1. Osmosis, Diffusion, Photosynthesis & Cell Division
Chapter 1, Section 4
Chapter 2, Section 1
Chapter 2, Section 3

2. The Cell in its Environment
As you know, the cell membrane is like the doors to the cell. Just as doors allow good things to come in and out, the cell membrane allows good things like food and water to come in and waste to go out.
The cell membrane also protects the cell from anything that may be harmful to it, just as a door does in your house.
These characteristics mean that the cell membrane is selectively permeable; which means that some substances can pass through the membrane while others cannot.

3. Moving In & Out
There are three ways that substances can move into and out of the cell:
Diffusion-The primary way in which small molecules move across the cell membrane.
Osmosis-The diffusion of water molecules through a membrane.
Active Transport-The movement of materials through a cell membrane using energy created by the cell.
What are molecules?

4. Diffusion
The process of diffusion is one that moves molecules from an area of higher concentration to an area of lower concentration.
Eventually the substances (such a oxygen) will be evenly distributed throughout the cell.
Example: A one celled organism living in pond water. There is more oxygen in the water than in the cell, high concentration. Because of this the oxygen begins to diffuse its way into the cell because of the low level of oxygen concentration within the cell.

5. O O O O O O O O O O O O O O O O O O O O O O O O O O O O
There is a high concentration of oxygen atoms outside the cell.
Because the concentration inside the cell is lower, the atoms will
begin to permeate (move through) the cell membrane, this will equalize the concentration.

6. Osmosis
Cells cannot function without water. In order for cells to obtain an adequate amount of water, osmosis must take place.
The concentration of water should be the same both inside and outside the cell.
Osmosis allows water to move into and out of the cell as needed.

7. Transportation
Passive Transport-The cell does not use its own energy to move materials through the cell membrane.
This occurs when there is a higher concentration outside the cell than inside the cell.
Active Transport-Requires the cell to use its own energy to move materials through the cell membrane.
This occurs when the cell needs to take in a substance that has a higher concentration inside the cell than outside the cell.

8. Passive O O O O O O O O O
High Concentration
Active O O O O O O O O O O O
Low Concentration

9. Photosynthesis
Photosynthesis-The process of capturing energy from sunlight and using it to make food for plants.
Nearly all living things gain energy either directly or indirectly from the energy captured during photosynthesis.

10. Let Me Explain…
A zebra grazes in the open grassland. It eats the green grasses that are filled with energy the plant gained from the sunlight.
Though the zebra is minding its own business, out of no where comes a very hungry lion! The lion also needs energy, so he hunts the zebra and uses It for energy.
The lion is using the energy that the zebra had stored, which the zebra had gained from the grasses he ate, that got their energy from the sun!
This is called the food chain. Plants are found on the bottom most layer of the food chain and therefore indirectly affect all other layers of this chain.

11. Food Chain

12. What’s For Dinner?
Some living things make their own food while others cannot.
Autotrophs-Make their own food.
Example: Plants, trees, and flowers
Heterotrophs-Cannot make their own food. They must gain their energy from eating autotrophs or other heterotrophs.
Example: Zebra, Lion, Humans

13. Two Stages of Photosynthesis
Stage 1: Capturing the Sun’s Energy
Chloroplasts-They are green in color because of the pigments (colored chemical compounds that absorb light). The main pigment is called chlorophyll.
Chlorophyll acts like a solar panel for the plant. It collects the energy from the sun and uses it to power the second stage of photosynthesis.

14. Photosynthesis Continued
Stage 2: Using Energy to Make Food
In this stage the cell uses the captured energy to produce sugars.
Two materials are needed for this stage:
H2O (water) & CO2 (carbon dioxide)
Water-Plants absorb the water from the soil using its roots
Carbon Dioxide-It is one of the gases in air. It enters the plant through small openings on the underside of the leaves called Stomata.

15. Stage 2 Continued
The water and carbon dioxide then move on to the chloroplasts.
Once inside, the substances go through a series of chemical reactions.
These reactions create a sugar, C6H12O6. The sugar is used as energy for the plant to carry out cell functions.
The other product of photosynthesis is oxygen (O2), which exits the leaf through the stomata.
All of the oxygen in the Earth’s atmosphere was produced by living things through the process of photosynthesis.

16. Cell Division How do living things grow?
Take a piglet for an example, the piglet’s cells continuously grow and divide until the piglet grows to be adult size.
Cell Cycle-The regular sequence of growth and division that cells undergo is known as the cell cycle. (The growth and division of cells.)
During this cycle, a cell grows, prepares for division, and divides into two new cells which are called “daughter cells”.
Each daughter cell then begins the cycle again, making an exact copy of itself.

18. Stage 1: Interphase
The first stage in the cell cycle is called interphase.
Interphase -This is the period before cell division. During interphase, the cell grows, makes a copy of its DNA (genetic material), and prepares to divide into two cells.

19. DNA

20. Interphase Continued Growing Copying DNA Preparing for Division
The cells grows to its full size and produces the structures it needs.
Copies of the cell parts like mitochondria and chloroplasts are made.
Copying DNA
The cell then makes exact copies of the DNA in its nucleus, this process is called replication.
This is very important because each daughter cell needs an exact copy of DNA in order to survive.
Two structures called centrioles are also copied.
Centrioles come in pairs. They make the spindle fibers that help to pull the chromosomes to each side of the cell so that they can be divided into two cells.
Preparing for Division
Once the DNA replication has taken place, the cell prepares to divide into two cells by producing structures it needs to create both cells.

21. Stage 2: Mitosis
When Interphase is complete, the second stage of the cell cycle begins.
Mitosis is the stage during which the cell’s nucleus divides into two new nuclei.
During this process, one copy of the DNA is distributed into each of the two daughter cells.
Mitosis is divided into four parts or phases:
Prophase
Metaphase
Anaphase
Telophase

22. Prophase
During this phase the threadlike chromatin in the nucleus condenses to form double-rod structures called chromosomes. (23 pairs or 46 individual chromosomes.)
Each chromosome has two rods because the cell’s DNA has replicated.
Each identical rod in a chromosome is an exact copy of the other and is called a Chromatid.
Two chromatids are held together by a structure called a centromere.
Finally the pairs of centrioles move to opposite sides of the nucleus.
Spindle fibers form a bridge between the ends of the cell. (Their job is to move chromosomes during cell division.)
The nuclear membrane then begins to break down.

24. Metaphase
During this phase chromosomes line up across the center of the cell.
Each chromosome attaches to a spindle fiber at its centromere.

25. Anaphase
During this phase the centromeres (small connecter) split. The two chromatids (stands of DNA) are then separated.
One chromatid is drawn by its spindle fiber to one end of the cell.
The other chromatid moves to the opposite end of the cell as it stretches out and the opposite ends are pushed apart.

27. Telophase
During this phase the chromosomes stretch out and lose their rodlike appearance.
A new nuclear membrane is formed around each region of chromosomes.

28. Stage 3: Cytokinesis Cytokinesis is the final stage of the cell cycle.
During cytokinesis, the cytoplasm divides and the organelles are distributed into each of the two new cells.
When this stage is finished two new cells, or daughter cells, have formed with about half the organelles.
Each daughter cell has the same number of chromosomes as the original parent cell.
At the end of cytokinesis, each cell enters interphase, and the cycle begins again.

29. That's All Folks!