Standard 2

Addison &

Claire

Homeostasis• Homeostasis- The ability of an organism or cell to

maintain a constant internal environment• Homeo= equal or same• Plant and animals both use this process.• Example: If a plant does not have enough water, then it

wilts. When the plant gets water, it is balanced again.• Example: When humans get too hot, we sweat so that

the body temperature will go down to normal.

• Active Transport- The cell actively moves to obtain food or water.• This process uses energy.• Active transport is used in animal cells.• Endocytosis and exocytosis are types of active transport.

ACTIVE Transport

AmoebaFood

1

1. Amoeba Actively getting food

2.

Amoeba with food inside

3.

Endocytosis• Endocytosis- The cell takes

in macromolecules (macro means large) and particles. The cell membrane surrounds the substance and pinches off to form an intracellular vesicle as shown

• Endo=inside• Cyt =cell• Osis = a condition• Endocytosis – a condition

when the cell takes something in

Exocytosis• Exocytosis – something

is being excreted or let OUT of the cell

• Exo=outside• Cyt = cell• Osis = condition• Something leaves the

cell.• It is the opposite of

endocytosis.

PASSIVE Transport• Passive Transport- The diffusion of a substance across a

biological membrane.• In other words, the cell just sits there and things go in

and out by themselves.• It does not use energy.• Diffusion and osmosis are types of passive

transport.

Diffusion

• Diffusion- The movement of a substance or particles from an area of high concentration to a lower concentration.

• The result is a slow mixing of the material. For example, when food coloring is dropped into a bowl of water, the coloring eventually spreads evenly throughout the water.

Osmosis• Osmosis- The diffusion of water across a

selectively permeable membrane.• The amount of water inside and outside

the cell determines whether it is isotonic, hypotonic, or hypertonic.

The sugar molecules are too big to fit through the membrane.

#1. Molecules move from areas of high concentration to areas of low concentration through the process of

A. osmosis B. diffusion C. passive transport D. active transport

The answer is…

•B- Diffusion•Diffusion causes molecules to go from high concentration to low concentration.

#2. Which statement describes a cell after it has been placed in a sugar solution?

A. It is larger because sugar entered the cell by diffusion.

B. It is larger because water entered the cell by osmosis.

C. It is smaller because sugar left the cell by diffusion.

D. It is smaller because water left the cell by osmosis.

The answer is…

• D- It is smaller because water left the cell by osmosis.

• Since more water is inside the cell, water goes from an area of high concentration, the cell, to an area of low concentration, the sugar solution.

#3.Is this an example of active transport or passive transport?

The answer is…

• Active Transport• The organism is actively moving to

get a particle.

#4. Which statement describes the cellular conditions in which passive transport would occur?

A. Energy is used to move molecules from an area of low concentration to an area of high concentration.

B. Energy is used to move molecules from an area of high concentration to an area of low concentration.

C. There is a concentration gradient across a semi-permeable membrane where molecules move from an area of low concentration to an area of high concentration.

D. Energy is not used to move molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration.

The answer is…•D- Energy is not used to move

molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration.

•In passive transport, energy is not used. Also, molecules are moved to an area of lower concentration.

#5. Study the diagram below.

Which arrow shows the direction the solute molecules would move to achieve homeostasis?

A. B.

C. D.

This diagram labels the solute molecules

The answer is…

• B• The molecules would move to

the left to achieve balance. It moves from the higher concentration to a lower concentration.

#6. Study the diagram below.

A potato slice is placed in distilled water in Breaker 1. Asimilar potato slice is placed in salt water in Breaker 2.

Which statement correctly explains the movement of wateracross cell membranes in one of the potato slices?

A. Water will move out of the potato cells in Breaker 1 because the solution is more concentrated.

B. Water will move into the potato slices in Breaker 1 because the solution is more concentrated.

C. Water will move out of the potato cells in Beaker 2 because the solution has less water.

D. Water will move into the potato cells in Beaker 2 because the solution is more concentrated.

The answer is…•C- Water will move out of the

potato cells in Beaker 2 because the solution has less water.

•Water moves out to dilute the salt water solution. The salt water solution has less water, so the water in the potato cell moves out to a lower concentration.

#7. Study the figure below.If the membrane shown is permeable to molecules of X but impermeable to molecules of Y, what will be the result of diffusion over time?

A. Molecules of X on each side of the membrane will become equal in concentration.

B. Molecules of Y on each side of the membrane will become equal in concentration.

C. Molecules of X will increase in concentration on the right side.D. Molecules of Y will increase in concentration on the right side.

Hint: Permeable means things CAN cross it.

Impermeable means nothing can cross it.

The answer is…

• A- Molecules of X on each side of the membrane will become

equal in concentration.• Because the membrane is permeable

to X molecules, they will diffuse from an area of higher concentration to an area of lower concentration.

#8. Study the information below. Two cells are separated by semi-permeable

membranes. The starch molecules cannot pass

through themembranes, but the salt

molecules can pass through the

membranes. Which statement describes the

process forachieving homeostasis

between the cells?

A. Salt will move from 2 to 1 by diffusion.B. Salt will move from 1 to 2 by diffusion.C. Salt will move from 2 to 1 by osmosis.D. Salt will move from 1 to 2 by osmosis.

The answer is…

• B- Salt will move from 1 to 2 by diffusion because more salt molecules are present in cell 1 than cell2.

• Letter D is NOT the answer because osmosis only involves the movement of WATER not salt.

#9. Which choice is NOT an example of homeostasis?

A. ShiveringB. SweatingC. GrowingD. Breathing

The answer is…•C- Growing.•Shivering, sweating, and breathing

are all examples of homeostasis. Shivering helps maintain body heat, sweating cools the body down, and breathing regulates the balance of carbon dioxide and oxygen; however growing is not an example of homeostasis.

#10. True or false:

Passive transport has do to do with the diffusion of particles.

The answer is…•True•Particles are diffused across a membrane.

#11. True or False:

Osmosis is the transfer of air particles around the cell.

The answer is…

• False• Osmosis is the diffusion of water

across a permeable membrane.

#12. What is the difference between exocytosis and endocytosis?

The answer is…

• Exocytosis- a substance leaves or exits the cell

• Endocytosis- a substance enters or comes into the cell

#13. Does passive transport use energy?

The answer is…•No•Things just pass in and out of the membrane in passive transport.

#14. Endocytosis and exocytosis are examples of

A. Passive TransportB. DiffusionC. Active TransportD. Osmosis

The answer is…

• C- Active Transport• Endocytosis and exocytosis use

energy, which means they are active.