CELL TRANSPORT

Normal homeostatic conditions require potassium concentrations to be about 1000 times higher inside the cell than in the blood.

What mechanism does a cell use to move these small potassium ions into the cell against the concentration gradient?

• passive transport by osmosis

• active transport by channel proteins

• active transport by endocytosis

• passive transport by diffusion

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Cells can function

• in a wide range of pHs and temperatures.

• only in a narrow range of temperature and pH.

• in rapidly changing temperatures and pHs.

• at any temperature and pH.

There are two main ways in which molecules are transported into and out of cells: active transport and passive transport. Which of the following is an example of active transport?

• plasmolysis

• sodium-potassium pump

• filtration

• osmosis

The fluid mosaic model shown above describes the structure and function of

• nuclei.

• cell membranes.

• chromosomes

• chloroplasts.

The ________ essentially aids in cellular homeostasis by providing the main transport mechanism for proteins within the cell.

• nucleus

• Golgi apparatus

• mitochondrion

• endoplasmic reticulum

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Emphysema is a health condition in which the lungs can no longer expel carbon dioxide normally. As a result, a person who has emphysema may have high blood acidity levels.

The body process that would attempt to return the blood pH to normal so that cells could function properly is called _______.

• homeostasis

• adaptation

• acidosis

• acidosis

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Osmosis causes water to move from areas of low salt concentration to areas of high salt concentration.

The internal NaCl concentration of red blood cells is 0.9 M. The diagram shows red blood cells submerged in solutions of four different NaCl concentrations—0 M, 0.65 M, 0.9 M, and 2 M.

Which of the diagrams shows red blood cells in the 2 M solution?

• 1

• 2

• 3

• 4

The cell membrane is a highly selective barrier that controls the movement of substances in and out of the cell. In fact, polar molecules are unable to go across unless

• they react with other substances to become nonpolar.

• they are broken down into smaller pieces.

• they pass through channels in the cell membrane.

• they are enclosed in water-filled vesicles.

To function normally, many types of animal cells must have a higher concentration of Na+ ions outside the cell and a higher concentration of K+ ions inside the cell. Which of the following forms of cellular transportation helps animal cells maintain Na+/K+ level homeostasis?

• diffusion

• endocytosis

• osmosis

• a cell membrane pump

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The sodium-potassium pump, in the picture, is a mechanism that allows cells to move sodium ions out of the cell and potassium ions into the cell, against a concentration gradient (i.e., from a low concentration to a high concentration).

This mechanism maintains the correct concentrations of sodium and potassium ions inside of a nerve cell. Although this pump uses energy, it is necessary to maintain these conditions so nerve impulses can be transmitted properly.

Which of the following statements does this information best support?

• Living organisms have processes and structures that help them maintain homeostasis.

• Evolution has increased the number of non-essential processes in living organisms.

• Energy is generated during most of the processes that occur in living organisms.

• Organisms that are living today use more energy than their ancestors.

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