Biochemistry 1: Amino Acids and Proteins
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Questions and Answers

What is the structure indicated by arrows in the general structure of amino acids?

Name of the structure

Which amino acid is not optically active?

  • Cysteine
  • Glycine (correct)
  • Glutamine
  • Arginine
  • Tyrosine

    • What type of bond is a peptide bond?

  • Hydrogen bond
  • Ionic bond
  • Metallic bond
  • Covalent bond (correct)

    • Draw and name the different forms of amino acids in an aqueous solution based on pH.

    <p>The different forms of amino acids based on pH</p> Signup and view all the answers

    What part of the amino acid gives it uniqueness?

    <p>Side chain</p> Signup and view all the answers

    Unfolding of a protein is termed as:

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

    Which of the following is not a factor responsible for the denaturation of proteins?

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

    What is true about size-exclusion chromatography?

    <p>Largest protein eluted first</p> Signup and view all the answers

    How are two chains of amino acids in an insulin molecule held together?

    <p>Disulfide bridges</p> Signup and view all the answers

    Who deduced the double-helical structure of DNA?

    <p>Watson and Francis Crick</p> Signup and view all the answers

    What is hemoglobin?

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

    Which metal forms a complex with functional groups in the protein's peptide bond in the Biuret method?

    <p>Cu^2+^</p> Signup and view all the answers

    According to the Biuret method, the intensity of the color is directly proportional to the amount of what substance present in the sample?

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

    What are the final products of starch enzyme hydrolysis?

    <p>Maltose and glucose</p> Signup and view all the answers

    During starch hydrolysis, what are the partial hydrolysis products of intermediate size called?

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

    Provide at least one similarity and one difference between the enzyme hydrolysis of starch and starch hydrolysis in the presence of hydrochloric acid.

    <p>One similarity is the breakdown of starch into smaller molecules; one difference is the final products formed.</p> Signup and view all the answers

    In the presence of hydrochloric acid, what are the final products of starch hydrolysis?

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

    Which of the following does not act as a restriction enzyme?

    <p>polydeoxyribonucleotide synthase</p> Signup and view all the answers

    What is E.cor1?

    <p>Restriction endonuclease</p> Signup and view all the answers

    Electrophoresis helps to separate what from each other?

    <p>DNA segments</p> Signup and view all the answers

    The number of milligrams of KOH required to neutralize the free and combined fatty acid in one gram of a given fat is called _.

    <p>Saponification number</p> Signup and view all the answers

    What is formed during the hydrolysis of starch and glycogen in acid catalysis?

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

    Name the branched polysaccharides.

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

    Identify the differences between amylopectin and amylose.

    <p>Amylose is unbranched, while amylopectin is branched.</p> Signup and view all the answers

    Identify the differences between cellulose and amylose.

    <p>Cellulose is a structural polysaccharide, while amylose is a storage polysaccharide.</p> Signup and view all the answers

    Identify the differences between enzymatic hydrolysis and acid-catalysed hydrolysis of polysaccharides.

    <p>Enzymatic hydrolysis is specific and gentle, while acid-catalysed hydrolysis is non-specific and harsh.</p> Signup and view all the answers

    Why can't cellulose be digested by humans?

    <p>Humans lack the enzyme cellulase to break down cellulose.</p> Signup and view all the answers

    What are the dextrins resulting from the hydrolysis of starch and what colors are formed with the iodine solution?

    <p>Dextrins are intermediate products, and the iodine solution forms a reddish brown color with them.</p> Signup and view all the answers

    The carbohydrate unit that makes up cellulose is:

    <p>β-D-glucose</p> Signup and view all the answers

    Glycogen is a:

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

    People cannot digest:

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

    What is the carbohydrate in the muscle cell:

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

    Which substance has a branched structure:

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

    What is the dark red carbohydrate with the iodine solution:

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

    The β-glycoside bond (1 → 4) exists in:

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

    In the animal body, glucose is stored in the form of:

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

    Which of the following is an example of monosaccharide?

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

    Which of the following is an example of disaccharide?

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

    Which of the following carbohydrates is a triose?

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

    Lactose is a disaccharide of which of the following sugar units?

    <p>Glucose and galactose</p> Signup and view all the answers

    When all the monosaccharides in a polysaccharide are the same type, such type of a polysaccharide is called a ________

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

    In which of the following forms, glucose is stored in the liver?

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

    Study Notes

    Here are the study notes for the provided text:

    Proteins

    • Amino acids are amphoteric molecules, meaning they can exist as cations, anions, or zwitterions depending on the pH.
    • Glycine is the only amino acid that is not optically active.
    • A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another amino acid.
    • The side chain of an amino acid gives it uniqueness.
    • Denaturation of proteins can be caused by pH changes, organic solvents, heat, and charge.
    • Size-exclusion chromatography separates proteins based on their molecular weight, with smaller proteins eluting first.
    • Disulfide bridges can form between two cysteine residues, linking multiple chains together.
    • Hemoglobin is a tetramer, composed of four polypeptide chains.

    Peptide Bond Formation

    • During peptide bond formation, a hydroxyl group is lost from the carboxyl group of one amino acid, and a hydrogen atom is lost from the amino group of another amino acid.
    • The resulting peptide bond is planar, rigid, and polar.

    Amino Acids

    • Alanine and phenylalanine can form dipeptides through a condensation reaction.
    • Glutathione is a cellular tripeptide formed by glutamic acid, cysteine, and glycine.
    • Oxytocin and vasopressin are synthesized in the hypothalamus and secreted from the posterior pituitary gland.

    Insulin

    • Insulin is a polypeptide hormone with two chains linked together by disulfide bridges.
    • It promotes the uptake of glucose from the blood into tissues.
    • Diabetes mellitus is a disease characterized by disturbed insulin secretion.

    Protein Structure

    • Primary structure refers to the sequence of amino acids in a polypeptide chain.
    • Secondary structure is stabilized by hydrogen bonds and includes α-helices and β-pleated sheets.
    • Tertiary structure is maintained by different interactions, including covalent, ionic, hydrogen bonds, and van der Waals interactions.
    • Quaternary structure refers to the arrangement of multiple polypeptide chains in a protein.

    Hemoglobin

    • Hemoglobin has four O2 binding sites per molecule.
    • It transports CO2 from tissues to lungs in the form of carbamate at the amino termini of chains.

    Enzymes

    • Heavy metal ions can bind to the -SH groups in the polypeptide chain, changing the conformation of the enzyme and altering the rate of the enzymatic reaction.
    • Malonic acid is a competitive inhibitor of succinate dehydrogenase, increasing the Km but not affecting the Vmax.
    • Enzymes can be saturated with substrate, and increasing the substrate concentration will not appreciably increase the reaction rate.
    • Noncompetitive inhibition decreases the Vmax without affecting the Km.

    Carbohydrates

    • Glucose and fructose are isomers, differing in their structure.
    • Sucrose, lactose, and maltose are the most abundant disaccharides, composed of glucose and fructose, glucose and galactose, and glucose and glucose, respectively.
    • Glycogen is a branched polysaccharide stored in the liver and muscles, composed of glucose residues.
    • Starch, cellulose, and glycogen are composed of glucose residues, but differ in their structure and function.

    Nucleotides and Nucleic Acids

    • Purine bases in nucleic acids include adenine and guanine.
    • RNA does not contain thymine, but instead contains uracil.
    • A nucleotide is composed of a base, sugar, and phosphate group.
    • Peptide nucleic acids (PNAs) are not components of RNA.### Nucleic Acids
    • A nucleoside consists of a base and a sugar.
    • A nucleotide consists of a base, a sugar, and a phosphate.
    • The sugar molecule in a nucleotide is a pentose.
    • Nucleotides are the building blocks of nucleic acids.
    • Adenine pairs with thymine with 2 hydrogen bonds, and guanine pairs with cytosine with 3 hydrogen bonds.
    • The ratio A + G / T + C is constant for DNA.
    • RNA does not have a double-stranded structure, and thymine is not present in RNA; instead, uracil is present.
    • UMP is not present in DNA.

    Lipids

    • Linolenic acid is an essential fatty acid.
    • Bile salts are polar derivatives of cholesterol.
    • Fatty acids with a higher degree of saturation have a higher melting point.
    • Lipids in tissues that are subjected to cooling are more unsaturated.
    • Naturally occurring unsaturated long-chain fatty acids are nearly always in cis-configuration.
    • Palmitic acid has 16 carbon atoms.
    • Triacyl glycerol is a storage form of lipid.
    • Cholesterol is a precursor for vitamin D, sex hormones, and bile salts.

    Proteins

    • Biuret reagent forms a purple-colored complex with compounds containing at least four peptide bonds.
    • The Biuret method is based on the complexation of Cu2+ to functional groups in the protein's peptide bond.
    • The intensity of the color is directly proportional to the amount of protein present in the sample.

    Carbohydrates

    • Dextrins are partial hydrolysis products of starch of intermediate size.
    • The final product of starch enzyme hydrolysis is glucose.
    • The final product of starch hydrolysis in the presence of hydrochloric acid is glucose.

    Enzymes and Biotechnology

    • EcorI is a restriction endonuclease.
    • Electrophoresis helps to separate DNA segments.
    • Polydeoxyribonucleotide synthase is not a restriction enzyme.

    Fats and Oils

    • The saponification number is the number of milligrams of KOH required to neutralize the free and combined fatty acid in one gram of a given fat.

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    Biochemistry 1_all EXERCISEs-1.docx

    Description

    Test your knowledge of proteins and amino acids, including their structure, forms, and properties. Quiz questions cover the general structure of amino acids, their optical activity, and more.

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