4.6 Organic Chemistry and Macromolecules Flashcards by oisin mcelwain

Denaturation of proteins involves disruption of the
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Covalent bonding

Answer is C: Protein “tertiary structure” is held together by the relatively weak attraction between different parts of the protein molecule known as “hydrogen bonding”. This structure is the most easily disrupted.

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One of the following is NOT a function of lipids in the body. Which one?
A. Function as coenzymes
B. Used in phospholipids
C. Used to make prostaglandins
D. Steroids are produced from them

Answer is A: Coenzymes are proteins (not lipids).

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Amino acids are the building blocks of all proteins. As more amino acids are added, the protein chain tends to fold upon itself in a characteristic way. This characteristic of a protein is called the:
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Quaternary structure

Answer is C: The shape produced by folding is the tertiary structure. Primary struc- ture is the sequence in which the amino acids are joined. Secondary structure is any repetition of the primary structure. Quaternary structure does not exist.

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Which of the following is the correct combination for the nucleic acid DNA?
A. Phosphate, ribose, uracil
B. Phosphate, deoxyribose, uracil C. Phosphate, ribose, adenine
D. Phosphate, deoxyribose, adenine

Answer is D: “Deoxyribose” supplies the “D” in DNA. The base uracil occurs in RNA (not DNA) where it substitutes for the thymine that occurs in DNA.

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To which of the following class of biological compounds do all enzymes belong?
A. Hormones
B. Proteins
C. Carbohydrates
D. Lipids

Answer is B: All enzymes are proteins.

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The twisting of a polypeptide chain into a characteristic shape such as a helix is an example of which of the following?
A. Primary structure
B. Secondary structure
C. Tertiary structure
D. Quaternary structure

Answer is C: The shape of the protein molecule is the tertiary structure of the protein.

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Which one of the following is NOT a steroid compound?
A. Stearic acid
B. Estrogen
C. Cholesterol
D. Testosterone

Answer is A: Stearic acid is a fatty acid. The sex hormones estrogen and testosterone are derived from cholesterol.

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Which of the following carbohydrates are able to pass through the plasma membrane?
A. Disaccharides
B. Sucrose
C. Glycogen
D. Monosaccharides

Answer is D: For example, glucose maybe absorbed from the gut by passing through the plasma membrane of the cells lining the gut. Glucose is also absorbed by cells for respiration inside mitochondria.

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Which of the following foods when catabolised in the body produces the highest yield of energy?
A. 100 g of fat
B. 100 g of chocolate
C. 100 g of carbohydrate D. 100 g of protein

Answer is A: Fat is higher in energy (kilojoules) than either protein or carbohydrate. Chocolate has sugar (carbohydrate) as well as fat as an ingredient.

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Fructose is a simple sugar or carbohydrate. What is it an example of? A:
A. Monosaccharide
B. Disaccharide
C. Polysaccharide
D. Oligosaccharide

Answer is A: Fructose is a simple sugar or monosaccharide – it cannot be converted to a simpler sugar by hydrolysis.

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Cells use glucose as an energy source but store it as glycogen. When needed the glycogen is broken down by a process called:
A. Glycolysis
B. Glycogenesis
C. Gluconeogenesis
D. Glycogenolysis

Answer is D: Glycogen – o – lysis refers to the lysis (splitting) of glycogen into smaller glucose units.

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A lipid such as oleic acid contains a number of double bonds in the carbon chain. Because of this, what term is applied to it?
A. Monounsaturated
B. Diunsaturated
C. Polyunsaturated
D. Saturated

Answer is C: “Unsaturated” because addition hydrogen atoms may be attached to the carbon bonds if the double bond was replaced by a single bond. “Poly-” because there is more than one instance of a double bond between adjacent carbon atoms.

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What are the structural components of proteins?
A. Amino acids
B. Fatty acids
C. Peptides
D. Monosaccharides

Answer is A: Peptides are used for several amino acids joined together.

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Which of the following chemical formulae represents a typical carbohydrate?
A. Ca10(PO4)6(OH)2
B. N2C5H12O4
C. C120H240O120
D. C57H110O6

Answer is C: A carbohydrate is composed of carbon, hydrogen and oxygen atoms. Usually there are twice as many H atoms as C atoms. Choice D, having relatively few O atoms, is typical of a lipid.

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Proteins perform a wide range of functions in the body including which one of the following?
A. They are our major source of energy.
B. They act as enzymes.
C. They are used to make sex hormones.
D. They are necessary for the absorption of vitamins A, D, E and K.

Answer is B: All enzymes are proteins. Carbohydrates should be the major energy source. Choice D lists the fat soluble vitamins.

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Which of the following refers to a carbohydrate?
A. Diglycerol
B. Adenosine diphosphate
C. Disaccharide
D. Dipeptide

Answer is C: A disaccharide is a sugar (hence a carbohydrate) that can be simplified into simpler sugars.

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What are the bonds that maintain the secondary and tertiary structure of proteins?
A. Hydrogen bonds
B. Covalent bonds
C. Ionic bonds
D. Peptide bonds

Answer is A: Hydrogen bonds acting between N and H. Covalent bonds act between the atoms of an amino acid, while peptide bond (=covalent bond) is the term used for the bond between one amino acid to the adjacent one.

Which of the following formulae would be most likely to represent a lipid?
A. C2936H4624N786O889S41
B. C57H110O6
C. C6H12O6
D. Ca10(PO4)6(OH)2

Answer is B: Lipids consist of carbon, hydrogen and oxygen, with relatively few O compared to C. Choice C is a monosaccharide; choice A is a protein (note the nitrogen). No one should have chosen D (= calcium hydroxyapatite).

What are the four most common elements found in proteins?
A. C, H, N, Ca
B. C, O, N, Fe
C. C, H, N, O
D. N, C, H, Na

Answer is C: Nitrogen must be present. Choice B is wrong as H is absent.

To what type of fatty acids is the term “saturated” applied?
A. Those with four single bonds around each carbon atom
B. Those with at least one double bond between carbon atoms C. Those that are not implicated in coronary heart disease
D. Those which are essential in our diet

Answer is A: Saturated refers to the number of single bonds around carbon atoms. The maximum is four if there are no double bonds.

Which of the following is a polysaccharide?
A. Glucuronidase
B. Glucagon
C. Glucose
D. Glycogen

Answer is D: Choice A is an enzyme (“-ase”), B is a hormone and C is a monosaccharide.

What holds the primary structure of a protein together?
A. Hydrogen bonds
B. Covalent bonds
C. Peptide bonds
D. Ionic bonds

Answer is C: Protein primary structure refers to the sequence of the linked amino acids. The link between adjacent amino acids is called a “peptide bond” – a special term reserved for the covalent bond between the C of one amino acid and the N of the adjacent amino acid.

Which of the following are NOT proteins?
A. Glycolipids
B. Enzymes
C. Haemoglobin
D. Albumin

Answer is A: Glycolipids are lipids not proteins.

What is a “saturated fat”?
A. One that contains cholesterol
B. A triglyceride that has three fatty acids
C. One where the carbon atoms that are connected by single bonds
D. One that must be included in our diet

Answer is C: Saturated means each carbon atom is directly bonded to four other atoms.

25. What is a function of carbohydrates in the body? A. To act as enzymes B. To provide energy C. Function as local hormones D. To provide the building blocks for proteins

Answer is B: Dietary carbohydrates are converted to simple sugars which are disassembled in mitochondria to produce ATP.

26. Which of the following is a typical formula for a polypeptide? A. C57H110O6 B. C18H29O2 C. C21H41O5N8 D. C6H12O6

Answer is C: A polypeptide is several amino acids joined together. Hence the element nitrogen must be present.

27. In what form is most of the lipid component of our food in? A. Triglycerols B. Polysaccharides C. Complex carbohydrates D. Polypeptides

Answer is A: Our dietary lipids are in the form of triglycerols (a glycerol molecule and three fatty acids).

28. In organic compounds, how many bonds do carbon atoms always form? A. Four single bonds B. Four covalent bonds C. Two double bonds D. Four ionic bonds

Answer is B: Carbon has four valence electrons and “would like” a share of four more to fill its outer shell. This is achieved by four covalent bonds, where a double bond counts as two covalent bonds.

29. A molecule of an organic compound can be thought of as having two portions: a radical with an attached functional group. What is the correct definition of a functional group? A. It consists of carbon atoms and hydrogen atoms. B. It is responsible for most of the properties of the molecule. C. It has a modest influence on the properties of the molecule. D. It consists of a ring of carbon atoms.

Answer is B: As organic molecules all contain C, H and O atoms in similar bonding situations, the differences in their chemical behaviour (function) is largely governed by the differences in structure of small groups of atoms that are bonded differently or contain atoms other than C, H and O. These groups of atoms are known as the functional group.

30. The one medicine may have many names. What is the “generic name” of a medicine? A. The name that describes the effect of the drug on the body B. The systematic name of the chemical involved C. The name given to the product by a manufacturer of the drug D. The name proposed by the inventor and approved by a government agency

Answer is D: A medicine has only one “generic” name, but each manufacturer will give it their own “trade” name. Choice A refers to the naming of a class of drugs each of which may be a different molecule.

31. When a protein is denatured, which aspect of its structure is affected the LEAST? A. Primary structure B. Secondary structure C. Tertiary structure D. Quaternary structure

Answer is A: Denaturation does not affect primary structure. That is, the sequence of amino acids within the polypeptide chain.

32. What chemical symbol for the element/atom occurs in an amino acid but not in fats and carbohydrates? A. N B. H C. O D. C

Answer is A: Amino acids contain an “amine” group – a nitrogen atom bonded to a hydrogen atom. Nitrogen atoms do not occur in fats or carbohydrates.

33. The element carbon is said to be tetravalent. This means it always has the following number of covalent bonds in neutral compounds. A. One B. Two C. Three D. Four

Answer is D: Carbon forms four covalent bonds. “Tetra-” refers to four.

34. Which of the following structures represents a molecule belonging to the alco- hol family? A. CH3 – COOH B. CH3 – OH C. CH3 – O – CH3 D. CH3 – CO– CH3

Answer is B: An “alcohol” has an oxygen bonded to a hydrogen (-OH) atom as a functional group. Choice A has a carboxylic acid (-COOH) functional group.

35. Which statement describing the chemical reactivity of organic molecules is FALSE? A. Reactivity depends on the nature of the functional group. B. Reactivity is independent of the number and nature of the carbon rings C. Reactivity is dependent on the nature and size of the radical group. D. Reactivity in the body may depend on the internal body factors such as temperature and pH.

Answer is B: Reactivity IS in fact influenced by the number and nature of the carbon rings. So the statement B is false.

36. Which of the following structures represents molecules belonging to the amide family? A. CH3 – SH B. CH3 – NH2 C. CH3 – CO – NH2 D. CH3 – OH

Answer is C: The “amide” functional group consists of a carbon, an oxygen and a nitrogen atom. The carbon atom is double bonded to an oxygen atom while also being single bonded to a nitrogen atom.

37. A hydrocarbon is a type of compound that contains: A. Only carbon atoms B. Carbon and hydrogen atoms C. Carbon, hydrogen and oxygen atoms D. Water and carbon atoms

Answer is B: Hydrocarbon means hydrogen combined with carbon.

38. A hydrocarbon molecule which contains at least one double bond could be an example of which type of compound: A. Alkane B. Alkene C. Alkyne D. Al Capone

Answer is B: Alkenes contain at least one double bond between carbon atoms. Alkanes have only single bonds, while alkynes have at least one triple bond between carbon atoms.

39. Which of the following structures represents a molecule belonging to the ketone family? A. CH3 – CO – NH2 B. CH3 – NH2 C. CH3 – O – CH3 D. CH3 – CO – CH3

Answer is D: A ketone has a “carbonyl” functional group (C double bonded to O), while the carbon atom of the carbonyl group is also bonded to two other carbon atoms (that is, is attached to two radicals). Choice C is incorrect as the O is single bonded to the carbon(s). Choice A is incorrect as the NH group is not a radical.

42. What is the sequence of amino acids in a protein known as? A. Primary structure B. Secondary structure C. Tertiary structure D. Quaternary structure

Answer is A: Primary structure refers to the order in which amino acids are attached to each other.

43. Which one of the following structure represents a saturated organic compound? O || A. CH3CH2 C OH B. CH3CH2OH C. CH3CHCHCH3 D. CH...CH

Answer is B: A saturated compound must have each carbon atom directly bonded to four other atoms. Only the arrangement in choice B can satisfy this requirement. In choices C and D, the arrangement CH means that there must be a double bond between two C atoms.