Chapter 5

Homeostasis and Cell

Transport

Palabra Palooza!

• Role #1: The Definer says:

– The word __________ can be

explained as _____________

• Role #2: The Re-stater says:

– Then I understand

__(word)____ to mean

_____________

– Words:

• Passive

transport

• Diffusion

• Equilibrium

• Osmosis

• Facilitated

diffusion

Finger Vote!

• How many people can define all five

terms?

Human Matching

1. concentration of molecules is the same

throughout the space

2. diffusion of substances across a cell

membrane with the aid of carrier proteins

3. movement of substances across a cell

membrane without the use of energy

4. the diffusion of water molecules from an

area of higher concentration to an area of

lower concentration

5. movement of molecules from an area of

higher concentration to an area of lower

concentration

___Passive

transport

___Diffusion

___Equilibrium

___Osmosis

___Facilitated

diffusion

What is homeostasis?

Homeostasis is the ability to maintain

normal internal conditions. This means

maintain a state of balance in living

things.

Cells must maintain homeostasis

What structure does a cell

have to help it maintain

homeostasis? • Cells are enclosed in a phospholipid

bilayer called a cell (plasma) membrane

that regulates their interactions with

their surrounding environment.

• A cell membrane has a specific

structure that allows it to be semi-

permeable.

What is the cell membrane’s

structure and function?

1. Semi/Selectively permeable (controls

what substances enters and leaves the

cell)

2. Helps organisms maintain homeostasis

What is selectively

permeable?

• Selectively permeable means that the

membrane will allow some substances

to pass through and will not allow other

substances to pass through.

What is permeable and

impermeable?

If a membrane allows a substance to pass

through, it is said to be permeable to

that substance.

If a membrane does not allow a

substance to pass through, it is said to

be impermeable to that substance.

How does a cell maintain

homeostasis?

Through the movement of different

molecules through the cell membrane

by:

1. Passive transport

or

2. Active transport

2. What is passive

transport?

• The movement of

substances across

a cell membrane

without the use of

energy by the cell.

3. What is diffusion?

• The simplest type of passive transport.

• The movement of molecules from an area of higher concentration to an area of lower concentration.

• Molecules move on their own kinetic energy.

Examples: When you add

a sugar cube to water

Aroma (smell) of microwave popcorn

What does it mean by

kinetic energy?

• Molecules are in constant motion because they have kinetic energy

• Molecules move randomly in a straight line until they hit another molecule, then bounce off and move in the opposite direction.

• Molecules have the tendency to move from high to low concentration.

4. What is equilibrium?

• When the concentration of molecules of

a substance is the same throughout a

space.

• Even at equilibrium there is a random

movement of molecules.

CHECK IT: Stand Up

• BRING YOUR NOTES!

• Find one partner that is wearing the

same color as you!

CHECK IT

Partner #1: Explain the structure of a cell

membrane and the term semi-

permeable.

Sentence starter:

The cell membrane is made up of _____

Semi or selectively permeable means ___

CHECK IT

Partner #2: Describe the term diffusion.

Be sure to include the term “passive

transport” in your answer.

Sentence Starter:

Diffusion is ________

5. What is a solution?

• A solution is composed of a solute dissolved in a solvent.

• Example: Salt water – Salt is the solute

– Water is the solvent

• In the case of cells, the solutes are organic* and inorganic compounds, and water is the solvent. – *Carbohydrates, Proteins, Lipids

6. What is osmosis?

• Osmosis is the movement of water across a cell membrane from an area of higher concentration to an area of lower concentration.

****Because water is moving from an area of higher concentration to an area of lower concentration, osmosis does not require cells to expend energy.

*****Therefore, osmosis is a type of passive transport!!!!!

What’s wrong with this

picture?

7. What determines the

direction of the water?

• The relative concentration of water and

solute on the two sides of the cell

membrane.

8. Some Definitions…

• Hypertonic-higher concentration of solutes

• Isotonic-even concentration of solutes

• Hypotonic-lower concentration of solutes

• In living systems, the point of reference

is always the cytoplasm, so the prefix

hypo- means that the extracellular fluid

has a lower concentration of solutes

than the cell cytoplasm.

• It also means that the extracellular fluid

has a higher concentration of water in

the solution than does the cell. In this

situation, water will follow its

concentration gradient and enter the

cell, causing the cell to expand.

Source: Boundless. “Water

8. Some Definitions… The outside

fluid is…

If the fluid

outside the

cell has…

Water

diffuses…

Effect on

the cell…

Isotonic Equal conc.

of H2O and

solutes

Into & out of

cell at the

same

rate

Cell is

normal

(shape and

size)

Hypotonic Lower conc.

of solutes

(higher conc.

of water)

Into the cell Cell will swell

and burst

(cytolysis)

Hypertonic Higher conc.

of solutes

(lower conc.

of water)

Out of the

cell

Cell will

shrink

(plasmolysis

or crenation)

9. What happens to the cells of

a freshwater fish when it is in a

saltwater tank?

• Fish-- Animal Cells No Cell Walls

• Salt

9. What happens to the cells of

a freshwater fish when it is in a

saltwater tank?

• Salt • Outside

solution is

hypertonic

• Plasmolysis

occurs

H2O leaves fish’s cells and fish will die

10. What happens to the cells

of a saltwater fish when it is in

a freshwater tank?

• Fish-- Animal Cells No Cell Walls

• Salt

10. What happens to the cells

of a saltwater fish when it is in

a freshwater tank?

• Salt

• Outside

solution is

hypotonic

• Cytolysis

occurs

H2O enters fish’s cells and fish will die

11. How do plant cells deal

with osmosis?

• Plant cells have cell wall and most live a

hypotonic environment. This moves water

into the cells by osmosis.

• These cells swell as they fill with water until

the cell membrane is pressed against the

inside of the cell wall. The water exerts of

pressure against the cell wall called turgor

pressure.

11. How do plant cells deal

with osmosis?

• In a hypertonic environment, water leaves the cells through osmosis. As the water leaves the central water vacuole, the cells shrink away from the cell walls, and turgor pressure is lost.

• This condition is called plasmolysis, and is the reason that plants wilt if they don’t receive enough water.

12. How do unicellular

organisms deal with osmosis? • Because most of them live in a

hypotonic environment, water is constantly entering the cells, so they must rid themselves of the excess water.

• Some of them, such as the paramecia have structures called contractile vacuole which remove the excess water by pumping it out of the cell.

• https://www.youtube.com/watch?v=vk5NFSvp8lY

14. What is facilitated

diffusion?

• Another type of passive transport in

which molecules that cannot readily

diffuse across a membrane are assisted

by carrier proteins in the membrane. » Example: glucose diffusing across a cell

membrane through the protein

https://www.youtube.com/watch

?v=mzo_B5F7pk4

Check your knowledge

We have talked about three types of

passive transport. Take a minute to

quietly look through your notes and

refresh you memory on the three types

of passive transport.

Circle the three types of passive

transport in your notes!!!

Check your knowledge With your table partner discuss the

following:

Partner 1: Explain the term passive

transport.

Passive transport is the movement of

molecules from and area of ______

Partner 2: Explain diffusion. What types of

substances diffuse through our cells.

Diffusion is the movement of ________ from

an area of______

Check your knowledge

Partner 1. Explain osmosis. What

substance is moved in our cells through

osmosis?

Osmosis is the movement of ________

from an area of______

Partner 2. Explain facilitated diffusion.

What substance is moved in our cells

using facilitated diffusion.

Facilitated Diffusion is the movement of

________ from an area of______

15. What is active

transport?

• The movement of substances, usually

across a cell membrane, against (up) a

concentration gradient which requires

cells to use energy.

16. What does “against” a

concentration gradient mean?

• When cells move substances from an

area of lower concentration to an area

of higher concentration.

17. How are carrier proteins

involved in active transport?

• Carrier proteins in animal cells are involved in

an active transport process called the

sodium-potassium pump. In humans this

process occurs in muscle cells and liver cells.

Cells have to expend energy to pump

Potassium (K+) ions into the cells and to

pump Sodium (Na+) ions out of cells.

https://www.youtube.com/watch

?v=6R2-AFcJrhs

18. How do macromolecules that

are too large to pass through the

cell membrane by the other

process get in and out of the

cells?

• 1) Endocytosis - the process by which

cells ingest external fluid,

macromolecules, and large particles,

including other cells.

•

Endocytosis

• Two types:

a) Pinocytosis -involves the transport of solutes or fluids

b) Phagocytosis -involves the transport of large solid particles or whole cells.

Example: White blood cells engulfing bacteria or amoeba engulfing a paramecium

• 2) Exocytosis- the process by which a

substance is released from the cell

through a vesicle that transports the

substance to the cell surface and then

fuses with the membrane to let the

substance out of the cell.

• Cells use exocytosis to release large

molecules such as proteins, waste

products, or toxins that would damage

the cell if they were released within the

cytosol. https://www.youtube.com/watch?v=r2PiumV8

KEY