Cell Structure (College Board AP® Biology): Exam Questions

During an investigation of a freshwater lake, an AP Biology student discovers a previously unknown microscopic organism. Further study shows that the unicellular organism is eukaryotic.

Identify FOUR organelles that should be present in the eukaryotic organism and describe the function of each organelle. 

Cystic fibrosis is a genetic condition that is associated with defects in the CFTR protein. The CFTR protein is a gated ion channel that requires ATP binding in order to allow chloride ions (CI^-) to diffuse across the membrane.

In the provided model of a cell, draw arrows to describe the pathway for production of a normal CFTR protein from gene expression to final cellular location.

Identify the most likely cellular location of the ribosomes that synthesize CFTR protein.

Identify the most likely cellular location of a mutant CFTR protein that has an amino acid substitution in the ATP-binding site.

The following data were collected by observing subcellular structures of three different types of eukaryotic cells. 

RELATIVE AMOUNTS OF ORGANELLES IN THREE CELL TYPES 

Based on an analysis of the data, identify a likely primary function of each cell type and explain how the data support the identification. 

A phosphotransferase enzyme, known as N-acetylglucosamine-1-phosphotransferase, catalyzes the addition of a mannose-6-phosphate (M6P) tag to newly synthesized hydrolase enzymes in the Golgi apparatus. The M6P tag acts as a sorting signal, allowing these hydrolases to be recognized by M6P receptors in the Golgi network. Lysosomal disorders can occur when mutations are present in the gene that codes for certain phosphotransferase enzymes; one example of such a mutation is the K4Q mutation. Figure 1 below shows the effect of the K4Q mutation on phosphotransferase enzymes in the Golgi.

(i) Identify the process taking place at the location labelled 4 in Figure 1 and

(ii) Describe the process identified in (i).

(iii) State the type of substance that is usually transported in this way.

(i) Describe the effect of the K4Q mutation on transport of phosphotransferase enzymes in Figure 1.

(ii) Predict the effect that this might have on a cell with this mutation.

Scientists compared the activity of the normal phosphotransferase enzymes with that of K4Q mutant phosphotransferase, and with that of another mutant known as S15Y. Their results are shown in Figure 2 below.

One researcher focused on comparing the normal enzyme with K4Q mutant enzymes.

(i) State the null hypothesis that this researcher would have chosen.

(ii) State the conclusion that they would draw from Figure 2 in relation to this null hypothesis.

(iii) Justify the conclusion in (ii).

A student hypothesised that the K4Q mutation would have a larger impact on cell activities more than the S15Y mutation. Evaluate the hypothesis using data in Figure 2.

Bacteria exhibit surface area-to-volume (SA/V) homeostasis, adjusting their size and shape to optimize cellular function. Scientists investigated how mutations affecting the biosynthesis of the cell wall polysaccharide peptidoglycan (PG) impact SA/V ratio, cell morphology, and nutrient uptake in Escherichia coli. They measured these parameters in wild-type (normal) bacteria and in three mutant strains. Results are shown in Table 1 below.

Table 1. The effect of three mutations on PG synthesis and cell growth in E. coli.

(i) Identify a dependent variable in this investigation.

(ii) Justify the inclusion of the wild-type strain.

Calculate the percentage decrease in surface area between wild-type E. coli and mutant strain A.

(i) Describe the relationship between bacterial shape and SA/V ratio shown in Table 1.

(ii) Predict how SA/V ratio will affect growth rates in E. coli.

(iii) Explain this prediction using information from Table 1.

(i) Use data in Table 1 to describe the effect of mutation B on the shape of bacterial cells.

(ii) Explain why this change may have occurred.

Allen’s rule, an ecogeographical rule, suggests that animals may have evolved differences in limb proportions due to environmental selection pressures. Scientists investigated the relationship between limb length, surface area-to-volume ratio (SA/V) and resting metabolic rate. Table 1 below summarizes their findings:

Table 1. The relationship between total limb length, limb SA/V ratio and resting metabolic rate.

(i) State a suitable hypothesis for this study.

(ii) Construct a suitably labeled graph based on the data in Table 1. Your graph should show the relationship between limb length and resting metabolic rate.

(i) Describe the relationship between limb length and resting metabolic rate.

(ii) Explain the relationship described in (i).

The scientists also carried out an analysis of lower limb (leg) length, considering the impact of the length of the lower leg (shank) and the upper leg (thigh). The data from this part of the study is shown in Table 2.

Table 2. Correlation between different lower limb measurements and resting metabolic rate.

*= correlation is significant at the 0.05 level

**= correlation is significant at the 0.01 level

State what can be concluded about the impact of shank and thigh length on resting metabolic rate.

Allen's rule states that animals in cooler climates have appendages (e.g. limbs, ears, and tails) that differ to those of their counterparts in warmer regions.

(i) Predict how environmental temperature would be expected to impact the evolution of limb length.

(ii) Justify your prediction.