The Cell 7 th Grade Science Mrs. Christopherson Mrs. Goede

The CellThe Cell

77thth Grade Science Grade ScienceMrs. ChristophersonMrs. Christopherson

Mrs. GoedeMrs. Goede

History of CellsHistory of Cells

1665: 1665: Robert HookeRobert Hooke used a compound microscope used a compound microscope to look at cork.to look at cork.

1674: 1674: Anton von LeeuwenhoekAnton von Leeuwenhoek observes observes microorganisms in pond watermicroorganisms in pond water

1838: 1838: Matthias SchleidenMatthias Schleiden concludes all plants are concludes all plants are made up of cells.made up of cells.

1839: 1839: Theodor SchwannTheodor Schwann concludes all animals are concludes all animals are made up of cells.made up of cells.

1855: 1855: Rudolph VirchowRudolph Virchow proposes that all cells proposes that all cells come from existing cells, completing the cell theory.come from existing cells, completing the cell theory.

Cell TheoryCell Theory

1.1. All organisms are composed of one or All organisms are composed of one or more cellsmore cells

– Organisms can be unicellular or multicellularOrganisms can be unicellular or multicellular

2.2. The cell is the basic unit of organization The cell is the basic unit of organization of organismsof organisms

3.3. All cells come from pre-existing cellsAll cells come from pre-existing cells– Cells reproduce to make exact copies of Cells reproduce to make exact copies of

themselvesthemselves

Two Types of CellsTwo Types of Cells

Prokaryotic Cells:Prokaryotic Cells:– No nucleusNo nucleus– No organellesNo organelles– Mostly unicellular organismsMostly unicellular organisms– Cell wall or membraneCell wall or membrane

Two Types of CellsTwo Types of Cells

Eukaryotic Cells:Eukaryotic Cells:– NucleusNucleus– Organelles Organelles

surrounded by surrounded by membranesmembranes

– Mostly multicellular Mostly multicellular – organismsorganisms– Cell wall or Cell wall or

membranemembrane

Prokaryotes

•No Nucleus

•Single celled

•Little or no organization within cell wall and membrane

Eukaryotes

• Have a nucleus

• Contain membrane-bound organelles that have specialized tasks

• Single-celled or multicellular

Both

•Cell wall

•Cell membrane

Cell SpecializationCell Specialization

Multicellular organisms have cells that do Multicellular organisms have cells that do many different jobs.many different jobs.– For example, there are blood cells, muscle For example, there are blood cells, muscle

cells, nerve cells, etc. These cells are said to cells, nerve cells, etc. These cells are said to be “specialized”.be “specialized”.

– Specialized cells perform only their specific Specialized cells perform only their specific functions and cannot live on their own.functions and cannot live on their own.

Levels of Organization Within Levels of Organization Within OrganismsOrganisms

In multicellular organisms, In multicellular organisms, cellscells are grouped are grouped together in together in tissuestissues..– A tissue is a group of similar cells that do a specific job.A tissue is a group of similar cells that do a specific job.– An example is our skin.An example is our skin.

Tissues that work together form Tissues that work together form organsorgans..– An example of an organ is the heart.An example of an organ is the heart.

Organs and tissues working together from Organs and tissues working together from organ organ systemssystems. Example: the digestive system. Example: the digestive system

The largest level of organization is the The largest level of organization is the organismorganism itself.itself.

Levels of Organization Within Levels of Organization Within Organisms Organisms

Cell OrganellesCell Organelles

Cell wall: a tough outer covering that Cell wall: a tough outer covering that protects the cell and provides support.protects the cell and provides support.– Only plant cells have cell walls. Can you Only plant cells have cell walls. Can you

guess why?guess why?


Cell membrane: a protective covering that Cell membrane: a protective covering that surrounds the cell.surrounds the cell.– Materials entering the cell must pass thru the Materials entering the cell must pass thru the

cell membrane. Some materials can easily cell membrane. Some materials can easily enter while others cannot cross at all.enter while others cannot cross at all.

– Selectively permeable.Selectively permeable.– Both plant and animal cells have cell Both plant and animal cells have cell

membranesmembranes


Cytoplasm: gel-like material found inside Cytoplasm: gel-like material found inside the cell, contains the organelles.the cell, contains the organelles.

Nucleus: genetic material is stored here in Nucleus: genetic material is stored here in the form of chromosomes, which are made the form of chromosomes, which are made of DNA. of DNA. – The nucleus is usually the largest organelle The nucleus is usually the largest organelle

found in the cell!found in the cell!

Nuclear membrane: surrounds and Nuclear membrane: surrounds and protects the nucleus.protects the nucleus.


Endoplasmic Reticulum: is responsible for Endoplasmic Reticulum: is responsible for transporting materials in the cell.transporting materials in the cell.– Smooth ER: does not contain ribosomes, Smooth ER: does not contain ribosomes,

makes lipids and membrane proteinsmakes lipids and membrane proteins– Rough ER: contains ribosomes, makes Rough ER: contains ribosomes, makes

proteinsproteins

Ribosomes: produce proteins and are Ribosomes: produce proteins and are attached to the endoplasmic reticulum.attached to the endoplasmic reticulum.


Mitochondria: transform the energy in Mitochondria: transform the energy in food to energy the cell can use to drive food to energy the cell can use to drive chemical reactions.chemical reactions.– The “powerhouse” of the cellThe “powerhouse” of the cell

Vacuoles: store substances in the cell.Vacuoles: store substances in the cell.

Lysosomes: involved in digestion of old Lysosomes: involved in digestion of old cell organelles as well as breaking large cell organelles as well as breaking large molecules into smaller ones.molecules into smaller ones.


Golgi Body: packages products from the Golgi Body: packages products from the ER and distribute them around or outside ER and distribute them around or outside of the cell.of the cell.


Cell Growth and DivisionCell Growth and Division

Multicellular organisms grow because cell Multicellular organisms grow because cell division increases the number of cells in division increases the number of cells in them.them.

Cells become specialized during the Cells become specialized during the development of an organism.development of an organism.

Cells that are damaged or worn out are Cells that are damaged or worn out are replaced by cell division.replaced by cell division.

Cell Growth and Division: The Cell Cell Growth and Division: The Cell CycleCycle

Interphase: The part of the cell cycle when Interphase: The part of the cell cycle when the cell is not dividing. the cell is not dividing. – This is the longest phase in the cell cycle.This is the longest phase in the cell cycle.– Cells grow and go about their daily routines in Cells grow and go about their daily routines in

this part of the cycle.this part of the cycle.– DNA (genetic material) replicates.DNA (genetic material) replicates.


Mitosis: the part of the cell cycle where the Mitosis: the part of the cell cycle where the nucleus divides. Occurs in non-reproductive nucleus divides. Occurs in non-reproductive cells and produces exact copies of the parent cells and produces exact copies of the parent cell.cell.– Prophase: The chromosomes condenseProphase: The chromosomes condense– Metaphase: The chromosomes line up in the Metaphase: The chromosomes line up in the

middle of the cell.middle of the cell.– Anaphase: The chromosomes separate and are Anaphase: The chromosomes separate and are

pulled to either end of the cell.pulled to either end of the cell.– Telophase: The new nuclear membrane forms.Telophase: The new nuclear membrane forms.– Cytokinesis: The cell splits in half.Cytokinesis: The cell splits in half.


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The Cell 7 th Grade Science Mrs. Christopherson Mrs. Goede