IB Biology HL Theme B: Form and function questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type
Multiple choiceWritten
Difficulty
EasyMediumHard

Question 1

Paper 2Easy6 marks

In a mammal, glucose is transported in the blood and stored in liver cells as glycogen. Figure 1 shows two monosaccharides in ring form and a fragment of glycogen.

(a)XOOHOHOHOHCH2OH(b)Glycogen fragmentYOOHOHOHCH2OHα-glucoseα-glucoseα-glucoseα-glucoseα-glucoseα-glucoseα-glucoseα-glucoseα-glucose
(a)

State which of X and Y is a pentose and which is a hexose.

[2]
(b)

State one feature visible in Figure 1(b) that contributes to the compact nature of glycogen.

[1]
(c)

Outline how the solubility and chemical stability of glucose relate to its transport in the blood, and state the benefit of glucose oxidation in cells.

[3]

Question 2

Multiple choiceEasy1 mark

A student is considering possible polypeptides assembled from the 20 amino acids represented in the genetic code. Which statements describe the possible chains?

I. Two chains can contain the same amino-acid types in different orders.
II. Each chain must contain all 20 amino-acid types.
III. Chains can range in length from a few amino acids to thousands.

Show answer and explanation

Answer: C. The 20 amino-acid types are possible building blocks, but their order and the length of a polypeptide chain can vary. Thus I and III are correct; a chain need not contain every type.

A: accepts variation in order but incorrectly assumes chain length cannot vary.
B: accepts variation in length but assumes amino-acid order is fixed.
D: mistakes the 20 amino acids available for a set that every chain must contain.

Remember: a polypeptide can use a subset of the 20 amino-acid types in different orders and chain lengths.

Question 3

Paper 2Easy2 marks

A researcher compares two proteins that contain the same types of amino acids but in a different order.

(a)

Explain why the proteins may have different three-dimensional conformations.

[1]
(b)

State the role of hydrogen bonds in stabilizing alpha helices and beta-pleated sheets.

[1]

Question 4

Multiple choiceEasy1 mark

A phagocytic cell encloses an engulfed particle and digestive enzymes inside a membrane-bound vacuole. Which effect of this arrangement helps protect the cell’s cytoplasm?

Show answer and explanation

Answer: D. The vacuole confines digestive enzymes with the engulfed particle, separating them from cytoplasmic molecules and reducing unwanted digestion.

A: confuses the vacuole’s role with the increased inner-membrane surface area of mitochondria. B: reverses compartmentalization by spreading the enzymes through the cytoplasm. C: describes a mitochondrial adaptation, not the protective effect of a phagocytic vacuole.

Remember: compartments can keep biochemical processes apart or concentrate their components.

Question 5

Paper 2Easy5 marks

Figure 1 shows a schematic mitochondrion and the fusion of a lysosome with a phagocytic vacuole.

AXmatrixYBlysosomephagocytic vacuolefusiondigestive enzymesengulfed material
(a)

Identify the mitochondrial adaptations indicated by X and Y.

[2]
(b)

In which mitochondrial compartment are enzymes and substrates of the Krebs cycle concentrated?

[1]
(c)

Explain one advantage of the compartmentalization shown in panel B for the cell.

[2]

Question 6

Multiple choiceEasy1 mark

A researcher is studying a stem-cell niche in an adult human hair follicle. Which statement describes a function of this niche?

Show answer and explanation

Answer: A. A stem-cell niche can maintain stem cells or promote their proliferation and differentiation; hair follicles are an example of a niche in adult humans.
B: assigns the stem cells’ capacity for continued division and differentiation to the niche.
C: recognizes the niche as a location but wrongly denies its role in maintaining or influencing stem cells.
D: confuses the niche with stem cells, which can differentiate along different pathways.
Remember: distinguish a stem cell’s properties from the function of its niche.

Question 7

Paper 2Easy5 marks

Cubes of different side lengths are used as simplified models of cells. Figure 1 shows the surface-area-to-volume ratio of the cubes.

012345600.511.522.533.544.555.566.5Side length of cube / cmSurface-area-to-volume ratio / cm⁻¹
(a)

Read the surface-area-to-volume ratio for a cube with a side length of 2 cm. Give the unit.

[1]
(b)

Determine the side length of a cube with a surface-area-to-volume ratio of 1.5 cm⁻¹. Give the unit.

[1]
(c)

Explain how the pattern in Figure 1 suggests a constraint on the size of a cell.

[3]

Question 8

Multiple choiceEasy1 mark

A student records a spirometer trace. Which statements correctly identify lung volumes from the trace?

012345678900.511.522.533.544.555.56Time / sLung volume / dm³

I. Tidal volume is 0.5 dm³. II. Inspiratory reserve volume is 2.0 dm³. III. Vital capacity is 4.0 dm³.

Show answer and explanation

Answer: D. Tidal volume is the change between ordinary expiration and inspiration; inspiratory reserve volume is measured from ordinary inspiration to maximum inspiration; vital capacity is the difference between maximum inspiration and maximum expiration.

  • Ordinary breaths range from 2.5 to 3.0 dm³, so tidal volume is 0.5 dm³.
  • Inspiratory reserve volume is 5.0 − 3.0 = 2.0 dm³.
  • Vital capacity is 5.0 − 1.0 = 4.0 dm³.

A: Confusing inspiratory reserve volume with vital capacity makes the 2.0 dm³ reserve seem to be the capacity. B: Measuring inspiratory reserve from ordinary expiration gives 5.0 − 2.5 = 2.5 dm³. C: Reading the ordinary inspiration peak as tidal volume gives 3.0 dm³ instead of subtracting the expiration level.

Remember: Reserve volumes are measured from the appropriate level of ordinary breathing to a forced maximum.

Question 9

Paper 2Easy6 marks

A student prepares a transverse section of a dicotyledonous leaf to examine the arrangement of tissues involved in gas exchange.

(a)

Draw a plan diagram of the section. Label the waxy cuticle, upper and lower epidermis, palisade mesophyll, spongy mesophyll, air spaces and a vein. Do not draw individual cells.

[4]
(b)

State one role in gas exchange of the air spaces and one role of the guard cells of a stoma.

[2]

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