Chapter 7 - Section 1: Introduction to Cells
Chapter 7 - Section 1: Introduction to Cells
Warmup: What parts of cells can you name?
Key Ideas
How were cells discovered?
Why does cell shape vary?
What enables eukaryotes to perform more specialized functions than prokaryotes?
The Discovery of Cells
Microscope observations of organisms led to the discovery of the basic characteristics common to all living things.
Robert Hooke first discovered cells in the 1600s using crude microscopes (30x) to look at thin sections of cork.
Hooke could see little boxes that he called cells.
Anton van Leeuwenhoek identified single-celled organisms with a microscope (300x) 10 yrs later.
Cell Theory
Observations made by 3 German scientists using microscopes in the 1800s led to the formation of the cell theory.
Schleiden discovered cells make up all parts of a plant.
Schwann discovered that animals are made of cells.
Virchow proposed that all cells arise from existing cells.
Cell Theory
All living things are composed of one or more cells.
Cells are the basic units of structure and function in an organism
Cells only come from the reproduction of existing cells.
Looking at Cells
Cells vary greatly in their size and shape.
A cell’s shape reflects its function. Cells can be multiple shapes including branched, flat, round, or rectangular.
Cell size is limited by a cell’s surface area-to-volume ratio.
All substances that enter or leave a cell must cross the surface of the cell.
A cell’s ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio.
Cells with greater surface area-to-volume ratios can exchange substances more efficiently.
Calculation of surface area and volume
Surface area = (height x width) x 6
Volume = Height x width x length
For a 1 cm cube
Surface area = (1cm x 1cm) x 6 = 6 cm2
Volume = 1cm x 1cm x 1cm= 1 cm3
Surface area : Volume :: 6 : 1
Calculate for a 2 cm cube
Relationship between Surface Area and Volume
Looking at Cells, continued
When comparing cells of the same shape, small cells have greater surface area-to-volume ratios than large cells.
So, small cells function more efficiently than large cells.
Features of Prokaryotic and Eukaryotic Cells
Features of Prokaryotic Cells
A prokaryote is an organism made of a single prokaryotic cell.
Prokaryotic cells do NOT have a nucleus or other internal compartments.
The genetic material of a prokaryotic cell is a single loop of DNA.
For millions of years, prokaryotes were the only organisms on Earth.
Features of Eukaryotic Cells
A eukaryote is an organism made up of one or more eukaryotic cells.
All multicellular organisms are made of eukaryotic cells.
The DNA of a eukaryotic cell is found in an internal compartment of the cell called the nucleus.
All eukaryotic cells have membrane-bound organelles.
An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell.
Each organelle in a eukaryotic cell performs distinct functions.
The complex organization of eukaryotic cells enables them to carry out more specialized functions than prokaryotic cells.
Comparing Prokaryotes and Eukaryotes
Summary
Microscope observations of organisms led to the discovery of the basic characteristics common to all living things –cells.
A cell’s shape reflects its function. Cell size is limited by a cell’s surface area-to-volume ratio.
The complex organization of eukaryotic cells enable them to carry out more specialized functions than prokaryotic cells.
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