BIOB111_CHBIO - Tutorial activity for Session 10 General Topics for Session 10 Week 5 Properties of the functional groups and examples. Amines, amides and Esters Physical properties and chemical reactions: examples Conceptual multiple choice questions: 1. Concept: Halogenated ethers Context: Both halogenated and non-halogenated ethers have been used as anaesthetic agents. Question: How could an ether compound be converted into a halogenated either (example below)? a) A two halogenation reactions are required to create a halogenated alkane that contains many halogen atoms, as multiple halogen atoms can replace hydrogen atoms in each chemical reaction b) Many halogenation reactions would be required to create the halogenated ether, as one hydrogen atom is replaced with one halogen atom in each halogenation reaction c) Many halogenation reactions would be required to create the halogenated ether, as two hydrogen atoms are replaced with one halogen atom in each halogenation reaction d) A single halogenation reaction is required to create a halogenated alkane that contains many halogen atoms, as multiple halogen atoms can replace hydrogen atoms in a single chemical reaction 2. Concept: Ether connections in carbohydrates Context: The ether is a two R-group functional group, meaning it can be used to connect two small compounds together to create a larger compound. Last Updated on 6-Feb-14 Page 1 of 7
Question: How does the ether functional group allow two single sugar unit compounds to attach together? a) The OH present in each ether group allows the two single sugar unit compounds to attach together, where the sugar units both attach to the same oxygen atom b) The OH within an ether group forms a covalent bond to each of the single sugar unit compounds, which connects the two sugar units together c) The OH present in each ether group allows the two single sugar unit compounds to attach together, where the sugar units both attach to the same hydrogen atom d) The oxygen within an ether group forms a covalent bond to each of the single sugar unit compounds, which connects the two sugar units together 3. Concept: Covalent bonding of nitrogen Context: The nitrogen atom belongs to group V on the periodic table, meaning it contains five valence electrons. Question: Which of the following best explain the covalent bonding of a nitrogen atom? a) The three unpaired valence electrons in the nitrogen atom allow nitrogen to form three covalent bonds, which can be single, double or triple bond(s) b) Nitrogen atoms only contain one pair of electrons in their valence shell, which means that nitrogen only needs to form a single covalent bond to be stable c) The five valence electrons in the nitrogen atom allow nitrogen to form five covalent bonds, which can be single, double or triple bond(s) d) The five unpaired valence electrons makes nitrogen very reactive, as it needs to form five covalent bonds to be stable 4. Concept: Identifying primary, secondary and tertiary amines Last Updated on 6-Feb-14 Page 2 of 7
Context: The number of carbons directly bonded to the nitrogen atom within the amine functional group specifies whether the compound is a primary, secondary and tertiary amine. Question: Which of the following compounds is a tertiary amine? a) b) c) d) 5. Concept: Amines in acid-base reactions Context: The amines present in dead fish react with the acids in lemon juice via an acidbase reaction. Question: Which of the following best describes the acid-base reaction between trimethylamine and citric acid (present in lemon juice)? Last Updated on 6-Feb-14 Page 3 of 7
a) The odourless trimethylamine donates a H + to citric acid, causing trimethylamine to become an pungent amine salt (conjugate base) b) The nitrogen atom within trimethylamine needs to form an additional covalent bond to be stable, which allows trimethylamine to accept H + from citric acid during an acidbase reaction c) The pungent trimethylamine accepts a H + from the citric acid, causing trimethylamine to become an odourless amine salt (conjugate base) d) The unshared pair of valence electrons in the nitrogen atom within trimethylamine allows the compound to accept a H + from citric acid in an acid-base reaction, with the compound becoming the conjugate base product with one extra H + 6. Concept: Cyclic amine: haeme Context: The haeme compound contains four cyclic amine rings that together hold an Fe atom in the centre of the structure. Question: Why is the haeme ring vital to the transport of oxygen within the body? a) The haeme compound binds to haemoglobin within red blood cells, with the oxygen molecule binding to the Fe atom held in position by the cyclic amine rings within haeme b) Oxygen molecules are carried by the haemoglobin protein inside red blood cells, with the haeme ring assisting in holding the structure of the haeme protein together c) The haeme compound binds to haemoglobin within red blood cells, with four oxygen molecules binding to the four cyclic amine rings within a single haeme d) Oxygen is carried by the red blood cells, with the haeme ring bound to the red blood cells playing a vital role in binding oxygen molecules with the help of the cyclic amine rings within haeme 7. Concept: Identifying primary, secondary and tertiary amides Context: The number of carbons directly bonded to the amide group specifies whether the compound is a primary, secondary and tertiary amide. Question: Which of the following compounds is a primary amide? Last Updated on 6-Feb-14 Page 4 of 7
a) b) c) d) 8. Concept: Amide formation in proteins Context: Amide links (aka peptide bonds) connect adjacent amino acids within a protein chain. Each amino acid contains two functional groups which are important to the formation of amide links. Question: Which of the following best explains how an amide link forms between two amino acids? Last Updated on 6-Feb-14 Page 5 of 7
a) The ketone group from one amino acid reacts with an amine group from a second amino acid to create an amide link (peptide bond), which fuses the two amino acids together and releases a H 2O molecule b) The ester group from one amino acid reacts with an amine group from a second amino acid to create an amide link (peptide bond), which creates a single compound that contains two amino acids c) The aldehyde group from one amino acid reacts with an amine group from a second amino acid to create an amide link (peptide bond), which fuses the two amino acids together and releases a H 2O molecule d) The carboxylic acid group from one amino acid reacts with an amine group from a second amino acid to create an amide link (peptide bond), which creates a single compound that contains two amino acids 9. Concept: Disulfide bonding by thiols Context: Two thiol functional groups can connect together to form a disulfide bond. The disulfide bond is a strong covalent attachment between two sulfur atoms. Question: What must happen to the thiol functional groups within two cysteine amino acids so that the amino acids can link together via a disulfide bond? a) The individual thiol groups in the cysteines must gain a hydrogen atom via reduction, which allows the thiol groups to link together via a disulfide bond b) The individual thiol groups in the cysteines must lose their hydrogen atoms via oxidation, which allows the remaining sulfur atoms to link together via a disulfide bond c) The individual thiol groups in the cysteines must lose their sulfur atoms before a disulfide bond can form between the sulfur atoms d) The individual thiol groups in the cysteines must lose their hydrogen atoms via reduction, which allows the remaining sulfur atoms to link together via a disulfide bond 10. Concept: Role of disulfides in protein structure Context: Proteins rely on a their specific shape are 3D arrangement to execute their specific function. Last Updated on 6-Feb-14 Page 6 of 7
Question: How do disulfide bonds contribute to the shape of a protein? a) Disulfide bonds allow any two non-adjacent amino acids to attach together, which allows the chain of amino acids to be held in a specific position b) Each pair of adjacent amino acids in a protein chain attach to each other via a disulfide bond c) Disulfide bonds allow two non-adjacent cysteine amino acids to attach together, which allows the chain of amino acids to be held in a specific position d) Each pair of adjacent cysteine amino acids in a protein chain attach to each other via a disulfide bond Last Updated on 6-Feb-14 Page 7 of 7