Homeostasis

This picture shows a contractile vacuole of a unicellular freshwater organism. The contractile vacuole regulates the flow of water into and out of the cell in an aquatic environment.

Which conditions cause the contractile vacuole to fill with water?

• The concentration of water is greater outside the cell than inside the cell.

• The temperature of water in the vacuole is higher than the temperature of its environment.

• The concentration of water inside the cell is the same as the concentration outside of the cell.

• The temperature of water in the vacuole is lower than the temperature of its environment.

Tags

NGSS.MS-LS1-1

NGSS.MS-LS1-2

The diagram shows the cellular activity across a cell membrane.

Which two processes does this diagram most directly model?

• Energy conversions and synthesis of new molecules

• Synthesis of new molecules and homeostasis

• Transport of molecules and energy conversions

• Homeostasis and transport of molecules

Both euglena and cyanobacteria are photosynthetic unicellular organisms found in pond water. The feature that distinguishes eugiena from cyanobacteria is the -

• ability to maintain homeostasis

• presence of ribosomes

• presence of a nuclear membrane

• ability to reproduce

Tags

NGSS.MS-LS4-2

Some students used vinegar to dissolve away the shells of three eggs and used these eggs as models of human red blood cells. The students observed the changes in the eggs when they were placed in different solutions.

Which statement best describes the role of the cell membrane in this model?

• The cell membrane is an impermeable barrier that prevents water from entering the cell.

• The cell membrane allows solutes to enter the cell, which causes the cell to shrink.

• The cell membrane allows water to enter and leave the cell - playing as a semipermeable barrier.

• The cell membrane removes solutes from the environment.

The cellular process known as the sodium-potassium pump was discovered in the 1950s by Jen Christian Skou, a Danish scientist. This process is a form of active transport that moves three sodium ions to the outside of a cell for every two potassium ions that it moves into the cell. Which of these best explains why energy is needed for active transport?

• Ions are negatively charged

• Ions are attached to large proteins

• Ions are trapped inside the plasma membrane

• Ions are moved against the concentration gradient