GED Science : Homeostasis

Study concepts, example questions & explanations for GED Science

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Example Questions

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Example Question #1 : Homeostasis

Which of the following factors does not affect the diffusion of molecules across the cell membrane?

Possible Answers:

The size of the molecule

The presence of a cell wall

Whether the cell is prokaryotic or eukaryotic

The presence of carbon in the molecule

The presence of hydrogen in the molecule

Correct answer:

The size of the molecule

Explanation:

The plasma membrane of the cell acts as a semi-permeable barrier, regulating what can enter and exit the cell. Only small, nonpolar molecules are able to cross the membrane via diffusion, without the assistance of protein channels. Larger molecules will be blocked, as will molecules that are charged or polar.

This principle is true for both prokaryotic and eukaryotic cells, and is not affected by the presence of a cell wall. Virtually all organic molecules contain carbon and hydrogen; the presence of these atoms will not affect the molecule's ability to cross the membrane.

Example Question #2 : Homeostasis

If a cell is placed into a hypertonic (concentrated) solution, in which direction will water flow?

Possible Answers:

Water will flow into the cell

Water will flow into the cell at the same rate it flows out of the cell (steady state equilibrium)

Ions will flow into the cell, but water will not move into or out of the cell

Ions will flow out of the cell, but water will not move into or out of the cell

Water will flow out of the cell

Correct answer:

Water will flow out of the cell

Explanation:

A hypertonic solution will have a higher solute concentration than the cell. To reach equilibrium, water must flow so that the concentration fo the solution is equal to the concentration of the cell. In order for this to happen, water must enter the solution, diluting it and reducing the concentration. Water will flow out of the cell and into the solution.

Note that the membrane of the cell will prevent ions from crossing.

Example Question #3 : Homeostasis

Which of the following statements about homeostasis is correct?

Possible Answers:

Positive feedback is designed to maintain homeostasis

Once a cell deviates from equilibrium it can be restored only if the right hormone is present

Once a cell deviates from equilibrium it cannot be restored and must be destroyed

Negative feedback is designed to maintain homeostasis

Both positive and negative feedback are designed to maintain homeostasis

Correct answer:

Negative feedback is designed to maintain homeostasis

Explanation:

Homeostasis describes the resistance of the body to change and serves to reinforce equilibrium. Concentration of ions and water in the blood and regulation of body temperature are examples of homeostatic regulation. These processes must be tightly regulated and maintained in order for the body to operate.

Negative feedback reinforces equilibrium and plays a key role in homeostasis. In a negative feedback system, deviations from equilibrium trigger processes that serve to return the body back to equilibrium. In contrast, a positive feedback system will respond to deviations from equilibrium by enhancing the changes, deviating farther and farther from the equilibrium state.

Hormones can play a key role in maintaining homeostasis, but many other molecules also help return the body to equilibrium.

Example Question #4 : Homeostasis

Water will diffuse across a cell membrane in an attempt to equalize concentrations of certain molecules inside and outside of the cell.

Which type of cell membrane transport is it when water moves across the cell membrane?

Possible Answers:

Diffusion

All of these are correct

Osmosis

Passive transport

Correct answer:

All of these are correct

Explanation:

Water can pass through the cell membrane without using energy. We call this passive transport. Diffusion is a type of passive transport and osmosis is specifically the diffusion of water molecules. So all of the answers are correct.

Example Question #22 : Biology And Life Sciences

How many layers comprise the plasma membrane of a living cell?

Possible Answers:

Three

Four

Two

Five

One

Correct answer:

Two

Explanation:

The plasma membrane of the living cell is made up of a phospholipid bilayer, meaning two opposed sheets of phospholipids with their hydrophilic heads facing outwards, and their hydrophobic tails facing one another. This structure allows the cell to remain fluid in shape while also staying "water tight".  

Example Question #23 : Biology And Life Sciences

Which of the following types of transport across a cell plasma membrane requires energy?

Possible Answers:

Active transport

Facilitated diffusion

Osmosis

Simple diffusion

Passive transport

Correct answer:

Active transport

Explanation:

Active transport is the movement of individual small molecules across the plasma membrane against their concentration gradient (from lower concentration to higher concentration). This is usually accomplished by proteins embedded in the membrane which use ATP energy to act as "pumps".

In contrast, osmosis, simple diffusion and facilitated diffusion are all forms of passive transport and do not require additional energy from the cell. These transport methods move with the concentration gradient, rather than against.  

Example Question #24 : Biology And Life Sciences

What is osmosis?

Possible Answers:

The diffusion of water across a selectively permeable membrane

The diffusion of small molecules and ions across a plasma membrane

The pumping of water through carrier proteins

The transport of large molecules in vesicles

The movement of water against its concentration gradient (from low concentration of water to high concentration of water)

Correct answer:

The diffusion of water across a selectively permeable membrane

Explanation:

Osmosis is the movement of water across a selectively permeable membrane, like the plasma membrane. It flows with its concentration gradient (from high concentration of water to low concentration of water).

Example Question #25 : Biology And Life Sciences

If a blood cell is in a hypotonic solution it will __________.

Possible Answers:

expand from taking in water

contract from losing water

remain the same size

expand from taking in oxygen

contract from losing oxygen

Correct answer:

expand from taking in water

Explanation:

A hypotonic solution is a solution that has a lower solute concentration than the fluid in the interior of the cell (the cytoplasm). When the cell is placed in this solution water will flow into the cell via osmosis, causing it to expand and potentially burst.

Example Question #26 : Biology And Life Sciences

If a blood cell is in a hypertonic solution it will __________.

Possible Answers:

contract from losing water

contract from losing oxygen

expand from taking in water

stay the same size

expand from losing oxygen

Correct answer:

contract from losing water

Explanation:

A hypertonic solution is a solution that has a higher solute concentration than the fluid in the interior of the cell (the cytoplasm). When the cell is placed in this solution water will flow out of the cell via osmosis, causing it to contract.  

Example Question #5 : Homeostasis

What is the transport process in which cells dispose of undigested waste or other substances via membrane enclosed vesicles? 

Possible Answers:

Passive transport

Endocytosis

Facilitated diffusion

Exocytosis

Osmosis

Correct answer:

Exocytosis

Explanation:

Exocytosis is the transport of waste materials or secretions from the cells. These molecules are packaged in membrane bound vesicles and are released across the membrane to the outside of the cell. 

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