1. Biology Unit Three Part II - Cells
Mrs. Pearson’s First Semester Biology
*For those watching by recording, watch for questions on the slides throughout
the presentation. me the answers to the questions within two days of the
lesson being presented in order to receive credit for watching the recording.

2. Biology Olympics
Context Clues: Use the picture, the word parts, and the paragraph to determine what “semipermeable” means.
Outdoor clothing is often made of semipermeable fabric. The material is waterproof yet breathable. Molecules of water vapor from sweat are small enough to exit the fabric, but water droplets are too large to enter.

3. Biology Olympics
Semipermeable is a property of an object which allows some materials to pass through but stops others from passing.
What are some ways, other than semipermeable clothing, in which this property could be useful?

5. KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

6. Lesson Objectives
Describe the structures and functions of the cell membrane.

7. Pearson’s Perfectly Pleasant Prefixes and Parts
Inter –
Intra –
Bi –
Semi –
Hyper –
Hypo –
Passive
Active
Endo –
Ecto –
Cyto -

8. Cell membranes are composed of two phospholipid layers.
The cell membrane has two major functions.
What do you think those functions are?
cell membrane
outside cell
inside cell

9. Cell membranes are composed of two phospholipid layers.
The cell membrane has two major functions.
forms a boundary between inside and outside of the cell
controls passage of materials
cell membrane
outside cell
**Those watching by recording, include in your the two major functions of the cell membrane.
inside cell

10. Cell membranes are composed of two phospholipid layers.
The cell membrane is made of a phospholipid bilayer.
There are other molecules embedded in the membrane.
Theorize what the other molecules in the membrane do.
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

11. Cell membranes are composed of two phospholipid layers.
The cell membrane is selectively permeable.
What does that mean?
**Those watching by recording, include in your the definition of selectively permeable.

12. Chemical signals are transmitted across the cell membrane.
Receptors bind with ligands and change shape.
There are two types of receptors.
intracellular receptor
What does Intra- mean?

13. Chemical signals are transmitted across the cell membrane.
Receptors bind with ligands and change shape.
There are two types of receptors.
intracellular receptor
membrane receptor

14. 3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes because of concentration differences.

15. 3.4 Diffusion and Osmosis
Passive transport does not require energy input from a cell.
Molecules can move across the cell membrane through passive transport.
There are two types of passive transport.
diffusion
osmosis
Water moves freely across the cell membrane
Describe the direction that the molecules move (not left or right or up or down).

16. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Molecules diffuse down a concentration gradient.

17. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
Osmosis is the diffusion of water molecules across a semipermeable membrane.
It helps keep all of the other “stuff” in the same concentrations inside and outside of the cells.
When we describe a solution, we look at how much of something is dissolved in the water.
So this solution has a higher concentration of “stuff” than the other solution.

18. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
If we wanted to make the concentrations the same but we couldn’t change the number of stars BUT we could change the amount of water, what would we do?
When we describe a solution, we look at how much of something is dissolved in the water.
So this solution has a higher concentration of “stuff” than the other solution.

19. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
There are three types of solutions.
isotonic
hypertonic
hypotonic
**Those watching by recording, include in your the difference between isotonic, hypertonic, and hypotonic solutions.

20. 3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport proteins.
Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins.

21. 3.5 Active Transport, Endocytosis, and Exocytosis
KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

22. 3.5 Active Transport, Endocytosis, and Exocytosis
Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient.
Passive transport requires no energy from the cell.
Active transport is powered by chemical energy (ATP).
Active transport occurs through transport protein pumps.
Cells use active transport to maintain homeostasis.

23. 3.5 Active Transport, Endocytosis, and Exocytosis
A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis.
Cells use energy to transport material in vesicles.
Endocytosis is the process of taking material into the cell.
If “endo-” means “in” and “exo-” means “out”, what do you think happens with exocytosis?
**Those watching by recording, include in your a description of the endocytosis process.

24. 3.5 Active Transport, Endocytosis, and Exocytosis
A cell can import and export large materials or large amounts of material in vesicles during the processes of endocytosis and exocytosis.
Cells use energy to transport material in vesicles.
Exocytosis is the process of expelling material from the cell.

25. Review
The cell membrane forms a boundary and controls the movement of particles into and out of the cell
The cell membrane is selectively permeable.
Chemical signals are transmitted across the cell membrane
Substances move across the cell membrane through active and passive transport
Solutions around a cell can be isotonic, hypertonic, or hypotonic.

26. Questions?