Unit 1: Introduction to biophysics - Practice Quiz

1 Which of the following is the monomer (building block) of proteins?

2 Which biomolecule serves as the primary source of quick energy in cells?

3 The monomer units that make up nucleic acids are called:

4 Which of the following is a major function of lipids in living organisms?

5 A nucleotide is composed of a nitrogenous base, a phosphate group, and a:

6 Which type of bond holds the two strands of the DNA double helix together?

7 The bond that links two amino acids together in a protein is called a:

8 Which of the following is generally the strongest type of chemical bond?

9 The backbone of a DNA strand is held together by which type of bond?

10 Weak interactions between nonpolar molecules that arise from temporary charge fluctuations are called:

11 The most common form of DNA found in living cells under physiological conditions is:

12 Which DNA conformation is a left-handed helix?

13 The process by which double-stranded DNA separates into single strands is called:

14 The temperature at which half of the DNA molecules are denatured is known as the:

15 DNA rich in which base pair has a higher melting temperature?

16 The process of synthesizing RNA from a DNA template is called:

17 Which enzyme is primarily responsible for synthesizing RNA during transcription?

18 In RNA, which base replaces thymine that is found in DNA?

19 Which type of RNA carries the genetic message from DNA to the ribosome?

20 Compared to DNA, RNA molecules are usually:

21 A polypeptide is being synthesized in which the amino acids are joined together. Which type of covalent linkage forms between adjacent amino acid residues?

22 A biochemist isolates a biomolecule that yields glucose and fructose upon hydrolysis. Which macromolecule class and specific compound does this most likely represent?

23 Which structural feature primarily determines whether a fatty acid is classified as saturated or unsaturated?

24 Which of the following interactions is generally the strongest per bond in a biological system?

25 The stability of protein secondary structures such as the -helix and -sheet is primarily maintained by which type of interaction?

26 The hydrophobic effect drives the folding of globular proteins mainly because

27 Two cysteine residues in a folded protein can form a covalent cross-link. What is this bond called and what conditions favor it?

28 Which DNA conformation is a left-handed helix typically favored by alternating purine-pyrimidine sequences under high salt conditions?

29 Compared to B-DNA, A-DNA is best described as

30 During DNA denaturation (melting), which measurable property increases as the double helix separates into single strands?

31 A DNA sample with a higher G-C content will generally have a melting temperature () that is

32 Negative supercoiling of a closed circular DNA molecule tends to

33 During transcription, which enzyme synthesizes an RNA strand complementary to the DNA template?

34 If the DNA template strand reads , what is the sequence of the transcribed mRNA?

35 Which of the following is a post-transcriptional modification of eukaryotic pre-mRNA?

36 The key chemical difference between the sugar in RNA and DNA is that

37 Why is single-stranded RNA generally less chemically stable than double-stranded DNA?

38 A tRNA molecule adopts a characteristic cloverleaf secondary structure and an L-shaped tertiary structure. This folding is primarily stabilized by

39 Ribozymes demonstrate an important biophysical property of RNA. What is that property?

40 In RNA secondary structure, which non-canonical base pair is especially common and adds to structural diversity?

41 A protein is denatured such that its tertiary structure is lost but its primary structure remains intact. Which statement best explains why the protein can sometimes spontaneously refold to its native state?

42 Consider a polysaccharide composed solely of -D-glucose units. Which structural feature distinguishes glycogen from amylose despite both being glucose polymers?

43 At physiological pH (7.4), which statement about the net charge of the amino acid glutamate (side-chain , -carboxyl , -amino ) is correct?

44 The energy of a hydrogen bond in biological systems is typically in the range of – kJ/mol, while a typical C–C covalent bond is about kJ/mol. Why are the weaker hydrogen bonds nonetheless critical for biological specificity?

45 The hydrophobic effect is a major driving force in protein folding. Which thermodynamic explanation best accounts for it?

46 Van der Waals interactions have an optimal distance and become repulsive if atoms approach too closely. Which relationship best describes the attractive (London dispersion) component of the interaction energy with distance ?

47 A DNA sequence rich in alternating purine-pyrimidine (e.g., ) can adopt Z-DNA under high salt conditions. Which structural characteristic uniquely defines Z-DNA?

48 Under dehydrating conditions (around 75% relative humidity), B-DNA transitions to A-DNA. Which change accompanies this transition?

49 A circular DNA molecule has a linking number . If its relaxed linking number , what is the superhelical density (to two decimal places)?

50 Negative supercoiling of DNA is biologically important because it:

51 During transcription, RNA polymerase synthesizes RNA using the template (antisense) strand. If the coding (sense) strand reads -ATGCGT-, what is the corresponding RNA sequence?

52 In eukaryotic pre-mRNA processing, which set of modifications is essential before the mRNA can be exported and efficiently translated?

53 RNA polymerase differs from DNA polymerase in a fundamental way that has consequences for transcriptional fidelity. Which difference is correct?

54 A mutation in a promoter's element (Pribnow box, consensus TATAAT in prokaryotes) most directly affects:

55 Ribosomal RNA and other functional RNAs fold into complex tertiary structures. Which non-canonical interaction is especially important for stabilizing RNA tertiary architecture?

56 Why can RNA, unlike DNA, act as a catalyst (ribozyme) in reactions such as self-splicing and peptide bond formation?

57 In transfer RNA (tRNA), the characteristic L-shaped tertiary structure arises from the coaxial stacking of its arms. Which pairing of stems forms the two coaxial helices of the L-shape?

58 Magnesium ions () are critical for RNA folding. What is their primary biophysical role?

59 Consider an RNA hairpin whose stem melts with a two-state transition. If the melting temperature is defined as the temperature where half the population is folded, which change would most likely raise ?

60 The Watson-Crick base pair G≡C is more thermally stable than A=T. Beyond the extra hydrogen bond, which additional factor contributes significantly to this stability?