Form and Function — Free IB Biology HL Practice Questions

1FoundationMCQMuscle structure and contraction mechanisms1 markPaper 1~2 min

A student examines a stained cross-section of human tissue under a light microscope. The cells are elongated and multinucleate, with nuclei positioned at the cell periphery. Striations are clearly visible, and the tissue is under voluntary control. Which additional microscopic feature would most specifically distinguish this tissue from all other muscle types?

Solutions

2MasteryMCQMuscle structure and contraction mechanisms1 markPaper 1~2 min

A researcher blocks ATP binding to myosin heads in a single sarcomere undergoing isometric contraction at a sarcomere length of

2.2\ \mu\text{m}

. Which of the following best describes the immediate effect on the cross-bridge cycle?

Solutions

3FoundationMCQStem cells and differentiation1 markPaper 1~2 min

A patient with severe burns requires a skin graft. Doctors take a small sample of the patient's own skin cells, reprogram them in the laboratory, and then differentiate them into new skin cells for grafting. This approach avoids immune rejection because the cells are derived from the patient's own tissue. Which statement correctly describes the key reprogramming step in this therapy?

Solutions

4MasteryMCQStem cells and differentiation1 markPaper 1~2 min

A patient with severe burns has lost large areas of skin. Doctors take a small biopsy of healthy skin, isolate the cells, and culture them with growth factors and signalling molecules. Over several weeks, the cells proliferate and form a sheet of epidermal tissue suitable for grafting. Which statement best explains why the cultured cells were able to form functional epidermal tissue?

Solutions

5FoundationMCQStem cells and differentiation1 markPaper 1~2 min

A researcher isolates a single cell from the inner cell mass (ICM) of a mouse blastocyst and cultures it in appropriate nutrients. The cell divides to form a cluster. A single cell from this cluster is then injected into a second mouse blastocyst, which develops into a healthy mouse containing cells derived from both the host blastocyst and the injected cell, but showing no contribution to placental tissue. Which term best describes the original ICM-derived cell?

Solutions

6FoundationMCQEnzymes as biological catalysts1 markPaper 1~2 min

A student adds catalase to equal volumes of the same concentration of hydrogen peroxide (

\text{H}_2\text{O}_2

) at 25°C and at 45°C. The initial rate of oxygen production is higher at 45°C, yet the total volume of oxygen collected after 10 minutes identical in both trials. Which of the following best explains why the initial rate is higher at 45°C?

Solutions

7MasteryMCQStructure of proteins: Primary to quaternary structure1 markPaper 1~2 min

Secondary structure in proteins (alpha-helices and beta-sheets) is stabilised primarily by hydrogen bonds between backbone carbonyl and amide groups. A scientist analyses the amino acid mixture produced in a Miller-Urey experiment and wants to determine whether these amino acids could form polypeptides with stable secondary structure. Which property of the amino acid mixture is most important to confirm?

Solutions

8FoundationMCQEnzymes as biological catalysts1 markPaper 1~2 min

A student investigates the effect of pH on the activity of pepsin by measuring amino acid concentration produced after 10 minutes at 37 °C. Each test tube contains identical concentrations of protein substrate and pepsin, buffered to a different pH. The results are shown below. pH — Amino acid concentration (mmol

\text{L}^{-1}

) 2 — 12 4 — 8 6 — 3 8 — 1 Which conclusion is best supported by these data?

Solutions

9FoundationMCQEcological niche concept1 markPaper 1~2 min

In a rocky shore ecosystem, Chthamalus and Balanus barnacles coexist. Chthamalus naturally occupies only the upper shore, but when Balanus is experimentally removed from the lower shore, Chthamalus colonises that zone as well. Balanus cannot survive in the upper shore regardless of competition. Which conclusion is best supported by this experiment?

Solutions

10MasteryMCQEcological niche concept1 markPaper 1~2 min

In a temperate grassland, three grasshopper species occupy distinct ecological niches. Species X feeds exclusively on grasses across all temperatures. Species Y feeds exclusively on forbs across all temperatures. Species Z feeds on both grasses and forbs, but only when air temperature exceeds 25°C. Which statement correctly describes the fundamental niche breadth of these three species?

Solutions

11FoundationMCQEcological niche concept1 markPaper 1~2 min

Two species of warblers coexist in the same forest and consume similar insect prey. Species A forages exclusively in the upper canopy, while Species B forages exclusively in the lower understory. Which term most precisely describes the mechanism that allows these two species to coexist?

Solutions

12FoundationMCQCirculatory systems: Open vs closed1 markPaper 1~2 min

An earthworm has a closed circulatory system with five pairs of aortic arches connecting a dorsal and a ventral longitudinal vessel. A cockroach has an open circulatory system with a single dorsal tubular heart. The maximum distance blood must travel from the heart to the most distant tissue is 2 cm in the earthworm and 0.5 cm in the cockroach. What is the most likely advantage of the earthworm's closed circulatory system over the cockroach's open system?

Solutions

13MasteryMCQCirculatory systems: Open vs closed1 markPaper 1~2 min

A researcher injects an equal volume of blue dye into the dorsal vessel of a cockroach (open circulatory system) and into the left ventricle of a rat (closed circulatory system). Both animals are similar in mass. After 10 seconds, the dye in the cockroach is found spread throughout a large haemocoel sinus surrounding the leg muscles, while in the rat the dye remains confined within narrow capillaries inside the leg muscles. Which conclusion about fluid pressure is best supported by these observations?

Solutions

14FoundationMCQCirculatory systems: Open vs closed1 markPaper 1~2 min

A biologist injects a blue dye into the heart of a live crab and into the heart of a live fish. The dye appears in the crab's leg joints within 30 seconds, but takes 2 minutes to appear in the fish's tail fin. Which conclusion is best supported by this observation?

Solutions

15FoundationMCQMetabolism of glucose1 markPaper 1~2 min

A patient has a mitochondrial disorder in which the enzyme complex that converts pyruvate to acetyl-CoA is non-functional. Which outcome is most likely in the affected cells compared to a healthy individual?

Solutions

16MasteryMCQStructure and function of carbohydrates and lipids1 markPaper 1~2 min

A polysaccharide isolated from plant cell walls is hydrolysed by acid into identical monosaccharide monomers. The glycosidic bonds linking these monomers are oriented so that alternating monomers are inverted relative to each other. Which polysaccharide is this?

Solutions

17FoundationMCQMetabolism of glucose1 markPaper 1~2 min

Under anaerobic conditions, yeast cells oxidise glucose to pyruvate during glycolysis. Which statement correctly describes the subsequent fate of pyruvate and its metabolic significance in these cells?

Solutions

18FoundationMCQRespiratory structures in animals and plants1 markPaper 1~2 min

In insects, a network of internal tubes branches repeatedly into finer tubes called tracheoles, delivering oxygen directly to respiring cells without the involvement of a circulatory pigment. Which term describes the larger branching tubes that form the main conducting portion of this system?

Solutions

19MasteryMCQRespiratory structures in animals and plants1 markPaper 1~2 min

A locust (Schistocerca gregaria) is sealed in a chamber fitted with a CO₂ sensor at 25°C. When CO₂ concentration is recorded every minute over 10 minutes, the total increase is 0.15%. Which pattern of CO₂ release is most likely observed, and what is its cause?

Solutions

20FoundationMCQRespiratory structures in animals and plants1 markPaper 1~2 min

In a fish, oxygen concentration in water entering the gills is

9.1 \text{ mg dm}^{-3}

and in water leaving the gills is

3.8 \text{ mg dm}^{-3}

. Which mechanism moves oxygen from the water into the blood, and what property of oxygen makes this possible?

Solutions

21FoundationMCQCompartmentalization of processes in eukaryotic cells1 markPaper 1~2 min

A eukaryotic cell carries a mutation that completely prevents Golgi apparatus formation. Which cellular process is most directly disrupted by this mutation?

Solutions

22MasteryMCQCompartmentalization of processes in eukaryotic cells1 markPaper 1~2 min

In eukaryotic cells, the reactions of aerobic respiration are divided between the cytoplasm and the mitochondria: glycolysis occurs in the cytoplasm, while the Krebs cycle and oxidative phosphorylation occur within the mitochondrion. Which of the following best explains a cellular advantage of this compartmentalization?

Solutions

23FoundationMCQCompartmentalization of processes in eukaryotic cells1 markPaper 1~2 min

A drug disrupts the membranes of all membrane-bound organelles in a eukaryotic cell. Following treatment, the cell is unable to digest its own damaged organelles. Which organelle is most directly responsible for this process?

Solutions

24MasterySAQ-SMuscle structure and contraction mechanisms6 marksPaper 2~9 min

A researcher investigates the relationship between sarcomere length and force generated by a single skeletal muscle fibre. The fibre is stimulated to contract maximally at various initial sarcomere lengths. Sarcomere length /

\mu\text{m}

— Force as percentage of maximum

2.0

—

95\%

2.2

—

100\%

2.8

—

80\%

3.6

—

20\%

(a)

State the sarcomere length at which the greatest number of cross-bridges can form. [1 mark]

(b)

Deduce why force generation at a sarcomere length of

2.0\,\mu\text{m}

is less than at

2.2\,\mu\text{m}

, despite greater actin–myosin overlap. [2 marks]

(c)

Explain, using sliding filament theory, why force generation decreases progressively as sarcomere length increases beyond

2.2\,\mu\text{m}

, and calculate the percentage decrease in force between

2.2\,\mu\text{m}

and

3.6\,\mu\text{m}

. [3 marks]

Solutions

25MasterySAQ-SMuscle structure and contraction mechanisms5 marksPaper 2~8 min

A student examines stained sections of three different types of muscle tissue under a light microscope. Tissue X shows long, unbranched fibres with multiple peripheral nuclei and visible striations. Tissue Y shows short, spindle-shaped cells with a single central nucleus and no striations. Tissue Z shows branched fibres with intercalated discs and a single central nucleus.

(a)

State two structural features visible under a light microscope that distinguish Tissue X from Tissue Y. [2 marks]

(b)

Identify which tissue (X, Y, or Z) is most likely found in the wall of a blood vessel. Justify your answer. [2 marks]

(c)

The student measures the image width of a single Tissue Z cell as

4.8\,\text{mm}

on a micrograph taken at a total magnification of

\times 400

. Calculate the actual width of the cell in micrometres (

\mu\text{m}

). [1 mark]

Solutions

26ChallengeLAQMuscle structure and contraction mechanisms10 marksPaper 2~15 min

Data

- Type I fibres: high myoglobin content, numerous mitochondria, high capillary density, Ca

^{2+}

-ATPase rate

= 0.5\,\mu\text{mol}\cdot\text{mg}^{-1}\cdot\text{min}^{-1}

, low myosin ATPase activity - Type II fibres: low myoglobin content, fewer mitochondria, lower capillary density, Ca

^{2+}

-ATPase rate

= 2.0\,\mu\text{mol}\cdot\text{mg}^{-1}\cdot\text{min}^{-1}

, high myosin ATPase activity - Maximum shortening velocity (

V_\text{max}

): Type I

= 0.8\,\text{ML}\cdot\text{s}^{-1}

; Type II

= 3.2\,\text{ML}\cdot\text{s}^{-1}

- Cross-bridge cycle duration: Type I

= 150\,\text{ms}

; Type II

= 40\,\text{ms}

Skeletal muscle contraction is explained by the sliding filament theory, which describes the interaction between actin and myosin filaments. However, this theory does not fully account for the differences in contractile properties observed between slow-twitch (Type I) and fast-twitch (Type II) muscle fibres.

(a)

Explain how the difference in Ca

^{2+}

-ATPase rate between Type I and Type II fibres contributes to the difference in their cross-bridge cycle duration. [4 marks]

(b)

Calculate the number of cross-bridge cycles per second for each fibre type. [2 marks]

(c)

A researcher proposes that the higher myoglobin content in Type I fibres could directly increase their force of contraction rather than affecting endurance. Using the data provided, evaluate this proposal. [4 marks]

Solutions

27MasterySAQ-SStem cells and differentiation5 marksPaper 2~8 min

A research team studies the differentiation of neural stem cells (NSCs) isolated from a mouse brain. NSCs are cultured for 7 days in the presence of the growth factor FGF-2. After 7 days, 150 of the original 200 NSCs have differentiated into neurons; the remainder are still undifferentiated NSCs. In a separate experiment, the same NSCs are cultured with BMP4 instead of FGF-2. After 7 days,

95\%

of cells have differentiated into astrocytes and

5\%

into neurons.

(a)

State what is meant by differentiation in the context of these neural stem cells. [1 mark]

(b)

Calculate the percentage of NSCs that differentiated into neurons in the FGF-2 experiment. [2 marks]

(c)

Using the results from both experiments, explain how growth factors direct the fate of NSCs during differentiation. [2 marks]

Solutions

28MasterySAQ-SStem cells and differentiation5 marksPaper 2~8 min

Scientists are studying the use of stem cells to repair damaged heart muscle after a heart attack. They compare two sources of stem cells: (i) mesenchymal stem cells (MSCs) from bone marrow, and (ii) induced pluripotent stem cells (iPSCs).

(a)

State one difference between MSCs and iPSCs in terms of their origin. [1 mark]

(b)

The scientists treat groups of mice with a chemical that causes heart damage, then inject either MSCs or iPSC-derived cardiomyocytes into the damaged area. After 4 weeks, they measure the percentage of the damaged area repaired. Treatment — Mean repair (%) — Standard deviation (%) MSCs — 12 — 4.1 iPSC-derived cardiomyocytes — 45 — 3.8 Deduce whether the difference in repair between the two treatments is likely to be significant. [2 marks]

(c)

Despite the greater effectiveness of iPSC-derived cardiomyocytes, some mice in the iPSC group developed tumours. Explain a possible reason for this observation, linking it to the properties of iPSCs. [2 marks]

Solutions

29ChallengeSAQ-LStructure of proteins: Primary to quaternary structure9 marksPaper 2~14 min

Data

- Glutamic acid has a charged, hydrophilic R-group; valine has a non-polar, hydrophobic R-group. - HbA is highly soluble in the cytoplasm of red blood cells and exists a tetramer (

\alpha_2\beta_2

) with quaternary structure. - Under low-oxygen conditions, HbS molecules aggregate into long fibrous polymers that deform red blood cells into a sickle shape. - A second mutant, HbC, has Glu at position 6 replaced by lysine (Lys), which has a positively charged R-group. HbC does not form polymers under low-oxygen conditions. - A third mutant, HbS-Memphis, carries the same Glu

\rightarrow

Val substitution at position 6 as HbS, plus a second substitution at position 23 where glutamic acid is replaced by alanine (Ala), which is hydrophobic. HbS-Memphis forms polymers more readily than HbS under the same conditions.

A molecular biology laboratory is studying a mutant form of haemoglobin, HbS, which causes sickle cell anaemia. Normal adult haemoglobin (HbA) has the following primary structure at the beginning of its beta-globin chain:

\text{HbA: } \ldots\text{Val-His-Leu-Thr-Pro-}\underline{\textbf{Glu}}\text{-Lys}\ldots

In HbS, a single nucleotide substitution in the beta-globin gene causes glutamic acid (Glu) at position 6 to be replaced by valine (Val). Additional

(a)

State the level of protein structure directly altered by the Glu

\rightarrow

Val substitution, and identify two higher levels of protein structure that are consequently affected in HbS. [2 marks]

(b)

Explain how the single Glu

\rightarrow

Val substitution leads to polymer formation under low-oxygen conditions. [3 marks]

(c)

Evaluate the statement: "The quaternary structure of a protein is entirely determined by its primary structure," using evidence from at least three of the haemoglobin variants described above. [4 marks]

Solutions

30MasterySAQ-SEnzymes as biological catalysts5 marksPaper 2~8 min

A student investigates the effect of pH on the activity of the enzyme catalase, which breaks down hydrogen peroxide (

\text{H}_2\text{O}_2

) into water and oxygen. A

1\,\text{cm}^3

cube of potato (a source of catalase) is added to

10\,\text{cm}^3

of hydrogen peroxide solution at five different pH values. The volume of oxygen gas produced in the first 60 seconds is recorded. pH — Volume of

\text{O}_2

produced /

\text{cm}^3

3 — 2.5 5 — 8.0 7 — 15.0 9 — 6.5 11 — 1.0 All experiments are conducted at

25\,^\circ\text{C}

.

(a)

State the pH at which catalase activity is highest. [1 mark]

(b)

Describe the effect of pH on the volume of oxygen produced, using the data provided. [2 marks]

(c)

Explain why catalase activity is lower at pH 3 than at pH 7. [2 marks]

Solutions

31MasterySAQ-SEcological niche concept7 marksPaper 2~11 min

In a tropical rainforest in Borneo, three species of fig wasp (Ceratosolen spp.) are the only pollinators of three closely related fig tree species (Ficus spp.). Each wasp species enters the figs of only one Ficus species, where it lays eggs and pollinates the flowers. The wasps are active at different times of day: Species A at dawn (

05\!:\!00

–

07\!:\!00

), Species B at midday (

11\!:\!00

–

13\!:\!00

), and Species C at dusk (

17\!:\!00

–

19\!:\!00

). Researchers recorded the mean number of wasp individuals captured per hour near each Ficus species. Near Ficus 1 — 45 — 2 — 1 — 48 Near Ficus 2 — 3 — 52 — 4 — 59 Near Ficus 3 — 2 — 1 — 48 — 51

(a)

Identify the primary host Ficus species for Ceratosolen Species B, and state the evidence from the data that supports this. [2 marks]

(b)

Calculate the percentage of all wasps captured near Ficus 2 that belong to Species B. [2 marks]

(c)

Explain how the concept of an ecological niche helps to explain why these three wasp species can coexist in the same rainforest. [3 marks]

Solutions

32MasterySAQ-SEcological niche concept7 marksPaper 2~11 min

Data

$

Both species of parrotfish feed on algae growing on dead coral on the Great Barrier Reef, but differ in feeding behaviour. Chlorurus microrhinos (steephead parrotfish) uses large beak-like teeth to scrape deep into the coral substrate, ingesting calcium carbonate. Scarus frenatus (bridled parrotfish) browses only surface algae. Researchers measured algae removal and coral substrate erosion in areas where each species was the dominant grazer. Species — Algae removed /

\text{g m}^{-2}\text{day}^{-1}

— Substrate eroded /

\text{g m}^{-2}\text{day}^{-1}

C. microrhinos —

120

—

85

S. frenatus —

95

—

12

(a)

Calculate the difference in substrate eroded per day between the two species. $ [2 marks]

(b)

Calculate the ratio of substrate eroded to algae removed for C. microrhinos, expressing your answer to two significant figures. $ [2 marks]

(c)

Evaluate how the feeding behaviour of these two parrotfish species illustrates niche differentiation and explain why this allows both species to coexist on the same reef. $ [3 marks]

Solutions

33MasterySAQ-SBlood circulation in mammals (cardiovascular system)6 marksPaper 2~9 min

During a medical examination, a doctor uses a stethoscope to listen to the heart sounds of a healthy adult. The characteristic 'lub-dub' sound is heard.

(a)

State what causes the first heart sound ('lub') and the second heart sound ('dub'). [1 mark]

(b)

Describe the function of chordae tendineae and papillary muscles during ventricular contraction. [2 marks]

(c)

A runner has a stroke volume of

85\,\text{cm}^3

and a heart rate of

150\,\text{beats per minute}

immediately after a sprint. Determine the cardiac output in

\text{dm}^3\,\text{min}^{-1}

. [1 mark]

(d)

Explain why heart rate increases during exercise, referring to the role of

\text{CO}_2

concentration in the blood. [2 marks]

Solutions

34MasterySAQ-SBlood circulation in mammals (cardiovascular system)5 marksPaper 2~8 min

A scientist investigates the structure of mammalian arteries and veins using a light microscope. She observes that the wall of an artery is much thicker and more muscular than the wall of a vein of similar diameter.

(a)

State how the thick, muscular wall of an artery relates to its function. [1 mark]

(b)

State the role of valves in veins. [1 mark]

(c)

Calculate the mean arterial pressure (MAP) for a patient with blood pressure

145/95\,\text{mmHg}

, using the formula:

\text{MAP} = P_{\text{diastolic}} + \frac{1}{3}(P_{\text{systolic}} - P_{\text{diastolic}})

[1 mark]

(d)

A patient is diagnosed with venous valve incompetence (leaky valves) in the legs. Explain the physiological consequences of this condition for venous return and tissue fluid balance. [2 marks]

Solutions

35MasterySAQ-SStructure and function of carbohydrates and lipids6 marksPaper 2~9 min

Glycogen and starch are both polysaccharides used for glucose storage, but they differ in structure and occur in different organisms. A student investigates the rate of glucose release from glycogen and starch by the enzyme amylase. The student incubates

1.0\,\text{g}

of each polysaccharide with

1.0\,\text{cm}^3

of amylase solution at

37°\text{C}

and

\text{pH}\;7.0

. The mass of glucose released is measured every 2 minutes for 10 minutes. Time / min — 0 — 2 — 4 — 6 — 8 — 10 Glucose from glycogen / mg — 0 — 12 — 22 — 30 — 36 — 40 Glucose from starch / mg — 0 — 8 — 15 — 21 — 26 — 30

(a)

State the structural feature of glycogen that allows amylase to release glucose more rapidly from glycogen than from starch. [1 mark]

(b)

Calculate the rate of glucose release from glycogen between 2 and 6 minutes. Show your working. [3 marks]

(c)

Explain why the rate of glucose release from starch would decrease if the experiment were repeated at

\text{pH}\;5.0

. [2 marks]

Solutions

36MasterySAQ-SStructure and function of carbohydrates and lipids6 marksPaper 2~9 min

Triglycerides are a type of lipid composed of glycerol and three fatty acid chains. A researcher compares the energy content of two triglycerides: one from butter (saturated) and one from olive oil (unsaturated). The researcher burns

0.5\,\text{g}

of each triglyceride separately in a calorimeter containing

100\,\text{g}

of water and records the temperature increase. Triglyceride — Temperature increase of water Butter (saturated) —

8.2\,°\text{C}

Olive oil (unsaturated) —

7.6\,°\text{C}

Specific heat capacity of water:

c = 4.18\,\text{J}\,\text{g}^{-1}\,°\text{C}^{-1}

Use

Q = mc\Delta T

where relevant.

(a)

State the structural difference between a saturated an unsaturated fatty acid. [1 mark]

(b)

Calculate the energy released per gram of butter triglyceride. Show your working. [3 marks]

(c)

Explain why olive oil triglyceride releases less energy per gram than butter triglyceride. [2 marks]

Solutions

37MasterySAQ-SRespiratory structures in animals and plants10 marksPaper 2~15 min

The shows a section through a human lung alveolus and a leaf mesophyll cell, both sites of gas exchange.

(a)

State one structural feature of the alveolus wall that reduces diffusion distance. [1 mark]

(b)

Explain how the arrangement of alveoli in the lung increases the rate of gas exchange. [2 marks]

(c)

The partial pressure of oxygen (

pO_2

) in the alveolar air is

13.3\,\text{kPa}

, and in the blood plasma entering the alveolar capillaries it is

5.3\,\text{kPa}

. The alveolar membrane has a surface area of

70\,\text{m}^2

and a thickness of

0.5\,\mu\text{m}

. Using Fick's law:

\text{rate of diffusion} = \frac{D \times A \times \Delta p}{t}

where the diffusion constant

D = 2.0 \times 10^{-5}

(arbitrary units), calculate the rate of oxygen diffusion across the alveolar membrane. Give your answer in arbitrary units. [3 marks]

(d)

A patient with pulmonary fibrosis has alveolar membrane thickness increased to

2.0\,\mu\text{m}

and effective surface area reduced to

40\,\text{m}^2

. Using your answer from (c), calculate the ratio of the healthy diffusion rate to the fibrotic diffusion rate, and hence evaluate the impact of pulmonary fibrosis on oxygen uptake. [4 marks]

Solutions

38MasterySAQ-SRespiratory structures in animals and plants5 marksPaper 2~8 min

A locust (an insect) and a human both use gas exchange systems — a tracheal system and lungs respectively.

(a)

State two ways in which the structure of the insect tracheal system differs from the human lung system. [2 marks]

(b)

In the locust, the tracheal tubes end in fluid-filled tracheoles. During intense activity, the fluid is withdrawn into the body tissues. Explain why this withdrawal increases the rate of oxygen delivery to muscle cells. [2 marks]

(c)

The tracheal system is highly efficient for gas exchange in small insects but becomes a limiting factor as body size increases. Explain why increasing body size reduces the effectiveness of the tracheal system for oxygen delivery. [1 mark]

Solutions

39MasterySAQ-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

40MasterySAQ-SCompartmentalization of processes in eukaryotic cells5 marksPaper 2~8 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

Form and Function — Free Biology HL Practice Questions