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AP Biology : 1.2 Elements of Life – Exam Style questions with Answer- MCQ

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Question

Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose.

The figure presents segments of two polysaccharides, and is labeled Comparison of segments of starch and cellulose. The upper segment is labeled Starch, and the bottom segment is labeled Cellulose. Each segment is constructed of four glucose monomers, shown in ring form, and each glucose monomer has a C H 2 O H group attached to a particular carbon atom in the ring. In the segment of starch, each C H 2 O H group is oriented upwards and all the O atoms that join one ring to the next are oriented downwards. In the cellulose molecule, both the C H 2 O H groups and the O atoms that join one ring to the next are oriented in an alternating up and down pattern.
A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study.

Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B.
Based on Figure 1, which of the following best compares the atomic structures of starch and cellulose?
A. Starch is composed of carbon, hydrogen, and oxygen, while cellulose also contains nitrogen.
B. Starch and cellulose are composed of repeating glucose monomers; however, in cellulose every other glucose monomer is rotated 180 degrees.
C. Starch is composed of monomers that each have a \(CH_2OH\) group, while cellulose only has a \(CH_2OH\) group on every other monomer.
D. Starch and cellulose are composed of identical monomers and therefore have identical structures.

▶️Answer/Explanation

Ans: B
Both starch and cellulose are both composed of repeating glucose molecules; however, the orientation of every other glucose in cellulose is upside down compared with the ones on either side.

Question

The figure shows the results of an experiment to investigate the effects of an enriched \(CO_2\) environment on plant growth. Identical plants were separated into different groups and grown either in a standard \(CO_2\) environment (400 ppm \(CO_2\)) or in an enriched \(CO_2\) environment (700 ppm \(CO_2\)). Of the plants in each environment, half were grown under ideal conditions and half were grown under stressed conditions.

The figure presents a bar graph. Two categories are given on the horizontal axis,  labeled Ideal Conditions and Stressed Conditions. Each category has two bars. A key indicates that one bar corresponds to 400 parts per million of C O 2, and that the other bar corresponds to 700 parts per million of C O 2. The vertical axis is labeled Total Dry Weight, in grams per plant, and the numbers 0 through 2.5, in increments of 0.5, are indicated. The data for each bar, by category, are as follows. Note that all values are approximate.  Ideal Conditions. 400 parts per million of C O 2, 1.9 grams per plant. 700 parts per million of C O 2, 2.1 grams per plant. Stressed Conditions. 400 parts per million of C O 2, 1.1 grams per plant. 700 parts per million of C O 2, 1.5 grams per plant.
Based on the figure, which statement best describes the observed relationship between atmospheric CO2 enrichment and plant growth under ideal and stressed conditions?
A. The increase in atmospheric \(CO_2\) had no observable effect on plant growth under either ideal or stressed conditions.
B. The increase in atmospheric \(CO_2\) resulted in a greater increase in plant growth under ideal conditions than under stressed conditions.
C. The increase in atmospheric \(CO_2\) resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.
D. The increase in atmospheric \(CO_2\) resulted in an inhibition of plant growth under both ideal and stressed conditions.
▶️Answer/Explanation

Ans: C
Based on the figure, the increase in atmospheric CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.

Question

Phosphorous (P) is an important nutrient for plant growth. Figure 1 shows Arabidopsis thaliana plants grown under phosphorus‐sufficient (left) and phosphorus‐starved (right) conditions for six weeks.

The figure presents two potted plants. The plant on the left is labeled Phosphorus Sufficient, and is large. The plant on the right is labeled Phosphorus Starved, and is small.
Figure 1. Arabidopsis thaliana plants grown for six weeks.
Which of the following is the most likely reason for the difference in leaf growth?
A. The phosphorus-starved plant was unable to synthesize both the required proteins and lipids, limiting growth.
B. The phosphorus-starved plant was unable to synthesize both the required proteins and carbohydrates, limiting growth.
C. The phosphorus-starved plant was unable to synthesize both the required nucleic acids and lipids, limiting growth
D. The phosphorus-starved plant was unable to synthesize both the required carbohydrates and nucleic acids, limiting growth.
▶️Answer/Explanation

Ans: C
Phosphorus is used to make nucleic acids and certain lipids. Without phosphorus atoms, nucleic acids and lipids cannot be made for the plant to use for growth.

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