Cellular Transport
and the Cell Cycle
Chapter 8
Chapter 8 Sections
► 8.1
Cellular Transport
► 8.2
Cell Growth and Reproduction
► 8.3
Control of the Cell Cycle
 Osmosis
 Passive Transport
 Active Transport
 Cell Size limitations
 Cell Reproduction
 Cell Cycle
 Normal
 Cancer
Cellular Transport
Section 8.1
Cellular Transport
► Substances
two ways:
move into and out of the cell in
1.) Passive Transport – No energy is used.
►Diffusion
►Osmosis
►Facilitated
Diffusion
2.) Active Transport – Energy is used.
►Endocytosis
►Exocytosis
► 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.
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.
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
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.
Channel and Carrier Proteins
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?
Classwork – Due Today!
►
Section Assessment page 200 (1-4) Q & A
Section 8.2
Cell Growth and
Reproduction
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)
Cell Division
► All
cells come from other cells.
(Schleiden and Schwann - Cell Theory)
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.
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.
The Cell Cycle
► There
cycle.
► The
are two primary parts of the cell
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.
The Cell Cycle
► G1
►S
INTERPHASE
► G2
► PROPHASE
► METAPHASE
► ANAPHASE
► TELOPHASE
► CYTOKENISIS
MITOSIS
The Cell Cycle
► Interphase
is divided
into three parts.
► G1 –Rapid Growth.
Protein production is
high. Chromosome not
visible.
► S – DNA copied.
► G2 –Organelles produced.
the cell goes into
mitosis (cell division)
Plant Cell
► Then
Animal Cell
► Steps
of mitosis:
1- Prophase: Chromosomes form
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).
2- Metaphase:
Chromosomes line up
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.
3- Anaphase:
Chromosomes begin to be pulled apart by
spindle fibers.
4- Telophase:
Sister chromatids reach
opposite ends of the cell
Telophase
► Telophase
► The
is the reverse of Prophase.
cells nucleus reforms.
► Chromosomes
► Spindle
►A
unwind into Chromatin.
breaks down.
new nuclear envelope is formed around each set
of chromosomes.
5- Cytokenisis:
Cell splits into two cells.
The plasma membrane is pinched into
two parts to form the new cells.
The Cell Cycle
► G1
►S
INTERPHASE
► G2
► PROPHASE
► METAPHASE
► ANAPHASE
► TELOPHASE
► CYTOKENISIS
MITOSIS
Section 8.3
Control of the Cell Cycle
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
► There
is uncontrolled cell division.
are many different possible causes of cancer
including environmental factors and viral infections.
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.
Cancer Prevention
► Diets
low in fat and high in fiber content.
► Vitamins
cancer.
► Daily
and minerals may also prevent
exercise and control of environmental
conditions.
Classwork – Due Today!
► Ch.
8 Worksheets