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

Cellular organelles are specialized compartments within cells that have a specific structure and function. Organelles are often membrane-bound in eukaryotic cells, allowing for compartmentalization of cellular processes. Figure 1 below shows a cellular organelle.

Identify the organelle in Figure 1, and the cellular process that takes place here.

Explain the benefit of compartmentalizing the process identified within the organelle shown in Figure 1.

The organelle in Figure 1 contains its own DNA and ribosomes. Table 1 below contains some information about the DNA and ribosomes shown, and compares them with equivalent DNA and ribosomes in mitochondria, bacteria and eukaryotic cells

Table 1. DNA and ribosomes in different locations.

Scientists theorise that the organelle in Figure 1 and mitochondria evolved from the ancestors of modern bacteria. Use evidence from Table 1 to support this claim.

Mutations are changes in the DNA sequence of an organism, they can be harmful, neutral or beneficial to the organism.

Predict how a harmful mutation in the DNA labeled in Figure 1 would affect the cell within which the organelle is located.

Compartmentalization and cell specialization are essential for maintaining efficiency and organization in eukaryotic cells. Compartmentalization refers to the division of cellular processes into separate regions within a cell.

(i) Describe how compartmentalization is achieved in eukaryotic cells.

(ii) Specialized cells have a structure that aids their specific function. Explain how compartmentalization can allow cells to specialize.

Scientists measured organelle density, as well as the rate of some cellular processes, in different cell types. Their results are shown in Table 1 below.

Table 1. Organelle density and rate of cellular processes in different cell types.

(i) In order to determine organelle number per cell, scientists obtained multiple images of slices through a cell, counted the number of organelles visible in each image, and then added the image totals together.

Describe how the data gathered using this procedure would need to be processed to determine organelle density.

(ii) State why organelle density has been measured, rather than organelle number.

(i) Identify the organelle that is likely to be the most abundant in muscle cells.

(ii) Use data from Table 1 to justify your answer to (i).

Pancreatitis is a condition that can affect the function of rough endoplasmic reticulum in the pancreas.

(i) Predict the effect of pancreatitis on pancreatic cells.

(ii) A student suggested that disrupted rough ER function would have a more significant effect on pancreatic cells than on other cell types. Use Table 1 above to evaluate this suggestion.

Synthetic biology uses engineering principles to create new biological parts and systems. Researchers studying synthetic cells wanted to determine the effect of protein localization strategy on cellular processes. Localization refers to the deliberate positioning of proteins within specific regions or structures of the cell.

To inform their work on synthetic cells, the researchers studied the effect of different protein localization strategies on enzyme-catalyzed reactions in bacterial cells.

Some of their results are shown in Table 1 below.

Table 1: The effect of enzyme localization strategy on the rate of substrate use and product yield.

Explain the result for condition C.

(i) State a suitable null hypothesis for the study described in part (a).

(ii) Justify the inclusion of condition A as a control in the study.

(iii) Calculate the percentage increase in product yield between condition A and condition C.

Microcompartments in synthetic cells can be generated in several ways. One method involves a process known as coacervation, during which a fluid separates into separate phases. Coacervation can be triggered by introducing solutes with particular properties; an example would be the production of water-in-oil-in-water double emulsions (DEs), shown in Figure 1 below. In this example, the DE has been stabilized by the addition of phospholipids.

(i) Use information in Figure 1 and your knowledge of phospholipids to explain why coacervation has occurred in this instance.

(ii) A student suggested that DE's could be used to simulate membrane-bound organelles inside synthetic cells. Justify this suggestion.

Scientists working in the field of synthetic biology are still a long way from producing synthetic cells that accurately mimic living cells.

(i) Identify a component of membrane structure, that has not been addressed in the production of microcompartments, that scientists will need to seek to replicate in synthetic cells that accurately mimic living cells.

(ii) Scientists hope to use synthetic organelles to deliver regulatory proteins to living cells.

Predict how the introduction of new regulatory proteins might affect these living cells.