Cellular Transport Review

The function of the cell membrane's lipid bilayer

• semipermable, allows only certain items in/out

• generates ATP

• packages items for transport

• produces proteins

Answer explanation

The cell membrane's lipid bilayer serves as a semipermeable barrier, allowing only certain items to pass in and out of the cell. This selective permeability helps maintain the cell's internal environment and regulate the exchange of substances with its surroundings. The other options, generating ATP, packaging items for transport, and producing proteins, are not the primary functions of the lipid bilayer.

The movement of materials across the cell membrane without using cellular energy

• Passive Transport

• Active Transport

Answer explanation

Passive transport is the correct answer because it involves the movement of materials across the cell membrane without using cellular energy. This process relies on the natural concentration gradient of the substances being transported, allowing them to move from areas of high concentration to areas of low concentration without the need for additional energy input.

The process by which particles naturally vibrate and move from an area of high concentration to an area of lower concentration

• diffusion

• aquaporin

• exocytosis

• endocytosis

Answer explanation

Diffusion is the correct answer because it refers to the natural movement of particles from an area of high concentration to an area of lower concentration. Aquaporin, exocytosis, and endocytosis are not related to this process. Aquaporin is a protein that facilitates water transport, while exocytosis and endocytosis are cellular processes involving the movement of substances in and out of cells.

This must be true in order for diffusion to occur:

• molecules or particles must have different sizes

• special protein channels must ALWAYS be available

• there must be areas of different concentrations

• energy must be available

Answer explanation

Diffusion is the passive movement of molecules or particles from an area of higher concentration to an area of lower concentration. For diffusion to occur, there must be areas of different concentrations, which creates a concentration gradient that drives the process. The other options are not necessary for diffusion to take place.

When both sides of the membrane reach similar solute concentrations.

• concentration

• osmosis

• equilibrium

• randomness

Answer explanation

Equilibrium is the correct answer because it refers to the state when both sides of the membrane have reached similar solute concentrations. In this situation, there is no net movement of solute particles, and the system is considered to be in balance. Osmosis is the process that leads to equilibrium, while concentration and randomness are not directly related to this concept.

Air has a higher concentration of oxygen molecules than does the cytoplasm of your lungs cells. Where in your lungs will there be a net increase of oxygen?

• in the air breathed out

• in the air breathed in

• outside of the lung cells

• inside of the lung cells

Answer explanation

Oxygen diffuses from areas of higher concentration to areas of lower concentration. Since air has a higher concentration of oxygen molecules than the cytoplasm of lung cells, there will be a net increase of oxygen inside the lung cells as it moves from the air to the cells.

The process by which molecules that cannot directly diffuse across the membrane pass through special protein channels

• facilitated diffusion

• endocytosis

• phagocytosis

• exocytosis

Answer explanation

Facilitated diffusion is the correct answer because it is the process by which molecules that cannot directly diffuse across the membrane pass through special protein channels. Endocytosis, phagocytosis, and exocytosis are different processes that involve the movement of substances into or out of the cell, but they do not involve protein channels for passive transport.

Which of the following statements tells how facilitated diffusion differs from simple diffusion?

• Particles move through cell membranes without the use of energy by cells.

• Particles tend to move from high concentration to low concentration.

• Particles move within channel proteins that pass through cell membranes.

• Particles tend to move more slowly than they would be expected to move.

Answer explanation

Facilitated diffusion differs from simple diffusion because it involves the movement of particles within channel proteins that pass through cell membranes. This process allows specific molecules to pass through the membrane more efficiently than they would in simple diffusion, which does not involve channel proteins.

facilitated diffusion of water through a selectively permeable membrane

• pinocytosis

• phagocytosis

• osmosis

• exocytosis

Answer explanation

Osmosis is the correct answer because it refers to the facilitated diffusion of water through a selectively permeable membrane. This process allows water molecules to move across the membrane from an area of higher concentration to an area of lower concentration, balancing the solute concentrations on both sides. The other options, pinocytosis, phagocytosis, and exocytosis, are not related to the diffusion of water through a membrane.

two adjacent solutions are ______ if they have the same concentrations of solute

• isotonic

• hypotonic

• hypertonic

Answer explanation

Two adjacent solutions are isotonic if they have the same concentrations of solute. This means that the solute concentration is equal in both solutions, resulting in no net movement of water across a semipermeable membrane. Hypotonic and hypertonic solutions have different solute concentrations, causing water to move in or out of cells.