Cellular Transport Cellular Transport and the Cell Cycleand the Cell Cycle

Chapter 8 Chapter 8

Chapter 8 SectionsChapter 8 Sections

► 8.1 Cellular Transport8.1 Cellular Transport OsmosisOsmosis Passive TransportPassive Transport Active TransportActive Transport

► 8.2 Cell Growth and Reproduction8.2 Cell Growth and Reproduction Cell Size limitationsCell Size limitations Cell ReproductionCell Reproduction Cell CycleCell Cycle

► 8.3 Control of the Cell Cycle8.3 Control of the Cell Cycle NormalNormal CancerCancer

Cellular TransportCellular Transport

Section 8.1Section 8.1

Cellular TransportCellular Transport

►Substances move into and out of the Substances move into and out of the cell in two ways:cell in two ways:1.) Passive Transport1.) Passive Transport – No energy is used. – No energy is used.

►DiffusionDiffusion►OsmosisOsmosis►Facilitated DiffusionFacilitated Diffusion

2.) Active Transport2.) Active Transport – Energy is used. – Energy is used.►EndocytosisEndocytosis►ExocytosisExocytosis

►DiffusionDiffusion is the movement of molecules from is the movement of molecules from high to low concentrations.high to low concentrations. Diffusion continues until dynamic equilibrium Diffusion continues until dynamic equilibrium

is reached (the same concentration is reached (the same concentration throughout).throughout).

►OsmosisOsmosis – – diffusion of waterdiffusion of water across a cell across a cell membranemembrane The cell membrane does NOT limit water movement. The cell membrane does NOT limit water movement.

Water crosses the membrane Water crosses the membrane freelyfreely. . It stops molecules that are dissolved in water from It stops molecules that are dissolved in water from

entering the cell.entering the cell.

DiffusionDiffusion

OsmosisOsmosis► What determines whether water flows What determines whether water flows

into or out of a cell?into or out of a cell? The The amount of dissolved substances amount of dissolved substances

inside the cell compared to outside the cell.inside the cell compared to outside the cell.

► Isotonic EnvironmentIsotonic Environment Amount of substances outside the cell is the Amount of substances outside the cell is the

same as inside cell.same as inside cell. Water flows into and out of the cell at Water flows into and out of the cell at

the same rate.the same rate.

► Hypotonic EnvironmentHypotonic Environment Amount of substances outside the cell is Amount of substances outside the cell is

less than inside the cell.less than inside the cell. Water flows into cell.Water flows into cell.

► Hypertonic EnvironmentHypertonic Environment Amount of substances outside the cell is Amount of substances outside the cell is

more than inside the cell.more than inside the cell. Water flows out of cell.Water flows out of cell.

Facilitated DiffusionFacilitated DiffusionFacilitated diffusionFacilitated diffusion

Diffusion of substances into or out of the cell with Diffusion of substances into or out of the cell with the help of transport proteins.the help of transport proteins.

Substances move from Substances move from high to lowhigh to low concentrations during facilitated diffusion.concentrations during facilitated diffusion.

There are two types of transport proteins:There are two types of transport proteins:►Channel proteinsChannel proteins►Carrier ProteinsCarrier Proteins

Active TransportActive Transport

► Active TransportActive Transport – Movement of substances across – Movement of substances across the cell membrane from areas of the cell membrane from areas of lower to higherlower to higher concentrationconcentration Active transport requires energy!Active transport requires energy!

► The substances move across the cell membrane The substances move across the cell membrane against the concentration gradientagainst the concentration gradient (from low to (from low to high concentration)high concentration) This is the opposite of diffusion (passive transport)This is the opposite of diffusion (passive transport)

► Like facilitated diffusion (a type of passive transport), Like facilitated diffusion (a type of passive transport), active transport occurs with the help of carrier active transport occurs with the help of carrier proteins.proteins.

Channel and Carrier Channel and Carrier ProteinsProteins

Transport of Large Transport of Large SubstancesSubstances

► Sometimes substances are Sometimes substances are too large to cross the cell too large to cross the cell membrane or move through membrane or move through a transport protein. a transport protein.

► EndocytosisEndocytosis Cell surrounds and takes in Cell surrounds and takes in

material that is too large for material that is too large for transport through the transport through the membranemembrane

► ExocytosisExocytosis Expulsion or secretion of Expulsion or secretion of

materialsmaterials The opposite of endocytosisThe opposite of endocytosis

► Both endocytosis and Both endocytosis and exocytosis require energy.exocytosis require energy. Are they types of passive or Are they types of passive or

active transport?active transport?

Classwork – Due Today!Classwork – Due Today!

► Section Assessment page 200 (1-4) Q & Section Assessment page 200 (1-4) Q & AA

Section 8.2Section 8.2Cell Growth and Cell Growth and

ReproductionReproduction

Cell Size LimitationsCell Size Limitations► Why are cells so small?Why are cells so small?

► Cell size is limited by 3 things:Cell size is limited by 3 things:

► Diffusion Limits cell sizeDiffusion Limits cell size It would be very difficult to get things into and out of the cell It would be very difficult to get things into and out of the cell

because diffusion is slow and inefficient over large areasbecause diffusion is slow and inefficient over large areas

► DNA Limits cell sizeDNA Limits cell size It would take too long to construct the # of proteins It would take too long to construct the # of proteins

necessary to support a large cell because there is a limit to necessary to support a large cell because there is a limit to how quickly DNA can be copied and read how quickly DNA can be copied and read

► Surface area to volume ratio limits cell sizeSurface area to volume ratio limits cell size Volume increases faster than surface area Volume increases faster than surface area

► (it gets bigger inside than it does outside)(it gets bigger inside than it does outside) It would require more nutrients, and have to get rid of more It would require more nutrients, and have to get rid of more

wastes, but through a smaller surface area (cell membrane)wastes, but through a smaller surface area (cell membrane)

Cell DivisionCell Division

►All cells come from other cells. All cells come from other cells.

(Schleiden and Schwann - Cell (Schleiden and Schwann - Cell Theory)Theory)

Cells divide to maintain their Cells divide to maintain their sizessizes

► Cells cannot become too large, so they Cells cannot become too large, so they divide to form more cells…….they reproduce.divide to form more cells…….they reproduce.

► When organisms grow, new cells are made.When organisms grow, new cells are made.

► When cells are damaged or die, they are When cells are damaged or die, they are replaced by new cells.replaced by new cells.

► The process of cell reproduction is called The process of cell reproduction is called cell cell division.division.

ChromosomesChromosomes► ChromosomesChromosomes can only be can only be

seen just before a cell seen just before a cell divides and they disappear divides and they disappear after it divides. after it divides.

► Chromosomes are tightly Chromosomes are tightly wound DNA molecules.wound DNA molecules. (They normally exist as chromatin)(They normally exist as chromatin)

► Chromosomes (DNA) are Chromosomes (DNA) are copied during cell copied during cell division and are passed division and are passed on from one generation on from one generation of cells to the next.of cells to the next.

The Cell CycleThe Cell Cycle

►There are two primary parts of the There are two primary parts of the cell cell cyclecycle..

►The first part is called The first part is called interphaseinterphase. . Cells spend most of their lifetime in this phase.Cells spend most of their lifetime in this phase.

►The second part is called The second part is called mitosismitosis. . Mitosis is a very short compared to interphase.Mitosis is a very short compared to interphase.

►G1G1► SS►G2G2

► PROPHASEPROPHASE►METAPHASEMETAPHASE►ANAPHASE ANAPHASE ► TELOPHASETELOPHASE► CYTOKENISISCYTOKENISIS

The Cell CycleThe Cell Cycle

INTERPHASEINTERPHASE

MITOSISMITOSIS

The Cell CycleThe Cell Cycle ► Interphase is divided Interphase is divided

into three parts.into three parts.►G1G1 –Rapid Growth. –Rapid Growth.

Protein production Protein production is is high. Chromosome high. Chromosome not not visible.visible.

► SS – DNA copied. – DNA copied.►G2G2 –Organelles –Organelles

produced.produced.

► Then the cell goes into Then the cell goes into mitosis (cell division)mitosis (cell division)

Plant Cell

Animal Cell

►Steps of mitosis:Steps of mitosis:

1- 1- ProphaseProphase: Chromosomes : Chromosomes formform

ProphaseProphase► Chromatin Chromatin coils up and becomes the visiblecoils up and becomes the visible chromosomes. chromosomes.

► Chromosomes consist of two halves (which are copies of one Chromosomes consist of two halves (which are copies of one another) called another) called sister chromatids.sister chromatids.

► A structure called a A structure called a centromere centromere holds the sister chromatids holds the sister chromatids together.together.

► The nucleus of the cell disappears.The nucleus of the cell disappears.

► CentriolesCentrioles migrate to opposite poles migrate to opposite poles (they help pull the chromatids apart when the cell divides). (they help pull the chromatids apart when the cell divides).

► Spindle fibersSpindle fibers made of microtubules form between made of microtubules form between centrioles (help pull sisters apart too).centrioles (help pull sisters apart too).

2- MetaphaseMetaphase:Chromosomes line up

MetaphaseMetaphase► Chromosomes become attached to spindle Chromosomes become attached to spindle

fibers at centromeres.fibers at centromeres.

► Chromosomes are pulled to middle of cell Chromosomes are pulled to middle of cell (equator) by spindle fibers. They all line up.(equator) by spindle fibers. They all line up.

► Each sister chromatid is attached to its own Each sister chromatid is attached to its own spindle fiber which is connected to the spindle fiber which is connected to the opposite pole of the cell.opposite pole of the cell.

3- Anaphase:

Chromosomes begin to be pulled apart by spindle fibers.

4- Telophase:

Sister chromatids reach opposite ends of the cell

TelophaseTelophase

► Telophase is the reverse of Prophase.Telophase is the reverse of Prophase.

► The cells nucleus reforms.The cells nucleus reforms.

► Chromosomes unwind into Chromatin.Chromosomes unwind into Chromatin.

► Spindle breaks down.Spindle breaks down.

► A new nuclear envelope is formed around A new nuclear envelope is formed around each set of chromosomes.each set of chromosomes.

5- CytokenisisCytokenisis: Cell splits into two cells.

The plasma membrane is pinched into two parts to form the new cells.

►G1G1► SS►G2G2

► PROPHASEPROPHASE►METAPHASEMETAPHASE►ANAPHASE ANAPHASE ► TELOPHASETELOPHASE► CYTOKENISISCYTOKENISIS

The Cell CycleThe Cell Cycle

INTERPHASEINTERPHASE

MITOSISMITOSIS

Section 8.3Section 8.3Control of the Cell Control of the Cell

CycleCycle

Control of the Cell CycleControl of the Cell Cycle

► Proteins called Proteins called CyclinsCyclins and enzymes that attach and enzymes that attach to the cyclins control the timing of the cell cycle. to the cyclins control the timing of the cell cycle. They are in charge of the cell cycle.They are in charge of the cell cycle.

► Sometimes there is a failure in protein and Sometimes there is a failure in protein and enzyme production and enzyme production and cancercancer results. results.

► Cancer is uncontrolled cell division.Cancer is uncontrolled cell division.

► There are many different possible causes of There are many different possible causes of cancer including environmental factors and viral cancer including environmental factors and viral infections.infections.

CancerCancer

► Cancerous cells form Cancerous cells form masses of tissue masses of tissue called tumors.called tumors. Tumors deprive normal Tumors deprive normal

cells of nutrients.cells of nutrients.

► Cancer can affect any Cancer can affect any tissue in the body.tissue in the body.

► 22ndnd leading cause of leading cause of death in US.death in US.

Cancer PreventionCancer Prevention

►Diets low in fat and high in fiber Diets low in fat and high in fiber content.content.

►Vitamins and minerals may also Vitamins and minerals may also prevent cancer.prevent cancer.

►Daily exercise and control of Daily exercise and control of environmental conditions.environmental conditions.

Classwork – Due Today!Classwork – Due Today!

►Ch. 8 WorksheetsCh. 8 Worksheets