Enzymes: Active Site and Chemical Reactions
Enzymes are the remarkable catalysts of life — almost all of them proteins whose folded chains create the pockets where chemistry happens. This quiz explores how protein architecture produces the active site, why ribozymes are the striking nucleic acid exception, and how enzymes differ from inorganic catalysts in their tolerance of heat.
You will also test your grasp of chemical versus physical change, the definition of rate as product formed per unit time, and the classic carbonic anhydrase reaction.
- Enzymes as proteins and the ribozyme exception
- Primary, secondary and tertiary structure in catalysis
- Active site as a crevice or pocket
- Thermal limits: enzymes, thermophiles and inorganic catalysts
- Rate, temperature effects and the carbonic anhydrase example
Difficulty: Medium — 15 questions. Answer from the lesson material alone.
Q1. According to the lesson, almost all enzymes are:
The lesson states plainly that almost all enzymes are proteins, which is why their catalytic power depends on protein structure.
Q2. Nucleic acids that behave like enzymes are called:
The lesson notes that some nucleic acids behave like enzymes and these are called ribozymes — a small but important exception to the protein rule.
Q3. The primary structure of an enzyme refers to:
Primary structure is defined as the amino acid sequence of the protein, running from the N-terminal to the C-terminal amino acid.
Q4. In proteins, the helix form of secondary structure observed is:
The lesson specifies that in proteins only right handed helices are observed, folded like a revolving staircase.
Q5. The tertiary structure of a protein is described in the lesson as the chain folding upon itself like:
The long protein chain folds upon itself like a hollow woollen ball to give the tertiary structure, providing a three-dimensional view of the protein.
Q6. The active site of an enzyme is best described as:
The lesson defines the active site as a crevice or pocket into which the substrate fits, formed where the chain criss-crosses upon itself.
Q7. The crevices and pockets of an enzyme arise because, in the tertiary structure, the chain:
When the tertiary structure is viewed, the chain criss-crosses itself and hence many crevices or pockets are made, one of which is the active site.
Q8. Which statement about tertiary structure is emphasised in the lesson?
The lesson states that tertiary structure is absolutely necessary for the many biological activities of proteins, catalysis being foremost among them.
Q9. A major difference between enzyme catalysts and inorganic catalysts is that inorganic catalysts:
Inorganic catalysts work efficiently at high temperatures and high pressures, whereas enzymes get damaged at high temperatures such as above 40°C.
Q10. Enzymes typically get damaged at high temperatures, for example above:
The lesson states that enzymes get damaged at high temperatures, say above 40°C, unlike inorganic catalysts.
Q11. Enzymes isolated from thermophilic organisms living in hot vents and sulphur springs remain stable and retain catalytic power up to:
Enzymes from organisms living under extremely high temperatures are stable and retain catalytic power even up to 80°–90°C; this thermal stability is an important quality.
Q12. A physical change is described in the lesson as:
A physical change simply refers to a change in shape without breaking of bonds; a change of state such as melting ice is also physical.
Q13. A chemical reaction is defined in the lesson as a transformation in which:
When bonds are broken and new bonds are formed during transformation, this is called a chemical reaction, as in the barium hydroxide and sulphuric acid example.
Q14. The rate of a physical or chemical process refers to:
Rate is defined as the amount of product formed per unit time, expressed as the change in product over the change in time.
Q15. In the worked example of the lesson, carbonic anhydrase catalyses the reaction of carbon dioxide and water to form:
The lesson gives ##\ce{CO2 + H2O -> H2CO3}## with carbonic anhydrase as the catalyst, forming carbonic acid; enzyme-catalysed rates are vastly higher than uncatalysed ones.