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Organelles and Compartmentalization · Paper 2 — Free Biology HL Practice Questions

What this topic covers

This theme is built on one repeated argument: structure exists because it does a job, and you can predict the job from the structure. Examiners test this exact logic at every scale — a motor protein's shape tells you which way it walks a microtubule, a red blood cell's missing nucleus tells you why it can pack more haemoglobin, a gill's countercurrent geometry tells you why it out-performs a lung-style parallel flow. Several chunks here — muscle and motility, enzyme kinetics, endosymbiotic theory, detailed phloem loading — exist only on the HL paper, and they're flagged below. Get the mechanism words right (troponin, not tropomyosin; ATP-binding, not hydrolysis) because that's where the marks actually sit.

Read the full Form and Function lesson notes →

1MasterySAQ-SCompartmentalization of processes in eukaryotic cells5 marksPaper 2~8 min

A patient with a mitochondrial disorder has muscle cells containing dysfunctional mitochondria. The patient experiences fatigue and muscle pain during mild exercise. A biopsy of the patient's muscle tissue shows an abnormally high concentration of lactate in the muscle cells.

(a)

Describe how compartmentalization within a eukaryotic cell allows aerobic respiration to produce ATP efficiently. [2 marks]

(b)

Explain why the patient's muscle cells accumulate lactate at high concentrations despite the presence of oxygen. [3 marks]

Solutions

2MasterySAQ-SCompartmentalization of processes in eukaryotic cells4 marksPaper 2~6 min

Scientists are studying a newly discovered eukaryotic unicellular organism that lives in acidic hot spring (

\text{pH} = 3.0

, temperature

70^\circ\text{C}

). The cell contains membrane-bound organelles including a nucleus and rough endoplasmic reticulum (RER).

(a)

Describe two benefits of compartmentalization that contribute to the survival of this organism. [2 marks]

(b)

The internal pH of the cell's lysosomes is

6.0

and the pH of the cytoplasm is

7.4

. (i) State the relationship between pH and

\left[\text{H}^+\right]

. [1]
(ii) Calculate the ratio of

\left[\text{H}^+\right]

inside the lysosome to

\left[\text{H}^+\right]

in the cytoplasm. [2 marks]

Solutions

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