1. The Cell Cycle: How do you grow?
Interphase – the cell grows and replicates its DNA.
Mitotic Phase (M-Phase) – the cell divides and transfers one copy of its DNA to two identical daughter cells.
The cell cycle is the series of events that takes place in a cell that results in DNA replication and cell division. There are two main stages in the cell cycle.

2. Interphase – the first phase
The longest phase of the cell cycle. Accounts for approximately 90% of the cell cycle.
The cell grows to its maximum size, perform normal cellular functions, replicates its DNA, and prepares for cell division.
This stage is divided into 3 parts:
G1 Phase
G2 Phase
S Phase
Interesting Fact Some cells no longer need to divide and exit the cell cycle. These cells may exit the cell cycle permanently, such as neurons, or they may exit the cell cycle temporarily. These cells are said to be in G0. G0 is not a stage of the cell cycle.

3. Interphase: G1
Occurs just after the two daughter cells have split and the cells have only one copy of their DNA
Cells in this stage synthesize proteins and increase in size.
Cells remain in this stage for a long time.

4. Interphase: S Is the stage during which DNA replication occurs
The cell makes an identical copy of each of its chromosomes
Chromosomes are found inside the nucleus of the cell and consist of long strands of DNA that contain the genetic information of the cell.

5. Interphase: G2 Occurs after the DNA has been duplicated in S phase.
During this phase the cell may continue to grow and undergo normal cellular functions.
Toward the end of this phase the cell will start to replicate its organelles in preparation for mitosis.

6. Mitotic Phase or M Phase
Consists of two tightly coupled processes: mitosis & cytokinesis
During mitosis the chromosomes in the cell nucleus separate into two identical sets in two nuclei. This is followed by cytokinesis in which the cytoplasm, organelles and cell membrane split into two cells containing roughly equal shares of these cellular components.
Stages:
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

7. M-Phase: Prophase
Chromatin material shortens and thickens into individual chromosomes (visible under the light microscope). Each chromosome consists of two strands or chromatids joined by a centromere.
The nuclear membrane and nucleolus disintegrate.
The centrioles separate and move to opposite poles. The centrioles give rise to the spindle fibers which form between the poles. (plant cells do not have centrioles to move to the poles)
Interesting Fact Human cells have 46 chromosomes. (23 from the mother and 23 from the father).

8. M-Phase: Metaphase Chromosomes line up on the equator of the cell.
Chromosomes appear in a straight line across the middle of the cell.
Each chromosome is attached to the spindle fibers by its centromere.
Interesting Fact HINT: The stages of the cell cycle (interphase, prophase, metaphase, anaphase, telophase) can be remembered by using the mnemonic IPMAT.

9. M-Phase: Anaphase
The chromatids are pulled to opposite poles of the cell by the shortening of the spindle fibers.
The chromatids are now called daughter chromosomes.
Interesting Fact In plant cells there are no centrioles to move to the poles, so spindle fibers form in the cytoplasm.

10. M-Phase: Telophase
A nuclear membrane reforms around the daughter chromosomes that have gathered at each of the poles.
The daughter chromosomes uncoil to form chromatin once again.

11. Cytokinesis The cytoplasm divides or splits in two.
In an animal cell the cell membrane constricts. This folding of the cytoplasm divides the cell in two. In a plant cell a cross wall is formed by the cell plate dividing the cytoplasm in two.

12. Mitosis Slides
View the onion cells in the back, undergoing mitosis. Draw and label what is happening in the cell for each slide. The slides are labeled with the phase that the cell is in.

13. Mitosis Models/Dance
Use small objects such as Legos to model cell division OR
Create a “dance” that uses everyone in your group to model a cell undergoing mitosis.

14. Transport in the cell
The cell membrane is selectively permeable, or “semipermeable”, which means that only some molecules can get through the membrane.
This is how the cell maintains a stable internal environment when the external environment is constantly changing.

15. What is Transport?
Water and small non-charged molecules such as oxygen and carbon dioxide can pass freely through the membrane by slipping around the phospholipids.
Larger molecules and charged molecules cannot pass through the plasma membrane as easily. Special methods are needed for transporting molecules across the plasma membrane and into or out of the cell.
The selectively permeable nature of the plasma membrane is due in part to the chemical composition of the membrane. Recall that the membrane is a double layer of phospholipids (a “bilayer”) embedded with proteins (See figure). A single phospholipid molecule has a hydrophilic, or water-loving, head and hydrophobic, or water-fearing, tail. The hydrophilic heads face the inside and outside of the cell, where water is abundant. The water-fearing, hydrophobic tails face each other in the middle of the membrane. At body temperature, the plasma membrane is fluid and constantly moving, like a soap bubble; it is not a solid structure.

16. Passive Transport
Small molecules can pass through the plasma membrane through a process called diffusion. Diffusion is the movement of molecules from an area where there is a higher concentration (larger amount) of the substance to an area of lower concentration (lower amount) of the substance.
The amount of a substance in relation to the volume, is called concentration.
Diffusion requires no energy input. Molecules move in both directions but there is a greater movement from high concentration to low concentration.

17. Osmosis: diffusion of Water across a membrane
The diffusion of water across a membrane due to concentration differences is called osmosis.
There are three types of solution:
Hypotonic
Isotonic
Hypertonic
Osmosis causes these red blood cells to change shape by losing or gaining water.

18. Hypotonic Solution
The solution has a lower concentration of dissolved material than what is inside the cell, water will move into the cell. This causes the cell to swell, and it may even burst.
Organisms that live in fresh water, which is a hypotonic solution, have to prevent too much water from coming into their cells. Freshwater fish excrete a large volume of dilute urine to rid their bodies of excess water.

19. Isotonic Solution
This is a solution in which the amount of dissolved material is equal both inside and outside the cell. Therefore, there is no net movement of water into or out of the cell. Water still flows in both directions, but an equal amount enters and leaves the cell.
In the medical setting, red blood cells can be kept intact in a solution that is isotonic to the blood cells. If the blood cells were in pure water, the solution would be hypotonic to the blood cells, so the blood cells would swell and burst.

20. Hypertonic Solution
The solution has more dissolved material in the outside environment than in the cell, water will leave the cell. That can cause a cell to shrink and shrivel.
Marine animals live in salt water, which is a hypertonic environment; there is more salt in the water than in their cells. To prevent losing too much water from their bodies, these animals intake large quantities of salt water and secrete salt by active transport.

22. Biology’s Biggest Loser
This is an inquiry lab. You will prepare and conduct an experiment to force your egg to lose the greatest percentage of its mass using osmosis.

23. Facilitated Diffusion
Sometimes diffusion across the membrane is slow or even impossible for some charged or large molecules. These molecules need the help of special helper proteins that are located in the plasma membrane.
This is a type of passive transport where a carrier protein aids in moving the molecule across the membrane.
Movement by ion channel proteins and facilitated diffusion are still considered passive transport, meaning they move molecules down the cell's concentration gradient and do not require any energy input.
Ion channel proteins move ions across the plasma membrane. Other molecules, such as glucose, move across the cell membrane by facilitated diffusion, in which a carrier protein physically moves the molecule across the membrane (See figure). Both channel proteins and carrier proteins are specific for the molecule transported.

24. Active Transport
During active transport, molecules move against the concentration gradient, toward the area of higher concentration. This is the opposite of diffusion.
Active transport requires both an input of energy, in the form of ATP, and a carrier protein to move the molecules. These proteins are often called pumps, because, as a water pump uses energy to force water against gravity, proteins involved in active transport use energy to move molecules against their concentration gradient.
Sometimes diffusion across the membrane is slow or even impossible for some charged or large molecules. These molecules need the help of special helper proteins that are located in the plasma membrane. Ion channel proteins move ions across the plasma membrane. Other molecules, such as glucose, move across the cell membrane by facilitated diffusion, in which a carrier protein physically moves the molecule across the membrane (See figure). Both channel proteins and carrier proteins are specific for the molecule transported. Movement by ion channel proteins and facilitated diffusion are still considered passive transport, meaning they move molecules down the cell's concentration gradient and do not require any energy input.

25. Transport through vesicles
Exocytosis moves large molecules outside of the cell. During exocytosis, the vesicle carrying the large molecule fuses with the plasma membrane. The large molecule is then released outside of the cell, and the vesicle is absorbed into the plasma membrane.
Endocytosis is the process by which cells take in large molecules by vesicle formation. Types of endocytosis include phagocytosis and pinocytosis.
Some large molecules are just too big to move across the membrane, even with the help of a carrier protein. These large molecules must be moved through vesicle formation, a process by which the large molecules are packaged in a small bubble of membrane for transport. This process keeps the large molecules from reacting with the cytoplasm of the cell. Vesicle formation does require an input of energy, however.
There are several kinds of vesicle formation that allow large molecules to move across the plasma membrane. Exocytosis moves large molecules outside of the cell. During exocytosis, the vesicle carrying the large molecule fuses with the plasma membrane. The large molecule is then released outside of the cell, and the vesicle is absorbed into the plasma membrane. Endocytosis is the process by which cells take in large molecules by vesicle formation. Types of endocytosis include phagocytosis and pinocytosis. During endocytosis, exocytosis and pinocytosis, substances are moved into or out of the cell via vesicle formation.

26. Endocytosis Phagocytosis Pinocytosis
Phagocytosis moves large substances, even another cell, into the cell. Phagocytosis occurs frequently in single-celled organisms, such as amoebas.
Pinocytosis involves the movement of liquid or very small particles into the cell.
These processes cause some membrane material to be lost as these vesicles bud off and come into the cell. This membrane is replaced by the membrane gained through exocytosis.