1. Cellular Transport and the Cell Cycle
Chapter 8

2. Chapter 8 Sections 8.1 Cellular Transport
Osmosis
Passive Transport
Active Transport
8.2 Cell Growth and Reproduction
Cell Size limitations
Cell Reproduction
Cell Cycle
8.3 Control of the Cell Cycle
Normal
Cancer

3. Cellular Transport
Section 8.1

4. Cellular Transport
Substances move into and out of the cell in two ways:
1.) Passive Transport – No energy is used.
Diffusion
Osmosis
Facilitated Diffusion
2.) Active Transport – Energy is used.
Endocytosis
Exocytosis

5. Diffusion
Diffusion is the movement of molecules from high to low concentrations.
Diffusion continues until dynamic equilibrium is reached (the same concentration throughout).
Osmosis – diffusion of water across a cell membrane
The cell membrane does NOT limit water movement. Water crosses the membrane freely.
It stops molecules that are dissolved in water from entering the cell.

6. Osmosis What determines whether water flows into or out of a cell?
The amount of dissolved substances inside the cell compared to outside the cell.
Isotonic Environment
Amount of substances outside the cell is the same as inside cell.
Water flows into and out of the cell at the same rate.
Hypotonic Environment
Amount of substances outside the cell is less than inside the cell.
Water flows into cell.
Hypertonic Environment
Amount of substances outside the cell is more than inside the cell.
Water flows out of cell.

7. Facilitated Diffusion
Diffusion of substances into or out of the cell with the help of transport proteins.
Substances move from high to low concentrations during facilitated diffusion.
There are two types of transport proteins:
Channel proteins
Carrier Proteins

8. Active Transport
Active Transport – Movement of substances across the cell membrane from areas of lower to higher concentration
Active transport requires energy!
The substances move across the cell membrane against the concentration gradient (from low to high concentration)
This is the opposite of diffusion (passive transport)
Like facilitated diffusion (a type of passive transport),
active transport occurs with the help of carrier proteins.

9. Channel and Carrier Proteins

10. Transport of Large Substances
Sometimes substances are too large to cross the cell membrane or move through a transport protein.
Endocytosis
Cell surrounds and takes in material that is too large for transport through the membrane
Exocytosis
Expulsion or secretion of materials
The opposite of endocytosis
Both endocytosis and exocytosis require energy.
Are they types of passive or active transport?

11. Classwork – Due Today!
Section Assessment page 200 (1-4) Q & A

12. Section 8.2 Cell Growth and Reproduction

13. Cell Size Limitations Why are cells so small?
Cell size is limited by 3 things:
Diffusion Limits cell size
It would be very difficult to get things into and out of the cell because diffusion is slow and inefficient over large areas
DNA Limits cell size
It would take too long to construct the # of proteins necessary to support a large cell because there is a limit to how quickly DNA can be copied and read
Surface area to volume ratio limits cell size
Volume increases faster than surface area
(it gets bigger inside than it does outside)
It would require more nutrients, and have to get rid of more wastes, but through a smaller surface area (cell membrane)

14. Cell Division All cells come from other cells.
(Schleiden and Schwann - Cell Theory)

15. Cells divide to maintain their sizes
Cells cannot become too large, so they divide to form more cells…….they reproduce.
When organisms grow, new cells are made.
When cells are damaged or die, they are replaced by new cells.
The process of cell reproduction is called cell division.

16. Chromosomes
Chromosomes can only be seen just before a cell divides and they disappear after it divides.
Chromosomes are tightly wound DNA molecules.
(They normally exist as chromatin)
Chromosomes (DNA) are copied during cell division and are passed on from one generation of cells to the next.

17. The Cell Cycle There are two primary parts of the cell cycle.
The first part is called interphase.
Cells spend most of their lifetime in this phase.
The second part is called mitosis.
Mitosis is a very short compared to interphase.

18. The Cell Cycle INTERPHASE MITOSIS G1 S G2 PROPHASE METAPHASE ANAPHASE
TELOPHASE
CYTOKENISIS
INTERPHASE
MITOSIS

20. The Cell Cycle Plant Cell Animal Cell
Interphase is divided into three parts.
G1 –Rapid Growth. Protein production is high. Chromosome not visible.
S – DNA copied.
G2 –Organelles produced.
Then the cell goes into mitosis (cell division)
Animal Cell

21. 1- Prophase: Chromosomes form
Steps of mitosis:
1- Prophase: Chromosomes form

22. Prophase Chromatin coils up and becomes the visible chromosomes.
Chromosomes consist of two halves (which are copies of one another) called sister chromatids.
A structure called a centromere holds the sister chromatids together.
The nucleus of the cell disappears.
Centrioles migrate to opposite poles (they help pull the chromatids apart when the cell divides).
Spindle fibers made of microtubules form between centrioles (help pull sisters apart too).

23. 2- Metaphase: Chromosomes line up

24. Metaphase
Chromosomes become attached to spindle fibers at centromeres.
Chromosomes are pulled to middle of cell (equator) by spindle fibers. They all line up.
Each sister chromatid is attached to its own spindle fiber which is connected to the opposite pole of the cell.

25. Chromosomes begin to be pulled apart by spindle fibers.
3- Anaphase:
Chromosomes begin to be pulled apart by spindle fibers.

26. Sister chromatids reach opposite ends of the cell
4- Telophase:
Sister chromatids reach opposite ends of the cell

27. Telophase Telophase is the reverse of Prophase.
The cells nucleus reforms.
Chromosomes unwind into Chromatin.
Spindle breaks down.
A new nuclear envelope is formed around each set of chromosomes.

28. 5- Cytokenisis: Cell splits into two cells.
The plasma membrane is pinched into two parts to form the new cells.

29. The Cell Cycle INTERPHASE MITOSIS G1 S G2 PROPHASE METAPHASE ANAPHASE
TELOPHASE
CYTOKENISIS
INTERPHASE
MITOSIS

31. Section 8.3 Control of the Cell Cycle

32. Control of the Cell Cycle
Proteins called Cyclins and enzymes that attach to the cyclins control the timing of the cell cycle.
They are in charge of the cell cycle.
Sometimes there is a failure in protein and enzyme production and cancer results.
Cancer is uncontrolled cell division.
There are many different possible causes of cancer including environmental factors and viral infections.

33. Cancer Cancerous cells form masses of tissue called tumors.
Tumors deprive normal cells of nutrients.
Cancer can affect any tissue in the body.
2nd leading cause of death in US.

34. Cancer Prevention Diets low in fat and high in fiber content.
Vitamins and minerals may also prevent cancer.
Daily exercise and control of environmental conditions.

35. Classwork – Due Today!
Ch. 8 Worksheets