Download The Cell in Action

The Cell in Action
The Exchange with the Environment, Cell Energy, and
the Cell Cycle
References
Information and Most Images
Holt Science & Technology, North Carolina, Grade 7. Holt, Rinehart and Winston: A
Hartcourt Education Company, 2005. Chapter 14: Pages 380 – 393.
Exchange with the Environment
What is diffusion and osmosis? Passive and Active Transport?
Endocytosis and Exocytosis?
Turn & Talk
• What would happen to a factory if its power were shut off or its supply of
raw materials never arrived?
• What would happen if the factory couldn’t get rid of it’s garbage?
Talk with your lab partner about these questions and write down your answers
in your interactive notebooks.
How is the cell like the factory?
An organism must be able to:
•
Obtain energy
•
Obtain raw materials
•
Get rid of wastes
These functions help keep cells healthy so they can divide. Cell
division allows organisms to grow and repair injuries.
At the cell membrane is where the exchange of materials takes
place.
Diffusion
Diffusion is the movement of particles from
regions of higher density to regions of lower
density.
In this experiment, dye is poured on top of
a layer of gelatin. At first, it is easy to see
where the dye ends and the gelatin begins.
But over time, the line between the two
layers will blur. The tiny moving particles
(which everything is made of) travel from
where they are crowded to where they are
less crowded.
The dye particles are more crowded at the top and they move to
where they are less crowded – inside the gelatin.
Diffusion also happens within and between living cells – and they
don’t need energy for diffusion.
Diffusion of Water
Cells of organisms are surrounded by and
filled with fluids that are mostly water.
Diffusion of water through cell
membranes is so important to life
processes.
Water is made up of particles, called molecules. Pure water has the
highest concentration of water molecules (H2O).
Osmosis – the diffusion of water through a
semipermeable membrane
When you mix something, such as sugar, with water, you lower the
concentration of water molecules.
Semipermeable – only certain substances
can pass through
Over time, as you can see above, water molecules move from the liquid
with the higher concentration of water molecules through the
semipermeable membrane to the liquid with the lower concentration of
water molecules (sugar water).
The Cell & Osmosis
Osmosis is important to cell functions by
keeping concentrations of cell particles in
balance.
Example: Red Blood Cells
Red blood cells are surrounded by plasma, which is made up of water, salts, sugars and other particles.
If red blood cells were in pure water, the water molecules would flood into the cells and cause them to burst (hypertonic).
When red blood cells are put into a salty solution, the concentration of the water molecules inside the cell is higher than the
concentration outside – this would make water move out of the cells and the cells would shrivel up (hypertonic).
Transport – Small Paricles
Passive transport – the movement of
substances across a cell membrane without
the use of energy by the cell.
Active transport – the movement of
substances across the cell membrane that
requires the cell to use energy
Transport – Large Particles
Endocytosis – the process by which a cell
membrane surrounds a particle and encloses
the particle in a vesicle (sacs formed from
pieces of cell membrane) to bring the
particle into the cell.
Transport – Large Particles
Exocytosis – the process in which a cell
releases a particle by enclosing the particle in
a vesicle that then moves to the cell surface
and fuses with the cell membrane
Cell Energy
Why do cells need energy?
Turn & Talk
• Why do you get hungry?
Talk with your lab partner about this question. Write your answers in your
interactive notebook.
Cells Need Energy
• Feeling hungry is your body’s way of telling you that your cells need energy
• All cells need energy to live, grow, and reproduce
• Plant cells get their energy from the sun (photosynthesis)
• Animal cells get their energy from food.
Plant Cells – Photosynthesis
• Plant molecules have molecules (pigments)
that absorb light energy.
• Chlorophyll is the main pigment used in
photosynthesis and is found in chloroplasts.
• Plants use energy captured by the
chlorophyll to change carbon dioxide and
water into food (glucose)
• When plants make glucose, they convert the
sun’s energy into a form of energy that can
be stored.
• Photosynthesis also produces oxygen.
Animal Cells – Cellular Respiration
• Cellular respiration – the process which
cells use oxygen to produce energy from
food
• Fermentation – the breakdown of food
without the use of oxygen
Cellular respiration will release more energy
from a given food than fermentation will.
Animal Cells – Cellular Respiration
•
During cellular respiration, food is broken
down into CO2 and H2O – and energy is
released.
•
Most of the energy released maintains body
temperature – and some of the energy is used
to form adenosine triphosphate (ATP) –
which supplies energy that fuels cell activities
•
In prokaryotic cells (no nucleus), cellular
respiration takes place in the cell membrane.
•
In eukaryotic cells (have a nucleus), cellular
respiration takes place in the mitochondria
The Connection:
Photosynthesis and Cellular
Respiration
Photosynthesis
Makes glucose and oxygen which is used by
animal cells to make ATP. Cellular respiration
releases carbon dioxide and water.
Cellular Respiration
Cellular respiration releases carbon dioxide and
water which is used by plant cells to make
glucose. During photosynthesis, oxygen is
released.
Fermentation
When your cells can’t get oxygen needed for
cellular respiration, they use fermentation to get
energy.
Example: Muscles
Fermentation in your muscles produces lactic
acid. The build up of lactic acid contributes to
muscle fatigue and a burning sensation.
Example: Yeast
Yeast forms carbon dioxide during
fermentation. The bubbles of the CO2 gas
cause the dough to rise and leave small holes in
bread after it is baked.
Review & Practice
• You and your lab partner complete the Cell Energy review pages.
• Glue into your interactive notebook.
• Hand in your interactive notebook to Mrs. Quick.
Lab – Fermentation with Yeast
• Making bread
• In your interactive notebook:
• What is your hypothesis on what is going to happen to the dough when we let it sit
during the rest period (after the dough is mixed)
• What are we going to see after we bake the bread?
• Were your hypothesis correct?
• If they were, what process was used by the yeast in order to create these situations?
The Cell Cycle
By the time you read this sentence, your body has made millions of
new cells!
The Life of a Cell
• Cell Cycle – the life cycle of a cell
• The cell cycle begins when the cell is formed and ends when the cell divides and forms new
cells.
• Before a cell divides – it makes a copy of the DNA (deoxyribonucleic acid)
• DNA is organized into structures called chromosomes (in a eukaryotic cell, one of
the structures in the nucleus that are made up of DNA and protein; the main ring
of DNA)
• Copying of the chromosomes ensures and exact copy of the parent cell to the new
cell.
Prokaryotic Cell
Reproduction
Binary fission – cell division of prokaryotic
cells (“splitting into two parts”)
Eukaryotic Cell Reproduction
Eukaryotic cells are more complex than
prokaryotic cells.
The chromosomes of eukaryotic cells
contain more DNA than those of
prokaryotic cells.
However, more complex eukaryotes do not
necessarily have more chromosomes than
simpler eukaryotes (for example: Fruit flies
have 8 chromosomes; potatoes have 48
chromosomes; and humans have 46
chromosomes)
Eukaryotic Cell Cycle Stages
Three Stages
• Interphase: the cell grows and copies
its organelles and chromosomes (after
the chromosome is duplicated the two
copies are called chromatids; held
together at the region called the
centromere)
Eukaryotic Cell Cycle Stages
• Mitosis: the process of cell division
that forms two new nuclei, each of
which has the same number of
chromosomes
• There are four phases of Mitosis
•
Prophase
•
Metaphase
•
Anaphase
•
Telophase
Eukaryotic Cell Cycle Stages
• Cytokinesis – the division of the
cytoplasm of the cell
• The cell membrane begins to pinch inward
to form a groove, which eventually pinches
all the way through the cell – forming two
daughter cells
• If a eukaryotic cell has a cell wall, a cell
plate forms in the middle of the cell. The
cell plate contains the materials for the new
cell membranes and cell walls. After the
split, a new cell wall forms where the cell
plate was.
Eukaryotic Cell Reproduction
Cells Alive!
Review & Practice
• You and your lab partner complete the Cell Cycle review pages.
• Glue into your interactive notebook.
• Hand in your interactive notebook to Mrs. Quick.
Lab Foldable – Cell Cycle
• Sheets are folded for you
• Project directions:
•
All rectangles should contain a title, illustration (picture), and detailed description of that stage of the cell cycle
•
•
•
•
•
•
•
•
•
The Cell Cycle (Title)
Stage 1: Interphase
Stage 2a: Mitosis – Prophase
Stage 2b: Mitosis – Metaphase
Stage 2c: Mitosis – Anaphase
Stage 2d: Mitosis – Telophase
Stage 3: Cytokinesis
Illustrations MUST be colored neatly and labeled with straight lines (use a ruler). Writing MUST be legible. NO PENCIL.
Grading Rubric should be turned in with your project