Amino Acids and Protein Structure
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Amino Acids and Protein Structure

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Questions and Answers

What type of protein structure involves the arrangement of multiple polypeptide chains?

  • Secondary structure
  • Tertiary structure
  • Quaternary structure (correct)
  • Primary structure

    • Which type of bond is responsible for stabilizing the compact folded structure of myoglobin?

  • Covalent bonds
  • Hydrogen bonds (correct)
  • Disulphide bonds
  • Peptide bonds

    • Which feature distinguishes the 'native conformation' of a protein?

  • It is completely denatured
  • It is a linear polypeptide chain
  • It has a unique three-dimensional structure (correct)
  • It contains only primary structure

    • What type of interactions primarily hold together the quaternary structure of proteins?

    <p>Non-covalent interactions</p> Signup and view all the answers

    Which of the following is NOT a role of proteins in their native conformation?

    <p>Gene replication</p> Signup and view all the answers

    What type of polysaccharide is primarily responsible for energy storage in animals?

    <p>Glycogen</p> Signup and view all the answers

    Which lipid is a homopolymer of glucose that provides structure in plants?

    <p>Cellulose</p> Signup and view all the answers

    What is the primary structural difference between amylopectin and amylose?

    <p>Amylopectin is branched every 24-30 residues</p> Signup and view all the answers

    Which of the following is NOT a classification of lipids?

    <p>Carbohydrates</p> Signup and view all the answers

    What type of lipid contains a backbone of glycerol?

    <p>Phospholipids</p> Signup and view all the answers

    Which description is characteristic of chitin?

    <p>A homopolymer of n-acetyl-glucosamine</p> Signup and view all the answers

    How are fatty acids categorized based on their structure?

    <p>By their saturation levels</p> Signup and view all the answers

    What do glycosidic bonds link together?

    <p>Monosaccharides</p> Signup and view all the answers

    What is the primary function of arachidonic acid in the body?

    <p>Synthesis of eicosanoids</p> Signup and view all the answers

    Which of the following describes a characteristic of omega-6 fatty acids?

    <p>They include arachidonic acid.</p> Signup and view all the answers

    What is the primary role of diabetic glycerol in the body?

    <p>To serve as a backbone for triglycerides</p> Signup and view all the answers

    Which type of lipid is a major component of cell membranes?

    <p>Glycerophospholipids</p> Signup and view all the answers

    What structure do steroids predominantly contain?

    <p>Fused ring system</p> Signup and view all the answers

    Which of the following fatty acids is classified as an omega-3 fatty acid?

    <p>Alpha-linolenic acid</p> Signup and view all the answers

    What is the significance of cholesterol in the body?

    <p>Precursor for Vitamin D and hormones</p> Signup and view all the answers

    What is one of the primary functions of eicosanoids?

    <p>Signaling in inflammatory responses</p> Signup and view all the answers

    What is the structure of triglycerides?

    <p>Three fatty acids and glycerol</p> Signup and view all the answers

    What is a primary characteristic of lipoproteins?

    <p>They transport lipids, including cholesterol, in the plasma.</p> Signup and view all the answers

    What defines essential amino acids?

    <p>They must come from the diet.</p> Signup and view all the answers

    Which of the following structures is a characteristic of secondary protein structure?

    <p>Alpha helix</p> Signup and view all the answers

    How is a peptide bond formed?

    <p>Between the carboxyl group of one amino acid and the amino group of another.</p> Signup and view all the answers

    Which of these amino acids can be phosphorylated?

    <p>Serine</p> Signup and view all the answers

    What keeps the tertiary structure of a protein stable?

    <p>Hydrophobic interactions and disulfide bridges</p> Signup and view all the answers

    Which type of lipid includes phospholipids and sterols?

    <p>Complex lipids</p> Signup and view all the answers

    Which amino acid is uniquely known for its role in protein bending?

    <p>Proline</p> Signup and view all the answers

    What is a glycosidic bond?

    <p>Bond between two monosaccharides</p> Signup and view all the answers

    What is the quaternary structure of a protein?

    <p>The arrangement of multiple polypeptide chains</p> Signup and view all the answers

    Which of the following fatty acids is classified as unsaturated?

    <p>Oleic acid</p> Signup and view all the answers

    What characterizes a monosaccharide?

    <p>Single sugar unit</p> Signup and view all the answers

    Which type of carbohydrate is formed by the linkage of multiple monosaccharides?

    <p>Polysaccharide</p> Signup and view all the answers

    What is the primary determinant of the behavior of amino acids within a polypeptide?

    <p>The properties of the side chains (R groups)</p> Signup and view all the answers

    Which term describes the natural three-dimensional shape of a functional protein?

    <p>Native conformation</p> Signup and view all the answers

    What is the result of phosphorylation in proteins?

    <p>Addition of a phosphate group</p> Signup and view all the answers

    Which type of protein modification results in a protein functioning as a glycoprotein?

    <p>Glycosylation</p> Signup and view all the answers

    What is the result of ubiquitination in protein modification?

    <p>Signal for protein degradation</p> Signup and view all the answers

    What type of monosaccharide is glucose classified as?

    <p>Aldose</p> Signup and view all the answers

    Which of the following is a characteristic of polysaccharides?

    <p>Consist of many monosaccharides</p> Signup and view all the answers

    What type of bond is formed between two monosaccharides in a disaccharide?

    <p>Glycosidic bond</p> Signup and view all the answers

    How is a beta (b) glycosidic bond characterized?

    <p>Hydroxyl group is in beta configuration</p> Signup and view all the answers

    What occurs during the cyclisation of monosaccharides?

    <p>Formation of a ring structure</p> Signup and view all the answers

    Which of the following monosaccharides is a ketose?

    <p>Fructose</p> Signup and view all the answers

    Which abnormal protein aggregation can lead to diseases like Alzheimer's?

    <p>Misfolded proteins into fibrils</p> Signup and view all the answers

    Which carbohydrate consists of only one sugar unit?

    <p>Monosaccharide</p> Signup and view all the answers

    What type of functional group is associated with acetylation in proteins?

    <p>Fatty acid</p> Signup and view all the answers

    What is the primary structure unit of carbohydrates?

    <p>Monosaccharides</p> Signup and view all the answers

    What type of amino acids contribute to the hydrophobic core of myoglobin's structure?

    <p>Hydrophobic amino acids</p> Signup and view all the answers

    Which type of bond stabilizes the quaternary structure of proteins?

    <p>Non-covalent interactions</p> Signup and view all the answers

    Which of the following determines the native conformation of a protein?

    <p>The primary, secondary, and tertiary structures</p> Signup and view all the answers

    In addition to cysteines forming disulphide bonds, which other type of bond is important for stabilizing myoglobin?

    <p>Hydrogen bonds</p> Signup and view all the answers

    What describes the quaternary structure of a protein?

    <p>The complex of multiple tertiary polypeptide chains</p> Signup and view all the answers

    What is the primary function of glycogen in animals?

    <p>Serving as a major energy storage</p> Signup and view all the answers

    Which lipid serves as a structural component of cell membranes?

    <p>Phospholipids</p> Signup and view all the answers

    What characterizes the structure of cellulose?

    <p>Long straight chains with β1-4 linkages</p> Signup and view all the answers

    Which type of fatty acid is classified by the presence of double bonds?

    <p>Monounsaturated fatty acids</p> Signup and view all the answers

    What distinguishes amylopectin from amylose?

    <p>Amylopectin has branched chains</p> Signup and view all the answers

    Which of the following lipids does not contain glycerol?

    <p>Steroids</p> Signup and view all the answers

    What type of polysaccharide provides structural integrity in plant cells?

    <p>Cellulose</p> Signup and view all the answers

    Which feature distinguishes lipoproteins from other lipid types?

    <p>Presence of proteins</p> Signup and view all the answers

    What is the primary function of eicosanoids in the body?

    <p>Signaling and inflammatory responses</p> Signup and view all the answers

    Which fatty acid is essential and cannot be synthesized by the body?

    <p>Linoleic acid</p> Signup and view all the answers

    What is the characteristic structure of steroids?

    <p>Fused ring system</p> Signup and view all the answers

    Which option is a major component of cell membranes?

    <p>Phospholipids</p> Signup and view all the answers

    What role does diacylglycerol (DAG) play within cells?

    <p>Intracellular signaling</p> Signup and view all the answers

    What is the significance of arachidonic acid in relation to eicosanoids?

    <p>It is a precursor for their synthesis</p> Signup and view all the answers

    Which of the following statements about essential fatty acids (EFAs) is correct?

    <p>They must be obtained from the diet.</p> Signup and view all the answers

    What is a primary role of lipoproteins in the body?

    <p>Transporting lipids in plasma</p> Signup and view all the answers

    Which of the following fatty acids is classified as an omega-3 fatty acid?

    <p>α-linolenic acid</p> Signup and view all the answers

    What is one of the key functions of cholesterol in the body?

    <p>Serving as a precursor for vitamin D</p> Signup and view all the answers

    Which of the following classifications of amino acids is defined by having a negative charge at neutral pH?

    <p>Acidic amino acids</p> Signup and view all the answers

    What structure represents the arrangement of amino acids in a polypeptide chain linked by peptide bonds?

    <p>Primary structure</p> Signup and view all the answers

    Which structural feature is characteristic of beta (b) pleated sheets found in proteins?

    <p>Regular repetitive folding stabilized by hydrogen bonds</p> Signup and view all the answers

    Which of the following amino acids can undergo phosphorylation?

    <p>Serine</p> Signup and view all the answers

    What type of bond connects monosaccharides to form disaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    What is true about essential amino acids?

    <p>They must be obtained from the diet.</p> Signup and view all the answers

    Which lipids are characterized by a backbone of glycerol?

    <p>Triglycerides</p> Signup and view all the answers

    Which type of carbohydrate is formed by the linkage of multiple monosaccharides?

    <p>Polysaccharide</p> Signup and view all the answers

    What describes the concept of 'native conformation' in proteins?

    <p>The folded structure that is functional</p> Signup and view all the answers

    Which fatty acids are classified as saturated?

    <p>Palmitic acid</p> Signup and view all the answers

    Which amino acids are typically found at bends in protein structures?

    <p>Proline</p> Signup and view all the answers

    What is a key feature of polysaccharides?

    <p>They have branching structures like glycogen.</p> Signup and view all the answers

    Which structural feature is characteristic of essential fatty acids?

    <p>Presence of double bonds</p> Signup and view all the answers

    What type of post-translational modification results in the addition of a sugar group to an amino acid?

    <p>Glycosylation</p> Signup and view all the answers

    Which protein modification is associated with adding a death signal to a protein?

    <p>Ubiquitination</p> Signup and view all the answers

    What structure is formed when two monosaccharides are linked together?

    <p>Disaccharide</p> Signup and view all the answers

    Which type of sugar has the empirical formula (CH2O)n, where n can range from 3 to 7?

    <p>Monosaccharide</p> Signup and view all the answers

    What type of glycosidic bond is present in lactose?

    <p>b (1→4) glycosidic bond</p> Signup and view all the answers

    What results from misfolding of proteins into amyloid fibrils?

    <p>Abnormal protein aggregates</p> Signup and view all the answers

    Which monosaccharide is classified as an aldose?

    <p>Galactose</p> Signup and view all the answers

    Which of the following modifications is characterized by the addition of a fatty acid chain?

    <p>Acylation</p> Signup and view all the answers

    What is an example of a polysaccharide?

    <p>Glycogen</p> Signup and view all the answers

    What happens during the cyclisation of monosaccharides?

    <p>Formation of ring structures</p> Signup and view all the answers

    Which monosaccharide is a ketose?

    <p>Fructose</p> Signup and view all the answers

    Which structure is categorized by the presence of multiple sugar units?

    <p>Polysaccharide</p> Signup and view all the answers

    What is the main characteristic of a glycoprotein?

    <p>Contains a protein linked to a sugar group</p> Signup and view all the answers

    What defines the alpha (a) configuration in glycosidic bonds?

    <p>Hydroxyl group below the anomeric carbon</p> Signup and view all the answers

    Which features contribute to the stability of the globular protein structure of myoglobin?

    <p>A combination of various interactions between side chains</p> Signup and view all the answers

    Which of the following is NOT a factor that determines the native conformation of a protein?

    <p>Environmental factors</p> Signup and view all the answers

    What is the primary feature of quaternary structure in proteins?

    <p>The interaction of multiple polypeptide subunits</p> Signup and view all the answers

    Which of the following correctly describes the arrangement of amino acids in a globular protein like myoglobin?

    <p>Hydrophobic AAs are found on the inside and hydrophilic AAs on the outside</p> Signup and view all the answers

    Which type of protein structure includes a combination of secondary structural elements like alpha-helices and beta-sheets?

    <p>Tertiary structure</p> Signup and view all the answers

    Which polysaccharide is primarily responsible for energy storage in plants?

    <p>Starch</p> Signup and view all the answers

    What type of glycosidic bond characterizes the structure of cellulose?

    <p>β1-4</p> Signup and view all the answers

    What best describes the branching pattern of amylopectin?

    <p>Branches every 24-30 residues</p> Signup and view all the answers

    Which type of lipid is characterized by a structure without a glycerol backbone?

    <p>Steroids</p> Signup and view all the answers

    How are fatty acids classified based on the number of double bonds present?

    <p>Monounsaturated and polyunsaturated</p> Signup and view all the answers

    What is the primary role of eicosanoids in human physiology?

    <p>Cellular signaling events</p> Signup and view all the answers

    Which lipid class includes lipids that are involved in cell membrane structure?

    <p>Phospholipids</p> Signup and view all the answers

    What characterizes the hydrocarbon chain of fatty acids?

    <p>Can be saturated or unsaturated</p> Signup and view all the answers

    What determines whether an amino acid is essential or non-essential?

    <p>The ability to be synthesized in the body</p> Signup and view all the answers

    Which of the following statements best describes the quaternary structure of proteins?

    <p>It refers to the combination of multiple polypeptide chains in a protein complex.</p> Signup and view all the answers

    Which of the following amino acids is classified as non-polar and aliphatic?

    <p>Alanine</p> Signup and view all the answers

    Which post-translational modification involves the addition of a phosphate group to proteins?

    <p>Phosphorylation</p> Signup and view all the answers

    What characterizes a glycoprotein compared to a standard protein?

    <p>Has a sugar group attached</p> Signup and view all the answers

    What role does phosphorylation play in proteins?

    <p>It frequently regulates enzymatic activity.</p> Signup and view all the answers

    Which type of carbohydrate contains several monosaccharide units linked together?

    <p>Polysaccharide</p> Signup and view all the answers

    Which of the following is a characteristic of secondary protein structure?

    <p>It includes patterns such as alpha helices and beta sheets.</p> Signup and view all the answers

    Which type of bond is formed specifically between an anomeric carbon and another carbon in a disaccharide?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which classification of lipids is primarily characterized by containing a glycerol backbone?

    <p>Acylglycerides</p> Signup and view all the answers

    What is the result of ubiquitination on a protein within a cell?

    <p>Targeting it for degradation</p> Signup and view all the answers

    What differentiates essential amino acids from conditionally essential amino acids?

    <p>Essential amino acids cannot be produced by the body.</p> Signup and view all the answers

    What structural feature is a characteristic of fatty acids?

    <p>A long hydrocarbon tail and a carboxylic acid group</p> Signup and view all the answers

    What distinguishes an aldose from a ketose monosaccharide?

    <p>The carbonyl group position</p> Signup and view all the answers

    Which amino acids can undergo glycosylation as a post-translational modification?

    <p>Threonine and asparagine</p> Signup and view all the answers

    Which type of bond is crucial for linking monosaccharides to form disaccharides?

    <p>Glycosidic bond</p> Signup and view all the answers

    Which amino acid is primarily known for its involvement in the bending of protein structure?

    <p>Proline</p> Signup and view all the answers

    What is a key characteristic of nitrosylation as a post-translational modification?

    <p>Involves the addition of nitric oxide</p> Signup and view all the answers

    Which of the following structures specifies the primary structure of proteins?

    <p>Linear sequence of amino acids</p> Signup and view all the answers

    Which structure represents a cyclic hexose monosaccharide?

    <p>Converted to a six-membered ring</p> Signup and view all the answers

    During cyclisation of monosaccharides, what is the newly formed carbon referred to?

    <p>Anomeric carbon</p> Signup and view all the answers

    Which of the following amino acids can be classified as acidic?

    <p>Aspartic acid</p> Signup and view all the answers

    How can misfolded proteins lead to diseases like Alzheimer's?

    <p>Through aggregation into amyloids</p> Signup and view all the answers

    Which protein modification allows a protein to function as a glycoprotein?

    <p>Glycosylation</p> Signup and view all the answers

    What is the primary characteristic of monosaccharides?

    <p>They consist of a single sugar unit.</p> Signup and view all the answers

    What type of monosaccharide is specifically identified as a pentose?

    <p>Ribose</p> Signup and view all the answers

    Which of the following statements about phosphorylation is incorrect?

    <p>It involves the addition of a nitric oxide group.</p> Signup and view all the answers

    What is the primary role of arachidonic acid in signaling pathways?

    <p>Precursor to eicosanoids like prostaglandins</p> Signup and view all the answers

    Which fatty acid is characterized as an essential fatty acid due to its inability to be synthesized by the body?

    <p>Linoleic acid</p> Signup and view all the answers

    Which statement correctly describes the structure of triglycerides?

    <p>Composed of three fatty acid chains attached to a glycerol</p> Signup and view all the answers

    Cholesterol serves multiple functions in the body. Which of the following is NOT one of those functions?

    <p>Storage form of energy in adipose tissue</p> Signup and view all the answers

    What is the half-life of prostaglandins in biological systems?

    <p>Seconds</p> Signup and view all the answers

    Which type of lipoprotein is primarily responsible for transporting cholesterol and triglycerides in the bloodstream?

    <p>VLDL (Very Low-Density Lipoprotein)</p> Signup and view all the answers

    What is the main characteristic of eicosanoids derived from arachidonic acid?

    <p>They have various functions including roles in inflammation</p> Signup and view all the answers

    Which structural feature is characteristic of steroids?

    <p>Fused ring system with a hydroxyl or keto group</p> Signup and view all the answers

    What type of fatty acid is α-linolenic acid classified as?

    <p>ω-3 (omega-3) fatty acid</p> Signup and view all the answers

    Which component of cell membranes is primarily represented by phospholipids?

    <p>Glycerophospholipids</p> Signup and view all the answers

    Study Notes

    Amino Acids

    • Basic building blocks of proteins.
    • Composed of an amino group (NH2), a carboxyl group (COOH), and a side chain (R group).
    • The chemical properties of amino acids depend on the nature of their R groups.
    • R groups can be polar, non-polar, acidic, or basic, influencing how amino acids behave in a polypeptide chain.

    Protein Structure

    • Primary structure: linear chain of amino acids linked by peptide bonds.
    • Secondary structure: Regular folding patterns formed by hydrogen bonds. Two main types: alpha helix and beta pleated sheet.
    • Tertiary structure: 3D structure formed by further folding of the polypeptide chain.
    • Quaternary structure: Arrangement of multiple polypeptide chains (subunits) in a protein.

    Essential and Non-essential Amino Acids

    • 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.

    Native Conformation

    • The functional, fully folded 3D structure of a protein.
    • Determined by the primary, secondary, tertiary, and sometimes quaternary structure.
    • Has a unique 3D structure that is crucial for protein function.

    Post-translational Modifications (PTM)

    • Chemical modifications that occur to a protein after it has been translated.
    • Add functional groups to amino acids, altering protein function.
    • Examples include phosphorylation, glycosylation, acylation, ubiquitination, and nitrosylation.

    Carbohydrates

    • Organic molecules composed of carbon, hydrogen, and oxygen atoms.
    • Classified as monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
    • Monosaccharides: Simple sugar units, classified by the number of carbon atoms (triose, pentose, hexose).
    • Disaccharides: Two linked monosaccharides.
    • Oligosaccharides: Short chains of 3-12 monosaccharides.
    • Polysaccharides: Long chains composed of hundreds of monosaccharides.

    Polysaccharides

    • Homopolymers of glucose with diverse functions.
    • Storage in animals: Glycogen, branched homopolymer of glucose.
    • Storage in plants: Starch, composed of amylose (unbranched) and amylopectin (branched).
    • Structure in plants: Cellulose, linear homopolymer of glucose.
    • Structure in invertebrates: Chitin, homopolymer of N-acetyl-glucosamine.

    Lipids

    • A diverse group of water-insoluble molecules with various functions.
    • Major sources of energy.
    • Important for structural components of cells.
    • Involved in various cellular signaling processes.

    Classification of Lipids

    • Fatty acids and their derivatives: Fatty acids, prostaglandins, leukotrienes.
    • Lipids containing glycerol: Neutral lipids (mono-, di-, tri-acylglycerol) and charged lipids (phospholipids).
    • Lipids not containing glycerol: Steroids, sphingolipids, terpenoids.
    • Lipoproteins and lipopolysaccharides: Complexes of lipids and proteins or lipids and polysaccharides.

    Arachidonic Acid

    • Arachidonic acid is a 20-carbon chain fatty acid with four double bonds.
    • It is an omega-6 fatty acid, meaning the terminal double bond is six carbons away from the omega carbon.

    Essential Fatty Acids (EFAs)

    • EFAs are fatty acids that the body cannot synthesize and must be obtained through diet.
    • Linoleic acid (omega-6) and alpha-linolenic acid (omega-3) are essential fatty acids.
    • EFA deficiency is rare, but can lead to scaly dermatitis, visual, and neurological abnormalities.

    Signalling Fatty Acids

    • Eicosanoids are a family of signaling fatty acids derived from 20-carbon polyunsaturated fatty acids (PUFAs).
    • Prostaglandins (PG) and Leukotrienes are examples of eicosanoids synthesized from arachidonic acid.
    • Prostaglandins are synthesized via cyclooxygenase (COX) and have a short half-life (seconds).
    • Leukotrienes are synthesized via lipoxygenase (LOX) and have a longer half-life (up to 4 hours).
    • Both prostaglandins and leukotrienes play a role in inflammation.

    Monoacyl, Diacyl & Triacylglycerol

    • Monoacylglycerol is a breakdown product of triacylglycerol (TAG) during fat digestion.
    • Diacylglycerol (DAG) is a potent intracellular signaling molecule that mobilizes calcium.
    • Triglycerides (triacylglycerols, TAG) are the principal storage form of energy in the body.
    • They are composed of three fatty acids and glycerol.
    • TAGs are stored in adipose tissue.

    Phospholipids (Phosphoglycerates) & Sphingolipids

    • Phospholipids are major components of cell membranes.
    • Lecithin is an example of a glycerophospholipid.
    • Sphingolipids are another type of lipid found in cell membranes.

    Steroids

    • Steroids contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3.
    • Cholesterol, Bile Acids, Progesterone, Adrenocortical Steroids, Androgens, and Estrogens are major steroid classes.
    • Cholesterol plays a vital role in the structure of membranes and is a precursor for Vitamin D, Bile Acids, and Steroid Hormones.

    Lipoproteins

    • Lipoproteins are spherical particles found in plasma that transport lipids, including cholesterol.
    • They have a hydrophobic core of triacylglycerols and cholesteryl esters.
    • A phospholipid layer surrounds the core and is associated with proteins.

    Amino Acids

    • The chemical properties of amino acids depend on the nature of their side chain (R group).
    • R groups can be polar, hydrophobic/philic, acidic, or basic.
    • Amino acid properties determine how they behave in a polypeptide chain.
    • Small amino acids: Glycine and Alanine
    • Branched amino acids: Valine, Leucine, Isoleucine
    • Sulphur-containing amino acids: Cysteine and Methionine
    • Amino acid found at a bend in a protein: Proline
    • Amino acids that can be phosphorylated: Serine, Threonine, and Tyrosine
    • Amino acids that can be glycosylated: Asparagine, Serine, and Threonine
    • Amino acid that can be nitrosylated: Cysteine

    Essential and Non-Essential Amino Acids

    • Essential amino acids cannot be synthesized in the body and must be obtained from the diet.
    • Non-essential amino acids can be synthesized by the body from other amino acids or precursors.
    • Some amino acids are conditionally essential, meaning their synthesis may not be sufficient to meet demand under all conditions.

    Protein Structure

    • Primary structure: Amino acids linked together with peptide bonds forming a polypeptide chain.
    • Secondary structure: Regular, repetitive folding patterns stabilized by hydrogen bonds.
      • Alpha (α) helix: Found in collagen and keratin in hair.
      • Beta (β) pleated sheet: Found in silk.
    • Tertiary structure: Further folding of the polypeptide chain into a globular form, stabilized by various bonds and interactions between side chains.
    • Quaternary structure: Arrangement of protein subunits in a multi-meric protein.

    Native Conformation

    • Functional, fully folded protein structure determined by primary, secondary, tertiary, and sometimes quaternary structure.
    • It determines the biological function of the protein, including catalysis, protection, regulation, signal transduction, storage, and transport.
    • Denaturation: Loss of native conformation, which disrupts protein function.

    Post-Translational Modifications (PTM)

    • Chemical modifications of a protein after translation.
    • Increases the diversity of the proteome.
    • Common examples:
      • Phosphorylation: Addition of a phosphate group to serine, threonine, or tyrosine residues.
      • Glycosylation: Addition of a sugar group to asparagine, serine, or threonine residues.
      • Acylation: Addition of a fatty acid.
      • Ubiquitination: Addition of ubiquitin, a signal for protein degradation.
      • Nitrosylation: Addition of nitric oxide.

    Abnormal Protein Aggregates and Disease

    • Misfolded proteins can form fibrils, known as amyloid.
    • Amyloid deposition in different tissues can lead to disease.
    • Alzheimer's disease is caused by the presence of misfolded proteins in the brain.

    Carbohydrates

    • Molecules containing carbon, hydrogen, and oxygen atoms.
    • Monosaccharides: Simple sugar units, such as glucose, fructose, galactose, and mannose.
    • Disaccharides: Two monosaccharides linked together, such as lactose (β-galactose + glucose) and maltose (glucose + glucose).
    • Polysaccharides: Many monosaccharides linked together, such as cellulose, starch (amylose and amylopectin), and glycogen.

    Monosaccharides

    • Empirical formula: (CH₂O)n, where n represents the number of carbon atoms (3-7).
    • Classified by the number of carbon atoms:
      • Triose: 3 carbons.
      • Pentose: 5 carbons.
      • Hexose: 6 carbons.
    • They are polyhydroxy aldehydes (aldose) or ketones (ketose).
    • Hexoses (C₆H₁₂O₆) are common dietary sources of sugar.

    Glycosidic Bond

    • A covalent bond between two sugar molecules.
    • The type of bond is determined by the number of connected carbons and the position of the anomeric hydroxyl group (alpha or beta configuration).
    • Lactose has a β(1 → 4) glycosidic bond.

    Polysaccharides

    • Oligosaccharides: 3-12 monosaccharides linked together.
    • Polysaccharides: > 12 monosaccharides linked together.
    • Variations in structure include chain length, branching, and glycosidic bond types.
    • Examples:
      • Amylopectin: A branched polysaccharide of glucose found in starch.
      • Amylose: A non-branched polysaccharide of glucose found in starch.
      • Cellulose: A straight chain polysaccharide of glucose found in plants.
      • Chitin: A polysaccharide of N-acetyl-glucosamine found in invertebrates.

    Polysaccharide Functions: Storage and Structure

    • Storage:
      • Glycogen: Stored in animals as a homopolymer of glucose.
      • Starch: Stored in plants as a homopolymer of glucose, composed of amylopectin and amylose.
    • Structure:
      • Cellulose: Provides structural support in plants.
      • Chitin: Provides structural support in invertebrates.

    Lipids

    • Heterogeneous group of water-insoluble (hydrophobic) organic molecules.
    • Play major roles in energy storage, cell structure, and signaling.
    • Major classifications:
      • Fatty acids and their derivatives.
      • Lipids containing glycerol: acylglycerols (neutral lipids) and phospholipids.
      • Lipids not containing glycerol: steroids, sphingolipids, and terpenoids.
      • Lipoproteins and lipopolysaccharides.

    Fatty Acids

    • Hydrocarbon chains with a carboxyl group at one end.
    • Chain length and saturation (presence of double bonds) vary.
    • Notation: Number of carbons:number and positions of double bonds.
    • E.g., 18:1(Δ⁹) represents an 18-carbon fatty acid with one double bond at the 9th carbon.

    Glycerol-Containing Lipids

    • Neutral lipids:
      • Mono-, di-, and tri-acylglycerol (triglycerides): formed by esterification of fatty acids to glycerol.
    • Charged lipids:
      • Phospholipids: Contain a phosphate group, making them amphipathic (hydrophilic and hydrophobic). Important components of cell membranes.

    Non-Glycerol-Containing Lipids

    • Steroids:
      • Four fused ring structures; important in cell signaling.
      • Cholesterol is a key steroid.
    • Sphingolipids:
      • Contain sphingosine (an amino alcohol) and a fatty acid.
      • Important components of cell membranes and involved in signaling.
    • Terpenoids:
      • Derived from isoprene units.
      • Include vitamins A, E, and K, carotenoids, and rubber.

    Lipoproteins and Lipopolysaccharides

    • Lipoproteins: Transport lipids in the blood.
    • Lipopolysaccharides: Found in the outer membrane of Gram-negative bacteria.

    Arachidonic Acid

    • Arachidonic acid is a 20-carbon fatty acid with four double bonds.
    • It is an ω-6 fatty acid, meaning the terminal double bond is six bonds away from the ω carbon.

    Essential Fatty Acids (EFAs)

    • Essential fatty acids are those that we cannot synthesize and must obtain from our diet.
    • Linoleic acid is an ω-6 fatty acid with the formula CH3(CH2)4(CH=CHCH2)2(CH2)6COOH.
    • α-linolenic acid is an ω-3 fatty acid with the formula CH3CH2(CH=CHCH2)3(CH2)6COOH.
    • EFA deficiency can lead to scaly dermatitis, visual and neurological abnormalities.

    Signaling Fatty Acids

    • Eicosanoids are a family of signaling molecules derived from 20-carbon polyunsaturated fatty acids.
    • Prostaglandins are synthesized from arachidonic acid via cyclooxygenase (COX).
    • Leukotrienes are synthesized from arachidonic acid via lipoxygenase (LOX).

    Monoacyl, Diacyl, & Triacylglycerol

    • Monoacylglycerol is a breakdown product of triacylglycerols during fat digestion.
    • Diacylglycerol (DAG) is a potent intracellular signaling molecule that mobilizes calcium.
    • Triacylglycerols (TAGs) are the principal storage form of energy in the body.
    • They are made up of three fatty acids and glycerol.
    • TAGs are stored in adipose tissue.

    Phospholipids

    • Phospholipids are major components of cell membranes.
    • Lecithin is an example of a glycerophospholipid.

    Sphingolipids

    • Sphingolipids are another type of lipid found in cell membranes.

    Steroids

    • Steroids contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3.
    • Cholesterol is a major steroid with 27 carbons and plays a vital role in the structure of membranes.
    • Bile acids are steroids with 24 carbons.
    • Progesterone and adrenocortical steroids are steroids with 21 carbons.
    • Androgens are steroids with 19 carbons.
    • Estrogens are steroids with 18 carbons.

    Functions of Cholesterol

    • Cholesterol is a metabolic precursor to vitamin D, bile acids, and steroid hormones.
    • We need a constant supply of cholesterol.

    Lipoproteins

    • Lipoproteins are spherical particles found in plasma that transport lipids, including cholesterol.
    • They have a hydrophobic core of triacylglycerols and cholesteryl esters.
    • They have a phospholipid layer associated with the core.

    Amino Acid Properties

    • The side chain (R group) of an amino acid determines its chemical properties, including polarity, hydrophobicity/hydrophilicity, acidity, and basicity.
    • Amino acid properties influence how they behave within a polypeptide chain.

    Amino Acid Characteristics

    • Small amino acids: glycine and alanine
    • Branched-chain amino acids: valine, leucine, isoleucine
    • Sulphur-containing amino acids: cysteine and methionine
    • Proline: found at bends in a protein
    • Phosphorylated amino acids: serine, threonine, and tyrosine
    • Glycosylated amino acids: asparagine, serine, and threonine
    • Nitrosylated amino acid: cysteine

    Essential and Non-Essential Amino Acids

    • Essential amino acids: cannot be synthesized by the body and must be obtained from the diet. Examples include methionine, arginine, threonine, tryptophan, valine, isoleucine, leucine, phenylalanine, histidine, and lysine.
    • Non-essential amino acids: can be synthesized by the body from other amino acids or precursors. Examples include alanine, aspartic acid, asparagine, cysteine, glutamic acid, glycine, proline, serine, and tyrosine.
    • Conditionally essential amino acids: their synthesis may not be sufficient to meet demand under certain conditions and may need to come from the diet. Examples include arginine and glutamine (in children).

    Protein Structure

    • Primary structure: amino acids are linked together in a polypeptide chain via peptide bonds. The chain has directionality, with the amino terminus (N-terminus) as the start and the carboxyl terminus (C-terminus) as the end.
    • Secondary structure: regular repetitive folding pattern stabilized by hydrogen bonds. Examples include alpha (α) helix and beta (β) pleated sheet.
    • Tertiary structure: further folding of the polypeptide chain into a globular form. Stabilized by various bonds and interactions between side chains, including disulfide bonds, hydrophobic interactions, ionic bonds, and hydrogen bonds.
    • Quaternary structure: arrangement of protein subunits in a multi-meric protein. It consists of two or more tertiary polypeptides, which may be the same or different, held together by non-covalent interactions and inter-chain disulfide bonds.

    Native Conformation

    • The functional, fully folded protein structure, which is unique and determined by the primary, secondary, tertiary, and sometimes quaternary structures.
    • It determines the biological function of the protein, including catalysis, protection, regulation, signal transduction, storage, and transport.

    Post-Translational Modifications

    • Chemical modifications that occur after protein translation, resulting in changes in protein function. Examples include:
      • Phosphorylation: addition of a phosphate group to serine, threonine, or tyrosine residues.
      • Glycosylation: addition of a sugar group to asparagine, serine, or threonine residues.
      • Acylation: addition of a fatty acid.
      • Ubiquitination: addition of ubiquitin, which can signal protein degradation.
      • Nitrosylation: addition of nitric oxide.

    Abnormal Protein Aggregates

    • Misfolded proteins can aggregate into fibrils, which can lead to diseases like Alzheimer's disease. Fibrils are known as amyloid and can be formed from over 20 proteins.

    Carbohydrates

    • Molecules containing carbon (C), hydrogen (H), and oxygen (O) atoms.
    • Monosaccharides: single saccharide units, also called simple sugars. Examples include glucose, fructose, galactose, and mannose.
    • Disaccharides: two monosaccharides linked together. Example: lactose, which is formed by a β (1→ 4) glycosidic bond between β-galactose and glucose.
    • Oligosaccharides: a few linked monosaccharides.
    • Polysaccharides: consist of many monosaccharides linked together. Examples include cellulose, glycogen, and starch.

    Monosaccharide Structure

    • Empirical formula: (CH2O)n, where n is the number of carbons.
    • Triose (n=3), pentose (n=5), and hexose (n=6) are common types.
    • They are polyhydroxy aldehydes (aldoses) or ketones (ketoses).

    Hexoses

    • Six-carbon sugars, including glucose, fructose, galactose, and mannose.
    • Isomers: same chemical formula but different structures.
    • Dietary sources:
      • Glucose: fruit juices, starch, glycogen, lactose, maltose, cane sugar.
      • Fructose: fruit juices, honey, cane sugar.
      • Galactose: milk (lactose).
      • Mannose: plants and gums.

    Cyclisation of Monosaccharides

    • Monosaccharides tend to cyclize, forming a ring structure.
    • In aldoses, cyclization occurs at carbon 1 (C1), which becomes the anomeric carbon. The anomeric carbon can have either an alpha (α) or beta (β) configuration.
    • In ketoses, cyclization occurs at carbon 2 (C2).

    Disaccharides and Glycosidic Bonds

    • A glycosidic bond links two monosaccharides together.
    • The type of bond depends on the connected carbons and the position of the anomeric hydroxyl group (α or β).

    Polysaccharides

    • Polymers of monosaccharides with varying chain lengths (oligosaccharides: n=3-12, polysaccharides: n>12).
    • Polysaccharides can have branches, different types of glycosidic bonds, and variations in structure.

    Polysaccharide Functions

    • Storage:
      • Glycogen: branched homopolymer of glucose in animals, storing energy.
      • Starch: homopolymer of glucose in plants, composed of amylopectin (branched) and amylose (unbranched).
    • Structure:
      • Cellulose: straight chain homopolymer of glucose in plants, providing structural support.
      • Chitin: homopolymer of N-acetyl-glucosamine in invertebrates, providing structural support.

    Lipids

    • Water-insoluble (hydrophobic) organic molecules.
    • Key functions:
      • Energy source: major source of energy in the body.
      • Structural components: of cells and organelles.
      • Cellular signaling: involved in signaling events (steroids, prostaglandins, leukotrienes).

    Lipid Classification

    • Fatty acids and their derivatives: including prostaglandins and leukotrienes.
    • Lipids containing glycerol:
      • Neutral lipids: mono-, di-, and tri-acylglycerol (triglycerides).
      • Charged lipids: phospholipids.
    • Lipids not containing glycerol:
      • Steroids: examples include cholesterol, testosterone, and estrogen.
      • Sphingolipids: examples include sphingomyelin and cerebrosides.
      • Terpenoids: examples include vitamin A and carotenoids.
    • Lipoproteins and lipopolysaccharides: involved in lipid transport and bacterial cell walls, respectively.

    Fatty Acids

    • Chain lengths are indicated by the number of carbons before the colon, and the location and number of double bonds are indicated after the colon.
    • Example: 18:2 (Δ9,12) indicates an 18-carbon fatty acid with two double bonds, located at the 9th and 12th carbons from the carboxyl group.### Arachidonic Acid
    • A 20 carbon chain with 4 double bonds
    • Also known as an omega-6 (n-6) fatty acid
    • The terminal double bond is 6 bonds in from the omega carbon

    Essential Fatty Acids (EFAs)

    • Essential for human health as we cannot synthesize them
    • Linoleic acid (omega-6): 18:2(n-6)
    • Alpha-linolenic acid (omega-3): 18:3(n-3)
    • EFA deficiency (rare) can lead to:
      • Scaly dermatitis
      • Visual and neurologic abnormalities

    Signalling Fatty Acids

    • Prostaglandins and Leukotrienes belong to the eicosanoid family
    • Synthesized from arachidonic acid - a 20:4 fatty acid
    • Prostaglandins are synthesized via COX (cyclooxygenase)
      • Potent
      • Short half-life (seconds)
      • Multiple roles including inflammation and platelet homeostasis
    • Leukotrienes are synthesized via LOX (lipoxygenase)
      • Longer half-life (up to 4 hours)
      • Multiple roles including inflammation and neutrophil adhesion

    Monoacyl, Diacyl & Triacylglycerol

    • Monoacyl glycerol is a breakdown product of TAG in fat digestion
    • DAG (Diacylglycerol) is a potent intracellular signal
      • Involved in the mobilization of calcium
    • Triglycerides (Triacylglycerols)
      • Made up of 3 fatty acids and glycerol
      • Principal storage form of energy in the body
      • Stored in adipose tissue

    Phospholipids (Phosphoglycerates) & Sphingolipids

    • Major component of cell membranes
    • Lecithin is an example of a glycerophospholipid
    • Sphingolipids are another class of lipids that are found in cell membranes

    Steroids

    • Contain a characteristic fused ring system with a hydroxyl or keto group on carbon 3
    • Major classes of steroids:
      • Cholesterol (27 carbons)
      • Bile acids (24 carbons)
      • Progesterone and adrenocortical steroids (21 carbons)
      • Androgens (19 carbons)
      • Estrogens (18 carbons)
    • Functions of Cholesterol:
      • Metabolic precursor of Vitamin D, bile acids, and steroid hormones
      • Plays a vital role in the structure of membranes
      • We need a constant supply of cholesterol

    Lipoproteins

    • Spherical particles found in plasma that transport lipids, including cholesterol
    • Hydrophobic core of triacylglycerols and cholesteryl esters
    • Phospholipid layer associated with the core

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    Description

    This quiz covers the fundamentals of amino acids and protein structure, including their classifications, chemical properties, and levels of structural organization. You'll explore both essential and non-essential amino acids and understand their role in building proteins.

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