The Processes of the Cell

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The Processes of the Cell
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What has to happen to your cells in order to grow
from a baby into an adult?
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How do we know our cells are working?

• What do you think your cells must do in order to
  stay alive?

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Your cells are constantly working to perform many
activities such as getting food, removing wastes,
growing, reproducing, and making new materials
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Your cells work to keep all of these activities
in balance, which is known as homeostasis.
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If your cells do not have the materials necessary
to conduct their activities, they send out
various signals to let the rest of your body know.
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Homeostasis is also important because if your
cells are not balanced, chemical reactions can
not occur. This means that your cells can not
perform their job correctly.
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How are our cells able to do all of these
activities when they are surrounded by a barrier,
the cell membrane?
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In our previous unit, we learned that the job of
the cell membrane is to allow materials in and
out of the cell.
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The cell membrane is semi-permeable. This means
that it can let some materials pass through while
others can not.
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Since we now know that materials can and must
move in and out of a cell in order for it to
survive, lets discuss the different ways in
which this occurs.
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Some small particles can easily move in and out
of a cell, this happens through diffusion.

• Diffusion is when particles move from an area
  where it is crowded (high concentration) to an
  area where it is less crowded (low concentration)

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Examples of Diffusion

• Smell of food, perfume, air freshener, and other
  substances

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Diffusionhttp//www.bbc.co.uk/scotland/education
/bitesize/standard/biology/investigating_cells/cel
ls_and_diffusion_rev3.shtml
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Osmosis is the diffusion of water. Water moving
from where it is crowded to where it is less
crowded.
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Examples of Osmosis

• Cooking rice, beans, and macaroni
• Watering a plant

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Pure water diffuses more than any other water
mixture because it is more crowded (has a higher
concentration) than any other water mixtures.
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In this picture a red blood cell is put in a
glass of distilled water (pure water with no salt
or sugar in it). 
Because there is a higher concentration of water
outside the cell, water enters the cell by
OSMOSIS. The cell bursts and dies
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Osmosishttp//www.bbc.co.uk/scotland/education/b
itesize/standard/biology/investigating_cells/cells
_and_diffusion_rev4.shtml
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If your cell needs a particle and the particle is
too big to diffuse into the cell membrane, does
your cell just go without that particle?
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Although some particles are too large to diffuse
into or out of a cell, they can still get in or
out of the cell membrane.How?
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If a particle is too large to naturally go
through a cell membrane, it can enter or exit in
two ways

• Particles can move in and out of a cell through
  protein doorways
• If a particle is still too large to fit through a
  protein doorway, it can be engulfed (eaten) by
  the cell

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Protein Doorways
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Engulfing
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Particles that have to go through protein
doorways can enter one of two waysPassive
transport -particles can enter easily through the
protein doorwayActive transport -particles
require energy to move through the protein doorway
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Active transport is different from passive
transport because it requires energy. Active
transport is necessary to make particles move
against their natural tendency. In active
transport, particles move from less crowded (low
concentration) to more crowded (high
concentration).
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Active Transport
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Active transport is important in organs such as
the kidneys when harmful particles are made to
stay in the organ when they naturally want to
diffuse
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If a particle is too large to fit through a
protein doorway, then it can enter the cell by
being engulfed, endocytosis, or it can be
released from the cell by exocytosis
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Endocytosis and Exocytosis
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Endocytosisand Exocytosis
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Do cells need energy?
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Cells need energy to carry out the activities
which allow them to live, grow, and reproduce
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Cells get energy from food. Plant cells make
their own food while animal cells must get their
food by eating other things.
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Plant cells make their own food through the
process of photosynthesis. In this process,
plant cells take in light energy and change it
into a food called glucose.
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PhotosynthesisSunlight Water Carbon Dioxide
C6H12O6 (Glucose) and Oxygen
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Photosynthesis
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Once food is obtained or made in animal cells and
plant cells, it must be broken down to release
energy. This process is called cellular
respiration.
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Cellular RespirationC6H12O6 (Glucose) Oxygen
Carbon Dioxide, Water, and Energy (ATP)
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Cellular Respiration
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Photosynthesis and Cellular Respiration are the
opposite of one another
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We have discussed all of the ways in which cells
live and grow by getting the nutrients they need,
but living organisms would not exist over long
periods of time if cells did not reproduce.
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Living organisms can reproduce sexually and/or
asexually.
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Sexual reproduction requires two parents to make
an offspring that has characteristics of both
parents
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Organisms that reproduce sexually

• Animals
• Plants
• Fungi

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Asexual reproduction requires one parent to
produce an identical offspring
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Organisms that reproduce asexually

• Bacteria
• Plants
• Fungi

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Bacteria reproduces asexually through a process
called binary fission
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Cells reproduce by making more cells or dividing
through a process called mitosis (one cell makes
two)This is a form of asexual reproduction.
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Cells make sex cells to help in the reproduction
of multi-cellular organisms through a process
called meiosis (one makes four)
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MeiosisThis is a form of sexual reproduction
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Meiosis