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Homeostasis and Transport
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2. If the water concentration inside a cell is higher than the water concentration outside the cell, water flows out
of the cell. This method of molecular transport is called
A. a sodium pump.
B. exocytosis.
C. osmosis.
D. endocytosis.
3. During heatstroke, the body can't dispose of excess heat. As a result, the homeostatic balance is disturbed,
and internal body temperatures can reach as much as 110°.
Heatstroke is dangerous to people primarily because
A.
B.
C.
D.
it causes pneumonia.
cells can't function properly at high temperatures.
blood pressure becomes too low.
blood vessels may rupture.
4. Permeability is the condition of being capable of having materials flow into and out of a membrane. The
permeability of a cell membrane is determined by how easily a molecule can diffuse across the membrane.
Usually, only molecules that are fat-soluble can permeate across a cell membrane. Why is this the case?
A. Water-soluble molecules are nonpolar.
B. Water-soluble molecules are too large.
C. Cell membranes are composed of a lipid bilayer.
D. Cell membranes are composed of cytosol.
5. When dry environmental conditions exist, guard cells close the openings in leaves to reduce the loss of
water from the plant. This process is an example of a feedback mechanism that plants use in order to
A. absorb more solar energy.
B. expend their resources.
C. produce more chlorophyll.
D. maintain homeostasis.
6. Examine the following diagrams of plant cells. Each cell has been placed in a different solution.
1
2
3
The cell in diagram 3 has been placed in a solution that contains _______ the interior of the cell.
A. water that is cooler than
B. a lower concentration of water than
C. water that is warmer than
D. a higher concentration of water than
7. Homeostasis is classified under which of the following?
A. photosynthesis
B. transcription
C. cell regulation
D. cell respiration
8. 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 _______.
A. active transport
B. acidosis
C. homeostasis
D. adaptation
9. Drowning is the second leading cause of accidental death for school-age children and the number one
cause of death for children under the age of 5. However, there have been cases when children have been
revived after being submerged in icy cold water for prolonged periods of time. This occurs due to a reflex
known as the mammalian diving reflex.
When submerged in very cold water, receptors in the nasal cavity and other areas of the face relay a message
to the brain that causes it to only circulate blood between the heart and the brain. This allows oxygen to be
conserved and enhances the chance of survival.
The mammalian diving reflex is an example of the body's attempt to maintain
A. respiration.
B. autoimmune responses.
C. homeostasis.
D. genetic viability.
10. All cells have a protective barrier that is formed of proteins and a lipid bilayer. What is the name of this
barrier?
A. cell wall
B. cytoplasm
C. phospholipid barrier
D. cell membrane
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12. Examine the illustration below.
Which of the following types of cellular transport is illustrated in the picture?
A. diffusion
B. endocytosis
C. osmosis
D. exocytosis
13. The ________ essentially aids in cellular homeostasis by providing the main transport mechanism for
proteins within the cell.
A. endoplasmic reticulum
B. nucleus
C. mitochondrion
D. Golgi apparatus
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15. The Golgi apparatus helps to maintain cellular homeostasis by
A. synthesizing ATP molecules from glucose during glycolysis.
B. transforming absorbed light energy to manufacture carbohydrates.
C. modifying, sorting, and packaging proteins prior to transport.
D. controlling which proteins are synthesized during the cell cycle.
16. 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?
A. osmosis
B. sodium-potassium pump
C. plasmolysis
D. filtration
17. There are two main ways in which molecules are transported into and out of cells - active transport and
passive transport. Which of the following statements is true of passive transport?
A. Molecules move up a concentration gradient during passive transport.
B. Carrier proteins are sometimes used during passive transport.
C. Endocytosis and exocytosis are two forms of passive transport.
D. Energy, in the form of ATP, is essential for passive transport.
18. How is homeostasis important to the survival of organisms?
A. Homeostasis makes all organisms hibernate.
B. Homeostasis makes organisms grow bigger and taller.
C. Homeostasis helps organisms locate food.
D. Homeostasis allows organisms to regulate their temperature.
19. In order to maintain homeostasis, human cells must have a higher concentration of sodium ions outside the
cell than inside the cell. In addition, the concentration of potassium ions must be higher inside the cell than
outside the cell. Which of the following forms of cellular transportation helps human cells maintain a relatively
constant sodium and potassium concentration?
A. osmosis
B. a cell membrane pump
C. endocytosis
D. diffusion
20. Which of the following best describes the process of diffusion?
Diffusion is the movement of molecules from an area of lower concentration to one of higher
A. concentration by random molecular motion.
Diffusion is the movement of molecules from an area of higher concentration to one of lower
B. concentration by random molecular motion.
Diffusion is the movement of molecules from an area of lower concentration to one of higher
C. concentration caused by an input of energy to the system.
Diffusion is the movement of molecules from an area of higher concentration to one of lower
D. concentration caused by an input of energy to the system.
21. Which of the following is a function of the cell membrane of a cell?
A.
B.
C.
D.
The production of energy from food molecules using cellular respiration.
The transport of genetic material within the cytoplasm of the cell.
The transport of molecules into and out of the cell through osmosis and diffusion.
The production of genetic material through DNA transcription.
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23. In carrying out normal activities, cells use oxygen and produce carbon dioxide. The concentration of
oxygen is higher in the blood than inside the cell, so oxygen moves into the cell. Similarly, carbon dioxide
moves out of the cell into the blood because the concentration of carbon dioxide inside the cell is greater than
the concentration outside the cell.
How are the small molecules of oxygen and carbon dioxide moving through the cell membrane?
A. active transport by endocytosis
B. active transport by carrier proteins
C. passive transport by diffusion
D. passive transport by osmosis
24.
The fluid mosaic model shown above describes the structure and function of
A. cell membranes.
B. chloroplasts.
C. chromosomes.
D. nuclei.
25. How do enzymes aid in cell regulation?
A.
B.
C.
D.
Enzymes speed up reactions that help sustain life.
Enzymes speed up reactions that stop life.
Enzymes stop reactions that help sustain life.
Enzymes slow down reactions that help sustain life.
26. Homeostasis is the regulation of metabolic processes within an organism in order to maintain the stable
internal conditions required for life.
The human respiratory system includes the nose, the larynx, and the lungs. This body system helps maintain
homeostasis by
A. removing solid waste from the body.
B. regulating hormone levels in the body.
C. enabling gas exchange in the body.
D. transporting oxygen to other organ systems.
27. Materials essential to life processes move across a cell membrane through a variety of methods. What cell
membrane structure allows water-soluble materials to be passively transported to the cytoplasm?
A. hydrophilic phospholipid tails
B. Golgi complex vesicles
C. carrier proteins
D. endocytosis vesicles
28. 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
A.
B.
C.
D.
they pass through channels in the cell membrane.
they react with other substances to become nonpolar.
they are enclosed in water-filled vesicles.
they are broken down into smaller pieces.
29. The secretion of hormones is an example of a physiological feedback loop. When hormones are needed,
they are secreted by glands. When the hormones are no longer needed, the glands are signaled to stop
secreting the hormones until they are needed again.
Thus, the basic function of a physiological feedback loop is
A. to end a process.
B. to create substances.
C. to destroy substances.
D. to regulate a process.
30. Look at the diagram below.
The yellow box represents a cell with a semi-permeable membrane. The small, blue dots represent molecules
of water, and the larger, gray dots represent a solute such as sugar or salt. The membrane is thin enough for
water to pass through, but it is not thin enough for the solute to pass.
What will happen to the substances in this diagram to bring the concentrations closer to equilibrium?
The solute will flow into the cell from the surrounding environment.
A.
B.
C.
D.
Nothing will change--it is already in equilibrium.
Water will flow into the cell from the surrounding environment.
Water will flow out of the cell and into the surrounding environment.
Answers
1. -2. C
3. B
4. C
5. D
6. B
7. C
8. C
9. C
10. D
11. -12. D
13. A
14. -15. C
16. B
17. B
18. D
19. B
20. B
21. C
22. -23. C
24. A
25. A
26. C
27. C
28. A
29. D
30. D
Explanations
1. -2. Water moves across cell membranes through a special type of diffusion called osmosis.
Osmosis is a type of passive transport because it is facilitated by concentration gradients — movement from
areas of high concentration to areas of low concentration - and the cell does not have to expend energy during
this process.
3. Cells function properly only in a narrow range of temperatures. The body attempts to maintain internal
temperatures within this range though the process of homeostasis. However, in cases of exposure to extreme
heat or cold, the homeostatic balance is disturbed, and cell die-off, organ damage, or even death can result.
4. Cellular fluid (cytosol) and the cell's organelles are contained by the cell's membrane, which is composed of
a lipid bilayer. Lipids are a type of fat. Because a cell's membrane is composed of fat, only fat-soluble
molecules are able to dissolve through the membrane into the cytosol.
5. Homeostasis refers to an organism's ability to maintain a relatively constant internal environment. In many
organisms, feedback mechanisms have evolved to help maintain homeostasis.
For example, plants require a certain amount of water for survival. When dry environmental conditions exist,
guard cells close the openings in leaves to reduce the loss of water from the plant. This feedback mechanism
helps plants maintain a relatively constant internal environment.
6. Diagram 3 shows plant cells in a hypertonic solution. This means that the solution has a lower
concentration of water than the interior of the cell. In this case, water flows out of the cell—causing it to
undergo plasmolysis.
7. Homeostasis describes the process through which a body maintains a stable internal environment. Thus,
homeostasis is a form of cell regulation.
Without cellular regulation, cells would not be able to control their water concentrations, temperatures, and
acidities, and cells would die.
8. Homeostasis is the body process that attempts to maintain balance of internal environment variables such
as pH, temperature, and blood sugar levels because cells and organs function properly in only a narrow range
of conditions.
9. Homeostasis is the process through which an organism regulates its internal environment in order to
maintain a stable and constant condition.
There are many examples of homeostasis. Sweating and shivering are two common methods that humans use
to regulate their temperature within a certain range. The pH and composition of blood are regulated by ion
concentrations and hormones, such as insulin and glucagon. The mammalian diving reflex is an example of
homeostasis because the body is attempting to maintain its blood oxygen levels.
10. All cells have a cell membrane. The cell membrane separates the cell's internal environment from the
external world. Cell membranes are constructed of proteins and a lipid bilayer that includes phospholipids. The
cell membrane controls the movement of materials into and out of the cell.
11. -12. Exocytosis is the process by which vesicles in the cytoplasm fuse with the cell membrane, releasing their
contents into the cell's external environment. Cellular wastes are often disposed through this process.
13. The endoplasmic reticulum essentially aids in cellular homeostasis by providing the main transport
mechanism for proteins within the cell.
Protein transport begins on the endoplasmic reticulum. Proteins are packaged within transport vesicles and
then moved along the membrane of the endoplasmic reticulum.
14. -15. The Golgi apparatus helps maintain cellular homeostasis by modifying, sorting, and packaging proteins
prior to transport.
Though proteins synthesized on the rough endoplasmic reticulum comprise the majority of the macromolecules
managed by the Golgi, it is also involved in the transport of lipids and the creation of lysosomes.
16. The sodium-potassium pump is an example of an active-transport system because it requires the input of
energy (ATP) in order to move molecules from an area of low concentration to an area of high concentration.
Sodium-potassium pumps are found in almost all animal cells and play a vital role in the transportation of nerve
impulses.
17. There are four main kinds of passive transport: diffusion, faciliated diffusion, filtration, and osmosis. All of
these forms involve molecules moving down a concentration gradient (i.e. from a high concentration to a low
concentration) and do not require the input of metabolic energy or ATP.
Small molecules such as oxygen, ethnanol, and carbon dioxide easily diffuse across membranes. Some larger
molecules, such as glucose, require the assistance of a carrier protein. This form of passive transport is known
as faciliated diffusion.
18. Homeostasis is the body's ability to regulate its temperature, as well as other internal conditions, even
when environmental conditions are changing.
Since an organisms' cells can only function properly in a limited temperature range, homeostasis is important
to the survival of all organisms.
19. For the cell to maintain a higher or lower concentration of a certain kind of molecule inside the cell than the
fluids surrounding the cell, the cell must use a form of active transport. Endocytosis and cell membrane pumps
are forms of active transport. A cell membrane pump known as the sodium-potassium pump maintains
homeostasis inside the cells.
20. Diffusion is the movement of molecules from an area of higher concentration to one of lower
concentration by random molecular motion. Some of the molecules that may be moved through diffusion
include oxygen, carbon dioxide, salts, sugars, and amino acids.
Diffusion results in a gradual mixing of the materials in a system. Diffusion does not require an input of energy
into the system because it is caused by random molecular motion.
21. One of the major functions of the cell membrane is the passive transport of molecules into and out of
the cell through osmosis and diffusion. The cell membrane also separates the cell's internal environment
from the external world.
22. -23. Small molecules, such as molecules of oxygen and carbon dioxide gas, can move passively through a cell
membrane as a result of concentration gradients. That is, molecules naturally flow from areas of high
concentration to areas of low concentration.
This process is called osmosis when water is the substance being transported and diffusion when the
substance is not water.
24. The fluid mosaic model shown in the question describes the structure and function of cell membranes.
The cell membrane controls the movement of particles and chemicals to and from the outside of the cells. The
"fluid" aspect of the membrane allows for this movement, as well as the transport proteins that are embedded
into the layer.
25. Enzymes speed up reactions that help sustain life. Without enzymes, organisms would not be able to
metabolize substances quickly enough to maintain their daily life processes.
26. The function of the human respiratory system is to enable gas exchange in the body. In order for the
cells of the body to function, a constant supply of oxygen is required, while a constant supply of carbon dioxide
is produced as a waste product and must be removed from the body.
27. Proteins in the cell membrane that assist with facilitated diffusion are known as carrier proteins, or
transport proteins, since they carry materials across the cell membrane.
Carrier proteins bind to a molecule on one side of the membrane, change shapes to shield the molecule from
the lipid bilayer, and then release the molecule on the other side of the membrane.
28. All cells have cell membranes. The cell membrane separates the cell's internal environment from the
external world. Cell membranes are constructed of proteins and a lipid bilayer that includes phospholipids.
Channels formed by doughnut shaped proteins are embedded within the cell membrane. These channels act
like locked doors and allow certain polar molecules to go across the membrane.
29. The basic function of a physiological feedback loop is to regulate a process.
In the hormone example, the function of the feedback loop is to regulate the release of hormones.
30. Because the solute cannot pass through the membrane, water is the only substance that can flow in order
to make the concentrations balanced on either side of the membrane.
Osmosis is the process by which water flows down its concentration gradient--that is, water will flow from an
area of high concentration (of water) to an area of low concentration. In this case, the concentration of water
relative to the solute is much greater inside the cell, and so water will flow out of the cell and into the
surrounding environment.