1. Cell Homeostasis

2. Acids and Bases
pH: A number that measures how acidic or basic a solution is.
Scale from 0-14; 7 = neutral.
Ex. Top of p. 43
pH is very important to living systems

3. Acids and Bases
Acid: Any substance that forms hydrogen ions (H+) when mixed with water.
Ex. Hydrochloric acid (HCl)
pH below 7, turns litmus paper red
Properties: corrosive, sour

4. Acids and Bases
Base: Any substance that forms hydroxide ions (OH-) when mixed with water.
Ex. Sodium Hydroxide (NaOH)
pH above 7; turns litmus paper blue
Properties: bitter, slippery

6. pH Scale pH is controlled via buffers.
Weak solutions (acids or bases) that prevent drastic changes in pH by reacting with strong acids or bases.

7. pH Scale Map 0-14
Basic
Acidic
Neutral

8. Solutions
Solution: when something is dissolved in something else; ex. saltwater
Solute: the thing being dissolved
Solvent: the thing dissolving it (usually water)
Concentration: solute/solvent; the amount of solute per amount of solvent
Your body is a solution and cells must maintain proper concentrations!

9. Transport across the plasma membrane

10. Diffusion
Diffusion : movement of particles from an area of high to low concentration (no energy required)
continues until there is no more concentration gradient.

11. Passive Transport
Passive Transport: the process of particles moving through a membrane with NO ENERGY (high to low concentration)
Water, lipids, and some lipid soluble substances can move by passive transport.
Molecules can move through proteins or the membrane itself.

12. Cellular Transport
Osmosis: The diffusion of water across a selectively permeable membrane.
Review:
Plasma Membrane- Phospholipid Bilayer
Concentration Gradient
Homeostasis
Fig. 8.1 p. 202

13. 3 Types of Solutions
Isotonic Solution: Concentration of solutes is the same inside and outside the cell.
No osmosis occurs
dynamic equilibrium: molecules are moving across membrane but no concentration gradient created.
Dynamic: Movement or change
Equilibrium: An equality or balance

14. Types of Solutions
Hypotonic Solution: The concentration of solutes is less outside the cell than inside the cell. See p. 186, Fig. 7.16
Water moves by osmosis into the cell!
The cell tends to swell.

15. Types of Solutions
Hypertonic Solution: The concentration of solutes is more outside the cell than inside the cell. See p. 186 Fig. 7.16
Osmosis causes water to flow out of the cell.
Cells will shrink or shrivel

16. Comparison of Hypo, Iso, and Hypertonic Solutions

17. Solutions Practice

18. Sample EOC Question1
A freshwater plant is placed in a container of saltwater. What will most likely happen to the cells of the plant? A They will swell because water will move into them. B They will swell because salt will move into them. C They will shrink because water will move out of them. D They will shrink because salt will move out of them.

19. Turgor Pressure: The pressure in a plant cell that results from water flowing into the cell.
Occurs with a hypotonic solution.
Gives plants their shape and ability to stand up. Without it they wilt!

20. Plasmolysis: Loss of pressure within a cell causing it to shrivel
Occurs with a hypertonic solution
In plants turgor pressure is lost (wilting occurs), animal cells just shrivel

21. Facilitated Diffusion: proteins helping large molecules across the plasma membrane.
No energy is used by the cell or its parts! (passive)
Movement is powered by the concentration gradient. (hi to lo)
See p. 187 Fig. 7.17

22. Cell Membrane Proteins*
Carrier Proteins: Span through plasma membrane (transport proteins) and change shape to help molecules get from one side to the other.
Their exposed ends open and close like a gate.
Channel Proteins: Span through plasma membrane (transport proteins) and create an opening where molecules can pass through.
They do not change shape.
Carrier
Channel

23. Active Transport
Active Transport: cell uses energy to move molecules across plasma membrane against the concentration gradient.
These molecules are moving the opposite way they would naturally move due to diffusion. (low-high)

24. Active Transport Endo- and Exocytosis
Phagocytosis and Pinocytosis is a form of endocytosis
Phagocytosis: one cell engulfing another.
Pinocytosis: tiny pockets form along the cell membrane fill with liquid and pinch off to form vacuoles within the cell.

25. Cell specialization

26. Specialization
When a cell or part of a cell has a specific job or function
Specialization often arises from some type of survival need
Often these are highly developed adaptations

27. Examples of Specialization in Humans
Red Blood Cells
Specialized to transport oxygen; contain hemoglobin (protein) and move oxygen from lungs throughout body
Sperm Cells
Have specialized flagella for propulsion; contain lots of mitochondria for energy production for movement

28. Examples of Specialization in Plants
Vascular Tissue: specialized tissue that transports water and nutrients in certain types of plants
2 TYPES:
Xylem:
Vascular tissue that carries water from roots to the rest of the plant
Phloem:
Vascular tissue that carries solutions of nutrients and glucose throughout plants

29. Examples of Specialization in Unicellular Organisms
Eyespots:
Group of cells that detect changes in amount of light; helps organism find light for photosynthesis
Found in Euglenas (plantlike protists)
Contractile Vacuole:
Contracts and removes excess water
Found in protists
Pseudopods: “false foot”
Temporary projection of cytoplasm used for feeding or movement
Found in protists; ex. amoeba

30. Examples of Specialization in Unicellular Organisms
Left – Euglena
Above - Amoeba

31. Resources
Some of the information included in these slides and some slides themselves are either adapted or directly used from powerpoints created by E. Terzian.