nucleic acids. (e.g. histones)
Protein Denaturation
- Partial or complete disruption of protein's tertiary structure.
- Cooking denatures proteins, making them easier to digest and killing microorganisms.
- Coagulation: Precipitation (denaturation) of proteins, such as in egg white.
Factors Affecting Protein Denaturation
- Heat
- pH
- Organic solvents
- Chaotropic agents
- Heavy metals
Disease Related to Protein Synthesis
- Scurvy: Deficiency of vitamin C.
- Osteogenesis Imperfecta (OI): Inherited disease due to genetic deficiency or mutation in collagen type I synthesis.
- Emphysema: Chronic obstructive lung disease caused by elastase (an enzyme that breaks down elastin) destruction of lung elastin.
- Parkinson's Disease: Misfolding of α-synuclein protein leads to Lewy body formation.
- Huntington's Disease: A genetic mutation causes huntingtin protein misfolding and aggregation.
Protein Structure and Function
- Proteins are essential macronutrients found in all living organisms.
- Proteins play a crucial role in various metabolic pathways within the body.
- Each organism possesses unique proteins, making them species-specific.
- Proteins are also organ-specific, meaning the composition of proteins in the brain differs from those in the muscles.
- Proteins are composed of 20 different amino acids.
- The properties of a protein molecule are determined by the specific amino acids present.
- Plants can synthesize all necessary amino acids to produce proteins, while animals cannot.
- Amino acids in proteins are linked together by peptide bonds.
- Peptide bonds form between the NH group of one amino acid and the COOH group of another amino acid.
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Description
This quiz explores the intricate structures and classifications of amino acids, focusing on their chirality and stereochemistry. Learn about the effects of pH on amino acid structure and the significance of enantiomers in protein composition. Dive into the world of polar and non-polar side chains and understand their properties.
