Question

question 12 (2.5 points)
____ are cellular structures that act like propellers to move a cell through fluid environments
pilli
microvilli
cilia
flagella
microfilaments
question 13 (2.5 points)
biofilms found in nature ____.
contain only bacteria
are composed of multicellular organisms

Explanation:

• Pili: These are hair - like structures that help bacteria attach to surfaces or other cells, not for movement like propellers.
• Microvilli: They are finger - like projections that increase the surface area of cells (e.g., in the small intestine for absorption), not for cell movement.
• Cilia: Cilia are short, hair - like structures that can move in coordinated waves. In some cells (e.g., in the respiratory tract), they move substances (like mucus) along the surface, but they are not the main structure for moving the cell itself through a fluid environment.
• Flagella: Flagella are long, whip - like structures. They rotate or undulate to propel a cell (such as a sperm cell or a bacterial cell) through a fluid environment, acting like propellers.
• Microfilaments: These are part of the cytoskeleton and are involved in cell shape changes, muscle contraction (in muscle cells), and intracellular transport, not for whole - cell movement through fluids.

Answer:

Flagella