Cellular Transport and the Cell Cycle

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Cellular Transport and the Cell Cycle

• Chapter 8

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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

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Cellular Transport

• Section 8.1

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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

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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.

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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.

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Facilitated Diffusion

• 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

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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.

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Channel and Carrier Proteins
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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?

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Classwork Due Today!

• Section Assessment page 200 (1-4) Q A

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Section 8.2Cell Growth and Reproduction
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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)

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Cell Division

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

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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.

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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.

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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.

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The Cell Cycle

• G1
• S
• G2
• PROPHASE
• METAPHASE
• ANAPHASE
• TELOPHASE
• CYTOKENISIS

INTERPHASE MITOSIS
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The Cell Cycle
Plant 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
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• Steps of mitosis
• 1- Prophase Chromosomes form

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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).

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2- Metaphase Chromosomes line up
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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.

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3- Anaphase Chromosomes begin to be pulled
apart by spindle fibers.
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4- Telophase Sister chromatids reach
opposite ends of the cell
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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.

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

• G1
• S
• G2
• PROPHASE
• METAPHASE
• ANAPHASE
• TELOPHASE
• CYTOKENISIS

INTERPHASE MITOSIS
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Section 8.3Control of the Cell Cycle
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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.

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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.

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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.

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Classwork Due Today!

• Ch. 8 Worksheets