Cell Energy and Transport Mechanisms

Which of the following types of transport requires energy?

• Facilitated diffusion

• Osmosis

• Active transport

• Simple diffusion

Answer explanation

Active transport requires energy to move substances against their concentration gradient, while facilitated diffusion, osmosis, and simple diffusion occur passively without energy input.

A red blood cell is placed in a hypotonic solution. What happens to the cell?

• It shrinks

• It swells and bursts

• It remains unchanged

• It loses water and becomes rigid

Answer explanation

In a hypotonic solution, the concentration of solutes outside the red blood cell is lower than inside. Water enters the cell, causing it to swell and potentially burst due to the increased internal pressure.

Tags

NGSS.HS-LS1-3

Which structure maintains cell shape and assists with intracellular transport?

• Endoplasmic reticulum

• Cytoskeleton

• Golgi apparatus

• Ribosomes

Answer explanation

The cytoskeleton is a network of fibers that maintains cell shape and facilitates intracellular transport, making it essential for cellular structure and function.

Which extracellular matrix component is found in bacterial cell walls?

• Cellulose

• Peptidoglycan

• Chitin

• Collagen

Answer explanation

Peptidoglycan is the key component of bacterial cell walls, providing structural support and shape. In contrast, cellulose and chitin are found in plants and fungi, respectively, while collagen is a protein in animal tissues.

What type of junction in animal cells forms a watertight seal like a ziplock bag, preventing fluid from passing between adjacent cells?

• Gap junctions

• Tight junctions

• Desmosomes

• Plasmodesmata

Answer explanation

Tight junctions create a watertight seal between adjacent animal cells, similar to a ziplock bag, preventing fluid from leaking between them. This is crucial for maintaining distinct environments in different tissue compartments.

What is the primary function of desmosomes?

• To form a watertight seal between cells

• To anchor adjacent cells together like Velcro, providing mechanical stability

• To allow ions and molecules to pass freely between cells

• To facilitate cell signaling

Answer explanation

Desmosomes primarily function to anchor adjacent cells together, providing mechanical stability, much like Velcro. This helps maintain the integrity of tissues under stress, distinguishing them from other cell junctions.

The function of plasmodesmata in plant cells is most similar to which structure in animal cells?

• A. Gap junctions

• B. Tight junctions

• C. Desmosomes

• D. Microfilaments

Answer explanation

Plasmodesmata allow communication and transport between plant cells, similar to how gap junctions facilitate intercellular communication in animal cells. Thus, the function of plasmodesmata is most similar to gap junctions.

The movement of water across a membrane via aquaporins is an example of:

• Active transport

• Osmosis

• Simple diffusion

• Endocytosis

Answer explanation

The movement of water through aquaporins is a specific type of osmosis, which is the passive movement of water across a selectively permeable membrane. This process does not require energy, distinguishing it from active transport.

What role do integrins play in the extracellular matrix?

• They help transport ions across the membrane

• They anchor cells to the extracellular matrix

• They facilitate cell signaling

• They form channels for water transport

Answer explanation

Integrins are proteins that anchor cells to the extracellular matrix, providing structural support and facilitating communication between the cell and its environment.

What is needed for simple diffusion to occur?

• Water

• Concentration gradient

• Electrochemical gradient

• Carrier protein

• ATP

Answer explanation

Simple diffusion requires a concentration gradient, which is the difference in concentration of a substance across a space. This gradient drives the movement of molecules from an area of higher concentration to an area of lower concentration.