Mrs. Degl1 The Cell The Cell Theory: 1.Cells are the basic unit of structure of all living things 2.Cells are the basic unit of function of all living.

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The CellThe Cell Theory: 1. Cells are the basic unit of structure of all living things2. Cells are the basic unit of function of all living things3. ALL cells come from pre-existing cells

Microscopes have better allowed scientists to develop The Cell Theory.

The eyes of a fly from Robert Hooke's Micrographia (London: 1665) 

Robert Hooke (1635-1703) – observed slices of cork through a magnifying glass and observed box-like structures and called them cells.

In 1831, Robert Brown used the word nucleus to describe the dark, central globule.  (The word nucleus is Latin for little nut.)   

Cheek Cells

Landmarks in Cell Biology

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Exceptions to the Cell Theory :

1. Viruses - are they alive ?

According to the Cell Theory we have to say "no" because a virus is not a cell.  Viruses are made of two chemicals, protein & nucleic acid, but have no membranes, nucleus, or protoplasm. They appear to be alive when they reproduce after infecting a host cell.

2. Mitochondria & chloroplasts.

These cell organelles (small structures inside the cell) have their own genetic material & reproduce independently from the rest of the cell.

3. Where did the first cell come from ?

According to statement #3 of the cell theory, all cells come from other living cells.  So how did the first cell ever appear ?  It's the old "chicken & egg" dilemma.  We will investigate this question (& its possible answer) in more detail during the Evolution Unit.

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Animal Cell

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Plant Cell

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Cell Structure and Organelles

Most cells possess the same organelles, however plant and animal cells do differ a bit.

1. Cell Membrane• Also known as Plasma Membrane• Surrounds the cell and controls what goes into and out of it• Selectively permeable (only allows certain materials in and out)• Double layered and composed of lipids and proteins

2. Cell Wall• FOUND ONLY IN PLANTS• Composed of cellulose• Protects cell

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3. Cytoplasm• Fluid like material that fills the space between the cell membrane

and the nucleus • Contains all of the organelles

4. Nucleus• Controls cellular metabolism and reproduction• Contains DNA and hereditary material• Surrounded by a nuclear membrane• Contains the nucleolus

5. Nucleolus• Produces and releases ribosomes into the cell

6. Ribosomes• Site where proteins are synthesized from amino acids• May be found in the cytoplasm or attached to the endoplasmic

reticulum

nucleolus

nucleus

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7. Endoplasmic Reticulum • System of fluid-filled canals• Associated with transport of materials throughout the cell

8. Lysosomes• Membrane bounded sacs that contain digestive enzymes• Involved in the digestion of food in unicellular organisms• Destroys damaged or old cell parts in multi-cellular organisms

9. Vacuoles • Fluid filled sacs found in the cytoplasm• Contain stored materials, such as food and wastes.• Contractile Vacuole is used to pump excess water out of the cell.

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10.Mitochondria• Powerhouse of the cell• Site where respiration produces

energy for the cell• Where ATP is produced for

energy • Contain their own DNA and can

duplicate themselves11.Centrioles• Found only in animal cells• Located near the nucleus• Have a part in cell division

12.Chloroplast• Found only in plant cells• Contains green chlorophyll pigment• Have their own DNA and can replicate• Site of Photosynthesis

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13.Cilia and Flagella• Organelles responsible for cell movement

•There are usually many cilia on the outside of a cell and they are very small (Paramecium have then•There are not many flagella and they are larger (Sperm have them)

Flagella

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14.Golgi Bodies• The Golgi apparatus consists of stacks of sacs with

vesicles pinching off from the edges of the sacs. • The function of the Golgi is to package materials for

export from the cell.• Also called the Golgi Apparatus or Golgi Complex

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Amoeba

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Prokaryotic cells have no nucleus or organelles enclosed within membranes. Species in the domains Archaea and Eubacteria have prokaryotic cells.

Eukaryotic cells have a nucleus and organelles that are surrounded by membranes. Each organelle does a specific cell function. All species in the Eukaryota domain (protists, fungi, plants, and animals) have eukaryotic cells. Individual protists have only one cell, while plants and animals can have trillions of cells. Complex creatures like humans have special cells for special functions like carrying oxygen around the body, digesting food, or making bone.