The Evolving Concept of Life

Cells

• Cells are the basic units of structure and function in living things.
• Just like bricks build a house, cells are the building blocks of life.
• Living things are made up of cells.
• One square centimeter of skin contains over 100,000 cells.

History of the Cell

• In 1590, Zacharias Janssen and Hans Janssen invented the first compound microscope.
• In 1665, Robert Hooke discovered and named cells while looking at cork under a microscope.
• Cork, made of dead oak tree tissues, looked like the small rooms monks lived in.
• Anton van Leeuwenhoek, a Dutch amateur scientist, observed some of the first living cells using a simple microscope (around 1683).
• He called these small organisms "animalcules".
• Some of the living cells observed were protozoa.

Microscope View of Cells

• Anton van Leeuwenhoek was the first to see living cells.
• He improved the design of the microscope.
• He was able to see red blood cells and bacteria.
• He also called them "animalcules".

The Development of Cell Theory

• In 1838 and 1839, Matthias Schleiden (botanist) and Theodore Schwann (zoologist) discovered plants and animals are made of cells.
• In 1855, Rudolph Virchow collaborated with them to develop the Cell Theory.

Scientists of Cell Theory

• Theodore Schwann: Observed that animal tissues have cells (1839).
• Matthias Schleiden: Observed that plant tissues have cells (1845).
• Rudolf Virchow: Proposed that all cells come from pre-existing cells.

Cell Theory

• All living organisms are made up of cells.
• Cells are the basic units of life.
• Cells only come from other pre-existing cells.

Terms

• Cell: The smallest unit that carries out life's processes.
• Unicellular: Consisting of only one cell.
• Multicellular: Consisting of more than one cell.

Basic Cell Structures

• Cell Membrane: The outer boundary of a cell.
• Nucleus: The control center of a cell, containing DNA.
• Cytoplasm: The material between the cell membrane and the nucleus.

Basic Types of Cells

• Cells come in various shapes and sizes.
• All cells have a plasma (cell) membrane—a boundary allowing materials to enter and exit the cell.

Differences in Cell Types

• Cells are divided into eukaryotes and prokaryotes.
• Eukaryotes: Have a membrane-bound nucleus and organelles.
• Prokaryotes: Do not have a membrane-bound nucleus or organelles (except ribosomes.)
• A nucleus is the central organelle containing genetic material (DNA).
• Organelles are specialized structures within cells carrying out vital functions.

Prokaryotic Cells

• Prokaryotic cells, often like bacteria, are unicellular.
• DNA is not found within a nucleus, but in the cytoplasm.

Eukaryotic Cells

• Eukaryotic cells, including animal and plant cells, have a membrane-bound nucleus.
• Eukaryotic cells also have membrane-bound organelles.