1. Chapter 7; Section 1 Introduction to Cells
Key Ideas:
How were cells discovered?
Why does cell shape vary?
What enables eukaryotes to perform more specialized functions than prokaryotes?

2. Discovery of Cells Robert Hooke (1665)
Coins term “cell” after looking at cork and seeking the cell walls

3. Robert Brown (1831)
Pointed out nucleus

4. Matthias Schleiden (1838)
Plants are made of cells

5. Theodore Schwann (1839) Declared that animals are composed of cells
First to create term
“cell theory”
German scientist
Declared that animals
are composed of cells
First to create term
“cell theory”

6. Rudolf Virchow (1858) “every cell comes from a cell”
German pathologist
Altered the ideas of cellular biology
“every cell comes from a cell”

7. Cell Theory states that: all living things are composed of cells
cells are the basic units of structure and function in living things
new cells come from existing cells.
The observations & ideas were put together to form the cell theory in the 1800s
It states that:
all living things are composed of cells
cells are the basic units of structure and function in living things
new cells come from existing cells

8. Cell Theory

9. Cells vary greatly in size and shape
shape reflects its function.
branched, flat, round, or rectangular.
size is limited by a cell’s surface area-to-volume ratio.
Cheek cells
vary greatly in size and shape
shape reflects its function.
size is limited by a cell’s surface area-to-volume ratio.
can be branched, flat, round, or rectangula
Nerve cell

10. Looking at Cells
To enter or leave a cell a substance must cross the surface of the cell.
ability to move substances across its surface can be estimated by finding its surface area-to-volume ratio.
greater surface area-to-volume ratios allows substances to be exchanged more efficiently.
All substances that enter or leave a cell must cross the surface of the cell.
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.

11. Relationship between Surface Area and Volume
small cells have greater surface area-to-volume ratios than large cells.
small cells function more efficiently than large cells.

12. Features of ALL Cells cell membrane
outer layer; covers a cell’s surface
acts as a barrier between the outside environment and the inside of the cell.
Cytoplasm: region of the cell within the cell membrane.
“shock absorber”
protects the organelles
ribosome
makes proteins.
DNA
provides instructions for making proteins
regulates cellular activities
enables cells to reproduce.

13. Features of Prokaryotic and Eukaryotic Cells

14. Characteristics of Prokaryotic Organisms
Single cell
NO nucleus or other internal compartments.
Genetic material is a single loop of DNA.
Single cell
NO nucleus or other internal compartments.
Genetic material is a single loop of DNA.
For millions of years – they were the only organisms on Earth.

15. Characteristics of Eukaryotic Organisms
Can be unicellular or multicellular
ALL multicellular organisms are made of eukaryotic cells
DNA is found in the nucleus.
have membrane-bound organelles.
An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell.
complex organization enables them to carry out more specialized functions than prokaryotic cells
organism made up of one or more eukaryotic cells.
All multicellular organisms are made of eukaryotic cells.
DNA is found in the nucleus.
have membrane-bound organelles.
An organelle is a small structure found in the cytoplasm that carries out specific activities inside the cell.
The complex organization of eukaryotic cells enables them to carry out more specialized functions than prokaryotic cells

16. Comparing Prokaryotes and Eukaryotes

17. Comparing Prokaryotes and Eukaryotes
Two cell Types
Prokaryotes
Eukaryote
No nucleus
Nucleus
No membrane bound organelles
Many organelles
Most 1 – 10µ in size
Many 2 – 1,000 µm in size
Evolved 3.5 billion years ago
Evolved 1.5 billion years ago
Only bacteria
All other cells

18. Summary
Microscope observations of organisms led to the discovery of the basic characteristics common to all living things.
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.