Ms. McKinley

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Antibiotic Resistance:
Case Study

MSU

 

UNIT 3: Cell Transport, Diffusion and Osmosis

What you should know:

Cells must be able to move substances into and out of the cell to maintain a stable internal environment. Movement and/or transport over a cell membrane can occur with or without the use of energy. When energy is not used, we call this process passive transport and molecules diffuse from areas of high concentration to low concentration. Similarly, when we talk about the movement or diffusion of water from areas of high concentration to low concentration we call this process osmosis. If a molecule is polar or is too large to cross through the cell membrane, then it may be able to go through a hole in a protein that sits inside the cell membrane.


Relating this process of osmosis to the environment of a cell, we can see a typical cell in one of three environments. The cell can be in an isotonic environment, which means that the concentration of water inside and outside the cell is equal. In an isotonic environment there is no net movement of water into or out of a cell. This is the state that most cells can be found in. A hypertonic environment has a higher concentration of solutes than the cell has. Water will move out of a cell that is in a hypertonic environment and the cell will shrink. In a hypotonic environment, water moves into the cell and the cell swells up like a balloon.


Cell transport can be accomplished with or without energy. It is called passive transport without the use of energy. With energy, the process is called active transport. In this case, the cell membrane is actively using energy to move molecules from one side of the cell membrane to the other. Typically, the movement of particles or substances involving active transport is from an area of low concentration to high concentration. Some processes that require energy include endocytosis, or the movement of substances inward through the cell membrane. In this process, the cell membrane engulfs the particle and the membrane actually pinches off to create a vesicle for the molecule within the cell. The opposite process is called exocytosis. This is the releasing of molecules through the membrane. Vesicles containing molecules hit the cell membrane and fuse with it releasing the contents. Cells can tell each other when to open or close protein channels by sending messages through signal molecules to receptor proteins on neighboring cells. Signal molecules sent from cell to cell can also change how enzymes function or they can set off a chain of reactions inside the cell.

 

How you make sense of things:

Inital EPE before lab

Observations you make
in your daily life:
Patterns you notice:
Explanations for the patterns:
When perfume is sprayed in one room you can smell it from another room in a few minutes.

Grocery stores have vegetable misters to keep the vegetables crisp.

Plants wilt when it is dry and stiffen when it is wet.

Salt is sometimes used to preserve meat.

If you sprinkle sugar on a bowl of fresh strawberries they will be covered in juice a few minutes later.

Some types of frogs and sharks can live in saltwater.

   

 

Goal EPE after lab

Observations you make
in your daily life:
Patterns you notice:
Explanations for the patterns:
Diffusion Demos
Observations of food coloring spreading out equally in water.

Observations of the smell of air freshener moving away from source to other parts of the room.

Grape Lab
Observations that grapes maintain the same size when soaked in grape juice overnight.

Observations that grapes increase in size when soaked in tap water overnight.

Observations that grapes decrease in size when soaked in sugar water overnight.

Plasmolysis Lab
Observations that the vacuole of red onion cells stays the same size when in tap water.

Observations that the vacuole of red onion cells shrinks when salt water surrounds the cells.

Observations that the vacuole of red onion cells swells when distilled water surrounds the cells.

Cell Membrane Activity
(previous week)
Observations that large candy can not get through the plastic bag.

Diffusion Demos
Substances distribute themselves equally.

Grape Lab
There is no net movement of water into or out of grapes when in an isotonic solution.

Water moves into grapes when they soak in a hypotonic solution.

Water moves out of grapes when they soak in a hypertonic solution.

Plasmolysis Lab
There is no net movement of water into or out of the cell when in an isotonic solution.

Water moves out of red onion cells when they are placed in a hypertonic solution.

Water moves into red onion cells when they are placed in a hypotonic solution.


Cell Membrane Activity
(previous week)
The only way to get the candy into the plastic bag without putting a hole in the cell membrane is to get the candy into a vesicle closed off with a rubber band, rubber band the cell membrane and cut in between the two rubber bands.

Diffusion Demos
Diffusion – substances move from an area of high concentration to an area of low concentration.


Grape Lab and
Plasmolysis Lab

Homeostasis – Cells maintain stable internal conditions in spite of changes in the external environment.

Osmosis – water moves down its concentration gradient into or out of cells.

Cell Membrane Activity
(previous week)
In active transport energy is required to move molecules against their concentration gradient.

Large molecules can get into cells when the cell membrane engulfs the molecule and a vesicle breaks away from the cell membrane. This process is called endocytosis.

Large molecules can only get out of cells when they are sent in a vesicle to the cell membrane, fuse with the membrane and are released to the outside of the cell. This process is called exocytosis.

 

What you should be able to do:

1. Explain the role of cell membranes as a highly selective barrier (diffusion, osmosis, and active transport.)
2. Explain that the regulatory and behavioral responses of an organism to external stimuli occur in order to
maintain both short- and long-term equilibrium.
3. Describe how organisms sustain life by obtaining, transporting, transforming, releasing, and eliminating
matter and energy.
4. Describe how human body systems maintain relatively constant internal conditions (temperature, acidity,
and blood sugar.)
5. Use your knowledge of osmosis to explain how cells maintain homeostasis in varying
external environments.