1. The Master of Homeostasis
The Cell Membrane
The Master of Homeostasis

2. Terms to Know Homeostasis Diffusion Osmosis Active Transport
Cell membrane
Plasma membrane
Selectively permeable
Gradient
Dynamic equilibrium
Hypotonic solution
Hypertonic solution
Isotonic solution

3. Homeostasis
An organism’s regulation of its internal environment to maintain conditions suitable for survival is known as homeostasis
One of the main structures of a cell responsible for maintaining homeostasis is the cell membrane or (plasma membrane)

4. The Cell Membrane

5. The Cell Membrane
The cell membrane or (plasma membrane) is a flexible boundary between the cell and its environment
It is the outermost structure making the outline of the cell

6. The Cell Membrane
The cell membrane allows certain things in, such as water and nutrients, and other things out
This ability of the cell membrane to allow certain things in or out is referred to as selective permeability

7. Diffusion
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
Activity: in a beaker, fill with corn syrup and place a few drops of food coloring on the top of the syrup in one location. Discuss that the concentration of food coloring particles is very high where the drops are located and that the particles of corn syrup and food coloring are randomly moving, even though you cannot see the individual particles moving. Ask the students what will happen if you leave the mixture overnight. Discuss that because of the net movement of particles from an area of higher concentration to an area of lower concentration, the food coloring should distribute itself evenly throughout the mixture until it reaches equilibrium.

8. Diffusion Click here to link to a diffusion animation online
Particles are usually moving about randomly and changing directions as they bump into one another
In diffusion, the particles in high concentration will migrate to areas of lower concentration until they fill in all of the empty space

9. Diffusion in Cells
Movement of particles from areas of high concentration to low concentration are said to be moving with the “gradient”
The particles move until they are evenly distributed, which is called “dynamic equilibrium”
Substances in cells are in a water solution and constantly move by diffusion

10. Osmosis
The diffusion of water molecules across a selectively permeable membrane is known as osmosis
The direction of osmosis is determined by whether the concentration of dissolved substances is higher inside of or outside of a cell membrane

11. Osmosis
If a cell has more dissolved substances (like sugar) inside the cell than outside, this means that there is a higher concentration of water outside than inside
Remember that osmosis is the movement of WATER across a membrane
Also remember that in diffusion, particles move from areas of HIGHER CONCENTRATION TO LOWER CONCENTRATION

12. Osmosis
Therefore the water is going to move INSIDE the cell with the gradient until dynamic equilibrium is reached
This cell is said to be in a hypotonic solution
You can remember this by using the word (HIPPO-Tonic) because the cell becomes fat and hippos are fat

13. Osmosis
If the concentration of dissolved substances is higher outside of a cell than inside, then the concentration of water is higher inside and the water will rush outside of the cell with the gradient until dynamic equilibrium is reached
This cell is said to be in a hypertonic solution
You may think of hyper students running outside of a classroom and the classroom, or (cell) shrinks in size

14. Osmosis
If the concentration of dissolved substances inside the cell are the same as the outside of a cell, there is no concentration gradient and water moves back and forth across the cell membrane at an equal rate
A cell in this case is said to be in an isotonic solution

15. Active Transport
Sometimes the cell needs to get things inside and outside of the cell against the concentration gradient
This requires energy from the cell and is called active transport

16. Cell Membrane and Homeostasis
Because of the selective permeability of the cell membrane, the cell only allows good things in and keeps bad things out of the cell. This helps the organism maintain healthy and able to survive

17. The Nuts and Bolts of a Cell
Cell Organelles
The Nuts and Bolts of a Cell

18. Terms to Know Organelle Plasma membrane Cell wall Mitochondria
Golgi apparatus
Lysosome
Vacuole
Centrioles
Chromatin
Endoplasmic reticulum
Ribosome
Cytoplasm
Nucleus
Nuclelous
Nuclear membrane

19. Centrioles
Nucleus
Endoplasmic
Reticulum
Cytoplasm
Cell Membrane
Lysosome
Golgi Apparatus
Mitochondria
Chromatin
Nucleolus
Nuclear Membrane
Ribosome
Vacuole

20. Cell Organelles
Like many organisms have organs within them that have specific functions, cells have organelles
Organelles are membrane-bound structures within a eukaryotic cell that have specific functions

21. The Cell Membrane
The cell membrane, or plasma membrane, is a selectively permeable layer on the outside of the cell, which contains all of the organelles within
Remember that the plasma membrane helps maintain homeostasis within an organism
All cells have a cell membrane

22. Cell Wall
A cell wall is a fairly rigid structure located outside the plasma membrane of plants, fungi, most bacteria, and some protists which provides support and protection
The cell wall allows the cell to become quite turgid without bursting

23. Mitochondria
A eukaryotic membrane-bound organelle that transforms energy stored in food molecules is called mitochondria
Mitochondria have highly folded membranes that produce energy-storing molecules
Mitochondria is the powerhouse of the cell

24. Golgi Apparatus
The Golgi apparatus is an organelle in eukaryotic cells with a system of flattened tubular membranes
It sorts and packages proteins and sends them to their appropriate destinations

25. Lysosome
A lysosome contains digestive enzymes and is responsible for digesting excess or worn out organelles, food particles, and engulfed viruses or bacteria

26. Vacuole
A vacuole is a membrane-bound space in the cytoplasm of cells used for the temporary storage of materials
The vacuole in a plant is very large

27. Centrioles
In animal cells, a pair of small cylindrical structures composed of microtubules called centrioles duplicate during interphase and move to opposite ends of the cell during prophase

28. Chromatin
Long strands of DNA found in the eukaryotic cell nucleus is known as chromatin and condenses to form chromosomes

29. Endoplasmic Reticulum
The endoplasmic reticulum is an organelle in eukaryotic cells with a series of highly folded membranes surrounded in cytoplasm
It is the site of cellular chemical reactions
Can be rough “ER” with ribosomes attached or smooth ER without ribosomes

30. Ribosomes
Ribosomes are non-membrane-bound organelles in the nucleus where proteins are assembled

31. Cytoplasm
Cytoplasm is the clear, gelatinous fluid in cells that is the site of numerous chemical reactions
In eukaryotes, it suspends the organelles

32. Nucleus
The nucleus is the central membrane-bound organelle that manages cellular functions and contains DNA
The nucleus is surrounded by a nuclear membrane which can dissolve or allow structures out to the cytoplasm

33. Nucleolus
The nucleolus is found in the nucleus and produces ribosomes

34. Review
To link to an Internet site on parts of the cell click here!