Chapter 3: Cell Structure and Function

What Are Cells?

Cells- A Look Inside

7.1 What are cells?

• A cell is the basic unit of structure and function in a living thing.

• Your body is composed of billions of cells.

7.1 What are cells?

• You have nerve cells, skin cells, muscle cells, blood cells, and many other types as well.

These are some of the types of cells found in your blood.

7.1 What are cells?• Each cell in your body shares the

characteristics of all living things.

7.1 Finding out about cells

• English scientist Robert Hooke (1635–1703) was the first to record his observations of cells.

• In 1663, he took a thin slice of cork and placed it under a microscope that he built himself.

7.1 Finding out about cells• As microscopes

improved, scientists made many discoveries.

• A modern fluorescent microscope enables scientists to use glowing proteins to see tiny cell parts such as DNA in these mouse cells.

7.1 The cell theory• The work of Schwann,

Leeuwenhoek, Schleiden, Schwann, Virchow, and others led to an important theory in life science.

• The cell theory explains the relationship between cells and living things.

Theodor Schwann (1810-1882).  Hulton Archive/Archive Photos/Getty Images

The Cell Theory states:

1 - All living organisms are composed of cells. They may

be unicellular or multicellular.2 - The cell is the basic unit of life.3 - Cells arise from pre-existing cells.

7.1 Similarities among cells

• In many-celled organisms like you, there are many different specialized cells.

• All cells share certain common characteristics.

7.1 Similarities among cells

1. All cells are surrounded by a cell membrane.

2. All cells contain organelles.

3. All cells contain cytoplasm.

4. All cells contain DNA.

7.1 Classifying cells

• Prokaryotic cells do not have a nucleus.

• Scientists believe that all life on Earth came from ancient cells of this type.

• Only bacteria have this type of cell.

7.1 Classifying cells

• Eukaryotic cells have a nucleus and membrane-covered organelles.

• They tend to be about ten times larger than prokaryotic cells.

• Animals, plants, fungi, and protists all have eukaryotic cells.

7.1 Comparing cell types