Transcript The Cell in Action

The Cell in Action
• The exchange of
materials between a
Cell
Membrane
cell and its
environment takes
“The Gate Keeper”
place at the cell’s
membrane.
• The cell membrane is
semipermeable which
means that only
certain substances can
pass through.
• To understand how
materials move into
and out of the cell,
you need to know
about diffusion.
What is Diffusion?
• Diffusion is the movement of
matter from an area of high
concentration to an area of low
concentration.
• In this process, cells do not
require energy because matter
moves naturally in this way.
• Diffusion happens within and
between living cells.
• The movement stops when a
state of equilibrium is reached.
• Diffusion is a form of passive
transport because no energy is
required.
Ed, Edd n Eddy Example
Ed, Edd and Eddy had the bright idea
to ride a shopping cart down a hill, so
they put Eddy in the cart and push him
up the hill. Did this require energy?
Yes! This task required a lot of energy because they had to
work in order to push Eddy and the cart up the hill. They
were pushing him from an area of low - to an area of high
potential kinetic energy. (kinetic means energy of motion)
• When they got to the top of the
hill where the potential energy
was high, they simply let go of
the cart and Eddy flew down the
hill and crashed!
• Was work required to push Eddy
down the hill?
• No, because moving from an area
of high concentration to an area
of low concentration happens
naturally! (ex. heat transfer,
potential kinetic energy, diffusion
and osmosis)
Osmosis
• Osmosis is the diffusion of
water through the
semipermeable cell
membrane.
• Semipermeable means that
only certain substances can
pass through.
• Osmosis is important to cells
because a cell cannot
function properly without
adequate water.
 For example, red blood cells are surrounded by
plasma. Plasma is made up of water, salts, sugars,
and other particles.
 The concentration of these particles is kept in balance
by osmosis. Water moves equally into and out of the
cell.
 If red blood cells were in pure water, water molecules
would flood into the cells and cause them to burst.
 When red blood cells are put into a salty solution, the
concentration of water molecules inside the cell is
higher than the concentration of water outside. This
difference makes water move out of the cells, and the
cells shrivel up.
Osmosis also occurs in plant
cells. When a wilted plant
is watered, osmosis makes
the plant firm again.
Passive Transport
• Passive transport moves
small particles, such as
sugars, cross the cell
membrane through
passageways called
channels.
• The movement of particles
across the cell membrane
without the use of energy
is called passive transport.
(ex. diffusion, osmosis)
• During passive transport
particles move from an
area of high
concentration to an area
of low concentration.
Active Transport
• Active transport moves
large particles into and
out of the cell using
energy.
• Large particles move into
and out of the cell by
processes called
endocytosis and
exocytosis.
• ATP energy is
needed!
Endocytosis
• Endocytosis is an active transport process by
which a cell surrounds a large particle, such
as a protein, and encloses it in a vesicle to
bring the particle into the cell.
Exocytosis
• Exocytosis is an active transport process
where large particles, such as waste, exits
the cell.
• During exocytosis a vesicle fuses with the
cell membrane and releases the particle to
the outside of the cell.
Cell Energy
Photosynthesis and Cellular Respiration
Photosynthesis
• Plants need water, carbon dioxide and sunlight for photosynthesis
to take place.
• Plants get the water they need through their roots and carbon
dioxide from small opening under the leaf called stomata.
• Plants have chloroplast, that are filled with a green pigment
called chlorophyll. The chlorophyll absorbs sunlight to use for
energy to produce glucose (sugar) during photosynthesis.
• Photosynthesis produces glucose and oxygen.
Cellular Respiration
•
•
•
•
Animal cells get energy from food through a process called cellular
respiration.
Animals inhale oxygen which is needed to break down food (glucose)
in the mitochondria and release large amounts of energy ATP to
fuel cell activities.
In plants, cellular respiration takes place in the cytoplasm.
Cellular respiration produces carbon dioxide, water and ATP.
The Cell Cycle
• The cell cycle is
the life cycle of
a cell.
• The cycle begins
when the cell is
formed and ends
when the cell
divides.
• Cell division in
prokaryotic cells is
called binary fission,
which means “splitting
into two parts.”
• The DNA ring and
ribosomes are copied
each new cell will
have one copy.
Life Cycle of a Eukaryotic Cell
Eukaryotic cells
divide in three
stages:
• Interphase
• Mitosis
• Cytokinesis
Interphase (stage 1)
• Chromosomes are copied.
• Each chromosome
becomes two chromatids.
Mitosis (stage 2)
There are four phases
of Mitosis:
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase (mitosis phase 1)
• Chromosomes condense
from long strands to
rod like structures.
Metaphase (mitosis phase 2)
• The nuclear membrane
is dissolved.
• Paired chromatid align
at the cell’s equator.
Anaphase (mitosis phase 3)
• The chromatid
separate and move
to opposite sides of
the cell.
Telophase (mitosis phase 4)
• A nuclear membrane
forms around each
set of chromosomes.
• Two nuclei are
formed.
Cytokinesis (stage 3)
• In cells that lack a
cell wall the cell
pinches in two. Two
new daughter cells
are formed.
• In cells with cell
walls a cell plate
forms between the
two new cells.
Animal and Plant Cell Cycle
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Human DNA
• Humans have 46 chromosomes.
• 23 pairs of homologous chromosomes.
• Homologous chromosomes are pairs of
chromosomes that have the same sequence
of genes and the same structure.
Human Cell Cycle