IB Biology HL Theme B: Form and function questions

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 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.

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

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?

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

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

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

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

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

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

Histology technicians are testing whether vessel type can be identified from transverse micrographs. Specimen A has been independently identified as an artery and specimen B as a vein. Wall thickness and lumen diameter were measured in three micrographs of each specimen.

The relative wall thickness index is calculated as:

At Kestrel Bay, marram grass (Ammophila arenaria) grows on exposed foredunes above the high-tide line, where the sand is dry and shifting and winds are strong. Grey mangrove trees (Avicennia marina) grow in the lower intertidal estuary, in a mangrove swamp with waterlogged sediment. Marram leaves roll inward during dry, windy periods; the stomata are on the inner surface of the rolled leaves. Grey mangroves have aerial roots that project above the sediment and have openings exposed to the air.

Table 1. Conditions measured in the two habitats

To estimate the number of grey mangrove trees in a 0.80 ha area of swamp, six non-overlapping 100 m² quadrats were selected at random. The numbers of trees counted were:

Seedlings of both species were also grown for eight weeks under two substrate conditions. The “dune-like” and “swamp-like” treatments reproduced the corresponding moisture, salinity and soil oxygen conditions in Table 1. Light, temperature and nutrient availability were kept constant. Each value is the mean dry-mass increase per seedling for 10 seedlings.

Table 2. Mean dry-mass increase after eight weeks

A prokaryote was cultured with identical mineral nutrients and no organic compounds; CO₂ availability was controlled as shown. The table gives the net change in biomass after 24 h. Which conclusion is supported?

A unicellular alga, A, and a photosynthetic prokaryote, P, were cultured separately or together. Each species present in a culture had an initial density of 100 cells mL⁻¹. Cultures were kept at the same temperature and pH, with inorganic carbon and mineral nutrients maintained at non-limiting concentrations. Light treatments received the same illumination for 12 hours each day; dark treatments received no light. The table shows mean cell densities after 10 days. Each mean is based on five replicate cultures.

A dash indicates that the species was not present.