Download Cells

Grade 8 – Chapter 5
Cells in Their Environment
 How
cell?
do substances enter and leave a
 The
cell membrane is a selectively
permeable membrane. It regulates the
movement of substances into and out of the
cell.
 Diffusion is one of the basic ways that
substances move into and out of cells.
 Osmosis moves water into and out of cells.
 The skills of scientific inquiry can be used
to conduct controlled experiments on
diffusion and osmosis.
 Cells use special processes to move nondissolved particles, or large amounts of
material, into and out of the cytoplasm
 Selectively
permeable
membrane
 Diffusion
 Concentration
gradient
 osmosis
 Tugor
pressure
 Endocytosis
 Phagocytosis
 Exocytosis
 Review…
 What
are the characteristics of living
things?
• Grow in size, reproduce, and are able to repair
•
•
•
•
themselves
Require energy
Respond to changes in their environment
Have a lifespan
Produce waste
 Where
do living things get their energy?
• Food
 What
happens to the wastes living things
produce?
• They eliminate them from their bodies
 What are the different parts to a cell?
• Organelles: small structures found within a cell; has a
•
•
•
•
•
•
•
•
specific function
Cytoplasm: watery substance found in a cell which
protects and holds the organelles
Cell Membrane: the outer layer of the cell which
holds the cell together
Nucleus: control center of the cell (the Big Boss)
Vacuole: storage compartments in the cell that hold
fluid
Cell Wall: firm structure surrounding the plant cells
which provides support and protection
Chloroplast: photosynthesis happens here – turns
the sun’s energy into food
Cilia: tiny hairs surrounding the cell
Flagella: tail on the cell to help it move
 Mitochondria
– produce energy for the cell
 Ribosome – tiny organelles that produce
proteins needed for cell growth, repair and
reproduction
 Endoplasmic Reticulum – folded
membranes that transport materials through
the cytoplasm
 Golgi Apparatus – stores and packages
proteins produced by the ribosome
 Lysosome – cleans the cytoplasm by
releasing digestive proteins that break
down large particles
 Cell
wall
 Chloroplast
 Everything else is
the same
 What
types of materials need to get
through the cell membrane in order for
the cell to survive?
• Food, nutrients, waste must be able to move out,
etc.
 Selectively
Permeable Membrane: the
membrane chooses what should pass
through
 Permeable
– allowing passage
 Impermeable – not allowing passage
 What
is the function of the cell
membrane?
 Why are cell membranes said to be
selectively permeable?
 In your own words, describe the structure
of a cell membrane.
 Explain how the cell membrane is
important to the health of a cell.
 Perfume
demonstration
 Raise your hand when you can smell the
perfume
 What did you notice about this
demonstration?
 This is an example of diffusion
 The
movement of particles from an area
of high concentration to an area of low
concentration
 The
difference in concentration of a
substance between two areas
• Particles move from where there is less room to
where there is more room
 Oxygen
rich blood cells diffuses into our
muscles by spreading out from an area of
high concentration to an area of low
concentration (they go to the muscles
that need it)
 It is then used to make energy
 Page
122
 Materials needed: 2 beakers, pencil,
paper, room-temperature water, hot
water, 2 tea bags
 Answer questions A-D
 Use terminology from the unit and the
previous unit we have talked about
 Apply the concepts
 How
have the concepts in this reading
added to your understanding of cells?
 Describe the process of diffusion in your
own words. Use the particle theory in your
explanation.
 What does the term “concentration
gradient” mean?
 How is the movement of particles in
diffusion determined?
 Give 2 examples in your everyday
experience where diffusion occurs. Can you
think of a situation where this might be
harmful?
 Water
particles are small enough to cross
the cell membrane by diffusion
 Osmosis: the diffusion of water across a
selective permeable membrane from an
area of high concentration to an area of
low concentration
• Osmosis is a type of diffusion
 Sugars, salts
and proteins are common
solutes in a cell and water is the solvent
 Cells need to have a certain amount of
solute un order to stay alive
 When there is a lower concentration of
water INSIDE the cell, the water moves in by
osmosis (too much will make the cell burst)
 When there is a lower concentration of
water OUTSIDE the cell, the water moves out
 In
a plant, water is stored in the vacuole
 When a plant needs water, it is released
from the vacuole and goes where it is
needed
 Turgor
pressure: outward pressure put on
a plant cell wall by the contents inside
the cell when water is taken in
• Think of when you fill a balloon with water
• What happens to the balloon when you keep
putting water in?
 Describe
an idea in the reading that you
found to be particularly important. Why do
you think this idea is important?
 Explain the process of diffusion in your own
words. Use a diagram.
 Explain the process of osmosis in your own
words. Use a diagram.
 Explain how osmosis creates turgor
pressure in plants.
 What cell organelle makes turgor pressure
in a plant cell possible? Describe the role of
this organelle in this process.
 The
cell moves large amounts of
materials from the outside environment
into the cytoplasm (inside the cell)
 Phagocytosis
 Large
amounts of material are moved
from a cell’s cytoplasm to the outside
environment
 Give
two examples of situations where a
cell might use phagocytosis and
exocytosis.
 A cell encounters a large piece of food.
Use a simple diagram to show how it
might move the food particles into the
cell cytoplasm. Include labels in your
diagram.
 What is exocytosis? Explain using a
diagram.
 Page
134 and 135
 Questions on page 136 and 137
 #1-15