AP Biology : Plant Biology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding Chloroplasts

Which of the following terms can be described as the green pigment located within chloroplasts?

Possible Answers:

Stomata

Photoreceptors

Chlorophyll

Mesophyll

Correct answer:

Chlorophyll

Explanation:

Chlorophyll is what gives plants their green color. The chlorophyll located in the chloroplasts captures the light energy that drives the synthesis of food molecules in the chloroplasts—photosynthesis.

Example Question #2 : Understanding Chloroplasts

Which of the following best describes where chloroplasts are primarily located?

Possible Answers:

Roots

Mesophyll

Stroma

Stomata

Correct answer:

Mesophyll

Explanation:

Chloroplasts are found mainly in the cells of the mesophyll, which is the tissue in the interior of the leaf. Stomata are the pores that allow carbon dioxide to enter and oxygen to exit the leaf. The stroma is the dense fluid content of the chloroplast.

Example Question #2 : Plant Structures

What is the organelle in plant cells that contains chlorophyll?

Possible Answers:

Smooth endoplasmic reticulum

Golgi apparatus

Chloroplasts

Mitochondria

Correct answer:

Chloroplasts

Explanation:

Chloroplasts are the organelles that contains chlorophyll. Mitochondria produce ATP and are not directly involved in capturing light and photosynthesis. The Golgi apparatus is involved in packaging substances, and Smooth endoplasmic reticulum are involved in lipid production.

Example Question #1 : Plant Structures

Inside the chloroplast, what is the name of a stack of thylakoids?

Possible Answers:

Granum

Mitochondria

Stroma

Thylakoidum

Correct answer:

Granum

Explanation:

A stack of thylakoids is known as granum. Stroma is the region outside the thylakoid membranes, but still inside the chloroplast. Mitochondria is the organelle that produces ATP, and there is no such organelle called thylakoidum.

Example Question #5 : Plant Structures

Plant cells  differentiate to perform different functions and enable the plant to grow. One cell type is present in young stems and petioles and functions to provide flexible support. This cell type is less resistant to bending forces because it lacks a secondary cell wall and the protein lignin, which causes rigidity in other plant cells. 

What differentiated plant cell is being described?

Possible Answers:

Parenchyma cells

Collenchyma cells

Sieve plate cells

Sclerenchyma cells

Correct answer:

Collenchyma cells

Explanation:

As described in the beginning of this question, collenchyma cells are found in young stems and petioles (leaves) and function to provide flexible support to the plant. This is because chollenchyma cells lack secondary cell walls and do not produce lignin to harden them—this protein is characteristic of sclerenchyma cells, which are also used to provide support/strength to the plant. 

Due to their lack of rigidity, collenchyma cells a also capable of elongating with the stems and leaves they support, allowing them to remain alive at maturity. Sclerenchymal cells lack this ability.

Example Question #1 : Plant Structures

Plant cells differentiate to be able to perform different functions and enable it to grow. One cell type has a critical job in supporting the plant. These cells have secondary walls that are further strengthened by a glue-like substance called lignin, which increases the cell's rigidity. At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing, forming a "skeleton" for the plant.

What type of differentiated plant cell is described?

Possible Answers:

Parenchyma cells

Secondary meristems

Collenchyma cells

Sclerenchyma cells

Correct answer:

Sclerenchyma cells

Explanation:

As described in the background to the question, sclerenchyma cells are specialized to support the plant as it grows. These cells have thick secondary walls that are further strengthened by the hardening agent called lignin.  As a result, these cells are highly rigid and inflexible.  

At maturity, these cells cannot elongate and are found in regions of the plant that have stopped growing. In some parts of the plant, the sclerenchyma cells may even be dead; however, the rigid walls remain and act like a skeleteon that supports the remainder of the plaint over its lifetime.  

Sclerenchyma cells can also further differentiate into two types called sclereids and fibers. Sclerids can provide hardness to nut shells. Fibers, as their name suggests, are usually arranged in long threads and have commercial uses, such as being made into rope.

Example Question #3 : Plant Structures

Which of the following is a key component of a plant's vascular system?

Possible Answers:

Pericycle

Xylem

Parenchyma

Cuticle

Correct answer:

Xylem

Explanation:

The vascular system in plants is designed to transport materials (water, nutrients, food) between the roots and shoots. There are two primary types of tissue dedicated to these processes. Xylem transports water and dissolved minerals upward from the roots; phloem transports sugars—the products of photosynthesis—from where they are synthesized to where they are needed, such as roots and new growth areas of leaves and fruits.

Both xylem and phloem are comprised of a variety of cell types that are specialized for transport and support. 

Example Question #1 : Plant Biology

What structure in plants allows for CO2 and O2 exchange and transpiration?

Possible Answers:

Chlorophyll

Xylem

Stoma

Apical bud

Plastid

Correct answer:

Stoma

Explanation:

The stoma allows for gas exchange and transpiration. The stoma usually opens following stimulation by sunlight and closes in low water environments. Other answers are parts of a typical plant, however do not play a role in gas exchange or transpiration.

Example Question #1 : Macrostructures

In plants, leaves contain specialized pores used for gas exchange. Each pore is formed by a pair of cells that control its closing and opening. What are these cells called?

Possible Answers:

Epidermal cells

Guard cells

Cuticle cells

Stoma cells

Correct answer:

Guard cells

Explanation:

For proper functioning, plants must take in carbon dioxide, expel oxygen, and limit the loss of water vapor. This gas exchange takes place via pores called stomata. These pores are formed by a pair of adjacent cells that can open and close in response to a number of factors. These cells are called guard cells.

The cuticle and epidermis are layers of leaf structure, and do not correspond to specific cell types. The stoma is the name of a single pore itself, not its surrounding cells.

Example Question #2 : Understanding Leaves

Which of the following are true of parenchyma cells?

Possible Answers:

They are the primary support cells of a plant

They carry out many metabolic functions such as photosynthesis

They contain sieve-tube members

Their main function is transport

They are strengthened with lignen

Correct answer:

They carry out many metabolic functions such as photosynthesis

Explanation:

Parenchyma cells are the main photosynthetic cells of a plant, but also function in storage of water and nutrients. Parenchyma cells are usually soft cells that are located in leaves and fruit. Phloem cells contain sieve-tube members, and function in transport of water and nutrients throughout the plant. Schlerenchyma cells are strengthened with lignen, and are support cells.

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