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Enzymes and Metabolism · Paper 2 — Free Biology HL Practice Questions

1MasterySAQ-SMetabolic pathways: Anabolism and catabolism5 marksPaper 2~8 min

The shows a metabolic pathway in Escherichia coli that synthesises product Z from substrate X via intermediate Y.

(a)

Identify the site at which product Z acts and state the term for this type of enzyme regulation. [2 marks]

(b)

Describe how end-product inhibition controls the concentration of product Z in the cell. [2 marks]

(c)

Evaluate the advantage of regulating Enzyme 1 rather than Enzyme 2 in this pathway. [1 mark]

Solutions

2ChallengeSAQ-LEnzyme kinetics and inhibition10 marksPaper 2~15 min

A pharmaceutical company is testing drug Y as a potential treatment for hypertension. Drug Y inhibits angiotensin-converting enzyme (ACE), which converts angiotensin I to angiotensin II. The kinetics of ACE were studied in vitro at fixed enzyme concentration.

\frac{1}{v} = \frac{K_m}{V_{max}} \cdot \frac{1}{[S]} + \frac{1}{V_{max}}

[\text{Angiotensin I}]\ (\text{nM})

—

v\ (\text{nmol min}^{-1})

— no drug —

v\ (\text{nmol min}^{-1})

— with

10\ \text{nM}

drug Y

2

—

0.80

—

0.50

5

—

1.50

—

1.00

10

—

2.20

—

1.70

20

—

2.80

—

2.50

50

—

3.30

—

3.20

(a)

Using the Lineweaver–Burk linearisation, calculate

V_{max}

and

K_m

for ACE both in the absence and in the presence of

10\ \text{nM}

drug Y. [4 marks]

(b)

Using your values from (a), deduce whether drug Y acts a competitive or non-competitive inhibitor of ACE. [2 marks]

(c)

Evaluate the use of non-competitive ACE inhibitors antihypertensive drugs, considering both their pharmacological advantages over competitive inhibitors and the limitations arising from their mechanism of action. [4 marks]

Solutions

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