Flashback Friday: Cell Transport

Emily is studying the process of diffusion in the human body. She reads that when you inhale, oxygen from the air moves into your lungs, and from there, oxygen molecules pass into the bloodstream. The concentration of oxygen is higher in the air compared to the bloodstream. Based on this information, which of the following best describes the process occurring in Emily's lungs?

• Diffusion is the movement of oxygen from an area of low concentration to an area of high concentration in the bloodstream.

• Diffusion is the movement of oxygen from an area of high concentration in the air to an area of low concentration in the bloodstream.

• Diffusion is the active transport of oxygen from the lungs into the bloodstream.

• Diffusion involves the movement of oxygen through the alveolar walls by osmosis.

Answer explanation

Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. In Emily's lungs, oxygen moves from the high concentration in the air to the low concentration in the bloodstream.

Sarah is observing a plant cell placed in a solution where the water concentration is higher outside the cell than inside. After some time, the cell becomes swollen and appears to be expanding. Which process is most likely responsible for this change, and why?

• Active transport, because the cell is using energy to move water in.

• Diffusion, because water molecules are moving from an area of low concentration to an area of high concentration.

• Osmosis, because water is moving into the cell where the concentration of water is lower.

• Facilitated diffusion, because water molecules are moving through a protein channel in the cell membrane.

Answer explanation

Osmosis is the process where water moves from an area of higher concentration (outside the cell) to an area of lower concentration (inside the cell). This causes the cell to swell as it takes in water.

During a biology experiment, a student places a piece of potato in a very salty solution. Over time, the student notices that the potato begins to shrink. This happens because water is leaving the potato cells. What process is responsible for the water leaving the potato cells?

• Active transport, as the potato cells are using energy to remove the water.

• Osmosis, where water moves from an area of higher concentration inside the cell to an area of lower concentration outside the cell.

• Diffusion, as water molecules move from the potato to the surrounding solution.

• Facilitated diffusion, as the water moves through protein channels in the potato cells.

Answer explanation

The potato shrinks because of osmosis, where water moves from the higher concentration inside the potato cells to the lower concentration in the salty solution, causing the cells to lose water.

In an experiment, a cell is placed in a solution where the concentration of salt is very low inside the cell, but the surrounding solution has a higher salt concentration. The cell begins to lose water. Which process is occurring in this scenario, and why?

• Active transport, as the cell is using energy to pump water out.

• Diffusion, because water is moving from an area of high concentration to an area of low concentration.

• Osmosis, where water moves from an area of higher concentration inside the cell to an area of lower concentration outside the cell.

• Facilitated diffusion, because water moves through specialized protein channels in the cell membrane.

Answer explanation

Osmosis is occurring as water moves from the higher concentration inside the cell to the lower concentration outside the cell, causing the cell to lose water due to the surrounding solution's higher salt concentration.

Tags

NGSS.MS-LS2-3

Molecule A cannot diffuse. What is a possible reason why?

• Molecule A is a macromolecule and it is too large to move.

• Molecule A is a building block and it is too large to move.

• Molecule A is a building block and it is too small to move.

• Molecule A is a macromole and it is too small to move.

Tags

NGSS.MS-LS1-2

The diagram represents a lab setup. The artificial cell (dialysis tube) contains a starch solution and the beaker contains a solution of starch indicator and water. The setup is left undisturbed for twenty minutes. Identify one molecule, present in this setup, that will be able to pass through the dialysis tubing

• starch

• dialysis tubing

• glucose

• starch indicator

Tags

NGSS.MS-PS1-2