Introduction to the Cell

The Cell Cell: the smallest unit of life Why do you think they weren’t discovered until the mid 1600’s?

Used an early compound light microscope The Cell Robert Hooke-first person to describe a cell 1665 British- Used an early compound light microscope

Looked at cork "little boxes”; reminded him of monastery rooms called The Cell Looked at cork "little boxes”; reminded him of monastery rooms called cells

Dutch; around the same time as Hooke; used a single- lens microscope The Cell Anton van Leeuwenhoek Dutch; around the same time as Hooke; used a single- lens microscope

Anton van Leeuwenhoek- The Cell Anton van Leeuwenhoek- made his own microscopes and looked at protists, animal blood, bacteria, and yeast

1838 botanist Schleiden 1839 biologist Schwann 1855 physician Virchow The Cell The Cell Theory: 1838 botanist Schleiden 1839 biologist Schwann 1855 physician Virchow

1. All organisms are made up of cells The Cell The Cell theory: 1. All organisms are made up of cells

1. All organisms are made up of cells The Cell The Cell theory: 1. All organisms are made up of cells 2. The cell is the basic unit of life

3. All cells come from existing cells The Cell The Cell theory: 1. All organisms are made up of cells 2. The cell is the basic unit of life 3. All cells come from existing cells

Parts of All Cells All cells are surrounded by a protective barrier called the cell membrane.

Parts of All Cells All cells have structures that perform specific functions within the cell called organelles

Parts of All Cells All cells contain DNA (some cells have a nucleus that holds the DNA)

Two Kinds of Cells: 1. Prokaryotes (single celled with no nucleus or membrane bound organelles) Example 1: Bacteria Smallest of all cells Common Strong cell wall

Two Kinds of Cells: Prokaryotes Example 2: Archaea Heat-loving, salt-loving, and methane-making Live in extreme conditions Thought to have evolved prior to nuclei developing

Two Kinds of Cells: 2. Eukaryotes (the largest cells; more complex; have a nucleus and other membrane bound organelles)

Two Kinds of Cells: Eukaryotes Many are multi-cellular (many cells) Great variety! Examples: Plants, animals, fungi, protists

Surface Area to Volume Ratio Why are most cells so small? As the cell’s volume increases, so does its surface area.

Surface Area to Volume Ratio Volume grows faster than surface area (inside grows faster than membrane)

Surface Area to Volume Ratio If gets too large- cell’s s.a. will not be large enough to take in enough nutrients or pump out wastes

Eventually there is just enough surface available to service all the interior; if it is to survive, the cell must stop growing! The cell must ÷ into smaller cells with smaller s.a. /volume ratios, or cease to function.

Surface Area to Volume Ratio Remember: The surface area to the volume ratio gets smaller as the cell gets larger.