characteristics of life regulated by cellular processes

The diagram shows a model of a section of cell membrane.

Predict what would happen if the sodium potassium pump in a cell stopped working.

• The cellular environment would become hypotonic and the cell would burst.

• The cellular environment would become hypertonic and the cell would shrivel.

• The cell would immediately shrivel and then return to an isotonic environment.

• Cellular homeostasis would be maintained because the sodium and potassium channels would compensate.

The graph shows the rate of enzyme activity in the presence of different pH in the cellular environment.

Why does the graph have this shape?

• At high pH, the enzyme functions more efficiently.

• At lower pH, the enzyme function remains the same.

• At a higher or lower pH, the enzyme’s shape/ability to bind is stable.

• At higher or lower pH, the enzyme’s shape/ability to bind can be altered.

For many years scientists debated whether viruses should be considered living organisms.

Which statement could a scientist use to support the position that viruses are living?

• Viruses infect both plant and animal cells.

• Viruses replicate to produce more viruses.

• Viruses have organelles similar to other organisms.

• Viruses undergo photosynthesis using chlorophyll molecules flowing freely in their cytoplasm.

What will happen to the plant when there is a higher concentration of water outside of a plant cell than inside of a plant cell?

• lose water and wilt

• decrease photosynthesis

• use more carbon dioxide

• gain water and become rigid

Doctors are always concerned when the body temperature of person rises above 98.6°, the normal body temperature for humans. Which of these best describes the possible effect of high body temperatures on a somatic cell?

• Mitosis would be altered affecting the healing process.

• Energy cannot be transformed to ATP due to the lack of water.

• Osmosis and diffusion across the cell membrane will stop causing dehydration.

• Chemical reactions in the cells may be disrupted due to the enzyme malfunction.

Plants are multicellular living organisms. What do cells of plants need to function?

• The cells of plants need molecules from food and a way to eliminate wastes.

• The cells of plants need molecules from food, but they do not need to eliminate wastes.

• The cells of plants need a way to eliminate wastes, but they do not need molecules from food.

• The cells of plants do not need a way to eliminate wastes, and they do not need molecules from food.

Which of the following kinds of cells perform basic functions such as making energy?

• both plant and bacteria cells

• neither plant or bacteria cells

• plant cells, but not bacteria cells

• bacteria cells, but not plant cells

What will happen to the plant when there is a lower concentration of water outside of a plant cell than inside of a plant cell?

• It will lose water and wilt.

• It will increase photosynthesis.

• It will use more carbon dioxide.

• It will gain water and become rigid.

Phytoplankton and Productivity

Phytoplankton are microscopic aquatic algae capable of photosynthesis. The rate at which light energy is converted to organic compounds by the photosynthetic organisms of an ecosystem is called productivity. Scientists have developed a method to determine the productivity of phytoplankton in an aquatic habitat using the following steps.

Method to Determine Productivity

1. Two bottles, one transparent and one opaque, are filled with equal volumes of water containing phytoplankton from the same depth of a lake.

2. Initial measurements of the concentrations of various dissolved gases for each bottle are determined from a separate water sample taken from the same depth.

3. The two filled bottles are sealed and suspended in the water for 24 hours.

4. After 24 hours, the concentrations of various dissolved gases in each bottle are measured and compared to the initial measurements of dissolved gases.

The diagram below shows the device used in the “Method to Determine Productivity.”

After 24 hours, which bottle will contain the most oxygen?

• The opaque bottle because more cellular respiration will occur.

• The transparent bottle because more photosynthesis will occur.

• The transparent bottle because the light will be changed into oxygen.

• The opaque bottle because there is less light to evaporate the oxygen.

In an aquatic ecosystem, which process acts to decrease the amount of dissolved oxygen?

• osmosis

• mitosis

• respiration

• photosynthesis