Unit 4 Target 3-6: Cell Transport & Homeostasis Quiz

When an animal cell is surrounded by fresh water, the concentration of solutes inside the cell is higher than the concentration outside. This creates a concentration gradient, causing water to move from an area of lower solute concentration (outside the cell) to an area of higher solute concentration (inside the cell). This movement of water into the cell is known as osmosis. As water continues to enter the cell, the cell membrane stretches and eventually bursts, leading to cell death. Therefore, the correct answer is "water to move into the cell."

Active transport is the process of moving molecules across a cell membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration. This requires the input of energy from the cell in the form of ATP (adenosine triphosphate). Osmosis, diffusion, and facilitated diffusion do not require energy input from the cell.

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. This process occurs in various mediums, including gases, liquids, and solids. However, the statement "only through a lipid bilayer membrane" is incorrect because diffusion can occur through any type of membrane, not just lipid bilayers. Therefore, the correct answer is "from an area of high concentration to an area of low concentration."

The process shown in the illustration is diffusion. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration, resulting in the equal distribution of molecules. In this process, molecules passively move across a semi-permeable membrane without the need for energy input. Osmosis, facilitated diffusion, and active transport involve specific mechanisms and energy input, which are not depicted in the illustration. Therefore, the correct answer is diffusion.

Diffusion does not expend energy because it is a passive process that occurs naturally due to the random movement of particles. It is the movement of particles from an area of high concentration to an area of low concentration, and it does not require any additional energy input. In contrast, active transport, a sodium-potassium pump, and endocytosis all require the expenditure of energy to transport molecules or particles against their concentration gradient or to engulf substances into the cell.

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. As particles diffuse, they spread out and become evenly distributed. Therefore, over time, the concentration of substances will become balanced on both sides of a membrane.

Isotonic solutions have equal concentrations of solute and water. This means that the amount of solute dissolved in the solution is balanced with the amount of water present. In an isotonic solution, there is no net movement of water from one solution to the other because the concentrations are already equal.

Osmosis is the correct answer because it refers to the diffusion of water molecules across a selectively permeable membrane. Osmosis occurs when there is a difference in solute concentration on either side of the membrane, causing water to move from an area of lower solute concentration to an area of higher solute concentration. This process is important for maintaining the balance of water and solutes in cells and is essential for various biological processes. Osmotic pressure, facilitated diffusion, and active transport are all different processes that do not specifically involve the diffusion of water molecules.

Facilitated diffusion is the process by which sugar molecules can enter cells. This process involves the use of transport proteins that help the molecules move across the cell membrane, from an area of higher concentration to an area of lower concentration, without the need for energy. Unlike ion pumps, which require energy to transport molecules against their concentration gradient, facilitated diffusion allows for the passive movement of molecules down their concentration gradient. Osmosis is the movement of water molecules across a membrane, while exocytosis is the process by which cells release molecules to the outside environment.

Exocytosis is the process by which a cell releases proteins or other molecules into the extracellular space. This involves the fusion of vesicles containing the protein with the cell membrane, allowing the contents to be expelled outside the cell. This is the correct answer because osmosis is the movement of water across a selectively permeable membrane, facilitated diffusion is the passive transport of molecules across a membrane with the help of transport proteins, and endocytosis is the process by which a cell takes in molecules or particles by engulfing them.

The diagram shows a cell membrane composed of a phospholipid bilayer with a channel protein. Facilitated diffusion is a passive transport process that allows molecules to move across the cell membrane with the help of channel proteins. In this case, the molecules represented by "x" are moving into the cell through the channel protein. This is because the channel protein provides a hydrophilic pathway through the hydrophobic phospholipid bilayer, allowing the molecules to move from an area of higher concentration outside the cell to an area of lower concentration inside the cell.

Facilitated diffusion is a passive transport process that moves substances across a cell membrane with the help of carrier proteins. It does not require energy input, as it relies on the concentration gradient of the substances. The other characteristics listed are all true for facilitated diffusion. However, moving substances against a concentration gradient is an active transport process called active transport, and not a characteristic of facilitated diffusion.

When a red blood cell is placed in pure water, the concentration of water molecules outside the cell is higher than inside the cell. According to the principles of osmosis, water molecules will move from an area of higher concentration (outside the cell) to an area of lower concentration (inside the cell) in order to equalize the concentrations. Therefore, there is a net flow of water molecules into the red blood cell, and this net flow occurs through the process of osmosis.

Placing a plant into a hypertonic environment means that the concentration of solutes outside the plant cell is higher than inside the cell. This creates a concentration gradient that causes water to move out of the cell through osmosis. As a result, the plant cell loses water and the vacuole, which is responsible for maintaining turgor pressure, shrinks. This leads to a decrease in turgor pressure, causing the plant to wilt.

Active transport is the process by which a sodium ion exits a cell through the plasma membrane. Unlike facilitated diffusion, which relies on a concentration gradient to move molecules across the membrane, active transport requires the use of energy to move substances against their concentration gradient. Osmosis is the movement of water molecules across a membrane, not ions. Exocytosis is the process by which substances are released from a cell, not the process by which ions exit the cell. Therefore, the correct answer is active transport.

The sodium-potassium pump is responsible for maintaining the concentration gradients of sodium and potassium ions across the cell membrane. It actively transports three sodium ions out of the cell for every two potassium ions it brings into the cell. This process requires energy in the form of ATP. Therefore, the correct answer is that the sodium-potassium pump pumps potassium into the cell.

Exocytosis is the process by which large molecules or particles are transported into the cell. It involves the fusion of vesicles containing the molecules with the cell membrane, releasing the contents into the extracellular space. This mechanism is particularly important for the uptake of large molecules that cannot pass through the membrane by diffusion or osmosis. Lipid carriers are not involved in the transport of large molecules into the cell.