Structure of Proteins: Tertiary and Quaternary Levels
Once a protein’s amino acid sequence is joined and its local helices and sheets have formed, the whole thread folds back on itself into a compact three-dimensional shape. This quiz explores that folding — the tertiary structure — and then the architecture that appears when several folded polypeptides assemble together, the quaternary structure.
- How a single chain folds upon itself like a hollow woollen ball
- Why tertiary structure is essential for biological activity
- How subunits are arranged with respect to one another
- Adult human haemoglobin as a four-subunit example
Work carefully through each question — the distinction between tertiary and quaternary structure is one of the most commonly confused points in the study of biomacromolecules.
Q1. The long protein chain folding upon itself like a hollow woollen ball gives rise to which level of protein structure?
The lesson states that the long protein chain is folded upon itself like a hollow woollen ball, giving rise to the tertiary structure.
Q2. According to the lesson, the folding of the protein chain into a hollow-woollen-ball form gives us which view of a protein?
The lesson states that this folding gives us a 3-dimensional view of a protein.
Q3. How does the lesson describe the importance of tertiary structure for proteins?
The lesson is explicit: tertiary structure is absolutely necessary for the many biological activities of proteins.
Q4. Which statement about a protein thread is correct according to the lesson?
The lesson states that a protein thread does not exist throughout as an extended rigid rod.
Q5. In the helix form of the protein thread, which type of helix is observed in proteins?
The lesson states that in proteins, only right handed helices are observed.
Q6. The helix form of the protein thread is compared in the lesson to which object?
The lesson compares the helix form of the thread to a revolving staircase.
Q7. Which level of protein structure concerns the manner in which individual folded polypeptides or subunits are arranged with respect to each other?
The lesson defines quaternary structure as the architecture arising from the arrangement of individual folded polypeptides or subunits with respect to each other.
Q8. The arrangement of subunits in the form of a linear string of spheres, or spheres arranged one upon another as a cube or plate, is described in the lesson as the:
The lesson gives these arrangements as examples of the architecture of a protein, otherwise called the quaternary structure.
Q9. How many subunits does adult human haemoglobin consist of?
The lesson states that adult human haemoglobin consists of 4 subunits.
Q10. Adult human haemoglobin is made up of which combination of subunits?
The lesson states that two subunits of α type and two subunits of β type together constitute the human haemoglobin.
Q11. In adult human haemoglobin, how many of the four subunits are identical to each other?
The lesson states that two of the four subunits are identical to each other, giving two α and two β subunits.
Q12. Which level of protein structure belongs to a single polypeptide chain folded upon itself?
Tertiary structure describes how one continuous chain is folded and packed into a compact three-dimensional form.
Q13. Which of the following best describes the quaternary structure of a protein?
The lesson states that some proteins are an assembly of more than one polypeptide or subunits, and their arrangement is the quaternary structure.
Q14. Which of the following is given in the lesson as an example of a protein with quaternary structure?
Adult human haemoglobin, with its four subunits, is the example supplied in the lesson for quaternary structure.
Q15. Which statement correctly distinguishes tertiary from quaternary structure?
Tertiary structure is the folding of a single chain upon itself, while quaternary structure is the arrangement of subunits with respect to each other.