Transcript 7.1 What are cells?

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.
Theodor Schwann (1810-1882). Hulton
• The cell theory explains Archive/Archive Photos/Getty Images
the relationship between
cells and living things.
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 membranecovered 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