1. Diffusion Through Cell Boundaries
Life began in the ocean.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
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2. Diffusion Through Cell Boundaries
The first unicellular organisms got everything they needed from the seawater around them.
Diffusion Through Cell Boundaries
Food O2
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Salt
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3. Diffusion Through Cell Boundaries
Then, things changed. Multicellular organisms evolved. Now, only the cells on the outside of the organism were in contact with seawater.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

4. Diffusion Through Cell Boundaries
And then things really changed. Organisms left the ocean and began living on dry land.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

5. Diffusion Through Cell Boundaries
How do cells inside a multicellular organism get what they need to live?
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

6. Diffusion Through Cell Boundaries
If the first living things got everything they needed from sea water, how can life exist on dry land?
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

7. Diffusion Through Cell Boundaries
Recall that living things consist mostly of water. It makes up 72% of the mass of our cells.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

8. Diffusion Through Cell Boundaries
Even organisms that live in the desert are still about 72% water. Even though we left the ocean, we still carry it inside us.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

9. Diffusion Through Cell Boundaries
Like the ocean, the liquid of our bodies is not pure water. Instead, it is a solution.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Solute
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10. + = Solution A mixture of water and dissolved solute. solute
PLASTIC SHEET DEMO. The cell membrane is sometimes called the plasma membrane, since it is in constant contact with plasma (fluid) outside of the cell.
A mixture of water and dissolved solute.

11. Ex: ocean water.
PLASTIC SHEET DEMO. The cell membrane is sometimes called the plasma membrane, since it is in constant contact with plasma (fluid) outside of the cell.

12. + = Solute The substance that is dissolved in a solution. solute
PLASTIC SHEET DEMO. The cell membrane is sometimes called the plasma membrane, since it is in constant contact with plasma (fluid) outside of the cell.
The substance that is dissolved in a solution.

13. PLASTIC SHEET DEMO. The cell membrane is sometimes called the plasma membrane, since it is in constant contact with plasma (fluid) outside of the cell.
Ex: glucose, O2, salt.

14. Diffusion Through Cell Boundaries
Like the first unicellular organisms, the cells of multicellular organisms are bathed in solution. We call the solution in our bodies plasma.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
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15. Plasma
Plasma
White blood cells
Red blood cells
Prokaryotes do not contain nuclei. They evolved BEFORE eukaryotes. This is a bacteria, a typical prokaryote. See how it has no nucleus? The DNA floats freely in the cell.
Solution found in multicellular organisms; contains dissolved solute that cells need to live.

16. Diffusion Through Cell Boundaries
Plasma is located in the blood.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

17. Diffusion Through Cell Boundaries
Since blood travels everywhere in the body, our cells are constantly bathed in plasma.
Diffusion Through Cell Boundaries
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

18. Cells get the solute they need from plasma by transporting it across the cell membrane.
Prokaryotes do not contain nuclei. They evolved BEFORE eukaryotes. This is a bacteria, a typical prokaryote. See how it has no nucleus? The DNA floats freely in the cell.
Cell

19. Diffusion Through Cell Boundaries
Since the cell membrane is in constant contact with plasma, it is sometimes called the plasma membrane.
Diffusion Through Cell Boundaries
Plasma membrane
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

20. Diffusion Through Cell Boundaries
Plasma is also located inside the cell, where it is known as cytoplasm.
Diffusion Through Cell Boundaries
Cytoplasm
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
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21. The concentration of plasma inside and outside the cell is not always the same.
Prokaryotes do not contain nuclei. They evolved BEFORE eukaryotes. This is a bacteria, a typical prokaryote. See how it has no nucleus? The DNA floats freely in the cell.

22. Concentration The amount of solute dissolved in a solution. 5 mg / 1 L
PLASTIC SHEET DEMO. The cell membrane is sometimes called the plasma membrane, since it is in constant contact with plasma (fluid) outside of the cell.
Less concentrated
More
concentrated
The amount of solute dissolved in a solution.

23. The amount of water in a solution also affects concentration (more water = less concentrated).
Cell Membrane
Less concentrated
More concentrated
Like the security guard in this photo, the cell membrane controls what enters and leaves the cell. The cell membrane also protects the cell against threats from outside, and supports the cell’s shape.
5 mg / 1 L
5 mg / 3 L

24. Copyright Pearson Prentice Hall
The concentration of plasma outside the cell changes frequently.
Cell Membrane
Like the security guard in this photo, the cell membrane controls what enters and leaves the cell. The cell membrane also protects the cell against threats from outside, and supports the cell’s shape.
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25. Diffusion Through Cell Boundaries
However, the concentration of plasma inside the cell must be kept constant.
Diffusion Through Cell Boundaries
unchanging
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

26. Diffusion Through Cell Boundaries
Activity
How it affects the concentration of plasma
How cell keeps concentration of cytoplasm constant
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

27. Diffusion Through Cell Boundaries
Exercise
Diffusion Through Cell Boundaries
= glucose
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

28. Diffusion Through Cell Boundaries
Activity
How it affects the concentration of plasma
How cell keeps concentration of cytoplasm constant
Decreases concentration
CM transports glucose into the cell
Exercise
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

29. Diffusion Through Cell Boundaries
Eating
Diffusion Through Cell Boundaries
= glucose
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

30. Diffusion Through Cell Boundaries
Activity
How it affects the concentration of plasma
How cell keeps concentration of cytoplasm constant
Decreases concentration
CM transports glucose into the cell
Exercise
CM prevents glucose from entering the cell
Increases concentration
Eating
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.

31. Diffusion Through Cell Boundaries
Starvation
The concentration of plasma inside the cell must be kept constant.
Diffusion Through Cell Boundaries
= glucose
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Copyright Pearson Prentice Hall

32. Diffusion Through Cell Boundaries
Activity
How it affects the concentration of plasma
How cell keeps concentration of cytoplasm constant
Decreases concentration
CM transports glucose into the cell
Exercise
CM prevents glucose from entering the cell
Increases concentration
Eating
Every living cell exists in a liquid environment. Even in a dry place like the desert, the cells of cacti and scorpions are bathed in liquid. This liquid is full of dissolved molecules of oxygen, CO2, salts, and all kinds of other substances. Some of these drifting molecules eventually enter the cell through pores and channels.
Decreases concentration
Cell opens up a vacuole
Starvation