Question 1

Which of the following statements is TRUE?

Accepted Answer

Cadherins on the surface of animal cells are responsible for cell-cell adhesion, allowing cells to adhere to other cells. Integrins, on the other hand, facilitate cell adhesion to extracellular substrates such as the extracellular matrix. Cadherins are not used in plant cells, as they have a different mechanism of cell-cell adhesion involving plasmodesmata. Integrins and cadherins do not directly interact with each other to promote cell adhesion.

Question 2

Which of the following are adhesion proteins that are present in both choanoflagellates and animals?

Accepted Answer

Cadherins are adhesion proteins that are present in both choanoflagellates and animals, whereas actins are cytoskeletal proteins, pectins are found in cell walls of plants, and hemoglobins are only found in animals.

Question 3

Some species of choanoflagellates can form multicellular structures in the presence of their desired food bacterium; however, not all choanoflagellate species will form multicellular structures. Multicellularity is induced in some forms of choanoflagellates because of signals released by the bacterium. This variation in the ability to develop multicellular structures is MOST likely the result of:

Accepted Answer

The variation in the ability to form multicellular structures in choanoflagellates is most likely due to the evolution of differential responses to environmental signals. This suggests that different species of choanoflagellates have evolved different mechanisms for sensing and responding to the signals released by their desired food bacterium. It is not likely due to changes in gene expression or the evolution of specific genes for cell-adhesion molecules or integrins.

Question 4

Which of the following is TRUE of plasmodesmata?

Accepted Answer

Plasmodesmata are microscopic channels traversing the cell walls of plant cells and some algal cells, enabling transport and communication between them. They allow the plasma membrane and endoplasmic reticulum of adjacent cells to be connected, facilitating the exchange of molecules and ions.

Question 5

Animals are to cadherins as plants are to:

Accepted Answer

Cadherins are cell adhesion proteins found in animals, while pectins are cell wall components found in plants that aid in adhesion and structure. Therefore, the best choice for the analogy is D) pectins.

Question 6

Which of the following is TRUE of gap junctions?

Accepted Answer

Gap junctions are channels in the plasma membrane of animal cells made of transmembrane proteins that allow ions and small molecules to pass between adjacent cells. They are important for intercellular communication and coordination of cellular activities. Plant cells have similar channels called plasmodesmata.

Question 7

The vegetative cells of the simple multicellular organism Volvox function in:

Accepted Answer

The vegetative cells of Volvox primarily function in photosynthesis, converting light energy into chemical energy to sustain the colony.

Question 8

For multicellularity to develop, there must be a mechanism of signaling among cells in the multicellular organism. Which of the following structures present in the cell membrane receives signals from the environment, or other cells?

Accepted Answer

Receptors on the cell membrane receive signals from the environment or other cells. Plasmodesmata are channels between plant cells, gap junctions are channels between animal cells, and cadherins are proteins that help connect cells to neighboring cells. While all of these structures are important for multicellularity, they do not serve the function of receiving signals from the environment or other cells.

Question 9

Which of the following molecules help maintain cell-cell adhesions in plants?

Accepted Answer

Pectins are a type of cell wall polysaccharide that act as a cementing agent between adjacent plant cells, helping to maintain cell-cell adhesions. Cadherins and integrins are cell adhesion molecules found in animal cells, and cellulose is a structural component of plant cell walls but does not play a direct role in cell-cell adhesion.

Question 10

Choanoflagellates are:

Accepted Answer

Choanoflagellates are unicellular organisms belonging to the protozoan group. They are characterized by a ring of microvilli surrounding a single flagellum, which they use for movement and feeding.

Question 11

Which one of the following induces multicellularity in a choanoflagellate species?

Accepted Answer

The presence of the preferred prey/food source in the environment can induce multicellularity in choanoflagellates, as they form colonies to better capture food.

Question 12

Cardiac muscle cells have gap junctions between adjacent cells. What is the function of those gap junctions?

Accepted Answer

Gap junctions in cardiac muscle cells allow for the quick and efficient transmission of signals between cells. This is crucial for coordinating the contraction of the entire heart, ensuring that it functions as a unit.

Question 13

Three superkingdoms, the opisthokonts, archaeplastids, and stramenopiles all have members with complex multicellularity. What must be TRUE about the members with complex multicellularity in these groups?

Accepted Answer

Complex multicellularity often involves the development of tissues and organs, some of which are internal and not in direct contact with the environment. This is a key feature that allows organisms to maintain internal environments and perform specialized functions.

Question 14

Differentiation of multiple cell types occurs in:

Accepted Answer

The answer of Differentiation of multiple cell types occurs in:
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Question 15

Adhesion molecules in choanoflagellates serve the same function as those in their sister group, the animals.

Accepted Answer

Adhesion molecules in choanoflagellates are primarily used for capturing prey, while in animals, they are mainly involved in cell-cell adhesion and communication.

Question 16

The lion's mane jellyfish can be up to 8 feet wide. In spite of its large size, it has no structures for bulk flow to deliver oxygen to its cells. How can it be so large, and lack a mechanism for bulk flow?

Accepted Answer

The answer of The lion's mane jellyfish can be up...

Question 17

What structures are used in animal cells to move molecules between cells?

Accepted Answer

Gap junctions are specialized tiny pores formed by connexins that connect adjacent animal cells and allow for the rapid movement of small molecules and ions between them. Plasmodesmata are similar structures found in plant cells, cadherins are cell adhesion molecules that help cells stick together, and plasma membranes are present in all cells and serve as a barrier between the inside and outside of the cell.

Question 18

Hormones released by endocrine glands function as signal molecules.

Accepted Answer

Hormones released by endocrine glands act as signal molecules that travel through the bloodstream to target cells or organs, where they activate or inhibit specific physiological processes.

Question 19

How can two cells of a complex multicellular organism have the same genome, but markedly different structures and functions?

Accepted Answer

Different cells within a complex multicellular organism may have the same genome, but their genes are expressed differently. This means that different cells have different sets of proteins that allow them to carry out different functions and develop different structures. Gene expression is regulated by a complex array of transcription factors and signaling pathways that are determined by the cell's environment and developmental stage. This allows cells to differentiate and develop specialized structures and functions while retaining the same genome.

Question 20

Which of the following signals is unlikely to cause a change in gene expression in complex multicellular organisms?

Accepted Answer

All of the listed signals (oxygen levels, nutrients in the environment, temperature, and hormones) can cause a change in gene expression in complex multicellular organisms. These factors can influence cellular activity and physiological responses, leading to alterations in gene expression to adapt to varying conditions.

Quiz 28: Being Multicellular