Download The Cell - De Soto High School

The Cell
7th Grade Science
Mrs. Christopherson
History of Cells
• 1665: Robert Hooke used a compound
microscope to look at cork.
• 1674: Anton von Leeuwenhoek observes
microorganisms in pond water
• 1838: Matthias Schleiden concludes all plants
are made up of cells.
• 1839: Theodor Schwann concludes all animals
are made up of cells.
• 1855: Rudolph Virchow proposes that all cells
come from existing cells, completing the cell
theory.
Cell Theory
1. All organisms are composed of one or
more cells
– Organisms can be unicellular or multicellular
2. The cell is the basic unit of organization
of organisms
3. All cells come from pre-existing cells
– Cells reproduce to make exact copies of
themselves
Two Types of Cells
• Prokaryotic Cells:
– No nucleus
– No organelles
– Mostly unicellular organisms
– Cell wall or membrane
Two Types of Cells
• Eukaryotic Cells:
– Nucleus
– Organelles
surrounded by
membranes
– Mostly multicellular
– organisms
– Cell wall or
membrane
Prokaryotes
•No Nucleus
•Single celled
•Little or no organization within
cell wall and membrane
Both
Eukaryotes
•Cell wall
• Have a nucleus
•Cell
membrane
• Contain
membrane-bound
organelles that
have specialized
tasks
• Single-celled or multicellular
Cell Specialization
• Multicellular organisms have cells that do
many different jobs.
– For example, there are blood cells, muscle
cells, nerve cells, etc. These cells are said to
be “specialized”.
– Specialized cells perform only their specific
functions and cannot live on their own.
Levels of Organization Within
Organisms
• In multicellular organisms, cells are grouped
together in tissues.
– A tissue is a group of similar cells that do a specific
job.
– An example is our skin.
• Tissues that work together form organs.
– An example of an organ is the heart.
• Organs and tissues working together from organ
systems. Example: the digestive system
• The largest level of organization is the organism
itself.
Levels of Organization Within
Organisms
Cell Organelles
• Cell wall: a tough outer covering that
protects the cell and provides support.
– Only plant cells have cell walls. Can you
guess why?
Cell Organelles
• Cell membrane: a protective covering that
surrounds the cell.
– Materials entering the cell must pass thru the
cell membrane. Some materials can easily
enter while others cannot cross at all.
– Selectively permeable.
– Both plant and animal cells have cell
membranes
Cell Organelles
• Cytoplasm: gel-like material found inside
the cell, contains the organelles.
• Nucleus: genetic material is stored here in
the form of chromosomes, which are made
of DNA.
– The nucleus is usually the largest organelle
found in the cell!
• Nuclear membrane: surrounds and
protects the nucleus.
Cell Organelles
• Endoplasmic Reticulum: is responsible for
transporting materials in the cell.
– Smooth ER: does not contain ribosomes,
makes lipids and membrane proteins
– Rough ER: contains ribosomes, makes
proteins
• Ribosomes: produce proteins and are
attached to the endoplasmic reticulum.
Cell Organelles
• Mitochondria: transform the energy in
food to energy the cell can use to drive
chemical reactions.
– The “powerhouse” of the cell
• Vacuole: store substances in the cell.
• Lysosome: involved in digestion of old cell
organelles as well as breaking large
molecules into smaller ones.
Cell Organelles
• Golgi Body: packages products from the
ER and distribute them around or outside
of the cell.
Cell Organelles
What happens if a vacuole
bursts??
• In plant cells:
– Vacuoles control whether plants wilt or stand up: if
there is plenty of water the plant will stand tall. If
water is lacking (or vacuoles aren’t working/have
burst) the plant will wilt.
• If they contain toxic materials, those materials
will enter the cell and possibly kill it.
• Contractile Vacuoles: pump out excess water.
– If these burst or aren’t working properly, the excess
water will cause the cell to burst.
Cell Growth and Division
• Multicellular organisms grow because cell
division increases the number of cells in
them.
• Cells become specialized during the
development of an organism.
• Cells that are damaged or worn out are
replaced by cell division.
Cell Growth and Division: The Cell
Cycle
• Interphase: The part of the cell cycle when
the cell is not dividing.
– This is the longest phase in the cell cycle.
– Cells grow and go about their daily routines in
this part of the cycle.
– DNA (genetic material) replicates.
Cell Growth and Division: The Cell
Cycle
• Mitosis: the part of the cell cycle where
the nucleus divides. Occurs in nonreproductive cells and produces exact
copies of the parent cell.
– Prophase: The chromosomes condense
– Metaphase: The chromosomes line up in the
middle of the cell.
– Anaphase: The chromosomes separate and
are pulled to either end of the cell.
– Telophase: The new nuclear membrane
forms.
– Cytokinesis: The cell splits in half.
Cell Growth and Division: The Cell
Cycle
More on Mitosis
• http://library.thinkquest.org/C0118084/Gen
e/Chromosomal_Inheritance/StagesMitosi
s.htm
• http://www.uoguelph.ca/zoology/devobio/2
10labs/mitosis1.html